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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 17th Jan 2020, 12:24 pm   #1
112stereo
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Join Date: Jan 2014
Location: St Albans, Hertfordshire, UK.
Posts: 95
Default Bang & Olufsen Beocord 5000 type 4923

I have just acquired one of these machines from a charity shop for next to nothing as a non worker.
It looks great with no marks anywhere so I thought I would take a chance with very little to loose.
Having taken the case off all the belts have turned to mush, it's what I expected.
Purchased a new set I can't find anywhere that shows you how they fit.
Capstan obvious and the counter, but the third not a clue.
Anyone changed these belts and kept a photo?
Another point is the tray won't open automatically or close, the belt here seems ok and if operated the pulley manually the tray seems free !
I have a service book for it and the voltage on the motor is low so trying to check that out, but any suggestions would help.
The manuals mechanics have been drawn so no actual images hence not being able to work out where the third belt goes.
Have included a couple of photo's.
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Old 22nd Jan 2020, 5:37 pm   #2
112stereo
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Join Date: Jan 2014
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Default Re: Bang & Olufsen Beocord 5000 type 4923

Have now fitted all new belts and it works and sounds great, never heard my tapes sound so good........amazing.

However, the draw still won't work.
I am thinking that when the draw is moved it sends a small voltage to the chip which activated the draw circuit.
I have checked all I can and all looks ok, I suppose it could be the chip its self, I have no way of checking without a scope which I no longer have.
Does anyone have any ideas ?
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Old 24th Jan 2020, 5:09 pm   #3
DMcMahon
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Default Re: Bang & Olufsen Beocord 5000 type 4923

In
Quote:
Originally Posted by 112stereo View Post
Have now fitted all new belts and it works and sounds great, never heard my tapes sound so good........amazing.

However, the draw still won't work.
I am thinking that when the draw is moved it sends a small voltage to the chip which activated the draw circuit.
I have checked all I can and all looks ok, I suppose it could be the chip its self, I have no way of checking without a scope which I no longer have.
Does anyone have any ideas ?
Am not familiar with the 5000 so cannot offer much of real use. Been having a quick look at the 5000 (but model 4716) on my mobile which is not easy.

This shows there are 2 active low control signals "Tape deck in" and "Tape deck out", these drive the motor via transistors.

The control signals connect to pins 13 and 12 of 1IC1 which is the 40 pin 8048 microcontroller chip.

So I would expect the "Out" signal to go low and the "In"
signal to go high when Open is requested and vicer versa for a close request. I see from the User manual a close request is done by selecting Open again when deck is open.

You could monitor these 2 signals with a DVM set to DC volts (this assumes it is practical to access 1IC1.

I cannot easily see how the 8048 determines that the deck is open or closed, there is some sort of protection circuit control at pin 6 but don't know how that works.

The Open button itself goes to pin 31 but this is a strobed signal so you might need a scope to see it changing state properly.

Last edited by DMcMahon; 24th Jan 2020 at 5:30 pm.
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