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First attempt at Beomaster 2400 'refurbishing'

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jesperb
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jesperb posted on Thu, Apr 26 2018 12:39 PM

Hello All,

Starting my first real repair project on a Beomaster 2400 - no previous BeoFixing experience, but lots of electronic DIY. This model came from my Dad, which is why i said yes to try to fix it, besides always having wanted to having fixed a Beomaster by myself (counting on a little help from my friends). It will be a rather long project, because summer is creeping up, but if it rains as much as last year, could be a quick fix after all.

Problem is 'no audio - hissing sound in both channels - volume control does not work'.

Took the lid off last night, things of immediate notice :

-End panel (left) missing - anyone got a spare in dark rosewood ?

-Sliders in really good condition, no dust, no coffee spills - nice and clean.

-Bass section, ceramic caps are 'crushed' (see pics) ?

-Output trannies (IC200,201,300,301) have been repaired previously and BADLY resoldered.

Cheers,


Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

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jesperb
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Hello and thank you,

Yes, i understand in-circuit testing is not the holy grail for tranny testing. But i needed to start somewhere and since Peak was the tool at hand, I used that (plus forgot all about the DC-out measurement).
My apologies, but  i am still trying to teach my brain to listen to good advice ;-)

I have a little problem measuring DC-out with a DMM though. Standby occurs a bit too fast for my (cheap) DMM to follow - even for an overload in the selected range.  May need to find an analogue one.

Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

sonavor
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To capture momentary signals you need an oscilloscope. Modern digital scopes can capture and store events like that.

jesperb
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Before i messed up the Beomaster,  DC-out was around 20mV for each channel, with sound in one channel and sound in both earphone channels. So i assume, measuring one output with your analogue meter in ex.100mV range, take the Beomaster out of standby, would give a full scale reading for a short burst, before the overload circuit triggers a standby again. This would indicate too high DC-out=short somewhere in the output stage for that channel (?)

Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

jesperb
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To show i actually DO listen to advice given, i have ordered a scope - It has been on my wishlist for too long anyways, so thank you for the friendly peer pressure Big Smile

Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

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