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Beogram 8002 Repair

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sonavor
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sonavor posted on Sun, Dec 30 2012 12:21 AM

This Beogram 8002 was a recent find. I picked it up as a learning unit because one of my primary, everyday turntables is a Beogram 8002 I bought way back in 1983.  That original 8002 is still working well.  I had a B&O technician look at it about eight years ago and he made some adjustments.  That was before I took on this vintage audio hobby.  When this recent aquisition became available I decided the price was too good for me to pass up.

In the picture you can see the lid assembly is off.  The main spring and lid attachement came apart.  I am going to fix that first.

Electrically, this new 8002 powers on and the turntable starts spinning as soon as it is plugged in.  None of the pushbutton controls work.  So this could be a real troublesome repair.

 


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tournedos
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sonavor:
The electrolytic capacitor I hate replacing the most on these BG8002 units is the one inside the processor housing (C28, 47uF, 10V).  It is in a difficult place to remove and replace.  You have to be very careful.

Seems similar to the cap inside the processor board shieldwork in pizza box Beomasters. They are very dificult to remove because the circuit board with a heavy ground plane conducts all heat away from the soldering spots. I tend to just cut the old cap off, leaving enough stubs on the board to solder the new cap on them. Much easier and helps to avoid circut board damage.

--mika

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sonavor
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I contacted Beoworld member auric about a Beogram 8002 repair post he created back in 2008 (now in the Beoworld Workbench archive forum).  His 8002 was having some electrical stability issues due to problems with the electrolytic caps and some solder joints.  He was able to get his 8002 back in good working order. This morning I made a quick run over to my local Mouser electronics warehouse and picked up replacement electrolytic caps for my 8002.  Pulling off the existing ones, there were several that were out of tolerance.  In particular, C24 (2200uF, 16V) measures 818uF !  My plan is to replace the electrolytics, then recheck the state of the 8002...and proceed trouble-shooting from there.  I will also check solder joints.  Auric advised me to concentrate on the PCB connector  solder points so I will definately check those.

-sonavor


sonavor
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On PCB1, the 2200uF C27 electrolytic capacitor is a different kind of mount than typically seen (typical being a single positive and negative lead).  The original C27 cap has a single, center lead that is the positive lead.  It has three negative leads.  The PCB1 then has four holes for mounting that C27 cap.  I am replacing the C27 capacitor with a two terminal, snap-in device.  To make it fit in the same area I had to solder on some extension leads.  I used some tacky glue to help secure the replacement to the PCB since it is a little wobbly with my extension pieces.  Once the glue dries I will jumper the negative terminal to the other two mounting holes where the original, four lead cap was soldered to.  I'll post a picture of the C27 cap after it is soldered in place.


Step1
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Step1 replied on Tue, Jan 1 2013 9:33 PM

sonavor:

I contacted Beoworld member auric about a Beogram 8002 repair post he created back in 2008 (now in the Beoworld Workbench archive forum).  His 8002 was having some electrical stability issues due to problems with the electrolytic caps and some solder joints.  He was able to get his 8002 back in good working order. This morning I made a quick run over to my local Mouser electronics warehouse and picked up replacement electrolytic caps for my 8002.  Pulling off the existing ones, there were several that were out of tolerance.  In particular, C24 (2200uF, 16V) measures 818uF !  My plan is to replace the electrolytics, then recheck the state of the 8002...and proceed trouble-shooting from there.  I will also check solder joints.  Auric advised me to concentrate on the PCB connector  solder points so I will definately check those.

-sonavor

OMG You lucky lucky lucky person being able to 'pop' round to mouser arghhhhhhh! That is THE number 1 electronics supplier IMO, no UK company touches it, or at least non that I have found, and it is the only place I can get capacitors of the same type across all the value range!

That capacitor checker is great, hehe, I can 'pop' in to Peak anytime as they are down the road from me, but would rather have Mouser any day!!!

Hope things go a bit more smoothly for you this time :-)

Olly

sonavor
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Yes, I can tell you that Mouser warehouse is a huge place.  It is really handy.  I still have to order some parts from other places but the majority of what I need I can get from Mouser.  I like those little Peak testers.

Today, I have made pretty good progress on the Beogram 8002.  It is kind of working now.

The first picture is of the recapped PCB1 board.  It shows the work around for replacing the four lead C27 2200uF electrolytic cap with a two lead, snap in cap.  I used jumpers on the backside of the board to connect up the holes where the original four lead cap went.


sonavor
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Here is another picture of the recapped PCB1


sonavor
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Here is the recapped OC1 and OC2 components on the chassis


sonavor
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On PCB2, I replaced the C28 electrolytic capacitor and put a new layer of thermal grease on the MPU. I remounted the heat sink bar then put the PCB1, PCB2 and control panel back into place in the 8002.


sonavor
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With the Beogram 8002 re-assembled to where I can plug it in and test again - plugging it in results in the turntable starting out correctly in STBY  mode (red dot).


sonavor
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Exercising the control buttons, the Turn, 33, 45, <<, >>, Play, Stop, "-" and "+" all work.  Here is a picture of the 8002 returning after spinning at 33.33.


sonavor
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Now a problem.

After exercising the controls for a bit and taking the 8002 back to Stop/Stby, the Beogram decided to start turning on its own in the opposite (counter clockwise direction).  The indicator light still showed the red dot.  I could press Play but the platter still turns in the wrong direction.  I unplugged the 8002, waited a few seconds, then plugged it back in again.  The turntable starts turning counter clockwise again.  So I unplugged it a second time, waited about fifteen minutes, then plugged it in again.  This time is stayed in the Stop/Stby position and the controls appeared to be working correctly again.

I will test this some more and see if it consistently starts doing bad things on its own again.  To start turning by itself and in the wrong direction - would that likely be an MPU signal problem?

-sonavor

sonavor
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Additional information - After the 8002 has been sitting idle (unplugged), when I plug it in and wait for a bit the turntable will start rotating in the counter clockwise direction.  Once it starts doing that it seems to be locked into rotating that opposite direction. 

-sonavor

Step1
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Step1 replied on Wed, Jan 2 2013 10:52 AM

When you say you have checked the joints, have you actually reflowed with fresh solder?

Olly

sonavor
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Well, this project has taken a turn for the worse. Deciding to start looking at voltages I plugged the 8002 in to make some measurements.  To my surprise the Standby light did not illuminate.  The turntable is no longer getting proper power.  I went ahead and measure voltages going to through the power supply section.  I get 5 VDC across C27.  It should be 15V.  I get -10 VDC across C29.  It should be -15 I believe. I don't get anything across C24.  If with just the transformer plugged in I do see various voltages (25 Vrms, 40 Vrms, 50 Vrms) on the transormer pins. I don't see or smell anything burnt so maybe there is just a bad connection somewhere.

sonavor
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Step1:

When you say you have checked the joints, have you actually reflowed with fresh solder?

I reflowed fresh solder on the transformer connector when I recapped PCB1.  I didn't reflow fresh solder on the other connectors.  With the power failure I am currently experiencing, I am missing voltages with other connectors (P1, P2, P3 and P4) on or off.  So the problem must be between PCB1, PCB2 and the transformer.

Step1
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Step1 replied on Wed, Jan 2 2013 12:48 PM

You must, at the very least reflow all headers and not stop there either!!! That I suspect, will resolve your current issues.

Olly

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