RCA 9TC240 Alignment...The start of my education (I hope!)
 

Hi all. I wanna thank everyone for their help on the long thread that helped me sort out power, sound, re-wiring et al on this TV. I now have a good picture with very good resolution and sound coming out of a speaker. I'd like to learn something about alignments, fed signals, scope traces, sweep and the like. I thought I would start simple with the discriminator and sound IF alignment. Below is the instruction section in the Rider's service manual for this:

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...and some traces and transformer location figures

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For those who have participated in helpful discussions before, you probably know what my level of experience is. I can talk some of the talk but there are some significant gaps there. I usually get over my embarrassment fairly quickly but please, be gentle!!!

Over the next few days, I hope to move through the VTVM and scope trace steps in this protocol. Ten fifteen pm on the east coast so tomorrow evening I'll begin. I have done a couple of min/max adjustments using the VTVM before so hopefully, I'll get off to a good start! TIA for the help!

Good luck. I suggest you also take a look at the Sams instructions. Thye often use language that makes more sense.

Hi and happy aligning. I have had experience successfully aligning this chassis for more than 50 years. It can be a challenge if you do not keep various factors in mind.

First you must have accurate marker frequencies. This is a split sound set and to achieve optimum picture quality with best sound, the marker accuracy is utmost. I use an HP5245L frequency counter with an HP 606B signal generator. Plus my favorite alignment combo is the HP8601a Sweep generator with HP8600 Digital Marker. The total net cost for all of this equipment combined was $150 and it was top of the line. There are many solutions available and all are now pretty cheap. It would be wise to review what equipment you have before you begin. Remember this set has more trap circuits than any other set! Two adjacent sound, two adjacent video, two co-channel sound, a baseband trap and an RF trap, each if misadjusted can adversely affect the video quality.

Second as this is a split sound receiver, the fine tuning control is adjusted for best sound, not best picture. If the alignment is not correct, when fine tune for best sound, the video will not look good. So it is essential as the manual advises to first proceed with the sound IF and descriminator alignment before proceeding with the video alignment.

Third, be aware the quality of the video IF amplifier tubes will affect the end result. Make sure you have fresh tubes in place you can trust. Because changing a tube in the video IF will affect the response curve.

Lastly before you start, the set uses an over coupled transformer between the tuner and first video IF stage. This is a broadly coupled link and it is essential to sweep align it. You must follow the instructions in the manual to get the curve depicted. I found it pointless to proceed unless I can get the proper response at this point because the subsequent video IF sweep adjustment will not be right.

I would suggest following the step by step process to the letter and if/when you reach a stumbling block, simply post it on the forum.

Yeah, you picked a very hard one as your first attempt for IF alignment, a real pain!

And as mentioned above, the way pointed out in the SAMS often makes more sense, it worked for me with the ARVIN, using a RF frequency generator and a meter to set the coils, I do not have a sweep marker generator, so I was not able to do the final overall IF alignment step, but as I said before, of all my BW sets, the ARVIN is the only one that gets snow W/O anything hooked to it, so I must have got it rather close to right!:D

Thank you so much for all of that information. I was looking at the HP606B generators on eBay but since they are analog, I thought they probably wouldn't be stable enough. At this stage, I'm probably going to need to purchase better equipment to do this right, at least from the generator/sweep end. I have a modern digital scope purchased last year and an HP scope that's about 30 years old both of which will do X-Y traces and are very accurate. I might try the Eico 369 I have just for practice until I can get better equipment. I'd be thrilled just to see a trace similar to the sound IF curve depicted. I have all NOS tubes in the TV

I'd like to treat this as an education journey and not a means to an end to get this particular TV perfectly aligned. How to feed in signals...set up scopes...interpret what changes in response curves mean etc... Other than adjusting coils for peak or minimum response on a VTVM is about all I have done in this realm! Believe me, I will ask questions but some of them may elicit an initial reaction of "He said what?...You're kidding me?"!!!!!

Thanks Bob...I do have both.

Does anyone have a suggestion for an accurate but affordable frequency generator? A working HP 606B generator goes for more than $300 on eBay. Sweep generators used during this TV's era, like the Hickock I had that was electromechanical (and had a destroyed speaker cone inside)...were they accurate like these modern digital equivalents? I thought getting and meticulously restoring the Eico, which is early 1980s technology, and getting new, custom built cables for RF out, demod in and scope out would have been more than accurate enough to align a TV from 1948. Am I missing something here? Like I posted in the other thread, I measured the RF frequency out of the Eico using the HP oscilloscope. It varied about 0.08 megacycles plus/minus around the intended frequency. Is using an oscilloscope in this manner an acceptable way to check the accuracy and stability of an RF generator?

Extremely accurate test gear is not so important in alignment EXCEPT for accurate frequency marks. Most of the alignment steps will be to peak or null the response at a certain frequency, or make two peaks of a double-peaked curve the same height, or make a particular marker 50% of the peak, for example. So accurate actual height of the curve is mostly irrelevant as long as you get the specified shape vs. frequency.

The touchiest part of the procedure often involves the signal injection cable/circuit, the ground point, length of leads, etc.

The Eico does have a variable marker frequency dial with adjustable amplitude but, I can't possibly know if a marker frequency selected on a crudely numbered dial scale is correct. My B&K alignment generator has all of the markers pre set and ready to go...for TVs aligned using frequencies around 20 mc higher.

Are referring to the B&K 415? It only has markers for 44MHz IFs.

Does your digital oscilloscope have a frequency read out? :scratch2:

jr

Yes

B and K 1077

1077 is not an alignment generator or fixed frequency RF generator - it only outputs test patterns. Composite or RF modulated video.

A basic grounding in superhet theory is a good starting point, along with knowing why stagger-tuning of the IFs is necessary in TV receivers.

Yes yes yes yes yes....I shouldn't talk about these things without them in front of me...I meant the 415...I have them both.

+1 the 1077 is for figuring out WHY your IF is dead, not for alignment....It's also good for signal injection troubleshooting on every other circuit in a TV (which is why I like mine it helps me fix dead sets faster).

I bought my HP 606B locally thru Facebook Marketplace for $35. It required some repair. But to obtain the accuracy with it or any other marker source, you will require a frequency counter.

Decent sweep generators are easy to find cheaply. Coupling the equipment should be straight forward if you follow the procedure outlined.

You will be able to get the responses depicted only if you have the proper equipment and you can trust your frequency source.

And I only ended up with the HP606B because it was cheap and available. I have have three different HP frequency counters which I obtained over time because they happened to be cheap and were readily available. I believe we live in a fortunate time where so much 1960s and 1970s test equipment which we once could only dream of are now available for next to nothing.

What have you to measure the frequency source accurately?

I want to reluctantly add that I have not be averse to dumpster diving. A local community college was throwing away Wavetek sweep marker generators. The cords were cut off and a few toggle switches were faulty. All easily fixed and it was free. I earlier used an old Precision generator made in Elmhurst NY which I got for free. It needed a few repairs but it worked well. The venerable HP5245L I bought for $25 with a few minor faults. The best addition I made to it was to replace the noisy original fan with a quiet modern computer fan.

I would suggest you first present here your equipment choices and we can provide advice.

Hi all...just a couple of things and questions.

I did the first two steps in the alignment that required the use of the VTVM and I think I was successful.

So yes Penthode, I will detail a list of the equipment I have. Below is what I bought, restored and thought would provide the entire package for doing these alignments.

https://imagizer.imageshack.com/v2/1...923/TwPh0Q.jpg

The way I understood this worked was the RF frequency out is selected using the dial on the right. You select signal strength with the attenuator dials. Sweep width is selected using the sweep dial. Maximum range on this is 10 megacycles. The signal is fed into the desired point(s) on the chassis. If the signal out requires demodulation, it comes back in from the desired point in the circuit using the demodulation cable back into the 369. At that point, a marker is added to the trace selected by the dial on the left and the marker size is adjustable. The processed signal comes out and goes to the scope by the scope out jack which is a funky, special jack that essentially provides a horizontal, vertical and ground signal interpreted on a scope using X-Y mode.

Here are my oscilloscopes...an HP 54600B and a Chinese scope...works well and cost a little over $200 (not that it indicates anything. It was well reviewed)

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https://imagizer.imageshack.com/v2/1...924/deULRa.jpg

That's what I got! I don't have a frequency counter or a separate RF generator and sweep generator. I think I have a shelf full of equipment that needs to be scrapped and I'll have to start from scratch! :no::no::tears::tears::tears::tears:


Some of this has already been done but if my friends can provide some shopping lists and maybe some information on how all of them work together it would be appreciated. I think, at this point, I don't have what I need to dive into the more detailed and intricate steps in this process.

I see the Eico sweeper marker generator has a crystal in it. What is it's resonant frequency?

The marker frequencies for the traps were 19.75, 21.25 and 27.25MHz. The bandpass markers that are most important are 22.1, 24.5 and 25.75MHz. The Eico could use the one or perhaps two or three crystals to calibrate it's variable frequency generator.

A cheap shortwave receiver with digital readout could be used to calibrate the marker. The marker accuracy needs to be roughly +/-10kHz particularly with the sound IF and sound traps vs the video carrier 45% position on the slope of the video IF response. The 27.25MHz traps must be fairly accurately set as they will affect the overall IF response. The 19.75MHz traps accuracy is least important.

Historical sidenote affecting the design of the 1948 thru 1952 receivers. This was the time of the TV station construction freeze. 1948 coincided with the sunspot peak and it played havoc with RF reception. Co-channel and adjacent channel interference between stations beyond the RF horizon created headaches for FCC planners. The double upper and lower adjacent channel traps were RCA's answer to alleviate the problem at the time. I recall the summer of 1972 the interference with another sunspot peak. From Toronto Canada reception, KMOX channel 4 in St Louis totally obliterated WBEN channel 4 Buffalo. KDKA channel 2 Pittsburgh would override EGR channel 2 Buffalo. I had an RCA 8T243 (the same chassis as yours which I still have more than 50 years later) and it worked better in these summers than many newer sets. Having more traps was a brilliant idea but it makes alignment more difficult.

It’s a 4.5 mc. I have some pictures of pages from the user manual I can post in a bit

For your reading enjoyment... Actually, I don't expect anyone to read all of this. My only hope is I can somehow use this piece of equipment to do some of the things, starting with the audio IF, I can do to optimize it's function.

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I skimmed through the instructions and it is pretty standard stuff. The 4.5MHz crystal was intended mainly for later intercarrier sets which this is not. It has little use in this alignment other than perhaps using a harmonic as a reference to set the variable marker frequency. I have to emphasize that a split sound set alignment, especially this chassis, is somewhat more complicated than the average intercarrier set and an accurate marker is essential.

The 4.5MHz crystal oscillator has a useful 5th harmonic at 22.5MHz and 6th harmonic at 27.0 MHz. These would be useful as a reference for calibrating the variable marker.

The bottom line is that you can use the Eico but it is going to be more difficult to use that a more modern set up. Good equipment is relatively cheap. My first suggestion would be try the Eico sweeper and find a separate RF generator and a frequency counter to obtain an accurate marker. A separate marker oscillator can be loosely coupled. You can also use the separate accurate marker to calibrate the Eico marker.

For my IF alignment the HP 8600a Digital Marker with the HP 8601a Sweeper is one of the best setups. The equipment dates from the 60's and 70's and provides five accurate bandpass markers. I bought them twenty years ago for about $40 each on eBay. The HP8601a is common: there are about six on eBay at the moment but the lowest price is about $165. The HP8600a was it's companion and is to integrated with the HP8601a for accurate markers and spot frequencies.

The pair of HP devices essentially is an RF Network Analyser. I do not know how much you are into electronics but a more modern and efficient approach (and cheaper too) is to you to use a modern RF network analysis tool. I see Chinese built ones on eBay for under $50 and with client software on a computer I would see this as a very accurate and spiffy way to align your set. I have for the last decade seen the cost drop and performance improve. I haven't tried this solution out myself but you should be able to see the trap notches and IF and tuner RF responses very clearly and accurately with this device. This thread has kindled my interest to finally buy one these things to try out in the application.
https://www.ebay.com/itm/126284122318

Here is another nifty one with a display. You should be able to see the IF response and accurately set the traps with one of these. I haven't tried it yet. But rather than using old clunky equipment, this may be the most efficient and yet least costly way to go.

https://www.amazon.com/Portable-Tiny...s%2C241&sr=8-4

I bought it. Maybe when it gets here we can take a shot at doing this together?

The second one, does it have a tracking generator? The first one which was cheaper has a tracking generator. The tracking generator feeds the network under test ( in this case the RF/IF section of the TV).
The second unit has also two connectors. But is one the tracking generator output?

What is required is a network analyser and not just the spectrum analyser. Need to find more information on the product.

I made a video on using the TinySA as a sweep gen for TV alignment. I think you'll find it useful.
https://youtu.be/BQJjgpHyWRs

Looks like it can be used in conjunction with a separate tracking generator

It is the tracking generator. I think you mean marker generator. Yes, you can loosely couple a second generator to create a marker blip

So I was thinking about this last night and couldn't sleep! Not exactly what a relaxing hobby should do for you! If I could get your thoughts on this, Bob and Penthode and anyone else who would like to contribute ideas, here is what I'd like to do...

I want to find the optimal method and equipment to do alignments on TVs from this era. I'm a bit tired of purchasing vintage equipment in an effort to do this. It seems to always be compromised by inaccuracy and reliability issues.

I was looking at these network analyzers last night and they run the range from bare bones circuit board setups to ridiculously high priced units. I would be willing to spend several hundred dollars on a modern alignment package and go through the process of aligning the RCA with anyone who would be willing to walk through it with me. I could document the process with photos and post a protocol start to finish here on VK. Maybe it could be helpful to others who have had similar struggles with this. I have a shelf full of vintage test equipment purchased with the intent of aligning these TVs that have led to frustration and getting nowhere.

So the path could look like this...I will purchase whatever is needed to do this in the optimal and simplest way with the desired outcome being a workbench decluttered of useless vintage test equipment replaced by a modern and reliable alignment station I can go to with confidence. Hopefully someone could walk through this with me and in doing so, help the community and perhaps satisfy their own curiosity about the process without the expense of actually buying the equipment.

Please, I welcome everyone's thoughts on this. If you think it's a ridiculous idea or you think I don't have the technical know-how to be your remote pair of eyes and hands please let me know. I want to learn the theory and process.

Thank you, everyone, for all of your advice and comments.

If you invest in a SW digital radio or a freqmeter, you can calibrate these old horses, and makes the investment cheaper, although with more time spending (alas, is a hobby, after all, but these busy times can call otherwise I know...)

Thank you so much for your thoughts. I'd really like to do this with reliable, accurate modern equipment.

Great to see you had the Tiny SA. You were highlighting my fear as it only would examine RF spectrum. It is not what I would call a network analyser since it does not have a sweep source that tracks with the spectrum analyser display.

The WinWT4 Spectrum Analyzer RF Signal Generator With Tracking Generator appears to be more appropriate and is cheaper too! It has a tracking generator output which is fed to the device under test, in this case the input to the IF amplifier. The output is applied to the RF input of the Spectrum analyser. Then you use the the software to provide the display of the sweep on a computer. No need for an oscilloscope.

Here is the link again:

https://www.ebay.com/itm/126284122318

Yes I looked at these in some detail last night. It's worth a shot, even just as a product review for everyone to comment on. The cheapest option isn't necessarily a requirement as I'd gladly spend up to $400 or so for a good quality instrument. I believe these are manufactured and shipped from China so I imagine QA might be an issue and shipping may take several weeks to get to me. I'll order one and we can use it when it arrives but I'm still open to other suggestions even if they are more expensive options.

I think the best approach is a secondhand HP Network analyser. I see a bunch on ebay from modest priced to the astronomical. The HP test equipment in its day was top notch. My HP8600a/HP8601a is essentially a network analyser requiring a separate oscilloscope. It is good for frquencies from 100kHz to 108MHz and use it to sweep align radio and TV sets. I last used it to aligh an RCA CT100 color set and and RCA AR88D Communications Receiver.

The HP8601a Sweeper Generator seems still easy to come by and remains fairly cheap. Mine which I bought on eBay for $40 had a power supply fault which was easily fixed when I received the unit. It however need the HP8600a to provide the true network analysis function as the two devices work in conjenction with each other.

The markr function in the HP8600a/8601a combo works by halting the sweep momentarily to create a blip marking the frequency. There are five independently adjustable marker blips which makes it ideal to simultaneously mark the three traps plus a coulpe to define the passband. Selecting a specific marker makesit brighter on the sweep display and you have a vernier adjustment with accurate digital readout so that the marker is precise to within a few Hertz at 21.25MHz.

New this eqipment in the 1970's was about $8,000 for the pair and I bought them at the time about twenty years ago for about $80 because they provided the best and cheapest solution for my vintage radio TV needs. I higly recommend them for this sort5 of work.

https://xdevs.com/doc/HP_Agilent_Key...0Operating.pdf

https://xdevs.com/doc/HP_Agilent_Keysight/HP8601A.pdf

Here are the HP8600a and HP8601a on ebay. The HP8600a is an earlier version with nixie tubes but otherwise the same. Mine is a bit later using an LED display

https://www.ebay.com/itm/35583162966...Bk9SR9C2oPCoZA

https://www.ebay.com/itm/22625900266...Bk9SR66FvPCoZA

I think you misunderstood. The TinySA is a sweep source. You set the start & stop frequency and sweep rate and it outputs swept RF. Newer versions also output a trigger pulse to sync your scope.

What it does not have is markers. For that you can use a second RF generator and loosely couple it at the injection point.

I think it is a great option for an accurate, easy to use sweep alignment tool.

My main issue is the small size. If I were using it regularly, I'd opt for the much bigger and more capable tinySA Ultra. I believe it can output two frequencies so it might be possible to sweep one output and use the other for a marker.

https://www.amazon.com/AURSINC-TinyS.../dp/B0BMPSSFTK

(edit)
Took a quick look at the specs. https://tinysa.org/wiki/pmwiki.php?n...calDescription
The second output is for calibration and only does 30, 15, 10, 4, 3, 2 or 1 MHZ

So perhaps use a TinySA Ultra for sweeping and TinySA basic for the marker (or any other RF generator for that matter).

Got both the eBay items, the HP8600a and HP8601a pair.

Wow that was fast. I have a lot of experience with these things and will be happy to help you set it up.

There is a fair bit of literature on the web about these devices. I would suggest when you obtain then to set up a test network and confirm operation. Generally there is rarely much wrong with this era HP stuff but it is best to make sure.

Looking forward to it!