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
Greetings all :-)
A strange problem on my 4002 occured:
Pressing 'Start' the carriage moves towards the record but the carriage motor stops after about moving 1.5cm ??
The main drive motor spins, I can even lower and rise the arm ??
Pressing 'Off' - No reaction at all.
If I get the carriage manually to the record start I can lower the arm and it plays from start to finish, lifts the arm but no carriage-return.
I also lost the 22.8V when I accidentially slipped measuring the 22.8V at 1R90....... :-((
Is it possible that either 0TR1 or one of the 4000uF caps got shortened ?
Really stepping in the dark here and would appreciate some expert advise...
Thank you guys :-):-):-)
ALF
Hi all,
Apologies, the 22.8V rails are all present......double-checked again at every point !
But still no reaction when pressing Start, Off, < or. > ??????
Help pleeeease !!
Cheers ALF
Hi everyone,
Let me rephrase what happened, in case it wasn't clear enough:
when On<< is pressed platter spins, carriage moves about 15mm until SO is switched and then stops - platter keeps spinning.
If carriage is moved forward manually to the record start the arm lowers automatically onto the record - it gets played to the run-out groove, the arm lifts, platter keeps spinning but carriage does not return to its resting position.
Are voltages as per SD were verified with the exception of the voltage drop 0.7-0V at
1TR17 when On<< is activated and those voltages from the motor-control table when measuring at MB point.
Assistance is really apreciated ...... anyone ???
Cheers - ALF
Hi Alf,
There are a lot of variables at play. I would start at the servo motor (where the failed functions are not driving the motor) and trace back to the controlling components. When you manually move the transport to where the arm lowers and plays, can you observe/detect the servo motor moving via the tracking control? You have verified you don't have a slipping servo belt, right? Assuming from your post that the tracking motor control is working I would start with the other control circuitry that operates on the servo motor for Start, Stop, Forward, Reverse. It sounds like the control switches are operating since you press Start and the platter motor starts up. That leaves some control path in the servo control being the problem with the tonearm. I'm afraid with this type of problem the solution is to carefully measure and analyze the signal path until you find the misbehaving component(s).
-sonavor
Hi Sonavor (john),
Thank you for you encouragement !
The belt is fine !
When the arm lowers onto the record the servo starts to operate without a problem until the runout-groove is reached !
There are two points where I can't seem to verify the voltages as per SD, one being at point MB and the other as I remember at 1R62 ???
Apart from that I am beginning to think I am turning in circles here ?
Just by looking at the CD thee are only so many paths that make sense to me.......which
Doesn't mean the world:-)
The moment the first switch clicks the carriage motor stops........'as simple as that'
Back to the 'dark-room' !!
cheers
One quick up-date:
1TR28 was faulty - after replacement the carriage moves now across and back !
One small win but now the arm does not lower.....meaning the job is not yet finished.
Cheers
Hello again,
Just reporting back - well, the news are not great ! I have put the job aside and will
Decide whether to part-out the table or have another go ?! This has to be the craziest
Project I has for a long time !
The carriage now moves :-):-) but the arm lowers at the record and lifts at 25cm mark, the carriage stops does not return and the the motor switches off ???
Sorry if that sounds confusing but that is exactly how the problems present themselves !!
One thing really worries me is the 'over-voltage' at 0TR1 collector where it should be
Off 41V/ on 35V/ lowering 31V instead I am getting about 4V more ???? Rectifier or transformer fault possible ?
Be it as it may, I am resting the project for now as it seems I fix one issue another one pops up .......!
Currently the table starts with 33rpm but switches to 45rpm for no apparent reason???
More than happy to get rescue-proposals..:-):-):-)...
hi everyone,
after a lengthy break work has restarted:
working on my BG4002 type 5503 - the one with the AC motor.
what happened in the meantime ?
the carriage moves freely again as it should:-)
a new cap-reservoir has been installed, allowing the main motor running smoothly :-)
solenoid lowers/raises the arm :-)
now the remaining problems:
arm does only sometimes lowers automatically, but mostly at the 25cm mark instead of the 30cm mark or the carriage moves right across without lowering the arm at all.
occasionally it lowers correctly at the 30cm mark though ??
1R35 is the detector am sensitivity trimmer, but how to adjust to what voltage ?
I adjusted that trimmer so 1TR9 sees 3V at the collector ?!! does not seem to help !
the other problem is a speed change from 33 to 45 the moment the carriage returns ??
does anyone has a suggestion what could be wrong here ?
looks like I am turning in circles - not good :-((
thanks guys for light and encouragement
cheers ALF