ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Some friends of mine really liked my Bang & Olufsen stuff... so much so, they adopted my Beomaster 1900 and set out to acquire a Beogram 4000 series. They obtained a cosmetically great Beogram 4002 from the original owner and it arrived very well packaged in an undamaged box... BUT.....
Upon an initial inspection it looks like it had a rough ride at some point! The question mark shaped PCB #3 has been shattered, apparently by being struck by the lower platter.
As the Beogram is in very good cosmetic condition, it seems a shame to scrap it over one small and simple Printed Circuit Board. So, after extracting the remains and gluing them back into the correct shape I scanned it into my computer and set about creating a stencil for a new B&O P/N 8005019 . A little time spent etching and carefully cutting the board to size and...
A new and very much stronger PCB 3 made of FR4! Try to break THIS one!
Put it all together and test it to see what else is wrong and... no action from the record detection light but the platter motor spins, the tangential drive operates, the lamps for the speed displays and arm tracking all work.
No power to the record detection light was a shorted 6.2v zener diode. Replace that and the failed record detection bulb and....
the PNP Darlington for the tonearm solenoid operates exactly once and fails shorted!
Replaced Zener diode 1D16 and Darlington 1IC4 and now the record detection and solenoid circuits operate! Electrically, the Beogram is fully working. But the mechanics are sticky and way out of adjustment.
So, disassemble , clean lubricate and adjust the tonearm mechanics, then disassemble the platter motor, extract the sinstered bronze bushings and re-infuse them with oil under high vacuum... sorry, didn't take any pics.
Next, I took out the main circuit board again and got rid of the little red time bombs, oops, Tantalum capacitors, noting that several had crept up in apparent value over 20%. One electrolytic had gone completely high in ESR at 26+ ohms, and the four 1W carbon composition resistors were visibly degrading from the outside with an odd smell, and creeping up in value, one at about 30% high.
The restored board, almost done,
Put the board back in, turned it on, it worked perfectly!
Set the platter speed, tangential tracking voltage and sensor voltage pot adjustments with no issues.
"Downgraded" the output from the previous "upgraded" RCA jacks back to a DIN5 connector, plugged it into their Beomaster 1900 and played some records.
Yay! another repair adventure draws to a close!
¡No entiendo Español!
NEIN! Nicht Versteh!
Я немного говорю по-русскии но не очень хорошо... и
I'm not very good at English either! Maybe someday I'll find a language I'm good at?
What a great job!Well done sir.
I think I'd apply some laquer to the pcb to protect it though,and also replace those axial blue Philips electrolytics on the main pcb,which are probably past their best.
Wisdom after the event I guess,and "if it aint broke don't fix it"?
A lucky find in such good condtion indeed,and well sorted
Enjoy
Nick