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Tandberg TR 2080 not producing any sound

T

TheSeanis

New Member
Hey guys, first post :)

I have a Tandberg TR2080 that was my fathers. I beat the crap out of it in my teenage years unfortunately so it is in need of some TLC. I convinced him to let me do right by my mistakes from when I was a younger man and offered to restore it as best I could.

It powers on perfectly fine, but no sounds come through any of the speaker sets or channels. I have it apart right now and I gave the internals a glance over, but I'm pretty new to working on amplifiers so I probably couldn't pinpoint something going wrong anyways... But, I did take a look and I didn't see anything blatantly obvious that would be interfering with something or looking damaged. I suspect at this point in it's age that some capacitors/resistors are likely retired and in need of replacement.

I was always told to check the output driver resistors as they are a common failpoint among amps, but, I don't know how to read a schematic... YIKES!

You guys are probably thinking at this point I'm going to obliterate this poor thing, but I'm a patient man and eager to learn.
 
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I found a Service Manual

Manual

Do you hear any relay click a few seconds after it's powered on?
Got Tools?
 
Ok, here's some standard check points for working on this model:

1) Are the pre-out/main-in jumpers installed? If missing, you can use a pair of RCA cables to connect them - jacks are at the top right rear corner of the receiver, viewed from the front (top left viewed from the rear). Also make sure the speaker selector is on (A, B, C etc.) and that you're connecting the speakers to the right set of rear panel jacks to match that.

2) If the jumpers are present & the speakers are switched on/wired correctly, need to check some voltages. First, connect it to AC power via a DBT (dim bulb tester) - numerous posts on this here on AK but effectively it is a home-made fixture that adds an incandescent lamp in series with one leg of the AC power line, usually in the 60-100W range (like you'd use for a table lamp). This will normally prevent damage to other internal components if something is shorted out internally.

3) Once connected, turn the receiver on, with a multimeter handy that's set to DC voltage (in the range of 0 to 50V is ok, if it doesn't autorange).

4) Does the lamp on the DBT light up brightly and stay on, or flash then fade out slowly? The latter is a good sign, if it stays on bright you have a short somewhere.

5) If it stays on bright, turn the receiver off. Then go to the power amp board, left hand end nearest the power transformer (big round guy at the left rear of the receiver looking at it from the front). There's a harness coming from that transformer that plugs into the power amp board between the transformer and the big filter capacitors. Unplug that, try powering up the receiver again. DBT lamp should not light up much, if at all. This would mean that you have something shorted on the power amp board which could range from output transistors to driver transistors to bad caps or a failed regulator, roughly in that order of likelihood.

6) Lift the tuner section, locate a single yellow wire that plugs into the preamp board. The preamp board is the one on the right, looking at the receiver from the front. At the left hand edge of that you should see that yellow wire plugged to a metal post on the preamp board. Use the meter to measure DC voltage beween the yellow wire and the chassis (any metal frame part is ok but I usually clamp the meter black cable to the little grounding screw that's at the right hand frame area of the preamp board, has a little black ground wire connected there with a ring terminal. Power the receiver on again. Do you have +25V on the meter? If yes the +25V regulated supply is working, which runs the preamp, tuner, and rear panel I/O board. It also has some impact on whether the protection relay works. Do you hear that relay (it's in the middle of the power amp board) click after several seconds? If so, that again speaks to a shorted component on the power amp board. Means the protection circuit is detecting DC offset and not closing the relay contacts so that the DC isn't sent out to the speakers.

That's about as far as you should plan to go for the initial testing. Post results and we can go from there. It gets more complex to track down the shorted component(s) but on the plus side these are pretty simple designs and quite stable in my experience, and they tend to fail fairly predictably if they fail at all.

John
 
Sadly I've just been incredibly busy with work, school, and the family but I intend to take care of the Tandberg and restore it to it's full glory before the end of March so I will let you know within a week or two how all this went.
 
roger that... Tom has just emerged victorious from his own 2080 repair, and will have some excellent first-hand suggestions for you when you're ready :-)

John
 
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