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Wednesday, July 29, 2015

Beocord 9000: Total Recap - Replacement of all Electrolytic Capacitors

I also did a full recap for my earlier Beocord 9000 restoration. While I think it is less urgent for Beocords and Beograms due to the generally lower operational temperature (than amplifiers/receivers), a replacement of all electrolytic capacitors is always a good idea if long term stability is desired. While the Beocord 9000 contains quite a few electrolytic capacitors, the good news is that its design is pretty service friendly. They definitely learned something between the 70s and the 80s. Even in comparison to the Beomaster 8000, the Beocord offers much easier access. In my opinion it is best to simply leave the main PCBs in the unit and instead remove the front and back panels. Here is a picture with the front panels removed. Their removal is straight forward and described in the service manual. Here is an impression of the top after removing the control panels and the glass cover:


The bottom PCBs can be accessed in a similar way by removing the bottom panel:


A good 'service position' for exchanging the capacitors is to put the unit upright opened like a book:


I put it on a towel, which allowed me to turn and move the unit while in this position. Once in this position it is time for some patience and concentration. One after another the caps are removed and new ones soldered in (in the correct polarity - as I said: concentration!! listen to some calm music and you will find some BeoZen in this..;-). Here are a few pictures:

Board #11 (DAC) is one of the two boards that need to be removed for the recap since they are sandwiched on top of another board:

 Before:
After:


The other one is #13 (Oscillator Detector)

Before:
After:


The following boards can be done while installed in the frame:

#8 Microphone Amplifier:

Before (the shield needs to be removed; it simply comes off when unsoldering the two spots that hold it in place):
After (shield already installed again):

#3 Rec/Play back circuit:

Before:
After:

#6 Rectifier

Before:
After:
It is worthwhile noting that the big 5000 uF cap was very close to be out of spec. It only yielded 4000 uF. This is still good enough for stabilizing the supply, but it shows that doing the recap was probably a good idea.

#4 Power Supply:

Before:
After:


#1 Microcomputer/display circuit:

Before:
After:
There is one cap on the upper part of this board. This shows it after replacement:

#2 Dolby circuits:

Before:
After:
O.k. done!














1 comment:

  1. Hi,
    thanks for the pictures. Nice work! Currently I exchange all the caps for supply voltage stabilization. That makes sense. I am not very sure to change the coupling capacitors (mostly 2.2 and 10µF). Is this really necessary? Is a realignment of the circuits the result of this?
    Greetings,
    Martin

    ReplyDelete

Comments and suggestions are welcome!