Beogram 8002 carriage transport issue

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ALF Posted: Tue, Aug 3 2021 9:07 AM

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Hi All,

just finished the recap on my BG8002….all looked good so far, but……..

there are issues with the carriage transport, not reaching the drop-down point intermittently ??

meaning, sometimes its spot on and at other times being short about 2cm.

i checked the pulses from the opto at P6 which were present.

i wonder whether some of the opto parts displays an intermittent fault ?

obviously the uP is counting incorrecly, stopping the carriage too early !

does someone can shed some light on this issue ?

Of course I could just replace the opto components on the off chance it may fix the issue ???

anyhow, some advice would  be fantastic - thanks

ALF

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sonavor replied on Tue, Aug 3 2021 4:19 PM

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Hi Alf,

Are the voltage levels for the forward/reverse scanninng LDR devices set correctly?  If not that can interfere with the tangential arm assembly movement.

John

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ALF replied on Sat, Aug 7 2021 7:01 AM

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Hi John,

i would have to revisit and check.

the opto components at the spindle-head were replaced and so was 1IC2 but no change:

first activation of PLAY and the carriage is shirt of the drop-down point…..STOP

second activation of PLAY and the carriage gets to the drop-down point and arm is lowering !!

Perhaps a bit of a long shot but I was wondering if the uP does not clear its counter correctly ??

any “left over” added to the new counts adding up to the required number of revolutions.

In the meantime I will revisit the LDR devices and verify the voltages.

thanks for your input 👍

ALF

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Dillen replied on Sat, Aug 7 2021 7:15 AM

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Yes, do what John suggests.
And if the servo motor doesn't run as easy as it did in its younger days, the voltage supplied by the electronics may not be enough to drive it
the last couple of milimeters up to the lead-in groove (where it runs slower).
Check the motor voltage.
The servo motors will all need a bit of restoring by now - or replacing - if they run rough.
If the motor runs fine and quietly and the LDR adjustments are reasonable, try increasing R25 from 10K to 12K.

Martin 

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ALF replied on Sat, Aug 7 2021 8:24 AM

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Hi John/Martin

Expert advice as usual - again thanks for that !

I have to confess I simply overlooked that adjustment - no further excuses !

the LDR voltages showed 1.082 VDC and 0.824 VDC and are now adjusted to 657mV and 652mV - as close as I was prepared to fiddle.

the carriage motor performed strong enough as It was (eventually) reaching the drop-down point but will keep an eye on things to see if 

the suggested resistor change is a necessary option.

once again - thank you all

ALF

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ALF replied on Sun, Aug 8 2021 4:35 PM

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good news, the BG8002 is back in business 🙏👍

thank you once again

ALF