Tandberg tr2030 smoke

Cmrib

Member
I need help, guys.

I bought a old non working Tandberg tr2030.

I changed the fuse and it turned on, but it started releasing smoke from the amp board, two distinct lines of smoke emerged from the where abouts of the R749 and R7501.
I'm not sure if I fried the resistors or overheated the transistors. But I turned it off almost instantly.

What caps should I replace? What could be causing this malfunction ?

Carlos


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Those are the emitter resistors on one channel (if you meant R751 for the 2nd).

You need to start checking for shorted transistors, starting with the outputs on that channel. Then check the drivers Q717/719. But, if the emitter resistors were smoking one or both output transistors is probably shorted.

If there are any gold-colored Frako branded electrolytic caps in there, plan on replacing them. There's a pair that tends to fail with age and cause excess DC offset and eventually output damage, plus in general that particular brand of caps are known these days for failing quite often.

Plan on building a dim bulb tester if you want to eliminate that kind of smoke experience in the future; allows you to power up the device under test with current-limiting to prevent damaging more components in the event something is shorted internally as is likely the case here.


John
 
NOT putting down the OP... I understand the eagerness of "plugging it in and hoping it will work" mentality It usually doesn't work!!! that's why thousands of people post here! Unless you can audition... or have a basic guarantee.

Obviously the seller plugged it in.. He's selling it. He knows it doesn't work.. and yet you buy it.
 
NOT putting down the OP... I understand the eagerness of "plugging it in and hoping it will work" mentality It usually doesn't work!!! that's why thousands of people post here! Unless you can audition... or have a basic guarantee.



Obviously the seller plugged it in.. He's selling it. He knows it doesn't work.. and yet you buy it.


:)

So far I've been lucky with other stuff.
I knew this one was broken, but smoke is always a bad sign.

Let's hope with your help I can repair it.

Carlos


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Those are the emitter resistors on one channel (if you meant R751 for the 2nd).



You need to start checking for shorted transistors, starting with the outputs on that channel. Then check the drivers Q717/719. But, if the emitter resistors were smoking one or both output transistors is probably shorted.

Bad news I guess.
Are there modern replacements for the output transistors? Can you give me the alternatives?


If there are any gold-colored Frako branded electrolytic caps in there, plan on replacing them. There's a pair that tends to fail with age and cause excess DC offset and eventually output damage, plus in general that particular brand of caps are known these days for failing quite often.

My unit have orange caps from Siemens, so I was hoping for a lesser problem.
Could the big 10000uf ones be the cause?
Also one cap that's mentioned very often is the C905 1000uf 63V, but I think a failure on this one doesn't cause this symptoms.

Plan on building a dim bulb tester if you want to eliminate that kind of smoke experience in the future; allows you to power up the device under test with current-limiting to prevent damaging more components in the event something is shorted internally as is likely the case here.
John


Will do. Thank you.
Should I use a lamp in parallel, to understand the power output.
When using a dimmer, I should look for overheating or wait for traces of smoke, probably...?
(Stupid question, but seems the way to go...)

Carlos


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I have a Tandberg 3030 that still works great. Hope you get your receiver back up and running quick!
 
Orange Siemens = good, means it's a newer production unit.

Very doubtful the PS filter caps (10,000uF) caused this. Same for C905 but that one does impact most of the receiver as it's the filter for the +25V regulated supply. I typically replace that one automatically as it can cause downstream issues if it starts leaking AC. Doubtful it caused this problem, more likely a shorted speaker wire took out one or more of the outputs on that channel.

The dim bulb tester (do a search for that on AK, you'll find copious notes on how to build one) puts a 120V lamp (typically 100w or thereabouts) in series with the AC "hot" wire going into the receiver. If there's a short inside the receiver, the lamp will light up and prevent excess current from flowing to the receiver and causing more component damage. Allows you to do a quick check for such damage in advance, and would have prevented the smoke incident.

At this point you need to start checking components with a decent multimeter, or finding a competent tech if DIY isn't your thing. First in line to check is the output transistors near where you saw smoke. My bet is one or both will be found shorted on two legs. You need to use the diode check function of the meter for this test. Modern equivalents do exist and are not particularly expensive, though you may also find you have some other component damage in that part of the amp circuit.

Binkman, if you don't have anything constructive to contribute, please stop posting. Not sure what's up with you but lately everything is negative, negative, negative. Not helpful here, the guy already made the mistake and we're trying to help him get through it so he can enjoy this nice receiver, not teach him a life lesson - ok?


John
 
At this point you need to start checking components with a decent multimeter, or finding a competent tech if DIY isn't your thing. First in line to check is the output transistors near where you saw smoke. My bet is one or both will be found shorted on two legs. You need to use the diode check function of the meter for this test. Modern equivalents do exist and are not particularly expensive, though you may also find you have some other component damage in that part of the amp circuit.

John


I already ordered Bd239 and bd238 (I think) for drivers replacement.
But, regarding the output transistors, there are apparently several alternatives.
Which are the best match and the easier to find ?
Can you point me to some thread here in AK?

Thanks,

Carlos


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OnSemi still makes these... should be BD809 and BD810 per the schematic, you can find at Mouser as BD809G and BD810G - about a buck apiece.


John
 
Be careful replacing those drivers, look in the datasheets for the original MPSU driver pinouts, and how it was actually mounted.
 
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+1

I should have mentioned that as well, the originals were MPSU06 and MPSU56. Quite likely the pin out from the BD drivers will not match.


John
 
Success!!!

I'm a lucky bastard!

I measured some points in the circuit, looking for differences between the right and left channels. Tested the drivers and all seemed ok.
But as you suspected John, the output transistors were bad.
I replaced them with BD911 and BD912, replaced fuse with a more fragile one, and decided to plug it in.

It's working!!!
Next thing to do is to compare voltages with schematics and maybe replace C905... Has I said before my unit has Siemens caps.
I ordered nichicon replacements but maybe I'll wait.

Another hard job will be changing the dial bulbs, I have only one working and I don't remember seeing something like that in my local shops.

What should I do? Do you think bd911 and Bd912 will do the job?
Should I recap? Are there other weak points I should take care of?
Are there alternatives to that strange lamps?

Thank you all,once more, for the support.

As soon as finish this reply I will search forum for other tips regarding Tandberg tr2030.

Carlos


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They should be fine. Slightly higher rating for voltage (100V vs. 80V) and collector current (15A vs. 10A) which is fine, and same wattage (90). Same pinout too, which is useful. They're a little faster, fT is 3MHz vs. 1.5MHz for the originals but I can't see that causing any major issues here. Good work!

Dial lamps are readily available on eBay, the lamp type itself isn't hard to come by nor expensive but the originals were frosted which you want to stick with if you want the display to look the same.

I wouldn't bother recapping if it sounds good (and/or measures good). With those Siemens caps it's probably several years away from cap issues, based on what I've seen. If you do recap, make sure to stick with low leakage type (like Nichicon KL) for any of the smaller orange originals (I know, can be hard to differentiate those from std. Siemens sometimes) so you don't end up introducing any noise where it shouldn't be. For C905, you don't really need an audio grade part, just a good cap intended for power supply filter use. Needs to have the right ripple rating etc. for that application. I've been using Vishay or Nichicon TVX because I prefer to retain the original axial installation.


John
 
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+1



I should have mentioned that as well, the originals were MPSU06 and MPSU56. Quite likely the pin out from the BD drivers will not match.





John


Wow.
The pin out is totally different!
Now I'm wondering where did I get that information?
I wroted it on a piece of paper from some forum.
And it's totally wrong... Lucky you guys have spotted that mistake.

Once more...thank you.

Carlos




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Heh... what that shows is that sometimes it's better to refer to REAL reference materials, i.e. datasheets & schematics, vs. taking everything you read in a forum as gospel. You can't assume everyone posting with advice has done their homework or actually has any real expertise on the subject - despite this particular receiver repair having gone quite well so far.


John
 
The TR2030 is working fine. Just a slightly warm C905 although as I mention it's Siemens branded not Frako.
I tried two 12V/7W wedge lamps on the meters side. They work but I will wait for the right ones.
I'm starting a new topic with a Onkyo receiver, a hard one I guess.

Any help is welcome, see ya.



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