Odd issue with reVox B215E

[Aega]

Hello everyone,

I recently acquired a little used B215, E-type, SN: 1100. Works very well, except one odd issue which some of you might have an idea how to tackle.

During the winter holidays I had time on my hands and binge-recorded my extensive Zappa collection to my very well preserved TDK SA 90 cassettes. Everything works really well, for a while - this usually is 6-8 hours.
At one point, I noticed that the left channel was not completely silent - on the display - between songs, indicating some signal sitting stable between the -20 and -14 dB.
Turned off everything, stopped the source, disconnected everything from the 215, the signal was still there: only on record, stable. Turning off then on does not make it disappear.

Powered down the machine, disconnected from mains overnight, in the morning the trash signal was gone, everything worked perfectly, until it returned.

I cannot sense any extra noise added - on my AKG K701s, but it seems that a signal recorded like this leaves a small mark on the tape. Odd behaviour, no idea how to go by it with my good old friend - the electronics repairman.

Any ideas, suggestions are most welcome! Btw, we did not replace the capacitors. any of them.

Awaiting your feedback, thank you in advance.
Aega

 

[revox-b77]

Sounds like you have some caps starting to fail.

 

[Aega]

Thank you, had a hunch this might be the issue.
Might you have a full list of capacitors (88, right?) that I should get before diving in?
Much appreciated,
Aega

 

[Aega]

Nevermind that last request, started using own brain. Found a service manual, dusted the oscilloscope and we'll start with the recording panel.
Thanks again, godspeed to you all,
Aega

 

[steerpike2]

Nevermind that last request, started using own brain. Found a service manual, dusted the oscilloscope and we'll start with the recording panel.

Start with the power supply / microprocessor board. If there are any Frako brand capacitors on there, they have to go. When these go short circuit they can destroy other components, so they must be eliminated ASAP.

 

[Aega]

Thanks, Steerpike2, I read a lot about these Frako caps going bust. I will take your advice and start replacing them there.
Much appreciated!

 

[Tinman]

Just re-cap the entire deck ONCE and enjoy it for many years to come. Don't just pick through a few. You will be well rewarded by this.
If the 2 reel motors need service, I can rebuild them with new precision ball bearings instead of the troublesome bushings.

Good luck!

 

[Aega]

Yes, thank you Tinman, that was my plan initially. But for some odd reason, my very senior and trustworthy repairman opposes this strategy.
He's agreed to come over and observe the deck's behaviour, then start working on it and I truly hope to be able to convince him to go through the deck plucking all old caps.

Btw, aiming for Panasonic caps of similar value and voltage, 85C.

 

[Tinman]

Experience with this brand has proven that at this age, a full re-cap is the best long term choice and often THE FASTEST way to fix all the problems.

I know that there are still many that cling on to dear life to the old method of finding and replacing the one or two OBVIOUSLY faulty parts only. But a lot of the capacitors are now basically crap. The amount of effort required to do the above, it takes only a LITTLE more to just do all of it. The deck will also sound better again, basically as it did when new.

However, keep in mind that the established method of repair usually means repeat trips to the shop and thus, repeat money. Maybe that's the real reason some oppose a proper restore job.

Anyway, when gear is fairly new, this would be a dumb thing to do. But after 30 years? Just do it and be done for another 30. I really hate re-caps, not my favorite job either. But it's the best way, in particular with Revox and Studer from that era.

I just checked out an old NIKKO receiver that has all Japanese capacitors in it.... Guess what, it needed only new lamps. It plays, after 30plus years, perfectly. So it is the brand of caps we are going after here.

Many European pieces use these things, and need the same attention. Frako, Roe, Philips, Rifa, get rid of them.

Use Panasonic and Nichicon caps.

On some things, you should troubleshoot and find the original cause of the problem first, as I do, but afterwards I recap the whole thing anyway.

That's my honest opinion after years of fixing gear. Some don't like it, but I really don't care.

BTW, only 15 years ago, I also opposed blanket recaps. They were actually not needed.
My, how times have changed.

 

[Aega]

Thank you, Tinman, I shall make this a mantra. We'll try to figure out the reason, and either way, successful or not, I will insist on the recap, even if I have to do it myself. I have that amount of skill, with some guidance, panel by panel.
I sit in the EU, need to find a good source of capacitors (probably Conrad).

Your support is greatly appreciated, will revert with relevant updates.

MY best regards,
Aega

PS: BTW, this is what the recording level indicator is showing, when recording to tape with nothing connected to the deck.

 

[Tinman]

Yes, Conrad is the place!

Do the simple things first, reseat all connections, check all voltages for noise and proper levels.

Good luck!

 

[Aega]

Understood, will do so.
Thanks!