[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

 

[alf]

Thise measurements are as follows:

C3+  = 28.8 VDC

IC1  In=112 mVDC,  G=0, Out=0

3TR5. E=0.130 VDC , C=0.220 unsteady jumping, B= 0

just an observation:

looking at the PS board of BC5500 I see a jumper in series connecting the track coming from rectifier to Input of IC1 instead of a resistor (R11?)

this board looks exactly the same as the one for the BC7000 except no jumper but R11?

ALF

 

 

[alf]

Sorry about the double reply – the last one is the one that should be there.

ALF

[alf]

Had another look at the PS to see why the 5V regulator isn’t getting enough voltage at its input.

there is a resistor R11 about 1MOhm (?) which can’t be found in any of the circuit diagrams listed and I begin to wonder if that resistor is actually out of spec, showing about 6VDC on the entry side and next to nothing at the lead up to the regulator input?

was the circuit diagram altered for the BC7000 model ? Martin might know ?!

looking at the IC7805 spec sheet its input voltage should be 7 – 25 V, so R11 would act as a input voltage limiter for IC7805 , correct ?

ALF

[alf]

Had another look at the PS to see why the 5V regulator isn’t getting enough voltage at its input.

there is a resistor R11 = 22MOhm (?) which can’t be found in any of the circuit diagrams listed and I begin to wonder if that resistor is actually out of spec, showing about 6VDC on the entry side and next to nothing at the lead up to the regulator input?

was the circuit diagram altered for the BC7000 model ? Martin might know ?!

ALF

[alf]

Ok, strange things but:

I replaced the 5V regulator for good measure but it does not get any decent voltage input nor would it then deliver the required 5V.

the 1.5ohm resistor at the transformer measures spot on.
The voltage at D3/D4 is about 28.8VDC and D6/D8 is about 6.1VDC which is a new development.

I also checked for injured tracks – all seem fine but I can’t work out why the 5V regulator isn’t getting enough ??

ALF

[alf]

Ok, time for a confession ?

i do remember the marking on C3 = 2200uF was confusing but I thought I read it correctly…..no, I did not as it turned out and put it in the wrong way. That was the reason of many blown fuses in the power-pack. That is  ow rectified after going over the whole board once again.

measuring on the power-pack across pin 1-2 = 6 VAC and pin 3-4 = 22 VAC.

at D3-D4= 29.8 VDC but at D6-D8 = 0.7 VDC which can’t be right ?!?!
Could this point to a leaky diode ??

I tested D5 to D8 but all tested ok quasi off-board. Well, in the end I had a nice day !

still, I am getting basically nothing at the pins on P2 or P3…..in other words, more help

is badly needed…..definitely no StandBy dot visible.

ALF

[alf]

i used the deck for years  mostly  with cassettes, recorded from a radio program.

during those years I owned the deck which is part of my 7000 system.

i say it AGAIN:

every component has been tested off-board from the PS-board…no adverse  findings.

C3 has been replaced just recently and meets its spec.

don’t have the circuit diagram in front of me but I presume C6 is on the PS board – yes, tested at 9.1uF. and dto all rectifier diodes………

don’t i need two different DC voltages -two rectifiers, remember !!

ALF

[alf]

The PSU does not see the drive as P2 and P3 are disconnected as the link to

the rest of the deck – in other words it should not matter

ALF

[Author]

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