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Problem with Revox Receiver and Amplifier

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DraKnight13

Active Member
I am recently jumped on a chance to buy some very interesting Revox Receiver (B780) and Amplifier (B242).
The problem with both of these unit are I can't seem to get any sound out of them at all (no noise, no cracking, no hiss, dead quiet).
On the B780, after messing around, I found out that I blew one of the fuse on the Power Supply Unit, and after it blew the fuse I put in, I took the power supply board out, measure couple of caps, they are bad. No problem, I replaced them all with Vishay caps (shout out to Arrow overnight shipping for free). Put it in, and still nothing. I know both replay on the speakers protection circuit kicked in. I am at a loss of what to do, unfortunately I don't have a signal generator and an oscilloscope to trace the signal (I know I should get one, but been chasing them through various auctions hoping for a deal).
The same problem on the B242, it dead quiet, no sound. The front meter on the faceplate show that there is signal coming through (or at least that what the meter is showing). I have not done any work to this amplifier so I am asking for any advice here.
I understand the need to do complete recap on them for preventative reason, but I want to hear them first to see how they are, before I commit myself to a full recap (I saw couple of threads on AK and the number of replacement parts are very discouraging). Also I am a sticker for original (even thought I know I shouldn't).
Thank you for reading!
 
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Show us pics front and back. Might be operator error, jumpers missing, or maybe something is really wrong with them.

When you replaced the blown fuse, did it blow again?
 
I can grab pictures. The B780 designed to be operate as single unit (no jumper or switch) unless you plug a 5 pin connector (DIN connector). When you plug the DIN connector in, it push a switch (on the input PCB board) to disengage the preamp - amp connection. In order to use it as separate unit, you have to use a DIN cable with 4 RCA connection (they do have a diagram of what pin is what (1 Pre Left, 2 Chassis, 3, PWR Left, 4 Pre Right, 5 PWR Right). I am ordering 1 of those adapter so I can test it with (but coming from China so may take a while). I have used deoxit on that preamp-amp switch, I have also identify the pin associated with what channel, and manually connect them to see if I can get some sound, but other than some very small static, I got nothing.
 
Many years ago I had the embarrassing experience of missing that the pre-out to power-in jumpers were not installed in a power amplifier. I checked out pictures of the B780 and as you say, it has that 5pin DIN socket labeled pre-out pwr-in. If, as you explained, not puting a plug there makes internal contacts engage, I would check if they actually engage. Dirt may have done it's magic.
Another possibility would be to have blown output fuses - if they exist.

Not many things that can cause dead silence. And usually these are simple reasons. You can eliminate causes by checking different parts. Like, does the rec-out provide signal to a tape deck or another power amplifier? If so, then the preamp is functional and powered so you can focus on the power amp.
 
I have cleaned and try to manually linked it. I also verify that the connection was made using a multimeter (there is continuity between 2 terminal). But the suggestion about using the record out to see if it pass signal. Thank you I did not think about that!!! Will come back with update. One good thing about Revox stuff, they build like a tank, but there is instruction to safely remove everything, make maintenance these thing a lot easier!
 
Hello, I wanted to keep you guys updated.
So, after countless efforts, the receiver have been doing nothing. I got mad and went out running some errands, my brother came home, thought I fixed it, plug it in and test with his beloved Spendor speakers, then have the audacity to call and complained that it didn't sound too good. I don't know what happened, I don't know how, but apparently it working great now, other than a burned out bulb in the signal meter. I let it run over night, no fuse blows, all the voltage out of the power supply unit is correct (within the +/- of the manual) and I am just at the loss.
Another Revox unit is also causing us the same problem. We have a Revox B242 we bought from the same gentleman, it didn't work. Turn on, display on the power meter that there is signal going through, but again, completely quiet. We tried every trick in the book (spray the input, check if relay clicked, see if any caps blown or damaged). Nothing works, so we put it aside and let it wait for it turns. Today, after came back from vacation, I started taking it out and try to work on it. And the stupid things work. I don't know what to say.
I would be very appreciative if someone can tell me what the heck happen. I am not complain cause right now I have 2 working pieces but I certainly would like to know how. The B242 is our favorite right now, I am not so impressed with the B780 so maybe I will pass that on.
 
That what me and my brother is debating on, we don't know if it is something we should keep or not. This is our first experience with Revox and at the same time we are more impressed with the B242. maybe I will play around with it a bit more before deciding. My main problem is I don't use the tuner section, at all. I purely just get my source from digital, my brother mess around with vinyl a lot, but we have never use the radio so it seem like keeping the B780 would be a waste.
And I have seen your post on the B780, I always wanted to ask what is the blue axial caps was (there was like 50 of them in your picture) that you replaced.
 
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