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This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi all,
I have an issue with a beomaster 3500 that a friend has asked me to take a look at, and wondered if you guys would be good enough to point me in the right direction??
So - on first power up, all is ok for the first 3-4 minutes. However then it just switches off... subsequent immediate attempts to switch on etc and it switches straight off again. Leave it 10 mins then it switches on ok for another minute. So something is getting hot somewhere...
There's no speakers connected, nor any input, however it seems like the heat is coming from around the heatsink area (which is strange since there is no output or input).... This was an initial check with the cover on - i now have the cover off so need to diagnose more a little later as to exactly where the source is.
Caps look fine - no bulging/leaking (even on the large 68000uf ones!). I'll have to get my infra-red thermometer out, however does anyone know if there are any known issues/fixes/problems on this? I only said i would take a quick look for a friend, and whilst i dont mind changing whatever is needed, im not overkeen on a full scale rebuild :)
Any advice would be appreiciated. Many thanks
Paul
Welcome to Beoworld !
I would replace the output hybrid IC as the first thing.
Martin
Hiya Dillen,
Many thanks for the pointer :)
Which would be the Hybrid IC? Are we talking the STK-4141-5 Power Amp chip on the Amplifier and Power supply board??
Many thanks
Yes.However, the fact that you weren't really sure where to find the amplifier could suggest that maybe youshouldn't be the tech guy in charge of the repair - with all due respect and in the best of meanings.It does take a little electronic knowledge and skills to repair things like this.
Dillen,
I understand what you say, however I'm a qualified electronic engineer. What confused me was that fact it was referred to as a "output hybrid IC" as opposed to the Stereo Amplifier, or maybe Power Amp, which is what it actually is. It may be a Hybrid device, however to someone new to this kit, i wouldn'thave a clue as to whether it was a hybrid or not :D
I knew where it was - You cant really miss it!! :)
On a related note, it's nice to be playing with "proper" electronics as opposed to the new junk you get nowadays :)
Cheers
Hybrids - Proper electronics ?Servicing today, I agree, couldn't be much easier but when that IC is no longer in production, we'll have a problem.Anyway, go ahead and let us know the result.
BTW: Did you know, there are some people claiming that proper electronics takes no less than a minute or so to warm up.
Thanks Martin :)
Ok well interestingly enough i have now removed the case, and also loosened the microcomputer (wanted to see if anything got excessively hot under there, or if there were any components looking a little worse for wear/hot/crispy!) and i find that it's no longer switching off.
Typical!.
So - have now re-seated the microprocessor unit and am currently leaving it running with the case off to see if it re-occurs. Maybe I disturbed something - time will tell!! Still a little worrying though! It's still running ok after 15 minutes with no cover on...
Luckily there seems to be plenty of stock of the Amp here in the UK, so i could change it anyway if recommended???
Thanks
Apologies - double post!
And as soon as i post that... it switches off again!!
I think I may take the board out later and go over it for dry joints etc since i know from experience that can cause these issues too when things warm up...
Back on again now with the Microprocessor in situ, however not screwed in....
Have checked and whilst the heatsink is warm, there's nothing in there that seems excessively hot...
I seem to remember a quite frustrating issue with these Beomasters related to the smallceramic capacitors at the CPU input/outputs intermittently shorting.I think it was Die_Bogener who also experienced this, I'm sure he will remember better. Maybe he reads this.However, the amp chip would still be my first choice.