[bobdave]

I just finished replacing all the electrolytic capacitors and all the lamps on my Beomaster 1900 and the repair went well regarding the issues to be fixed: before completely achieving the re-assembling, I tested the amplifier and everything was fine: no more hum, good sound and all the lamps operating as expected. However, when I went further in the remounting, the Beomaster could not be operated as explained below.

With the Beomaster partially remounted, i.e before mounting the front panel, everything works fine: selection of program (phono, tape, FM), volume adjustment, on/off switching work perfectly by directly touching the pins on PC-board with my finger. However, with the front panel in place (with the sensitive keyboard), nothing happens: the amplifier is in stand-by and it is impossible to switch it on, only the stand-by LED is on. I dismounted and remounted the front panel again and I carefully checked that all the bronze forks grip their respective pins (not easy and quite long): the problem remains the same, the amplifier perfectly responds to any programming action by directly touching any pin while there is no operation possible through the front panel. I probably missed something but I cannot see what. Any help or suggestion would be very helpful. Many thanks.

[Dillen]

One or more components being pushed by the frontpanel so something shorts?
Perhaps a component fitted too high?

Martin

[bobdave]

Hi Martin. Thanks for your feedback. This is indeed possible as I replaced many components. I will check and let you know.

Robert

[bobdave]

Hi Martin.

I could not find any part that could be pushed by the front panel. But I noted that, once the amplifier is on, there is a slight vibration that can be felt when touching any metallic part that is connected to electric ground. It looks just like if there was an issue with the insulation between secondary and primary parts (I suppose this vibration is 50Hz). I removed the front panel and I checked again that programming was possible by directly touching any pin. Then I did the same while touching with my other hand a metallic part of the device: the programming was no more possible until I stop touching the metallic part. So I wonder whether I found the nature of the problem – even though I still have to find the source of the problem. On the other hand, maybe this has nothing to do with the sensitive keyboard issue because it seems to me that I already felt this kind of faint vibration on the metallic part of the front panel at the time when the amplifier was working nominally.

Any idea about this vibration when the amplifier is on? Thanks.

Robert

[bobdave]

Maybe it is normal that programming be not possible when I touch a metallic part with my other hand because, by doing that, I get “grounded” so capacitive coupling probably cannot occur.

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