Hello everone I just bought on fleabay a Heathkit SG-8 Signal Generator that I intend to use to help me realign the radio that I restore, the unit itseld is in near mint condition, but the unit doesn't have its original probes with it anymore and it doesn't have its manuals anymore either.

I was wondering how hard it would be to source some probes for this unit or to make some, and if I could get a manual for this thing online somewhere?
Would also like to know how to use one of these with radio alignment.

Any help would be appreciated.

There is a little thing called "Google". You ought to try it sometime.
http://pdf.textfiles.com/manuals/SCANNERS-F-R/Heathkit-SG-8.pdf

The connector used on that unit are what was known as microphone connectors. The end that goes onto the cable end can be found but a better solution is to replace the connectors on the generator with BNC jacks. There are even pre-made cables with BNC plugs made. I believe that the stock cables were coax with alligator clips on the other end.
There are a number of sources for general instructions on AM radio alignment. Usually the service data for each radio gives further details.
Most of the time you can connect the generator cable clips to a small coil of wire (4-6 inch diameter) with something like 8-10 turns. This coil sends a signal to the radios antenna loop. Some radios don't have antenna loops and the coupling is done another way. Sometimes the signal is injected into the radios IF circuits various ways.
I recommend a book like this one.
https://www.amazon.com/Old-Time-Radios-Restoration-Repair/dp/0830633421/ref=sr_1_1?dchild=1&keywords=restoration+and+repair+of+old+radios&qid=1587091398&s=books&sr=1-1

This is the type of BNC jack you could replace the microphone connectors with.
https://www.mouser.com/ProductDetail/TE-Connectivity-AMP/5227755-1?qs=sGAEpiMZZMuLQf%252BEuFsOrtKdKMPPpnQyzdb4bk0FG lA%3D

There is a little thing called "Google". You ought to try it sometime.
http://pdf.textfiles.com/manuals/SCANNERS-F-R/Heathkit-SG-8.pdf

The connector used on that unit are what was known as microphone connectors. The end that goes onto the cable end can be found but a better solution is to replace the connectors on the generator with BNC jacks. There are even pre-made cables with BNC plugs made. I believe that the stock cables were coax with alligator clips on the other end.
There are a number of sources for general instructions on AM radio alignment. Usually the service data for each radio gives further details.
Most of the time you can connect the generator cable clips to a small coil of wire (4-6 inch diameter) with something like 8-10 turns. This coil sends a signal to the radios antenna loop. Some radios don't have antenna loops and the coupling is done another way. Sometimes the signal is injected into the radios IF circuits various ways.
I recommend a book like this one.
https://www.amazon.com/Old-Time-Radios-Restoration-Repair/dp/0830633421/ref=sr_1_1?dchild=1&keywords=restoration+and+repair+of+old+radios&qid=1587091398&s=books&sr=1-1

Yeah, I ended up finding the manual after someone on the Philco Phorum told me about it, (I wrote this thread before I saw the reply on the Philco Phorum).

Anyways I also bought a Radio City Products Model 705A Signal Generator that also needs test leads and a manual.

Although I'm kind of regretting asking about those signal generators on the Philco Phorum because the person who replied to my thread on there is trying to make me feel bad about my purchases by telling me that they are going to be crappy and telling me that I should of instead bought a Hewlett-Packard one instead (even though I could never afford to buy one).

Well the Heathkit doesn't have a very nice sine wave output but it usually does not matter. The SG-8 like many generators used for radio-tv repair are what is known as "service grade" as opposed to "lab grade". A sinewave that doesn't have the right shape has harmonic distortion. That means that a 1Mhz output also could contain 2MHz, 3MHz, 4MHz, 5MHz, etc. Many times just the odd harmonics. However the tuned circuits in a radio-tv reject the harmonics for the most part, so they don't really matter in practice.
Also the service grade generators do not keep the signal amplitude the same as you change the frequency. However you can monitor the amplitude if you need to and adjust the amplitude as you change frequency. Maybe not as convenient, but you can make it work. Most of the time you don't change the frequency that much anyway.
The frequency dials on service grade generators are not as accurate so if you must have the frequency exact a frequency counter is a good addition to the set-up.

Well the Heathkit doesn't have a very nice sine wave output but it usually does not matter. The SG-8 like many generators used for radio-tv repair are what is known as "service grade" as opposed to "lab grade". A sinewave that doesn't have the right shape has harmonic distortion. That means that a 1Mhz output also could contain 2MHz, 3MHz, 4MHz, 5MHz, etc. Many times just the odd harmonics. However the tuned circuits in a radio-tv reject the harmonics for the most part, so they don't really matter in practice.
Also the service grade generators do not keep the signal amplitude the same as you change the frequency. However you can monitor the amplitude if you need to and adjust the amplitude as you change frequency. Maybe not as convenient, but you can make it work. Most of the time you don't change the frequency that much anyway.
The frequency dials on service grade generators are not as accurate so if you must have the frequency exact a frequency counter is a good addition to the set-up.

That's what I thought. The guy on the Philco Phorum basically said the same thing. But the thing is, I'm just repairing old tube radios and stereo receivers so lab quality gear like the Hewlett-Packard units are not what I need.

I just need something to get me close enough to make the radios work again as intended, it's not like I'm designing new radio circuits where you would need something like a lab grade unit for.

Most of the units I'm repairing are units that are already working circuits but just need to be touched up, so a regular bench grade unit is more than enough for the work I'm doing.

I've gotten working 70s HP gear for under $10 before. It is all a matter of being in the right place at the right time.

Some many service generators are inaccurate enough on frequency that if you don't have a frequency counter to check them they can sometimes mess up alignment. Some frequency counters will get confused if the carrier is not sinusoidal enough. My old lab grade generators lack modulation capability (which is important for some alignment work) so I calibrate my service grade generator by dialing the lab gen to the right frequency on the counter, connecting the lab gen to my scope, counting the time divisions with 1-3 cycles on screen, then connecting the service gen and dialing it for the same number of time divisions.
If you haunt enough big ham radio swapmeets you'll eventually have enough decent budget equipment.

I've gotten working 70s HP gear for under $10 before. It is all a matter of being in the right place at the right time.

Some many service generators are inaccurate enough on frequency that if you don't have a frequency counter to check them they can sometimes mess up alignment. Some frequency counters will get confused if the carrier is not sinusoidal enough. My old lab grade generators lack modulation capability (which is important for some alignment work) so I calibrate my service grade generator by dialing the lab gen to the right frequency on the counter, connecting the lab gen to my scope, counting the time divisions with 1-3 cycles on screen, then connecting the service gen and dialing it for the same number of time divisions.
If you haunt enough big ham radio swapmeets you'll eventually have enough decent budget equipment.

Well the problem is, there are no swap meets near me, and trust me, I've already checked, the closest ones to me are in Indianapolis, and Chicago, and I don't want to drive to those areas because they are horrible to drive around.

The cheapest Hewlett-Packard signal generators on eBay are $150 and $50 shipping, there's no way I can afford that on my meager budget.

Fort Wayne?

http://fortwaynehamfest.com

jr

Fort Wayne?

http://fortwaynehamfest.com

jr

That's another city I'd rather not drive around in because traffic is terrible there and my mom doesn't want me to drive around there unless someone is with me for the reasons I mentioned.

Plus activities like that are canceled until further notice because of the corona virus.

It is great that HP equipment is more affordable now. I have some myself and I don't usually spend a whole lot on things. That being said, you have to keep in mind that a piece of HP test equipment built in the 1950's will require re-capping just as a radio or TV from that era. HP used very high quality parts so they hold up better than others, but there are limits on how well anything lasts. Solid state test equipment made more recently are less likely to need restoration before they can be used. Repair shops in the 40's through the 70's seldom had HP equipment.
There are brands that fall between HP and say Heathkit in precision. Heathkit items are very easy to work on since they were intended for assembly from scratch. There are service grade brands with better performance that are factory built but are simpler than HP. B&K, RCA, EICO, Sencor, Leader and Tektronix, etc.
Here is my modified SG-8. My B&K 2005A RF generator and HP 5382A frequency counter. Also my Leader LAG-27 audio generator, a home-built 455KHz generator and my RF coupling loop. I think I found the SG-8 locally on Craig's list. The others were very carefully selected form ebay. The B&K RF generator had some broken front panel pieces (poor packing) that I was able to glue back together. Except for the SG-8 the equipment shown is solid state, but I think I replaced the electrolytics in all of them.

It is great that HP equipment is more affordable now. I have some myself and I don't usually spend a whole lot on things. That being said, you have to keep in mind that a piece of HP test equipment built in the 1950's will require re-capping just as a radio or TV from that era. HP used very high quality parts so they hold up better than others, but there are limits on how well anything lasts. Solid state test equipment made more recently are less likely to need restoration before they can be used. Repair shops in the 40's through the 70's seldom had HP equipment.
There are brands that fall between HP and say Heathkit in precision. Heathkit items are very easy to work on since they were intended for assembly from scratch. There are service grade brands with better performance that are factory built but are simpler than HP. B&K, RCA, EICO, Sencor, Leader and Tektronix, etc.
Here is my modified SG-8. My B&K 2005A RF generator and HP 5382A frequency counter. Also my Leader LAG-27 audio generator, a home-built 455KHz generator and my RF coupling loop. I think I found the SG-8 locally on Craig's list. The others were very carefully selected form ebay. The B&K RF generator had some broken front panel pieces (poor packing) that I was able to glue back together. Except for the SG-8 the equipment shown is solid state, but I think I replaced the electrolytics in all of them.

OK, thanks for the info.
I'm just curious, how do you hook up a frequency counter to a signal generator if I got one?

Good question. That points out a bit of a problem normally. The output of a typical RF generator is very small. It only takes something like 10 uV ( 10 one millionth of a volt) of signal at the radio antenna for the radio to receive it. The problem is many frequency counters need something like at least 100 mV for them to work. One thing to do is turn the generator output up to max to read the frequency and then turn the output down before connecting to the radio. Another thing that sometimes works is to modify the generator and bring out the signal before it goes into the output attenuator to a separate connector. The B&K 2005A has this already done. It has the normal output connector that the amplitude can be varied and a frequency monitoring output connector. Some people have bought small frequency counter modules and install them in the generator if there is room. I don't think the modules have a very precise timebase oscillator in them however.

Good question. That points out a bit of a problem normally. The output of a typical RF generator is very small. It only takes something like 10 uV ( 10 one millionth of a volt) of signal at the radio antenna for the radio to receive it. The problem is many frequency counters need something like at least 100 mV for them to work. One thing to do is turn the generator output up to max to read the frequency and then turn the output down before connecting to the radio. Another thing that sometimes works is to modify the generator and bring out the signal before it goes into the output attenuator to a separate connector. The B&K 2005A has this already done. It has the normal output connector that the amplitude can be varied and a frequency monitoring output connector. Some people have bought small frequency counter modules and install them in the generator if there is room. I don't think the modules have a very precise timebase oscillator in them however.
It the counter is microcontroller based and has a crystal osc it can be very precise.

Depends on how good the crystal oscillator is more than anything. You get what you pay for.

Unfortunately I can't seem to find any frequency counters on ebay that are under $100 except for the cheap Chineseum kits, but they don't have a case and they require a 9V battery to operate and use a WiFi Antenna style input plug, and they don't seem to have any sort of adjustments on them like the factory built ones that are going for over $100 and as much as $25,000 for a Hewlett-Packard Agilent model from the 1970s...:sigh:

Oh my. You need to sharpen your ebay skills.
Search on "frequency counter", select "pre-owned" and something like a max of $ 50. I saw at least half a dozen decent ones, even a HP or two. Out of those you have to look at the shipping costs and add that to find a total below $100. Some of the remaining have technical factors like a minimum of 20 MHz that disqualifies them. That might only bring it down to one or two or so. But if none look right you may have to try again in a couple of days.
You want to get one that covers the frequency range you will be working with, for broadcast AM maybe 10Hz to 2 MHz, Shortwave 10Hz to 25MHz, FM 10Hz to 120 MHz or TV 10Hz to 250 MHz. BNC input connector. You may have to do some research, you definitely want one with a crystal timebase oscillator, usually 10MHz. Hopefully you will have the time to run it past the forum for opinions.

Oh my. You need to sharpen your ebay skills.
Search on "frequency counter", select "pre-owned" and something like a max of $ 50. I saw at least half a dozen decent ones, even a HP or two. Out of those you have to look at the shipping costs and add that to find a total below $100. Some of the remaining have technical factors like a minimum of 20 MHz that disqualifies them. That might only bring it down to one or two or so. But if none look right you may have to try again in a couple of days.
You want to get one that covers the frequency range you will be working with, for broadcast AM maybe 10Hz to 2 MHz, Shortwave 10Hz to 25MHz, FM 10Hz to 120 MHz or TV 10Hz to 250 MHz. BNC input connector. You may have to do some research, you definitely want one with a crystal timebase oscillator, usually 10MHz. Hopefully you will have the time to run it past the forum for opinions.

Well I don't use eBay on a regular basis which is why I'm a little rusty with my eBay skills.

I'll search again using the tips you suggested and see what I come up with.

Thanks so much for your help.

The units linked below are some units I have found that are in my price range that seem like decent units.

https://www.ebay.com/itm/Heathkit-IM-4100-Frequency-Counter-EIA-416-25-watts-1-10-100-kHz-MHz-per-freq/193426296722?hash=item2d091b0f92%3Ag%3AXUIAAOSwvLt emKBU&LH_BIN=1&LH_ItemCondition=4

https://www.ebay.com/itm/Elenco-F-100L-Frequency-Counter/164144076675?hash=item2637bfd783%3Ag%3Ae3gAAOSw4kN egkaA&LH_BIN=1&LH_ItemCondition=4

What do you think?
I'm leaning heavily towards the Heathkit unit, as its cheaper and it does cover the basics as far as all the frequencies I would be using in radio and TV repair goes.

Those two are about equivalent. The Heathkit has a upper frequency limit of 30 MHz. I found a manual online.
The Elenco has all those switches so that might be a source of problems (cleaning etc.). I could not find a manual after a quick search.
So if 30 MHz is OK ( for AM Broadcast and SW radios I think it would be), then if I had to choose between the two I would go with the Heathkit. You wouldn't be able to check the frequency of a generator that is producing a signal for a FM radio (88-108MHz) for instance.

Those two are about equivalent. The Heathkit has a upper frequency limit of 30 MHz. I found a manual online.
The Elenco has all those switches so that might be a source of problems (cleaning etc.). I could not find a manual after a quick search.
So if 30 MHz is OK ( for AM Broadcast and SW radios I think it would be), then if I had to choose between the two I would go with the Heathkit. You wouldn't be able to check the frequency of a generator that is producing a signal for a FM radio (88-108MHz) for instance.

There were a couple of multifunction frequency counters that tested upto 250 Mhz or something like that that were Hewlett-Packard branded ones that were under $40 but they were listed as "as-is" untested condition.

https://www.ebay.com/itm/Victor-VC3165-Radio-High-Frequency-Counter/302934846435?epid=19016475418&hash=item468852ebe3%3Ag%3AsxwAAOSwvhxb0x4J&LH_ItemCondition=4

https://www.ebay.com/itm/BK-Precision-1850-Frequency-Counter/174073783612?hash=item28879b253c%3Ag%3A7VEAAOSw5fB dr69b&LH_ItemCondition=4

https://www.ebay.com/itm/HP-5382A-SINGLE-CHANNEL-FREQUENCY-COUNTER-B/193396759470?epid=1123833476&hash=item2d07585bae%3Ag%3Adc4AAOSwOxdbM-fR&LH_ItemCondition=4

Here's 3 frequency counters I have found including a Hewlett-Packard 225 MHz unit that is only 29.99 but the shipping is $64, which is twice the price that the unit itself costs! :thumbsdn:

OK, something very important here. You want to get something that you can find service data on. Units like the Elenco that you can find nothing about (except if they have a manual with them that has the service data) are not a good choice. If something goes wrong with them, no one is going to be able to help. That was a good thing about the Heathkit.
The Heathkit counter would be a good companion piece to the SG-8. The SG-8 upper band (E) doesn't work well on my unit. The amplitude is very low if it works at all. The next lower band ends at 25 MHz which matches that counter. Unless you are sure you need more frequency range, that would do.
The HP is gone now. You don't have a lot of time with ebay to decide.

OK, something very important here. You want to get something that you can find service data on. Units like the Elenco that you can find nothing about (except if they have a manual with them that has the service data) are not a good choice. If something goes wrong with them, no one is going to be able to help. That was a good thing about the Heathkit.
The Heathkit counter would be a good companion piece to the SG-8. The SG-8 upper band (E) doesn't work well on my unit. The amplitude is very low if it works at all. The next lower band ends at 25 MHz which matches that counter. Unless you are sure you need more frequency range, that would do.
The HP is gone now. You don't have a lot of time with ebay to decide.

I got the Heathkit Signal Generator today and it looks like its not going to need a lot of work done to it, in fact it looks like it was hardly ever used, it does have modern film caps and modern electrolytics in it which makes me think that it may have been recapped already.

pictures below are of the inside of the unit.

You'll see how clean it is inside and you'll see what I mean by having modern components inside.

I think that someone did it already for you! Unless there was a wiring error, you should be good to go.

I think that someone did it already for you! Unless there was a wiring error, you should be good to go.

That's what I was thinking.

All I need to do is just change out the jacks for modern BNC jacks and get some probes for it and I'll be all set! :yes: :thmbsp:

Does the name David Hamm sound familiar to you guys? He's the guy I got it from, he out in Marion, Iowa which I believe is Eastern Iowa.

He packed it really well it was packed in several layers of thick foam packing and then wrapped in a couple of plastic bags to protect it.
It arrived in one piece with the only thing that happened to it in shipping was that the front of the case popped out of the back cover but easily popped back into place without any damage. :thmbsp:

You know I thought you already had the SG-8.
Great that it has been re-capped. I'm not sure the selenium rectifier was replaced correctly.
Are you going to get the Heathkit IM-4100 ?
The manual I was able to find on the counter seems to be missing some pages at the front, but the service data is all there. There are also some videos about the counter.
Just so you know, a couple of years ago it was easier to find good info on Heathkit units. A company bought the rights to the info, I believe, and now charges for the manuals. There are still some copies still left here and there on the internet.

You know I thought you already had the SG-8.
Great that it has been re-capped. I'm not sure the selenium rectifier was replaced correctly.
Are you going to get the Heathkit IM-4100 ?
The manual I was able to find on the counter seems to be missing some pages at the front, but the service data is all there. There are also some videos about the counter.
Just so you know, a couple of years ago it was easier to find good info on Heathkit units. A company bought the rights to the info, I believe, and now charges for the manuals. There are still some copies still left here and there on the internet.

No, I had just bought it on ebay at the time but it hadn't been delivered until today.

As for the frequency counter I do need one that can do the FM Bandspread because I do Work on AM/FM Stereo Receivers as well.
So I will need a frequency generator that can do at least up to 200 MHz.

What do you mean the selenium rectifier wasn't replaced correctly? I think its original to the unit, which I'm thinking of replacing it with a 1N4007 Diode.

https://www.ebay.com/itm/Victor-VC3165-Radio-High-Frequency-Counter/302934846435?epid=19016475418&hash=item468852ebe3%3Ag%3AsxwAAOSwvhxb0x4J&LH_BIN=1&LH_ItemCondition=4

https://www.ebay.com/itm/Heathkit-Model-IB-101-Nixie-Display-Frequency-Counter-in-Working-Condition/143577743621?hash=item216de68105%3Ag%3AV%7EUAAOSww gVekS4L&LH_BIN=1&LH_ItemCondition=4

https://www.ebay.com/itm/B-K-Model-1850-Frequency-Counter-Untested-no-cord/303545237588?hash=item46acb4c054%3Ag%3A9KMAAOSwtLt enO1v&LH_BIN=1&LH_ItemCondition=4

Here's 3 more I've found that look promising, neither of them have a power cord though, specifically the last two, which uses the old style computer plug.

what do you think? Which one would be the best out of these 3 units?

I don't know anything about the Victor brand.
The Heathkit is older because Nixie tubes were used before LED displays were used. Also the corrosion on the BNC is not a good sign,
My first counter was similar to that B&K. The display on mine became unreliable, I believe because of a connector issue. My model didn't go very high in frequency so I decided to trade up.
Note that both the Heathkit and the B&K used a power cord connector with
round pins, unlike the common power cords now which have flat blades.
I not wild about any of those three.

What do you mean the selenium rectifier wasn't replaced correctly? I think its original to the unit, which I'm thinking of replacing it with a 1N4007 Diode.

Apparently some restorers connect a Si rectifier diode across the selenium one without disconnecting the selenium. I even saw that in a book about radio restoration. It isn't a good idea because the old rectifier can leak reverse current.Since your generator had been re-capped I thought that might be the case.

I don't know anything about the Victor brand.
The Heathkit is older because Nixie tubes were used before LED displays were used. Also the corrosion on the BNC is not a good sign,
My first counter was similar to that B&K. The display on mine became unreliable, I believe because of a connector issue. My model didn't go very high in frequency so I decided to trade up.
Note that both the Heathkit and the B&K used a power cord connector with
round pins, unlike the common power cords now which have flat blades.
I not wild about any of those three.

Well that Hewlett-Packard one that that I previously Posted about that's like yours is still available, I'm just not too keen on having to pay over $60 for shipping on an item that's only $30, I'm not even quite sure why that the shipping on that is over $60 when other frequency counters that are similar in size and traveling a similar distance to get to me have only $10-$15 shipping costs.

Well that Hewlett-Packard one that that I previously Posted about that's like yours is still available, I'm just not too keen on having to pay over $60 for shipping on an item that's only $30, I'm not even quite sure why that the shipping on that is over $60 when other frequency counters that are similar in size and traveling a similar distance to get to me have only $10-$15 shipping costs.

In some cases that is the difference between packing it to survive shipping abuse, and just throwing it in box loosely or in the case of a friend who bought a used BT modulator off eBay throwing it in a plastic bag with a shipping label pasted on....but then again some sellers try to profit off the shipping if they can't get the margin they want on the item it's self...

Apparently some restorers connect a Si rectifier diode across the selenium one without disconnecting the selenium. I even saw that in a book about radio restoration. It isn't a good idea because the old rectifier can leak reverse current.Since your generator had been re-capped I thought that might be the case.

It has no silicone diode going across the selenium in this unit, its just the selenium rectifier.

In some cases that is the difference between packing it to survive shipping abuse, and just throwing it in box loosely or in the case of a friend who bought a used BT modulator off eBay throwing it in a plastic bag with a shipping label pasted on....but then again some sellers try to profit off the shipping if they can't get the margin they want on the item it's self...

I agree about packing things well so that it doesn't get damaged but that doesn't require a $60 shipping charge though, my Heathkit signal generator had a $20 shipping charge and it was well packed and survived the trip undamaged, and the packing job that was done on that didn't require no $60 shipping charge, I think that person is just trying to cover his butt because he probably isn't going to pack it well.

I don't know anything about the Victor brand.
The Heathkit is older because Nixie tubes were used before LED displays were used. Also the corrosion on the BNC is not a good sign,
My first counter was similar to that B&K. The display on mine became unreliable, I believe because of a connector issue. My model didn't go very high in frequency so I decided to trade up.
Note that both the Heathkit and the B&K used a power cord connector with
round pins, unlike the common power cords now which have flat blades.
I not wild about any of those three.

Isn't there a way that you could change the power cord plug-in on the back of the B & K unit so that it fits a modern PC Style plug in? If so then I would think that the B & K unit would be a fine alternative to the Hewlett-Packard one that has the rediculous shipping charges.

https://www.ebay.com/itm/Heathkit-Digital-Frequency-Counter-SM-2420/324143171630?hash=item4b7870482e%3Ag%3A8R0AAOSwxMF en7hD&LH_ItemCondition=4

I just found a Heathkit SM-2420 512 Mhz Frequency Counter on ebay buy it now price of $24.99 and $27.99 shipping costs, and it has a hardwired cord rather than an old school style computer cord.

OK, so I just figured out that by reading the manual for the Radio City Products Signal Generator I'll be getting, that it actually has a hookup on it that can be used to hook up a frequency counter and monitor the frequency.

So the RCP unit might actually be a better unit than the Heathkit one in this case. :thmbsp::yes:

Isn't there a way that you could change the power cord plug-in on the back of the B & K unit so that it fits a modern PC Style plug in? If so then I would think that the B & K unit would be a fine alternative to the Hewlett-Packard one that has the rediculous shipping charges.

There are three different in compatible old style 'computer' power cord receptacles in old test equipment (somewhere here I posted a picture of them). They range from somewhat common to 'OMG this is the only cord for this I have ever seen' my Heathkit Nixie DMM had the later and I needed the cord for a much rarer Sony Badged Setchell Carlson monitor so I converted it the DMM to use a modern computer power receptacle(IIRC pirated off a dead PC PSU)... I had to enlarge the case opening with a file but it was easy enough to do....I could have converted it to a hard wired cord too but I wanted it detachable for convenience.

There's always a way to power something with a weird 120v power receptacle...I keep a cord with insulated alligator clips around specifically for portable TVs with weird proprietary jacks for Missing power cords....

There are three different in compatible old style 'computer' power cord receptacles in old test equipment (somewhere here I posted a picture of them). They range from somewhat common to 'OMG this is the only cord for this I have ever seen' my Heathkit Nixie DMM had the later and I needed the cord for a much rarer Sony Badged Setchell Carlson monitor so I converted it the DMM to use a modern computer power receptacle(IIRC pirated off a dead PC PSU)... I had to enlarge the case opening with a file but it was easy enough to do....I could have converted it to a hard wired cord too but I wanted it detachable for convenience.

There's always a way to power something with a weird 120v power receptacle...I keep a cord with insulated alligator clips around specifically for portable TVs with weird proprietary jacks for Missing power cords....

That's all I needed to know, I might just go for the B & K unit then because its will only come out to a little over $40 including shipping and taxes.

I ended up getting the Heathkit SM-2420 Frequency Counter as it was basically the same price with shipping and taxes as the B & K unit and also had the same specs as well, and it had a hardwired power cord with it so then I wouldn't have to worry about messing around with changing out the plug-in for the cord, like I would of had to of done with the B & K unit.

I think the 2420 was a good choice. I found a manual for it online.
https://www.audioservicemanuals.com/h/heathkit/heathkit-im/26788-heathkit-im-2420-manual
The crystal oscillator in an oven is definitely a very good thing.

Do you have or intend on getting the Radio City Products generator?
I don't think there were many digital frequency counters back then.

I think the 2420 was a good choice. I found a manual for it online.
https://www.audioservicemanuals.com/h/heathkit/heathkit-im/26788-heathkit-im-2420-manual
The crystal oscillator in an oven is definitely a very good thing.

Do you have or intend on getting the Radio City Products generator?
I don't think there were many digital frequency counters back then.

Yes I did get it. And I found out it was made specifically for AM/FM alignment work as well as Shortwave work.
And it also has an RF Output that is a higher voltage/volume output that can be used independently of the Attenuator for monitoring the frequencies with a frequency counter (which back then would of been nixie tubes).

Apparently some restorers connect a Si rectifier diode across the selenium one without disconnecting the selenium. I even saw that in a book about radio restoration. It isn't a good idea because the old rectifier can leak reverse current.Since your generator had been re-capped I thought that might be the case.

I definitely double checked the Selenium Rectifier and it definitely doesn't have a Silicone Diode across it, so it was done correctly! :thmbsp: :yes:

It's not a bad idea to replace the original selenium rectifier in it with a modern 1N4007 or similar as preventive maintenance or you can be a Daredevil and run it with the original till it smokes.... I've taken both approaches.

It's not a bad idea to replace the original selenium rectifier in it with a modern 1N4007 or similar as preventive maintenance or you can be a Daredevil and run it with the original till it smokes.... I've taken both approaches.

What size of resistor should I use if I were to replace the old selenium with a 1n4007 diode?

What size of resistor should I use if I were to replace the old selenium with a 1n4007 diode?

Since there is a 3.3K resistor in the filter circuit, which suggests there isn't much current draw, I ended up not adding a resistor.
I made several modifications to my SG-8 to see if I could improve the modulation, etc., including adding a tube. I won't go into all I did, it was mostly experimentation and probably not worth it.

Since there is a 3.3K resistor in the filter circuit, which suggests there isn't much current draw, I ended up not adding a resistor.
I made several modifications to my SG-8 to see if I could improve the modulation, etc., including adding a tube. I won't go into all I did, it was mostly experimentation and probably not worth it.

OK, so then I can just take out that Rectifier and just replace it with a 1N4007 and be done with it.

About that 2420 counter, since it is capable of high accuracy there are a few things you should understand about frequency counters.
The oven crystal oscillator is very stable, however there is an adjustment, a calibration, that is critical so that the display is as accurate as it can be.
The oscillator is capable of staying on frequency within better than 1 ppm (one part per million) that is 0.0001 %, much better than any voltage, current or resistance meter measurement. You need that much accuracy if all 8 digits of the display will mean anything.
However if the crystal oscillation is only calibrated to an accuracy of, say, 0.1% then the display will be off that much. So the calibration needs to be checked from time to time against a frequency source of even more accuracy.
One way is by using super accurate frequency radio broadcasts from stations like WWV and WWVH. More modern methods use GPS managed frequency standards.

About that 2420 counter, since it is capable of high accuracy there are a few things you should understand about frequency counters.
The oven crystal oscillator is very stable, however there is an adjustment, a calibration, that is critical so that the display is as accurate as it can be.
The oscillator is capable of staying on frequency within better than 1 ppm (one part per million) that is 0.0001 %, much better than any voltage, current or resistance meter measurement. You need that much accuracy if all 8 digits of the display will mean anything.
However if the crystal oscillation is only calibrated to an accuracy of, say, 0.1% then the display will be off that much. So the calibration needs to be checked from time to time against a frequency source of even more accuracy.
One way is by using super accurate frequency radio broadcasts from stations like WWV and WWVH. More modern methods use GPS managed frequency standards.

So basically the atomic clock stations in Fort Collins, Colorado and Kekaha, Kauai, Hawaii?

I got the selenium rectifier replaced with a 1N4007 Diode in the Heathkit signal generator.

Picture of the repair is shown below.

So basically the atomic clock stations in Fort Collins, Colorado and Kekaha, Kauai, Hawaii?

Right. Probably more than you really need. Just wanted to let you know how involved things get when you deal with things at high accuracy levels.
One way is to tune in WWV at 10MHz using a receiver with an S-meter and zero beating with the crystal oscillator output.
Anyway that would be something for another thread.

Right. Probably more than you really need. Just wanted to let you know how involved things get when you deal with things at high accuracy levels.
One way is to tune in WWV at 10MHz using a receiver with an S-meter and zero beating with the crystal oscillator output.
Anyway that would be something for another thread.

Couldn't I just tune it in on one of my old shortwave radios? Also what's an S-meter and wh as t do you mean by zero beating with the crystal oscillator output?

Zero beating: ever run 2 am radios at once and tune 1 through the band and find a point where they both squeal despite not having touched the one you weren't tuning? That's the local osc zero beating with the osc or station of the other set... In Toulouses example you would tune the Chrystal osc to the frequency of the station and listen for the zero beat then tune for minimum signal on the S-meter (exact frequency zero beat).

Zero beating: ever run 2 am radios at once and tune 1 through the band and find a point where they both squeal despite not having touched the one you weren't tuning? That's the local osc zero beating with the osc or station of the other set... In Toulouses example you would tune the Chrystal osc to the frequency of the station and listen for the zero beat then tune for minimum signal on the S-meter (exact frequency zero beat).

Ok, I get it now. So then somehow I would basically have to somehow tune the crystal oscillator in the frequency counter to the same frequency as the 10 Mhz signal of WWV in Colorado. And then tuning a shortwave radio to that same frequency and adjust the oscillator in the frequency counter until they cancel each other out in a sense on a tuning meter?

Ok, I get it now. So then somehow I would basically have to somehow tune the crystal oscillator in the frequency counter to the same frequency as the 10 Mhz signal of WWV in Colorado. And then tuning a shortwave radio to that same frequency and adjust the oscillator in the frequency counter until they cancel each other out in a sense on a tuning meter?

Yup.

Yup.

OK, got it.

I got the selenium rectifier replaced with a 1N4007 Diode in the Heathkit signal generator.

Picture of the repair is shown below.

Looks to me like the diode is in backwards....

OK so I got my parts in to get my signal generator fixed up the rest of the way (BNC Jacks and a new set of cables for it so I could hook it up to a radio), and I got it all wired up and I went to test it out on an old Zenith Royal 500 Transistor Radio I had laying around and I couldn't get the signal generator to do anything, it wouldn't put out a tone or a signal to the radio or anything, I'm assuming with a transistor radio you don't need a capacitor inline with the test leads like you do an AC powered set.

Also I got tons of line interference through the signal generator similar to the line interference I said I had been getting on my radios.

I had my test probes hooked up the RF output jack which I'm assuming that's the hookup I was supposed to use to test the generator out on the radio.

any ideas as to what the problem could be?

Looks to me like the diode is in backwards....

You were right it was in wrong, just shortly after I read your comment and I was trying to test it out on an old Zenith Transistor radio I have and I heard a "Pop" noise and I checked it out and sure enough the filter cap that was attached to the diode had vented, thankfully i had a 22 MFD 160 VDC electrolytic in my stash that I was able to replace the vented cap with and now its fine, although I found out that apparently my Zenith radio was way out of adjustment because the 455 kHz IF tone couldn't be heard until around 600 kHz on the radio dial rather than at the end of the dial.

I'm assuming with a transistor radio you don't need a capacitor inline with the test leads like you do an AC powered set.

Also I got tons of line interference through the signal generator similar to the line interference I said I had been getting on my radios.



Do you have a copy of the manual?
http://pdf.textfiles.com/manuals/SCANNERS-F-R/Heathkit-SG-8.pdf
You should have a manual for all your equipment.

If you look at the schematic you will see that the RF output does not have any DC blocking capacitor, therefore if you connect it directly to the a point in the radio that has any DC voltage on it that point will be connected to ground through the resistors in the generator output circuit. When in doubt use a external capacitor.
Also the two capacitors in the generator that are connected to the power cord and ground can put a 60 Hz signal on the case. With a battery powered radio the ground connector of the RF cable needs to connected to the radio. A small capacitor in the signal line to the radio will block the 60 Hz but pass the RF. If you use a coupling loop on the generator output you don't need the capacitor.
Another thing, I added a 0.01 uf capacitor in the generator between the wiper of the output pot and the output switch pin 7. There is a DC current running through the output pot from pin 3 (cathode) of the 12AU7. This can cause a DC voltage on the output.

, although I found out that apparently my Zenith radio was way out of adjustment because the 455 kHz IF tone couldn't be heard until around 600 kHz on the radio dial rather than at the end of the dial.

There is something else wrong. First of all 455KHz is out of range of the AM radio dial, it usually doesn't go below 540KHz.
The second thing is that the 455KHz from the generator probably is so strong that it will get through the front section of the radio circuit so you should hear it regardless of the dial setting.
You should probably not use a direct connection unless the alignment instructions indicate doing it that way. I would use a loop unless the radio isn't working at all. In that case you would be using a type of signal tracing.

There is something else wrong. First of all 455KHz is out of range of the AM radio dial, it usually doesn't go below 540KHz.
The second thing is that the 455KHz from the generator probably is so strong that it will get through the front section of the radio circuit so you should hear it regardless of the dial setting.
You should probably not use a direct connection unless the alignment instructions indicate doing it that way. I would use a loop unless the radio isn't working at all. In that case you would be using a type of signal tracing.

Well the radio only has a ferrite bar antenna and that's it inside it so I was trying to just do a loose coupling by just dangling the test probe next to the ferrite bar antenna to see if I could get a response out of the radio (like I said I I don't have the service manual for this radio because I don't want to pay $25 for it over at Sams and I don't know if they covered it at beitmans or riders because of it being a transistor radio and it was a little after those companies went out of business.)


Also I tried using it to realign my old Philco 116B using the alignment instructions given in Riders and it actually ended up making it worse, and the instructions in the riders called for the IF Alignment to be done by having the positive lead (red lead) of the signal generator hooked up to the grid cap of the 1st detector tube with the grid cap connector out of the circuit (removed from the tube) and then the ground lead connected to the ground connection on the chassis (antenna ground lead).

Which when I did that I was able to peak up the IF really nicely but then when I went to the alignment of the individual tuning bands thats when I had problems on some of the tuning bands I couldn't get the signal to come through, it was completely deaf it wouldn't make any noise but the tuning meter moved though.

The only bands I got response from were the AM Band, the Police Band and the Long Wave Band, the two Shortwave Bands I couldn't get any response from, and once I finished the alignment and I went to test the radio's responsiveness with an antenna, I couldn't get anything in, it was completely deaf.

Is there something I did wrong?

The Philco 116B Manual is posted below.

Sounds puzzling alright.
What you did with the transistor radio was OK. I don't quite know what to think of the results.

On the Philco, I don't know if the generator they specified has a capacitor isolated output or if it is at DC ground. That would effect the grid bias of the first detector tube, I don't know if that would make a difference to the alignment though. Was the radio working before? The tuning meter moving would mean that something was getting through the IF circuits, it usually works off the AGC generated at the 2nd detector, but maybe this radio is different.
Unless you have that frequency counter or another working radio that can pick up the short wave bands, you really don't know what the SG-8 is putting out.

Sounds puzzling alright.
What you did with the transistor radio was OK. I don't quite know what to think of the results.

On the Philco, I don't know if the generator they specified has a capacitor isolated output or if it is at DC ground. That would effect the grid bias of the first detector tube, I don't know if that would make a difference to the alignment though. Was the radio working before? The tuning meter moving would mean that something was getting through the IF circuits, it usually works off the AGC generated at the 2nd detector, but maybe this radio is different.
Unless you have that frequency counter or another working radio that can pick up the short wave bands, you really don't know what the SG-8 is putting out.

Yes the philco was working before but not very well, it had a lot of issues with not picking up very many stations/not very good sensitivity.

And I could try a capacitor inline with my tester on the philco.
Another thing is that when I had my signal generator hooked up to my philco radio it had a nasty ground loop hum coming through the speaker the entire time.

Another thing is that when I had my signal generator hooked up to my philco radio it had a nasty ground loop hum coming through the speaker the entire time.
If you come across a problem like that hum, you should solve that problem before charging ahead and possibly wasting your time and effort. One thing that you could try to get rid of the hum is reversing the power plug on the radio. Has that radio been recapped? There are caps from the power lines to the chassis in that radio as well as in the SG-8.
When you get a new piece of test equipment the first thing you need to do before using it is to confirm that it is working right.
Do you have a well working AM radio that you can use to see if the generator puts out a signal that you can pick up at the right place on the radio dial? That would test the generator frequency and modulation at least on that one band.
The frequency counter will not be able to test for modulation very well.

If you come across a problem like that hum, you should solve that problem before charging ahead and possibly wasting your time and effort. One thing that you could try to get rid of the hum is reversing the power plug on the radio. Has that radio been recapped? There are caps from the power lines to the chassis in that radio as well as in the SG-8.
When you get a new piece of test equipment the first thing you need to do before using it is to confirm that it is working right.
Do you have a well working AM radio that you can use to see if the generator puts out a signal that you can pick up at the right place on the radio dial? That would test the generator frequency and modulation at least on that one band.
The frequency counter will not be able to test for modulation very well.

Well the problem is, the hum went away as soon as I disconnected the signal generator and reattached the 1st Detector Tube's Grid Cap and ran the radio like normal.

Also I figured out why the Philco Signal Generator Specified in the service manual to align my Philco 116B radio doesn't need a capacitor inline with the positive lead of the signal generator, its because its a battery operated unit so it doen't have to worry about DC current on its parts like an AC powered unit would, so DC Current leakage from an AC powered Radio isn't going to affect its circuitry since its a purely DC Circuit design to begin with.

Hope that helps.

That's what I thought. The guy on the Philco Phorum basically said the same thing. But the thing is, I'm just repairing old tube radios and stereo receivers so lab quality gear like the Hewlett-Packard units are not what I need.

I just need something to get me close enough to make the radios work again as intended, it's not like I'm designing new radio circuits where you would need something like a lab grade unit for.

Most of the units I'm repairing are units that are already working circuits but just need to be touched up, so a regular bench grade unit is more than enough for the work I'm doing.
When I was acquiring test equipment in the early 60's, I bought Allied Knight Kit equipment because they had a store in Milwaukee and I didn't have wait for mail order. Most of my test equipment was kit form. I was in my early teens at the time. It was good enough for simple alignment procedures.
Later on, I was able source a GI unit that was more impressive and stable.
I am really amazed at some of the test equipment that is available today.

When I was acquiring test equipment in the early 60's, I bought Allied Knight Kit equipment because they had a store in Milwaukee and I didn't have wait for mail order. Most of my test equipment was kit form. I was in my early teens at the time. It was good enough for simple alignment procedures.
Later on, I was able source a GI unit that was more impressive and stable.
I am really amazed at some of the test equipment that is available today.

I had a friend I went to church with who built an old Allied Knight Kit Stereo System that he built a solid walnut Console Cabinet for when he was in High School back in the 1960s (he's probably about the same age as you are), and it had a push-pull 6BQ5 Amplifier, a Stereophonic AM/FM Tuner with a Magic Tuning Eye Tube for the tuning meter, and a Warwick Built/Sourced 4 Speed Record Changer, and a set of Knight 3 way Coaxial Speakers all built into the solid walnut console cabinet that he had built for it in shop class when he was in High School.

Unfortunately by the time he gave me the unit the amplifier's power transformer was blown, so I salvaged the tubes out of the unit and installed an old Kenwood amplifier into the cabinet to continue using the tuner and turntable and speakers but then the tuner died as well and so I ended up saving the tubes out of the tuner and scrapped the rest of the unit out and sold the Kenwood amplifier and just used the cabinet for my LCD Projector Video system since.

Besides a loop of wire mounted on a little stand I also have a couple of capacitors, 0.01 uf and 0.1uf, each one with a small alligator clip on one lead, to use with my generator.
The voltage rating can be fairly low, NEVER connect to generator to the plate side of a tube. If the instructions call for a cap, or I think I need one, I clip the hot lead from the generator to one cap lead and use the clip on the cap other lead to connect to the radio.
Here is a link to the Antique Radio Forums Archives. They scanned in a book from 1947, "Elements of Radio Servicing". Of course equipment like frequency counters, dual channel oscilloscopes, etc. were uncommon or non-existent in 1947.
https://antiqueradios.com/archive.shtml
No clubs are meeting now because of the virus, but generally they are a good resource. There is a fellow in the club I'm in who presents quite a few technical talks. Sometimes the text is kept online. I don't know if he was a teacher or something. Here is one by Mike McCarty about aligning radios.
http://vrps.org/documents/Alignment.html

Besides a loop of wire mounted on a little stand I also have a couple of capacitors, 0.01 uf and 0.1uf, each one with a small alligator clip on one lead, to use with my generator.
The voltage rating can be fairly low, NEVER connect to generator to the plate side of a tube. If the instructions call for a cap, or I think I need one, I clip the hot lead from the generator to one cap lead and use the clip on the cap other lead to connect to the radio.
Here is a link to the Antique Radio Forums Archives. They scanned in a book from 1947, "Elements of Radio Servicing". Of course equipment like frequency counters, dual channel oscilloscopes, etc. were uncommon or non-existent in 1947.
https://antiqueradios.com/archive.shtml
No clubs are meeting now because of the virus, but generally they are a good resource. There is a fellow in the club I'm in who presents quite a few technical talks. Sometimes the text is kept online. I don't know if he was a teacher or something. Here is one by Mike McCarty about aligning radios.
http://vrps.org/documents/Alignment.html

Ok, thanks, I'll keep that in mind. I do have a .1 MFD and a .01 MFD capacitor in my stash I think so I'll just rig them up to alligator clips.

...

OK, I have a question about my Heathkit Signal Generator,
Band 1 works fine and produces a the 400 Hz test tone for the IF Alignment like I need it to, but when I go to use Band 2 which is the 550-1600 kHz band used for aligning the AM tuning band on the radio dial it doesn't produce any sound, but it does on Bands C-F which are for SW and Long Wave and FM Alignment work.

Is it possible that there's something wrong with the circuitry inside the signal Generator that's causing it not to produce the 400 Hz test tone on Band 2 of the signal generator, like a bad tube or a bad coil?

Any help with this issue would be great.

By the way I am using a blocking capacitor inline with the test leads on this signal generator.

Also I just got my new (to me anyways) Frequency counter and I need to get a Male BNC to Male BNC cable so I can hook my signal generator to my Frequency Counter, and I see a 50 Ohm version and a 75 Ohm version, does it matter which verion I use or do I need to use the 50 Ohm version for proper function of the frequency counter?

Thanks for your input on this matter.

OK So a little update on this Signal Generator:

My SG-8 is having some problems that may or may not be related to a modification I did to it to it so that I could have continuous Monitoring of the signal generator with a frequency counter, apparently the first 2 bands on the signal generator (Bands A and B) put out a 400 Hz test signal but its not very loud, and then Bands C-E don't put out any 400 Hz test signal at all just a loud humming noise that is somewhat affected by the RF Output Knob.

Any Ideas as to what could be causing this issue?

What say you Notimetolooz?

The standard output impedance for a RF generator would be 50 ohms, so that would be the best coax type. However low cost generators like the SG-8 don't bother with exact impedance. An attenuator that is marked in db will not be correct if the connecting impedance is wrong, but otherwise it doesn't matter unless the coax is very long. 75 ohms is used for a few things like TV RF and video signals.

The same modulation is used on all bands in the SG-8. The modulation puts a audio sinewave on the output tube grid along with the RF. This is not the best way to modulate the RF, but it works OK. It is possible that the audio is changing the tube bias somehow and effecting the operation.
The frequency counter will only function correctly without modulation. You need to use a working radio or an oscilloscope to check fo modulation.
I don't know exactly what you did and I don't know how you did it, so I can't know what the problem might be.

The standard output impedance for a RF generator would be 50 ohms, so that would be the best coax type. However low cost generators like the SG-8 don't bother with exact impedance. An attenuator that is marked in db will not be correct if the connecting impedance is wrong, but otherwise it doesn't matter unless the coax is very long. 75 ohms is used for a few things like TV RF and video signals.

The same modulation is used on all bands in the SG-8. The modulation puts a audio sinewave on the output tube grid along with the RF. This is not the best way to modulate the RF, but it works OK. It is possible that the audio is changing the tube bias somehow and effecting the operation.
The frequency counter will only function correctly without modulation. You need to use a working radio or an oscilloscope to check fo modulation.
I don't know exactly what you did and I don't know how you did it, so I can't know what the problem might be.

The Modification I did is kind of hard to explain unless you saw the original post from the Philco Phorum that discussed the modification.

Basically the modification was taking the AF Input jack and disconnecting it from the Modulation Control Switch and hooking it to R10 through a .001 MFD Capacitor which leads to pin 3 of the 12AU7A tube.

see the original post linked below, it will be on post #24.

https://philcoradio.com/phorum/showthread.php?tid=21197&page=2

This thread is turning out to be very long considering it is about a simple SG-8 sig gen!
Heathkit products had to make some compromises because they were kits that could be assembled with simple hand tools by someone that did not have a lot of electronics knowledge, they had to make the products cheaper than factory made products. They were a great way for folks to learn about how electronics were made. Not everyone were successful with assembly however.
After looking at the thread on the other forum and the Radio City Products generator, I have to commend you on your goals given your problems.
So a few things. When dealing with RF you need to keep in mind the whole reason it is used to transmit signals, it can travel through the air (space). Every piece of wire is one plate of a capacitor, any other piece of metal nearby is the other plate, so the signal can travel for one to the other. To a lesser extent every wire is also an inductor. It comes down to "lead dress", how wires are routed from one place to another. Wire carrying RF need to be as short as possible and not pass near other wires or parts that could effect it or be effected by it. I think the wire you added should have been kept away from the parts that are in the oscillator circuit. It would be better to go from the output pot terminal, through the cap and the then the BNC connector. Keep it all near the front panel, that way if it couples to anything it will be the grounded case. In fact using a piece of coax cable (with a grounded shield) would be better that a single wire. Wire dress is not shown on schematics and is something that has to be learned.
Another thing, never assume that something that is not touching when you close the case will stay that way. A year from now you could bump the generator on the bench and your connection to that cap could move and short. Fasten parts in place, don't depend on thinking things will not move unless they can't.
Troubleshooting an RF oscillator circuit is difficult and much more so without more test equipment.
On the bright side the Radio City Products generator looks to be a better design. That will have to be a separate thread of course.
I'm sorry I don't have the time and resources to be your tutor. You might want to find an old copy (say 35th to 55th edition) of the ARRL Radio Handbook. ARRL (American Radio Relay League) has published their handbooks since the 1920's. The first several chapters contain info on electrical laws and circuits as well as design technique. There is also a website. http://www.arrl.org/tech-portal

This thread is turning out to be very long considering it is about a simple SG-8 sig gen!
Heathkit products had to make some compromises because they were kits that could be assembled with simple hand tools by someone that did not have a lot of electronics knowledge, they had to make the products cheaper than factory made products. They were a great way for folks to learn about how electronics were made. Not everyone were successful with assembly however.
After looking at the thread on the other forum and the Radio City Products generator, I have to commend you on your goals given your problems.
So a few things. When dealing with RF you need to keep in mind the whole reason it is used to transmit signals, it can travel through the air (space). Every piece of wire is one plate of a capacitor, any other piece of metal nearby is the other plate, so the signal can travel for one to the other. To a lesser extent every wire is also an inductor. It comes down to "lead dress", how wires are routed from one place to another. Wire carrying RF need to be as short as possible and not pass near other wires or parts that could effect it or be effected by it. I think the wire you added should have been kept away from the parts that are in the oscillator circuit. It would be better to go from the output pot terminal, through the cap and the then the BNC connector. Keep it all near the front panel, that way if it couples to anything it will be the grounded case. In fact using a piece of coax cable (with a grounded shield) would be better that a single wire. Wire dress is not shown on schematics and is something that has to be learned.
Another thing, never assume that something that is not touching when you close the case will stay that way. A year from now you could bump the generator on the bench and your connection to that cap could move and short. Fasten parts in place, don't depend on thinking things will not move unless they can't.
Troubleshooting an RF oscillator circuit is difficult and much more so without more test equipment.
On the bright side the Radio City Products generator looks to be a better design. That will have to be a separate thread of course.
I'm sorry I don't have the time and resources to be your tutor. You might want to find an old copy (say 35th to 55th edition) of the ARRL Radio Handbook. ARRL (American Radio Relay League) has published their handbooks since the 1920's. The first several chapters contain info on electrical laws and circuits as well as design technique. There is also a website. http://www.arrl.org/tech-portal

Ok. Thanks for the info.

I'm sorry this thread turned out to be longer than it needed to be, this is my first foray into signal generators.

I do have an old electronics repair textbook that I found at goodwill once.
See picture below.

Ok. Thanks for the info.

I'm sorry this thread turned out to be longer than it needed to be, this is my first foray into signal generators.

I do have an old electronics repair textbook that I found at goodwill once.
See picture below.

If you want to read old electronics books there's plenty on PDF format for free download at World Radio History.

They're are all great for a reference for the older stuff.
The Gernsback and Howard Sams books were excellent.
Here's the links. There's a signal generator book in the Sams section that is worth a read.

https://worldradiohistory.com/BOOKSHELF-ARH/Bookshelf_Gernsback.htm

https://worldradiohistory.com/BOOKSHELF-ARH/Bookshelf_Sams.htm