Tandberg 64x Left channel not working? - UK Vintage Radio Repair and Restoration Discussion Forum

zastin17 · 27th Jun 2017, 8:58 pm

So I posted over at tapeheads but I think this site would have more experts on tube equitment. I have a tandberg 64x that I recently got ahold of.
It records fine on the right channel with some occasional dropouts.
The left channel does not work. The strange thing is, a day after noticing the left channel was not working. It suddenly worked. A day later I woke up and it was not working again.

This has happened 3 times. When I release the right channel. The left channel indicator moves. I think its put into mono though. Where the right channel would indicate on the left channel tube and record on mono.

I originally thought it was in need of deoxit. I applied deoxit on all switches and pots. Also gave the valve sockets a dose. No change

The guys over at tapeheads.net told me to change the miniprint rifa caps located all over the amp board.

There are .015mf, .047mf and .022mf all rated @ 400v. I also noticed that several of the caps had cracks near the top of the casing. Definitely in need of a replacement.

I have since then ordered modern Metallized polyester capacitors of the same value that have good reviews from Amazon that are built fore tube amps. Still waiting on those.

MY QUESTION IS. Would the left channel working and sometimes not working be a result of these caps. I find it hard to believe that they would suddenly work then not work then work again. If anyone has worked on any of these machines, Is there anything else I should check?

I also checked for cold solder joints and have not found any. All tubes light up and work.

Michael Maurice · 28th Jun 2017, 6:04 pm

Its unlikely to be capacitors that cause this but they should be changed anyway.

The only way of taking the guessing out of this is to use a signal generator and a scope when the fault occurs.

ricard · 2nd Jul 2017, 9:15 pm

I agree with Michael that the old paper capacitors used are not normally intermittent in the way described, on the other hand the leakage current can depend on temperature, and if a coupling cap is bad enough it will cause silence so it's perhaps not out of the question.

At any rate also as Michael says, those old Rifas will cause severe performance degradation anyway so they need to be replaced. Whatever you find today that meets the specs on capacitance and temperature will be vastly superior to the original ones anyway.

27th Jun 2017, 8:58 pm	#1
zastin17 Retired Dormant Member Join Date: Jun 2017 Location: Portland, Oregon, USA. Posts: 2	Tandberg 64x Left channel not working? So I posted over at tapeheads but I think this site would have more experts on tube equitment. I have a tandberg 64x that I recently got ahold of. It records fine on the right channel with some occasional dropouts. The left channel does not work. The strange thing is, a day after noticing the left channel was not working. It suddenly worked. A day later I woke up and it was not working again. This has happened 3 times. When I release the right channel. The left channel indicator moves. I think its put into mono though. Where the right channel would indicate on the left channel tube and record on mono. I originally thought it was in need of deoxit. I applied deoxit on all switches and pots. Also gave the valve sockets a dose. No change The guys over at tapeheads.net told me to change the miniprint rifa caps located all over the amp board. There are .015mf, .047mf and .022mf all rated @ 400v. I also noticed that several of the caps had cracks near the top of the casing. Definitely in need of a replacement. I have since then ordered modern Metallized polyester capacitors of the same value that have good reviews from Amazon that are built fore tube amps. Still waiting on those. MY QUESTION IS. Would the left channel working and sometimes not working be a result of these caps. I find it hard to believe that they would suddenly work then not work then work again. If anyone has worked on any of these machines, Is there anything else I should check? I also checked for cold solder joints and have not found any. All tubes light up and work.

28th Jun 2017, 6:04 pm	#2
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,222	Re: Tandberg 64x Left channel not working? Its unlikely to be capacitors that cause this but they should be changed anyway. The only way of taking the guessing out of this is to use a signal generator and a scope when the fault occurs. __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

2nd Jul 2017, 9:15 pm	#3
ricard Octode Join Date: Mar 2006 Location: Lund, Sweden Posts: 1,632	Re: Tandberg 64x Left channel not working? I agree with Michael that the old paper capacitors used are not normally intermittent in the way described, on the other hand the leakage current can depend on temperature, and if a coupling cap is bad enough it will cause silence so it's perhaps not out of the question. At any rate also as Michael says, those old Rifas will cause severe performance degradation anyway so they need to be replaced. Whatever you find today that meets the specs on capacitance and temperature will be vastly superior to the original ones anyway.