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Beomaster 1900-2 T2903 dead after recap

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Andreas
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Andreas posted on Tue, Dec 1 2020 12:35 PM

Hello, i wanted to rejuvenate my Beomaster 1900-2 Type 2903 which i own for a very long time. I replaced all my capacitors, rectifier, lamps and idle trimmers with Martins kit. I also changed the 2 big reservoir capacitors with two F&T Al-Elko 4700uF -10+30% 40v 

I took my sweet time and worked very carefully, double/tripple checked everything and checking polarity of capacitors. When plugging it to a power source the machine is just dead. There is no click, no light, nothing...

I again checked every solder joint but everything seems to be fine. Do i have to do anything else when swapping so many parts ? My BM worked fine before i just wanted to give it back some freshness in sound and to get rid of the humming noise on my left channel. I got the capacitor kit from Martin and from the 100uF there were only ones with 50v where as some original capacitors read 100uF 16v so i guess that is ok ? I of course used these for all the 100uF capacitors. There is also this big 2200uF radial capacitor in the kit for C92 which has arrows pointing in both direction, usually the arrow points to negative. I went with the dented end to be positive. Is that correct ? 

I uploaded two pictures on to my profile, somehow i cant insert it into my text here.

I really need to get this beauty back running, every help is very much appreciated 

 

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manfy
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manfy replied on Sun, Dec 6 2020 5:17 PM

Congratulations! That went better than I thought.
It proves that you've done a good job with your recapping works and we can be reasonably safe to assume that all will be ok with the power amp too.

Here's the final steps:
- unplug the unit and reconnect the wires to the 31V supply
- keep the voltmeter connected to TP15 and GND because this will be our first adjustment
- keep the speakers disconnected and turn the volume to minimum
- plug in the cord and switch on the mains switch
- bring the unit out of standby by selecting an FM preset
- if there's any smoke from power amp side turn off the unit. I don't expect to see smoke but the change of capacitors may have changed the idle currents in the output stages -- it's unlikely that a massive change happened but it's possible
- if everything looks good adjust TP15 to 15.0V with 2R151 (as per service manual)
- now check and adjust the output transistor idle currents on both channels as per service manual
- leave the unit on for 10 minutes and check or readjust these idle currents

All should be good now and you can connect your speakers to test all functions. If you're unsure or if you have very expensive speakers, you may want to try this with some low cost test speaker first. If you don't have test speakers, you don't need to worry too much. There is some circuitry in the ouput amp that should protect the speakers from fatal conditions.

Andreas
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YES! It's alive !! The BM is running like a charm. The 12mV at the trimmers are very stable and everything sounds like new. Thank you so much, youre amazing Manfy ! A big thank you also to Sonavor and Martin ! 

Andreas
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DM me your address :)

sonavor
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Yeah, nice job manfy. 

-sonavor

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