I picked one up and tried to calibrate it,,, seems I can get it close on teh B and C bands, but the A and D (highest and lowest) won't calibrate... Recapped the PS so far, but that didn't help as the voltages stayed about the same,,, Anyone have any repair or calibration experience with this guy?
Thanks...
Thanks...
You need to replace all of the capacitors, especially the wax coupling capacitors.
If you are getting a stable waveform, but the dial is way off, check the resistors in the wein bridge. They probably have drifted significantly. Just be aware the dial being off about 10% was considered good enough back then.
If you are getting an unstable waveform on the highest and lowest scale, you may have some leaky capacitors to deal with. Possibly some resistors have drifted way out of spec. You may also have the incorrect lamp in the socket underneath the chassis.
If you are getting a stable waveform, but the dial is way off, check the resistors in the wein bridge. They probably have drifted significantly. Just be aware the dial being off about 10% was considered good enough back then.
If you are getting an unstable waveform on the highest and lowest scale, you may have some leaky capacitors to deal with. Possibly some resistors have drifted way out of spec. You may also have the incorrect lamp in the socket underneath the chassis.
Thanks for replying,,,
I got this last spring, and IIRC it calibrated fine, according to my notes... Went to use it a couple days ago, and found these problems... I have replaced all caps, except the two 8mF lytics or PIOs, not sure what they are,,, I have 10mF lytics, if they will work...
Also, just finished replacing all out of range resistors, except "special ones" on the band selector switch...
You may be right about the bulb, it is supposed to read between 15-20V RMS with a VTVM... I used a DMM and could only get 8.9VAC with teh pot maxed out...
The gen will calibrate on teh B, C, and D scale fairly close, but not on "A" (or LF) scale... are there any other tests for teh bulb? It has 455 ohm resistance...
I got this last spring, and IIRC it calibrated fine, according to my notes... Went to use it a couple days ago, and found these problems... I have replaced all caps, except the two 8mF lytics or PIOs, not sure what they are,,, I have 10mF lytics, if they will work...
Also, just finished replacing all out of range resistors, except "special ones" on the band selector switch...
You may be right about the bulb, it is supposed to read between 15-20V RMS with a VTVM... I used a DMM and could only get 8.9VAC with teh pot maxed out...
The gen will calibrate on teh B, C, and D scale fairly close, but not on "A" (or LF) scale... are there any other tests for teh bulb? It has 455 ohm resistance...
10uF electrolytic are close enough the original 8uF electrolytic coupling capacitors. The low band is always the hardest to get operating properly. It is also the band most affected by an incorrect bulb. If you have gotten it working satisfactorily before, it is unlikely the bulb.
Do you have a un-stable waveform, or is just the frequency off? If the frequency is just off, replace the 9.5Mohm resistors on the band switch. You will need to use resistors in series or parallel to come up with the correct 9.5M value.
Do you have a un-stable waveform, or is just the frequency off? If the frequency is just off, replace the 9.5Mohm resistors on the band switch. You will need to use resistors in series or parallel to come up with the correct 9.5M value.
Thanks again ...
I'll swap in the last two caps and report back...
The problem I noticed is that it won't calibrate on the low band, and doesn't hold the 10.5VAC I used to calibrate it through out the range... All the tubes test very strong, by the way...
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C6 is probably a ceramic or mica, not specified in the manual I have from BAMA. If it is short then you have a problem.
Good idea to clean the switches with isopropyl alcohol (before you try anything more exotic) and make sure that all of the wipers are working well.
I collect Eico:
Good idea to clean the switches with isopropyl alcohol (before you try anything more exotic) and make sure that all of the wipers are working well.
I collect Eico:
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Yes you do!!!
I'll try it again with the original 50pF cap, just to see if it was the cap or operator error on this end... I scrubbed all the pots and switches already... Anxious for this to work, just finished an amp, and want to see its frequency range,,,
Does your manual show VAC range for the other Bands? as i noticed, B,C,D hold about teh same, A is lower...
I also have an Eico 147A signal tracer that seems to be the go to gear for most repairs...
Thanks again...
I think we got it!! I was able to get waveforms from the bands/frequencies I tried,,,, this generator should last a long time now! And should do anything I'll ever need it for...
Do you use your Eico gear? Is it all rebuilt and working?
Thanks for the link,,, I'll try to get deja vu to work, didn't have any luck with it in the past...
Do you use your Eico gear? Is it all rebuilt and working?
Thanks for the link,,, I'll try to get deja vu to work, didn't have any luck with it in the past...
I have a users manual for the 377, not a service manual, tho... Don't trouble yourself with the doc,,, I'll try to get deja vu to work...
Oh, I also have an Eico mono FM tuner I restored a while ago,,, works good...
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