Beomaster 8000 right channel went up in smoke, what to do next?

26 replies
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BeoMaster4 (archived2)
Bronze
Posted October 21, 2012 at 21:34 GMT
#2244050

Hey guys,

My first post here at beoworld. My parents had an old Beomaster 8000 set in the garage (beomaster, beocord, beogram and beovox ms150) which has been unused for 8 years or so. We brought the set back to life two days ago. All the devices have their problems, but the beomaster was working ok (apart for half of the buttons on it). We have used the beomaster for about two days now and some time at full volume, all was well.

Today we were just watching TV and had the volume set about half way when suddenly it made a loud pop on the right channel and smoke came out on the right side of the heat sink.

I disassembled the unit right away to look for anything obvious. No visible damage can be seen, but a very distinct burned smell comes from the number 3 column of metal plates on the heatsink (numbering the columns from left to right, so 3 and 4 being the right side). I have no idea what these things do, but apparently they get hot...

I hope you can advise me on what to do next. I guess these machines have common problems. I already read about the right channel running hot. It's strange I can't see any damage, while it produced a fair bit of smoke and smell.

mexking
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mexking
Bronze
Posted October 21, 2012 at 21:44 GMT
#2244051

Where do you live, its easier to help if we know at least your country

Location: Mexico city

Retired
Printing machine technician
Restored various 1960-70 items
Rock and Roll music
Collecting Vinyl
Restored Jukebox Wurlitzer 1050
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BeoMaster4 (archived2)
Bronze
Posted October 21, 2012 at 21:57 GMT
#2244052

I live in The Netherlands

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Leslie (archived2)
Bronze
Posted October 21, 2012 at 22:04 GMT
#2244053

We have some well experienced and respected Dutch members such as Blackrix, Ipaul and Beobuddy who can help you. Try the Dutch forum en ik weet zeker dat je antwoord zult krijgen...

mexking
Offline
mexking
Bronze
Posted October 21, 2012 at 22:21 GMT
#2244054

Leslie wrote:

We have some well experienced and respected Dutch members such as Blackrix, Ipaul and Beobuddy who can help you. Try the Dutch forum en ik weet zeker dat je antwoord zult krijgen...

Hey hey, dont run away to the Dutch forum, we like to know what happens, and if we have to use the Google translator it gets kind of problematis😁

 

Location: Mexico city

Retired
Printing machine technician
Restored various 1960-70 items
Rock and Roll music
Collecting Vinyl
Restored Jukebox Wurlitzer 1050
C(
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chartz (archived2)
Bronze
Posted October 22, 2012 at 07:40 GMT
#2244055

Hi,

Sometimes when a transistor gives up the ghost, there is a tiny crack on its surface and you will really have to look with a magnifying glass to see it!

Probably bad caps and idle (quiescent) current trimmer caused that...

OR
Offline
orava
Bronze
Posted October 22, 2012 at 08:26 GMT
#2244056

And that crck might be towards heatsink, invisible to front. Power resistors (0,18ohm) has possibly burnt too.

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ipaul (archived2)
Bronze
Posted October 22, 2012 at 09:44 GMT
#2244057

...and obviously all depends how experienced you are with electronics :)

Probably indeed (unfortunately) some short in a power output stage which causes a smoking resistor :(, which will than need some soldering, replacing and probably adjusting.

Maybe a magnifying glass will help, sometimes it's just hard to see.

Nice set though, too good for a garage :), hope it was dry and not cold there, as that may cause trimmers to go bad etc...

DI
Offline
Dillen
BronzeModeratorFounder
Posted October 22, 2012 at 12:25 GMT
#2244058

Typical case of an open idle current trimmer.
The output stage heats up and makes whats called a thermal runaway with the output stage pulling maximum from the power supply.
The power supply will deliver a good 700 Watts so the output stage, however beefy, becomes the weakest point.
It all ends in a blown output stage, most often dragging driver transistors etc. with it in the fall.

Replace all components in the output stage of the affected channel, preferably all components on the board plus those on the cooling fin
and replace trimmers and capacitors in the other channel to prevent it from happening here too.

This is a job for a skilled tech guy but worth it for an otherwise good Beomaster 8000.

Martin

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BeoMaster4 (archived2)
Bronze
Posted October 22, 2012 at 12:48 GMT
#2244059

Thanks for all the advice so far.

The Beomaster also has some other problems, the tp2 channel is not working and pretty much all the controls on the controls panel are non responsive. (bass, treble, filters etc). So... maybe it is not worth rescuing anymore?

I do have a fair bit of experience soldering electronics, so that shouldn't be a problem. On the other hand, I don't have a lot of knowledge about stuff like this.

Martin, I also just ordered a cap kit for my Beogram from you. Do you also sell components to fix up the beomaster? Or do I have to start disassembling the output stage and source new components locally?

Is there a guide or something to the PCB's and it's components on this machine?

or
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