[alf]

Hi Chris,

many thanks for your reply….sounds like I have done everything correctly ?!?

yes, the newly designed idler came from Beoparts, not ebay !

you are right, that little felt tip of the brass tongue is missing – I had ordered a replacement….but fitting that tiny thing turned out to be unsuccessful, instead I used some similar material. That should not cause the issue I would think.

yes again, the new belt came from Beoparts ?

sounds like I have to get back to the 1203 and do some further searching…..but I am running out of ideas…..so, keep them coming please.

regards

ALF

[alf]

Thanks Filip,

my thoughts precisely – nice to see the carriage moving correctly again.

always interesting how many challenges this table can throw at you……

ALF

[alf]

Hello Christian,

thank you for your reply – very sorry to say you just missed out on a 10/10,

But a  9/10 for inspiration isn’t too bad either I thought ?!

I did check that 1cm track under the magnifier, than clean that short track with a fiber glass pen as well and still did not see any damage…..which sidetracked me.

assuming that there may be a wire issue further on stopped me for now but thanks to

you I simply connected a short wire jumper between SI and C of 1TR20…..success ??

and now the platter starts at 33rpm as it should.

many thanks again ?

ALF

 

 

[alf]

Tested the mentioned transistors – off board ! – and both tested fine.

obviously one other (or more) component(s) is faulty as this issue was not a gradual decline but appeared suddenly.

at this stage I want to rule out a contact issue as the table performs normal once the carriage has moved in via FE to its drop-down point.

ALF

 

[alf]

Thank you for your input, I will test those two transistors.

just a brief recap:

i verified 6V at The C of  1TR20, but when measuring the SI on the mainboard the max I see is 2V ?

i assume this is the signal 3IC4 is receiving ?
it seems the logic has locked-in the 45rpm as the platter starts only with 45 when ON is activated.

the components of the SI circuit are working ! The. Platter motor adjustment is another matter but should not interfere with the start-up of the carriage, moving in !

i hope my explanation didn’t lead to misunderstandings here.

any help is most welcome ?

ALF

[alf]

Hi,

i revisited the adjustment of the platter motor as the table seem to have 45rpm locked in ?

yes, I can operate a speed change manually, but….

adjusting the motor as per SM I set all trimmers – 4VR1/2, 1VR1/2/3 – in their center position.

I can adjust the corresponding  33rpm voltage at about 15V at 42Hz, 45rpm at about

15V at 53Hz – not 59Hz as the training manual suggests.

checking the SI signal I should see 6V after a 10ms delay…..what I am getting though

is just under 2V which is obviously far too low……but why ????

6V are present at the suppy, 1TR20 measures fine 1C15 is 10uF / 16V – no 6V cap at hand.

the 24V supply is on the low side at about 23.4V ?!

would really appreciate some input

thanks guys

ALf

 

[alf]

Hi Christian,

refer to the service manual page 5-7 explosion drawing:

remove motor from the turntable by unscrewing from its 3 anker points and disconnect.

take off idler wheel (one thing less to worry about)

take off the cover – item 184

separate stator from the motor – item 177

remove motor bracket, held in position by 3 rods and secured by one nut – item 164

that frees up the rotor and its bottom bearing – item 178

remove and replace bearing with its oil-soaked felt ring after cleaning.

hope that gave some idea how to remove the bottom bearing

ALF

 

[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

[Author]

Posts