[hcraig244]

Mark

Thanks for the detailed explanation above, your bang on with the LDR / Aperture Sensor Drift in the Control Panel being responsible for the issue….and following replacement of the lamp and both LDR’s (changed them out as I was in there anyway) as detailed above, the set appears to be working fine. I still need to set the carriage travel sensitivity, as I have disturbed the original setting during the work carried out, will need a cartridge fitting to complete this…..watch this space ;¬)

Craig

[hcraig244]

Belt replaced with new one and re-assembly commenced, had to think about this as its a while since I took it apart ;¬)

 

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[hcraig244]

Replaced the lamp box cover and connected the control box up…powered up and with a disc on the platted hit start, everything operated correctly, the platter spun, tone arm moved the drop position, and it dropped onto the disc, with no cartridge so I hit pause and the tonearm lifted and waited for the next instruction..,,I adjusted the LDR adjusting screws and managed to get them both to around 560mv (should be around 600 to 700) so we’ll see…..it may be due to slightly different LDR’s fitted? however when I operated >> and << everything worked fine….so I’m calling this a win!

Just need to replace the carriage drive belt on this, replace the double sided tape on the wayward panels, set the carriage travel sensitivity once we have a cartridge fitted and this is done (famous last words I know)

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[hcraig244]

Separated the control panel PCB from the pushbuttons and de-soldered the two LDR’s and the lamp, soldered in the new components…the new LDR’s are smaller than the originals however I’m confident they will function correctly.

 

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[hcraig244]

New components have arrived….decided to replace the lamp and both LDR’s

 

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[hcraig244]

Lampbox cover back off…..the voltages at P5 pins 4 and 6  840mv  and 630mv respectively….and the pickup moved nicely across the platter and returned to rest….looking good.

New lamp and photo cells is my conclusion…unless anyone has anything to add? maybe replace the lamp alone would be enough?

Craig

[hcraig244]

Lamp box cover back on, adjustment screws would all the way out and could not get the voltages at P5 pins 4 and 6 below 1,5v and 960mv respectively…and the pick up moved its usual 2cm and actually did wander very slowly further in…

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[hcraig244]

However I was astonished to see the platter spinning and the pick up marching happily across the deck and back!

I have a very bright flourescent lamp above the workbench along with the desk top magnifier lamp, when I turned off the magnifier lamp the unit still functioned as above, when turning off the flourescent tube the pickup arm moved to the drop area and held up there….I will try later with the lampbox cover in place to see if it can be adjusted but having seen the above I’m thinking a new lamp with more lumens will be required, and in doing so i feel the photo resistors should be replaced at the same time….any advice Mark/Dillen?

 

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[hcraig244]

Connected the control panel back up with the cover still off the lampbox to view the operation of the lamp itself…I know these old incandescent lamps go off in time, and when I powered up sure enough the glow was a little subdued

 

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[hcraig244]

And again with the desk lamp switched off, again not very close but I’m encouraged by the change in resistance from lamp on to lamp off.

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[hcraig244]

Removed the cover from the lightbox and with a meter checked continuity across the lamp….all good, checked the resistance of the LDR’s with the light from my desk lamp on and got the following readings…not the same but they should be ok?

 

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[hcraig244]

Happy with the encoder signals from the drive carriage im looking at the forward/Reverse Scanning Sensors (Control Panel LDRs)..

not the best image i know, existing wisdom tells that if the voltage goes high at either P5 pins 4 or 6 a high signal will be fed to I1C pin 31 thus disabling the pick up arm after approx 2cm travel…..just what I’m getting

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[hcraig244]

And if I’m not mistaken someone has carried out a full recap too…

 

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[hcraig244]

Ok…..gone to full service position now!

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[hcraig244]

is there a problem with the site today? can’t seem to post pictures?

• This reply was modified 2 weeks, 5 days ago by hcraig244.

[hcraig244]

Right……measured the voltage signals above at R10 & R11 on the Beogram that is functioning normally, drive belt removed to enable the encoder wheel to be turned by hand, and the voltages measured are the same…0-2.9vdc so its looking very like the encoder circuit is working fine?

Craig

[hcraig244]

When I measure the voltage at pins 4 and 6 of plug P2 and turn the encoder wheel by hand I measure between 14.3vdc and 0,7vdc suggesting that the photo diodes are functioning correctly…however the measurement at the input to uIC1 taken at R10 &R11 respectively only returns  0-2,9vdc as I rotate the encoder wheel by hand….I suspect this is low and should be nearer 0-5vdc?

Craig

[hcraig244]

Further to the above I am measuring 1.24vdc at pin 7 of plug P2 (IR Diode power supply) which would indicate that the diode is fine…will hook up my scope and see if i’m getting the required pulse’s from the pins 4 & 6 of plug P2

[hcraig244]

Mark

This morning I have performed the same test with the platter in place….same results, pressing STOP instead of >> has no effect, the carriage remains stationary 2cm from its start point, the platter continues to rotate until I manually drive the carriage back to the start position upon which everything closes in the normal way.

Craig

[hcraig244]

Cheer Mark

I have now placed the 3rd and final BG8002 in service position and following a visual inspection of the carriage servo motor belt and confirme everything looked like it was sitting in the right place i pressed play….motor spun, screwed shaft rotated and the pick up arm moved inward for about an inch and stopped dead…I was able to return it back to the start position using >> button.

The platter turned and all lamps appeared to be functioning correctly, I repeated the above several times and got the same results….I’m suspecting the optical encoder as per one of Rudi’s blogs so will need to get the scope out and look for signals across R10 and R11 I should get the square wave outputs…….assuming all is well?

 

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