Hello:

I'm trying to restore a Beogram 8002 and could use some pointers.

When I plug it in, sometimes the unit will power up and respond. Sometimes it is dead.

When working, I am able to engage the turn function and it is able to hold speed 33 and 45. Often it takes a while before the servo reaches steady state. The motor is very weak The pitch adjustment for the most part works (increments and decrements) but if I increment to the maximum step, the microprocess or will freeze and the display will show a "2" or "3" rather brightly.

When I hit play, the tone arm will advance to the correct location but will not lower. I can move the tone arm to the left but not to the right. When it reaches the end it will not return rest position.

The mechanics of the deck is working properly. This appears to be an issue with the electronics.

I've recapped all of the electrolytics on the control board and checked for cold solder joints. The voltages on all regulators seem to be correct.

Any ideas?

Derek

Derek,

The "When working ..." line suggests an intermittent failure.

Are you sure you replaced ALL the electrolytic caps ?

- And checked ALL the solders for cracks ? 

Martin

Martin:

I did not replace the bipolar electrolytic cap in the transformer.

I did not replace the bypass caps on the regulators on the chasis.

All caps on the control board have been replaced.

 The intermitent problem seems to be getting the MPU to "boot" properly. By unplugging and plugging the power cord, I am able to get it to run again. Gently flexing the pcb has no effect so it looks less to me like cold solder joints/cracks. Yes they've been all reheated.

Derek

What about the cap inside the CPU metal housing ?

Martin

Hi Martin:

Making some progress on my 8002.

You will recall that I recapped the unit and was still getting an unstable CPU. It turns out that this is because of a substitute capacitor that I used.

4 prong electrolytics are nearly impossible to find in North America. In the 8000/8002 there is a large 4 prong Frako  electrolytic that I replaced with a 2 lead radial version. The Frako configuration is the positive terminal is in the center and the outer 3 prongs are negative. It turns out that the PCB layout requires 2 of 3 the outer prongs to be electrically tied together. So a simple jumper wire solves the problem.

The CPU is stable now and now responds to commands (sort of.)

 With tone arm at rest everything works fine. I am able to turn, stop, change speed, increment speed, program for multiple play.

When I hit "play" the arm goes advances and stops. The Right Arrow is illuminated on the tone arm. Forward control works, but Backwards does not. Stop also does not work and the speed is stuck at 33.33 RPM. You can not change to 45 RPM or inc/dec the speed.

If you manually trigger the switch at the stop position of the tone arm all controls works again.

The other question that I have is, can you adjust the height of the center bearing on the turntable? I notice that the aluminum pan/dish is very close to the inner chassis and rubs slightly as it rotates.

 Ideas?

Thanks,

Derek

 

The 3-prong cap thing is explained in the cap kit with photo etc.
So are the other caps.
Did you replace them all ?
Also the one inside the CPU casing ?

The subplatter will ride very low if the main bearing bottom insert is badly worn or broken.
This happens too often if the Beogram is shipped with its platter installed.
The insert can be pushed up from below through the tiny hole in the brass bearing using a tiny screwdriver and a pair of long-nosed pliers.
Only a few 1/10 mm more and the bearing can block the spindle completely.
There's no adjustment for this and the correct thing to do would be to replace the insert.
Replacement inserts are available (repro in very strong nylon).

Martin

Hi Martin:

All caps have been replaced including  the one inside the CPU housing.

In "parked" position all controls functions properly except left arrow on sensor arm is illuminated. Only when I hit play do things stop responding as they should.

I should say prior to the recap, the MPU was displaying funny digits so the recap has definitely helped.

I also replaced IC2 - LF324 but this made no difference.

I'll try to adjust the sub platter in the manner which you suggest for now. I'll get one of your nylon replacements and a few other things once I am able to get the electronics working again :).

Thoughts?

Derek
 

Cracked solders maybe. Run them over even if they look fine, especially in the powersupply and rectifier areas and at the connectors.

Martin

yep .... did all that... resoldered cpu ribbon, power supply edge connector, cables to platter motor. It's amazing how many cold solder joints there are on these circuit boards.

all voltages are present on the regulators. 

The CPU socket can give problems in rare cases. I like to replace it with the type with round pins (tulip-type), sometimes a re-seat of the CPU will tell. If still bad, you will have to measure around to see where the problem is.

Martin