Beogram 8002 problem

[robbyd]

Hi there –

new member here… hopefully someone could give me some pointers…?

Have a Beogram 8002 here, (they seem to accumulate), that I’d like to get properly sorted.

when ‘play’ is pressed, the arm just moves right across, as though the arm can’t see the record.

if I press ‘play’ and then manually cue it with the  forward/back arrow buttons I can position the arm; then pressing play will let it drop and play as normal.

I’m good mechanically and can solder, but using an oscilloscope is out of my expertise.

have already changed the servo belt and adjusted the arm alignment etc. The lights are working on the sensor arm and I under the carriage…

The wires are hanging off the mute board, but that’s another job and I don’t see it interfering with the sensing of a disc (could be wrong)…

is there something that would be a likely cause/first thing to check??

best regards

Rob

[Dillen]

Bad opto sender IR LED at the threaded shaft.
https://www.dksoundparts.com/product/ir-led-for-beogram-6006-8000-8002-beomaster-8000/

Martin

• This reply was modified 1 month, 1 week ago by Dillen.

[robbyd]

Thanks Martin – much appreciated…

 

you’re talking about the segmented end by the drive belt?

regards

Rob

[robbyd]

Hi again –

this is unfortunately turning into a tale of woe!

Had the 8002 with its case in open/service position and was running the carriage up and down , observing the spindle shaft/sensor end, when it suddenly stopped dead…

main fuse in power supply box blown.

I thought something may have earthed out on the chassis by accident,(my fault) so swapped in a new IR sensor anyway. Got some slo-blo 160mA main fuses – but they keep blowing; sometimes instantly, other times within a second (you see it glow up and then blow).

disconnected the 4x connector blocks from main pcb, so motors, carriage etc not powered, but it still blows. If power supply not connected to main pcb, fuse doesn’t blow…

what would be your guess as to what might have happened?

I can’t see any visible damage to components on the board, or in the tin box, but obviously can’t look at any voltages there because the fuse blows every time..

thanks in advance,

Rob

[robbyd]

Well after further investigation, the fuse is no longer blowing, but if I leave it connected to the mains for a couple of seconds, I get smoke from the area of pcb1 where the power block connects…

diodes?? Why?

anyone?

thanks

[Glitch]

In general, a lack of replies is more likely to be caused by people not having enough information to make an educated guess than people not being willing and able to help.

There are many things that could have gone wrong. Did you remove a connector and reinstalled it backwards or misindexed? Do you have a wire pinched somewhere? Did you inadvertently cause a short when you were working on something else? Did you simply get really unlucky and had some unrelated failure at an inopportune time?

Are you considering attempting to fix this yourself? or are you trying to gather info for taking it to a qualified repair shop? Note that often when things start smoking that the debugging and repairs are more difficult due to a cascade effect.

Glitch

[Dillen]

Not sure if this is what you are doing, but NEVER run these decks without the subplatter and platter!

Martin

[robbyd]

Dillen – thank you – it was run briefly without the platter. My bad – too late; but useful information for the future!

 

Glitch – thank you –

there were no connections mis-placed. A wire may have been pinched to the motor (as the subbplatter was on the base board – I only saw this today- but not certain it broke the insulation).

I would really like to fix this myself… but appreciate it may be beyond my knowledge at the moment.

I have other 8002s I could swap parts with but don’t want to risk killing those too!

It has occurred to me that this may be an unfortunate coincidence where something failed, as I don’t believe anything shorted at the time…

have tried measuring the output pins on the supply brick, but cannot find a reference for earth. Which pins should give what voltage? Cannot find info on that… but it must be outputting something if the pcb is smoking!!

several caps do not measure their intended values, but can they cause the problem I have? I sense not…

 

again, thank you for the replies.

[Glitch]

The first step that I would take is to build a “dim bulb tester”. This will give you a bit of a safety net during testing.

I’ll defer to others about fixing any damage caused by running without a platter/subplatter. I suspect many people that have worked on a BG800x inadvertently have run it without the platter/subplatter, me included. This was a case where the dim bulb saved me from self-inflicted damage.

I don’t think that board swapping would be a good idea. Most of the parts that could fail are on the main board. The spare BG800x would be better used as a known good reference.

Glitch

 

[robbyd]

Thanks –

 

I believe the problem now to be with either the power supply ‘brick’, though there isn’t much inside it, or the main pcb.

I don’t see why running it without the top platter could cause damage, especially if you don’t try to land the arm…

 

best regards

[Glitch]

robbyd wrote:

I don’t see why running it without the top platter could cause damage, especially if you don’t try to land the arm…

The BG800x uses a feedback speed regulation in conjunction with the tangential drive. I believe that without the subplatter, the circuitry doesn’t get the feedback signal for speed regulation and runs the drive coils continuously at full power (overheating the electronics). Without the platter, the rotational inertia is not what is expected by the circuitry and it doesn’t work as intended. I have a vague recollection of the subplatter running backwards if powered on without the platter (?) .

It is best to follow Martin’s advice and not run it without the platters. If you must power on without the platters, I think that pulling the connector to the motor drive is safe, but verify this with someone else to be sure.

Glitch

 

[robbyd]

Understood now – thanks

[Author]

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