[hcraig244]

“The first is at the base of 1TR14 and the collector of 1TR17”

Looking at the schematic I dont see a point showing a scope reading at the collector of 1TR17 ?

[hcraig244]

The main forum product section contains manuals for the BG4000 and also some training notes donated by a member who was a one time repair engineer who went on a training course and reatained the course notes…..these notes identify the abbreviations and are a very usefull guide…..they are available to silver members and above, take a look…..do you have a transistor tester available?…….seems like your machine is only a short way from being sorted…..

[hcraig244]

Is the platter spinning with the tone arm over the rotating ribs in the scope readings?…..looks like it is….so the photovoltaic cell looks like its still working, good news.

Are you sure the readings are taken at the points you identify above? and as the tone arm will drop under some conditions then the solenoid and associated linkages/damper pot etc are all working, more good news.

I think the potentiometer you refer is the one installed to enable playing transparent disks? does the tone arm stop at the correct place when a disk is played….or just run to the left side then run back to the rest point?

Craig

[hcraig244]

Had a look at the leaf spring contacts and they look clean, gave them a squirt of Deoxit non the less…..once dry I will re install the control panel and try it again….I do recall having issues in the past once the panel screws are tightened down, i think if they are not evenly tightened they flex the PCB causing erroneous signals…….

[hcraig244]

Well……..got to this today, removed the control panel for a visual inspection and all looked fine, ran her up and she works perfectly?…….

[hcraig244]

Martin

Whats the best way to do that?…..

Craig

[hcraig244]

Alf

The service notes say “speed switching (33-45rpm) is performed by altering the values of R1 and R2 so that the oscillator frequency will be approx 42 and 59hz respectively” seems to me if everything works fine on 33rpm that the oscillator is working fine, could be wrong of course…….have you checked the trimmers and associated solder connections?

Craig

[hcraig244]

All reassembled and functioning flawlessly………very odd. However I will fire her up again from time to time and see if the issue returns…..I still suspect a sticking switch or switch nipple on the control panel.

Craig

[hcraig244]

Send me a picture ?

[hcraig244]

Dillen (Martin) from this site is your man……he can supply the correct lamps for you, send him a line.

 

[hcraig244]

Just spotted this post justin, picked up a chest infection from soewhere ;¬(

The tone arm dropping sharply sounds like not enough dampoing, try winding the srew in very slightly…..and I would check out the down switch contact…..if its playing up the tone arm will dot stay up when ^ is pressed

[hcraig244]

You may consider checking out diodes 1D8/1D14 also, you could also try exchanging the inboard drive transistors with the outboard drive transistors one at a time and testing as you go….if it is a failed transistor you will get to a point where you lose inboard and gain outboard travel.

I invested in one of these…….it has been a very usefull tool over the years, can test transistors and diodes

[hcraig244]

Found this in a 2012 – 2022 archived post “justins BG4000”

Powered up and this is what transpired:

unit sat powered up with no actions
upon hitting Start the platter drive started up at 33rpm
the panel ilumination lamps came on
the 33rpm speed selector lamp cam on
However the transport drive motor didn’t run, I could change the speed from 33rpm to 45rpm but no other functions responded. Time to look at the circuit diagrams……

This is what I found….the following components where shot:

 

1D11 Diode
1TR33
1TR31
1TR30
1TR32

All of the components on the opposite side of the motor tested good.

 

[hcraig244]

Read on through section 3.21….this gives a full description of the three functions associated with the drive for the transport system, you should be able to test the voltage levels at the associated transistor points when the control panel switches are operated, the notes are a little truncated and “solder ron” may be able to fill in the missing information as they where kindly donated by him.

Craig

[hcraig244]

Sorry…..i misunderstood your problem, didnt realise everything was fine when playing a record.

[hcraig244]

[hcraig244]

Ok…..check this set of switch contacts also…I know i keep banging on about switches but if nothing else you will eliminate them from the search. If these contacts dont operate your motor wont operate as a servo, the contacts should open when the solenoid energises.

[hcraig244]

Ok…..start by checking the switch contacts on the carriage transfere mechanism, sounds like this unit has been stood idle for a while, they are a little awkward to get at but sounds to me they will need cleaning even if they are not responsible for your problem. Dont adjust any of the position screws.

Craig

 

[hcraig244]

Dont force it…..let it soak, WD40 isn’t popular on this site (I think the popular term for it is snake oil ) De Oxit is the cleaner of choice, however i would go for something like 3 in one penertrating oil…..leave it overnight.

Craig

[hcraig244]

A very high percentage of problems experienced with these decks result from switches, either on the control panel or the transport slider. A switch out of position be it open or closed will play havoc with the boolean logic control gates, I have chased my tail for weeks trying to locate a problem that turned out to be nothing more than an intermittent sticking contact on a transport slider switch……an issue that had been identified as a possible cause by Dillen at the outset….however as it was intermittent when I tested the switch it worked fine…turned out that the silicone grease i had blobbed onto the plastic nipples (which I thought would help keep them free) was causing them to bind due to the viscosity……thorough cleaning and has worked fine since…….I’m rambling I know ;¬)

Craig

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