Ferrograph Series 3 No Playback

[MeanDumpsterCat]

Hello everyone.

Just today I got hold of a Ferrograph Series 3. I've just done some quick tests before I start proper work on it.
Everything comes up okay, the amp to me seems a little on the quiet side but it works.

I got no sound when playing back a tape I recorded on my working Series 5 Ferrograph.

I made a recording and while it didnt play back, it did in fact play on the other machine so it is recording okay but not playing back. I also get sound when plugging in a mic to input 1.

Swapped out V1 for a known working one on the off-chance since it looked like a replacement and there was no change.

Anyone have suggestions on a good place to start with this?

My plan at the moment is to put a signal onto the grid of V1 and see what happens and also check there's a signal coming from the head into the grid. Anything else I should try as a first step?

Someone it seems has already replaced quite a few of the wax capacitors so that makes things a little easier.

All the best.

[MeanDumpsterCat]

Swapped out that transformer with the one on my series 5, I now get playback.

I've noticed that I now get an osscilation if I turn the volume up past a certain point when playing a tape. This doesnt happen if I plug a source into input 1.

The red light under the meter also flashes with the osscilation.

Strange that this only happens when playing back a tape..

[Uncle Bulgaria]

Have you checked all the DC conditions as per the manual? Could be a PSU problem - reservoir/filter capacitor etc. The neon is just an indicator for the HT supply, so an oscillation here suggests sagging DC. The manual is comprehensive for tests here, so I'd run those and post the results if it doesn't immediately pinpoint your issue.

[MeanDumpsterCat]

I took measurement from the valve anodes in the amp as per the service manual (which is for a series 2, but from my understanding they are virtually the same)

I've put them into a table and attached the image here.

I noticed that the voltage on V3 is especially low.

I'll do some further investigating this weekend and see what I can find out. Any help in the meantime is greatly appreciated.

[Uncle Bulgaria]

I think you need to go back before then. In my Series 4 manual (I think they are indeed all very similar) it's section 19.1 with measurements taken on the power supply chassis in the bottom of the case.

[MeanDumpsterCat]

Originally Posted by Uncle Bulgaria

I think you need to go back before then. In my Series 4 manual (I think they are indeed all very similar) it's section 19.1 with measurements taken on the power supply chassis in the bottom of the case.

Thanks, i'll take a look at those voltages as well!

[Uncle Bulgaria]

I assume you have a relevant copy of the manual (if not, get one - they're brilliant). I've attached the PSU parts of my 4A manual in case they help you navigate the area at all.

[MeanDumpsterCat]

Originally Posted by Uncle Bulgaria

I assume you have a relevant copy of the manual (if not, get one - they're brilliant). I've attached the PSU parts of my 4A manual in case they help you navigate the area at all.

Thanks, I believe I have the same diagram in the Series 2 manual i'm looking at.

Not had a lot of time to look at this machine these last few days but i'll update this thread when I do some more digging