I re-executed my simulator for the "Off" position and the +15 VDC does eventually start dropping. I realized my simulation circuit needed some sort of load resistance on the +-15 VDC outputs to properly show the way the supply works. Here is the "On" condition with dummy loads on the +-15 VDC outputs.

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sonavor 

...and here is the simulation of the "Off" condition. Both the +-15 VDC outputs should turn off.
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I think that means you need to look at the P6-4 signal disconnected but measuring on the processor side of the signal to see if it is operating.

sonavor

I disconnected P6-4. As soon as I plug in the BG it has 4.88V on P6-4. When I press play it goes to 1.22V, stop and it goes back to 4.88. The BG will operate for about 5 seconds this way, then won't respond at all showing various nonsense in the display, or nothing.

The resistance I measure from processor pin to P6-4 is 3.24K, corresponds nicely to R11 so the trace and resistor seem fine

I think there is something going wrong inside the can. Maybe I'll change the electrolytic capacitor (gets hot in there I guess), and maybe I'll check the 4n7 caps, I read you found some faulty ones.

And not to forget, thanks for the explaining diagrams! That seems like some very handy software you are using.

Premiumverum wrote:

And not to forget, thanks for the explaining diagrams! That seems like some very handy software you are using.

I used National Instruments MultiSIM. There is a free version of that software available

I replaced TR21. Unfortunately it made no difference.

I still think something is wrong inside the can.

I took out C28 but it measures good. 46.7uF and 1.4ohm. I'll replace it just to be sure, it was an 85 degrees type.

So to recap where you are on this...The On/Off signal from the processor appears to work when it isn't loaded by TR21 but when TR21 is connected the base of TR21 just stays at around 0.7 volts (keeping the 15 VDC power supplies off).  Can you remove TR21 and verify that the base would receive the On/Off signal from the processor?  The reason I ask is because you checked the processor signal earlier by disconnecting a connector. I would like to verify the On/Off from the processor functions normally with everything connected (except just TR21). If it does function correctly that way then I would start thinking that the processor is unable to drive that signal low and maybe the processor is suspect. Check out C15 and R11 first though (including their solder connections). On a couple of my Beogram 800x units I had some problems with those small capacitors inside the metal box. One other thing...inspect the processor leads going into the socket and make sure a pin didn't get bent somewhere along the line.

sonavor

I finally got round to working on the BG again. Checked processor leads, checked connectors on the can.

I replaced C28 in the can, I had already removed it last time for testing its value. This changed everything, I think for the better! BG starts with the red dot and responds to buttons, drives the arm and platter looking stable with correct display. This makes me think the PSU and on/off from uP are OK. However, not all is well yet...

New symptoms

When play is pressed the arm drives in but never stops. It goes all the way across, the BG does not switch to 45, the motor keeps running when the arm has reached its ultimate position. Pushing stop makes it return to base, the motor does stop there and BG goes back in standby.

The BG can manually be switched to 45, this will make the platter spin faster.

Records on the platter are not detected, the arm behaves the same with or without record.

The arm responds to << >> and play. The arm can be moved onto the record with << and >> and will then sink down on the record when pressing play. The arm will move tangentially with the grooves for half a minute, after that it stops as if it has reached the end of a record and goes back to standby position.

What changed?

I'm still having the BG turned on to test stability, but maybe the first issue is now solved. Maybe either C28 was bad (was rather high voltage spec, about 50V. I read bigger caps sometimes get 'lazy' doing low voltage 5V work) or maybe a connection on C28 was bad and now the processor is stable again.

What now?

For the problem that remains my differential diagnosis is as follows, in order of likelihood:

- P2 connector was changed by me, maybe made a mistake. Counting of the worms rotations happens through there so quite likely to cause the running arm.

- maybe bad adjustments make the BG not read the ribs on the platter. The detector and pickup arm were adjusted by me somewhere during the repair process because they seemed misadjusted somehow. Probably just had everything wrong because both are now too low. If the BG proves stable I'll do adjustments, will be necessary anyway if I get everything working again.

- If C28 was bad, maybe some of the other caps replaced by previous owner are bad. Might replace them all.

Questions:

Do these symptoms point to another specific place for the problem? Am I on the right track? Any other/better suggestions on where to look?

Of course I could still be seeing one of those intermittent 'it seems to be working again' moments now. Keeping thumbs crossed...

Hi,

Have you checked the surroundings of the OPE1

I had this problem (on a 8000) (the carriage going on and on forever). On mine, the cause was a burnt IR led in the OPE1. If I remember correctly, at each turn of the lead screw, the IR led "shines" on two phototransistors. Depending on the order the signals are sent to the microprocessor, the machine knows if it's going forward or back. This is also what makes pausing right in the middle of an album, possible (the machine goes back to it's resting position and then, if play is pressed again, the carriage return exactly were it was)

When the IR led is burned, the microprocessor does not count anything, thus, when play is pressed, the symptom described is possible.

When you say that the arm move tangentially with the grooves for half a minute, do you actually see the lead screw turning? If not, that's the reason why the machine stops. If it does turn, and the OPE1 is deffective, the microprocessor won't see any movements from it so it will stop anyway (this is an assumption). Perhaps a safety trick for skipping records!

The OPE1 (with the IR LED and the 2 phototransistors) is right behind the motor, in the upper right corner.

These are assumptions based on my sole (but successful) attempt in repairing thes decks :

http://archivedforum2.beoworld.org/forums/p/7246/64676.aspx

Guillaume