[alf]

I guess it would have been tricky to explain……the good news is: i worked it out myself.

isn’t that nice ?! ???

ALF

[alf]

Hi Craig,

adjusting 1VR3 in combination with fine adjusting the 33 & 45 trimmers dud the trick.

if you listen to the motor noise you get a good feel when its right.

and thank you Martin, I feared there was more serious stuff to investigate…..

its back to working order ??

ALF

 

[alf]

Thanks Martin & Christian fir replying.

Yes, with the “finger-test” I can feel the motor vibrating but not spinning at 45rpm.

Question is what course of action I have to engage with ?

ALF

[alf]

thanks Tim,

exactly the guy I was after ?

contact has been established !

ALF

[alf]

Thank you so much for letting me know – that is good news ???

enjoy – regards, ALF

[alf]

I did replace 1D20 as it tested very different from a new ZDP one.

the uP supply is 5.12 VDC at P6-1 which would allow a tolerance of 2.5% for the regulator.

still, no StBy dot present. I “reinforced” the pressure of the two flat connectors that plug into the P6 connector to make sure there is proper contact.

i am sure some of you have been at a dead-end and that is where I am at the moment.

no issues found yet with missing continuity, the DC voltage after the rectifier looks normal and yet no StBy dot, meaning no turn-on possible.

yes, I had very briefly the StBy dot and the -/+15 supply but something must have died? Lets hope it is not the uP.

Without turning on the BG I won’t get any reference voltages (except the 5V line) which may point to other problems ?!

it might be best to shelf the BG again to “free my mind” and start again some other time.

thank you all who have been on board with pointers and suggestions, very much appreciated.

ALF

[alf]

Hi John,

i thought I actually did answer your question ??
Yes, the black wire to 7P1 is always connected.

i did reflow the connection at 7P1 and at the uP and there is continuity.

how likely is it though that the multivibrator chip on board 7 could have issues ?

as being the “controller” of the uP or did I get this wrong ?

i lost count how often I did check the various connections such as the P6 connector for instance and its two flat-connectors which to me sit rather “loosely” in that connector, slipping out quite easily. I very slightly altered its angle to make it easier for the flat connectors.

its been years ago when I purchased that BG and honestly can’t remember whether it was partially or not at all working – too long ago ?

i wish I’d know where this is going from here……..but not giving up yet !!

ALF

[alf]

Ok, back on the job but no good news so far.

in the meantime the 5V supply played up, getting up to 6V for reasons unkown ?

so far I have tried half a dozen 5V regulators and the best one delivers still too much

at 5.3V. The question I like to through into the round is the uP getting damaged or simply won’t work when supplied with 5.3VDC at P6-1 ?

I also ckecked 7TR1,2,3 & 4 – all tested fine. the uP connection to 7 P1 has continuity and I also checked the ground connection to uP Pin 15 – all fine.

as John pointed out there’s still no turn on without the StBy dot which totally puzzles me.

is the uP faulty or is there something else fishy on the uP control board 7 like

7IC1 = CD4528 or 4098 ??

seriously, there has to be an explanation…….

ALF

 

[alf]

Hi John,

that black wire is & was connected. I just have reflown its connection points on the add-on board as well as in the uP box.

again, I briefly had the StBy dot, the table turned on when play was pressed with the carriage moving in a short distance but I could not turn off – I also briefly had the 15V supply.

it is obviously as you suspected a connection issue of a kind, just finding it. I do remember one of your comments from way back about the importance of the correct adjustment of the << and >> function (630mV?). anyway, there is more investigating to do.

Again, thank you very much for lending your expertise trying to help ?

ALF

[alf]

Hello John,

many thanks for your clarifications.

please bear in mind the BG is missing its StBy dot in the display – so I am pretenting

the BG is in StBy mode when connected to mains.

there is definitive continuity from P6-4 to pin 38 on IC1, soldering looks good

and the measurement from P6-4 to pin38 of IC1 is exactly the same as from its flat band connector to pin38 at IC1.

continuity from P6-4 to Base of 1TR21 is verified.

whenever I press play the voltage of that signal remains basically unchanged from

0.72 VDC.

i know, what you are saying is correct but I don’t know yet why its happening.

are there any other potential players in the game ? I tested TR21 off-board ok, so is should not change things just by replacing TR21.

what voltage should I expect at P6-4 without pressing play and what when pressing play?

is it possible there is a issue with the keyboard ?? But The StBy dot should be present

with or without the keyboard connected, right ?!

ALF

 

[alf]

Ok John, here is goes:

Thank you for confirming the 25 VDC at the rectifier ??

continuity from 0TR1 directly to either -/+ of 1C28 is confirmed.

i did not connect the scope to either P6-4 or 1TR21: StBy or Play showing identical voltage of about 0.725 VDC when measured.

P2 – 8: 24.2VDC StBy= Play

P2 – 9: 21mV StBy, 16mV Play

P2 – 10: 24.2 VDC StBy = Play

1TR21 B : 0.725 VDC / 0.720 VDC StBy/Play

C : 49mV / 51mV StBy/Play

E : 0 / 0 V StBy / Play

P6-4 about 0.72 VDC

are these measurements providing us with some further pointers ?

ALF

 

[alf]

Well John,

this one looks like a very tricky rescue. Frankly, I am running out of idea what else to measure or check.

sadly a repeated wiggling of P2 did not delivery a desired result.
The connection between P2 and 0TR1 is fine, all grounds checked fine as well as continuity between points of -/+15VDC and their involved TRs, Ds and Cs.

i understand there has to be a reason/source of the missing -/+15VDC lines. i even lifted the uP to make sure it sits properly in its socket – no impact.

whether the voltage of +/- 25VDC after the rectifier is fishy I am not sure.

fact is I have the 5VDC supply, P6-1 gets 5.06VDC which should make the uP happy.

a long distance analysis is always tricky and I really appreciate your input……just

-/+15 V would be nice to start ?

ALF

 

[alf]

Hi again,

so far I spend probably a couple of hours (incl. some needed breaks ) with various magnifiers to scan across the main board in search of broken tracks…….nothing to see !

going back to the elusive -/+15VDC search:

At the anode junction of 1D21/D24 I get about -25.3VDC, at the cathode junction of

1D22/D23 I get about +25.3VDC.

after having tested the involved TRs and Diodes to produce the 15V lines without any adverse findings I really have arrived at a dead end …….!

what kind of AC voltage should I see at the junctions 1D21/D222 and 1D23/D24 ???

unless the board has suffered a particular nasty almost invisible hairline fracture it looks even more like another shelving exercise ?

so far only once very briefly have I been able to see the -/+15 VDC by giving P2 a serious wiggle – that was when I suspected a connection issue but…., that is only good if it can be reproduced which I can’t , no matter what.

the usual question, where from here -Shelf of Multimeter ??

ALF

[alf]

Hi again,

i have tested all previously mentioned transistors inc. D25/26…..all tested fine – that’s the good news but still no +/-15 supply.

P2-9 sees about 25VDC. That kind if voltage I see at 0TR1 as well, no surprise here.

I am afraid John your worst “fears” seem obvious: I found 1 cracked track so far but it is a very tedious undertaking to find more.

there is definitely a connection issue after fiddling with P2 the table suddenly sprang into action.

i tried to minimise the degree of bent in the PCB by slightly shifting the uP box backwards but sadly that didn’t have an impact in terms of restoring function.

looks very much like getting the magnifier glued to the eye ball again……..

there is no point replacing 0TR1 as it tested ok – i also did check for OL but nothing showed up so far……

will get back shortly

ALF

[alf]

Hi John,

its been quite a while but from memory(?) this was probably one I eventually shelved to be looked at again as other (easier) projects came in……

i know, that PCB is pretty terrible and not that flexible as it showed in various examples.

all those transistors I mentioned must have been tested off-board before but will be looked at again after I have taken out the board again plus without the Standby Dot present I would not expect to be able to turn on the Beogram anyhow.

will get back with further findings – thanks again for helping ?

ALF

 

[alf]

Hi John,

thanks for your input.

Looking at the circuit diagram, the +15VDC should be taken care of 0TR1/1TR18/1D25 and the -15VDC by 1TR19/1TR20/1D26.

the 5V regulator produces 5.06VDC which is also present at P6-1, so that’s ok.

As for the -\+15VDC I am only getting about +/-25.06VDC which is also present at P2.

it looks as I have to dig out TR18/19/20 and D25/26 for testing ?!

0TR1 = TIP32 tested ok with hfe=138.

ALF

 

 

[alf]

I am trying to follow the 12V entry for the drive, which I should measure at p16-4…..

but nothing anywhere near it.

I should also see 12V at the “emitter crosspoint” of TR37 and TR38…..nothing again.

both Transistors have been tested off-board as ok which made me believe I should actually see the 12VDC at that crossing or shouldn’t I ?!

i can see the entry voltages – 14.1V & 15.5V – at R171 and R172 …..so, what is it that I am missing here and why isn’t the capstan getting the 12V either.

the drive unit looks like being hard-wired to the control board #2.

ALF

 

 

 

[alf]

Is your glass cover broken or just scratched ?

i still have the glass cover – it is good but not mint.

please send a PM so I can mail a photo and you decide them.

ALF

[alf]

i will have a second look at the colour rings of that resistor but the 4…..? could

indeed be right ?!

lots of other corners to check – the drive itself could have issues as well, although the capstan runs if fed by the benchtop dc power supply.

ALF

[alf]

Some minor development:

after the previous measurements it all made no sense. I took out that mysterious R11

and measured it…..OL !! Which explains why IC1 did not deliver the 5V.

i can not identify that resistors value as its colour markings made no sense – discoloured ??

I decided to replace the dead resistor with a 690 Ohm one for now which seemed ok as the BC5500 board just has a jumper in that position.

the display lights up, the drawer closes but shortly after the deck shuts off again.

the drive does not engage……meaning there is still lots more to check….☹️

ALF

 

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