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Kaarelt
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Kaarelt Posted: Sun, Apr 14 2019 10:42 AM

Hi

I have decided to try and restore 2x beomasters 1900-s. First a little backstory:

Beo nr.1:

got it for free about 5 years ago, it powered on, but the usual lamps were blown, one channel was weak etc. So i got the lamp and capacitor kit and replaced everything, also got the weak channel working by fixing the bass and balance sliders. It worked well for some time but then started switching off and going to standby so it went to the shelf and is been sitting there. Now the stupid part was that I did not replace the large power caps/rectifier or anything else that didnt come with the caps kit from Martin also didnt check the idle currents. So trying to power it up now it went to stand by power but nothing else. after second try the stand by light doesnt go on anymore also. i managed to get some measurements and while checking the D50 rectifier DC voltage if i connect the multimeter to positive and negative to D50 the stand by light comes on. 

Beo nr.2: got it recently, again for free, this one powered up, all the lamps and controls were even working but went to stand by after a couple of minutes and no more power up. I tried to connect the TR27 transistors C and B as in this thread https://forum.beoworld.org/forums/t/23042.aspx and it fired up, so seems this one might be a bit easier to save hopefully. Not going to touch it before I get new caps and parts.

For now I will try to get the nr.1 working. I have ordered new d50 rectifiers, power caps and idle current trimmers. Im hoping the caps and lights on nr.1 are still okay since they have been just sitting for a couple of years. 

nr.2 i will recap and and also replace rectifier and trimmers before doing anything else.

what else should I check or do before trying to power them up again? I measured the speaker outputs, didnt see any dc there.

Some voltages that I measured in standby: 229volt AC otlet, AC to transformer is 115v. the 2 copper mains to the main board are 18v

D50 is 18AC and 24DC, TR27 B is10v, C10v, E24v, TR31 is B10v, C0v, E10v

Any pointers would be greatly appreciated. 

 

Kaarelt
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Update

 

Beomaster nr 1 is up and running. I didnt really think it would actually start up but has been playing for 5 hours now. Replaced the rectifiers, darlingtons, 2 transistors and trimmers also fixed some loose soldering points. Also fixed the balance slider with superglue for now, lets see how long it will hold up but i did the bass and treble 5 years ago and they still work.

 

First startup had loud hum in speakers, but thankfully that was the mains switch on 240v. put it back to 220, no hum, had to readjust the 15volt supply though as it was around 17volts.

Question: has anybody tried to integrate a bluetooth receiver to the beomaster? Im playing with the idea since I have some small bluetooth boards lying around. would like to have it wired to tape input and somehow controllable with the tape switch also. 


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