Heathkit SG-8 Signal Generator

[Notimetolooz]

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

[vortalexfan]

Originally Posted by Notimetolooz

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.

[vortalexfan]

...

[vortalexfan]

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.

[vortalexfan]

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?

[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.

[vortalexfan]

Originally Posted by 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 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/showt...d=21197&page=2