[hcraig244]

Fascinating stuff……I have always thought it best to shy away from this subject due to the test equipment required and also the expertise required to perform it, but would love to learn more and explore the use of the TinySA piece of kit, I do have a BM4400 that has a less than perfect reception.

Craig

[hcraig244]

Couple of things here….firstly take out OTR4 and check it, if this is good you need to look at the power limiting part of the circuit….the set of contacts (those leaf spring contacts again) that need to be closed, thus shorting 7R1 to ground,  when the solenoid is initially activated allowing max current to pull in the solenoid coil before opening up when the armature moves to drop the tone arm…..its possible you dont have a good connection at these contacts..

Craig

[hcraig244]

Yes…..Martin recommends doing this as the transistor does run quite hot, I did this on one of my units that I was having an issue with, didnt solve the problem as that turned out to be a contact issue as previously discussed

[hcraig244]

Martin recommends moving the voltage regulator 2TR6 from the 2 PCB and mounting it away due to heat issues…..I cant recall exactly but I have a feel ing the logic switches state around 0.5 to 2.5vdc and its the IC that supplies the power to “wet” the switch contacts I have a feeling that it all goes tits up if you dont have 4vdc min……

[hcraig244]

Well…..thats that little conundrum solved, shying away from what would be a difficult and expensive undertaking.

[hcraig244]

I’ve just had a look at the video on the b&o website…..and if i’m looking at the right one it yet again identifies the BG4002 or maybe BG2004 deck, none of the illustrations depict a BG4000 deck, is this because of the complexity involved……if one was to send them a BG4000 would a BG4002 be returned?…….I’m confused.com ;¬)

[hcraig244]

It may well be something entirely different, however it only takes one switch to be out of step to create havoc with the logic controls. I do suspect the old timer design engineers decided to create the most complicated deck ever built, integrating complicated logic gates simply because they could…..logic gates that are still in lots of modern day control systems (albeit in sotware format these days)…bear in mind the only thing that opens the switch is the quite light pressure of the leaf spring contact….take a look i nothing else other than to eliminate them from your enquiries

[hcraig244]

Alf

When you say you have cleaned the “those brass contacts” are you talking about the carriage transport switches?

I have had similar strange behaviour on a BG4000 deck that was eating my lunch for days….intermittent faults. Finally traced it to the transport switches (one in particular) and it turned out that the actuating plastic nipple that operated the brass leaf switch was sticking every so often….I had thought i would lubricate these switches with silicone grease to keep them moving freely…..mistake! cleaned all the lubrication off them and everything was fine…..just a thought.

[hcraig244]

There’s no question that it looks very attractive, and that its modelled on a 4002 unit. In my view it lacks the over engineered and massively complicated  charm of a 4000 deck, the boolean logic controlling the 4000 is a work of art in itself…and the delicate reed relay stop start circuit is just so baffling that i suspect it must have been reverse engineered from an alien spacecraft dug up from the gobi dessert ;¬)

And does anyone know what the device is that Eric is injecting the circuit board with is, soldering flux perhaps. Looks like he is upgrading an existing deck from the oxidation on the internals, an old Elco Capacitor and the tone arm solenoid coil looks like it has warmed up the insulation over time…is image 2 the finished article Steve?

[hcraig244]

This could also be a noisy transistor……I have had this problem in the past.

[hcraig244]

Alf

Does the record detection circuit work with the replacement bulb….or are there still issues?

Craig

[hcraig244]

Bernie

this pic shows the failed transformer wiring and measurements from my problematic transformer……the only problem with it turned out to be the low measurement on the 230v secondary output to the neon lamp, the rest of the measurements where the same as those on a fully working machine…..as can be seen the 0.89k should have been 1.3k

[hcraig244]

Have you checked the transformer out fully?….measured the primary and secondary windings to be sure there’s an issue? tried disconnecting the secondary outputs and powering up?…..I did a lot of checks before I finally condemned the transformer due to them being impossible (mostly) to source….and bespoke toroidal transformers being so expensive to commission.

[hcraig244]

this is the final wiring with the load resistor (not shown) wired to the input of the regulator before the small capacitor 

[hcraig244]

Another thing that will help is if you look in the archive forum 2012-2022 you should be able to find the first part of this thread…….may make things clear for you

[hcraig244]

Bernie

Sorry for the late reply…..been a bit busy with work etc. The GL90 neon was connected directly to the incomming 230vac supply down stream of the fuses…..the supply needs to be connected through the reed relay contacts just as it is now (so the lamp only comes on when start is pressed) I think all the parts I used are documented in this post….but if you need any more info let me know

Regards Craig

[hcraig244]

I would also replace ZF18 Zener diode….check the other transistors around the voltage regulator too…..something caused may have caused the SE8002 to short out.

Craig

[hcraig244]

Ok……one thing at a time.

1. For some strange reason the internal wiring which connects the AUX signal DIN to the amp is wired differently to the TAPE input DIN, I found this out the hard way. Connect your signal to the phono plugs instead of the DIN connector for the AUX input and see if you then get sound to your speakers.
2. The Hi and Lo s are latching switches that need to be pushed forwards to engage or disengage….these are used if your input needs to go through the pre amp stage or not…a low signal will need to (I think this is right…..). The + and – trim pots can be set by ear….they adjust the volume of each speaker to balance the sound.
3. I will need more info for this question….and maybe some pics?

[hcraig244]

This is a pic showing the lamp still on the push fit tab

[hcraig244]

You need to take the top off, remove the screws holding the amp PC down….it’s on a hinge so will lift up and can be put into the service position which is vertical. This allows access to the power on bulb, its a push fit onto a tab and can ce carefully pulled backwards untill released, you can then unscrew the lamp and replace it…..make sure you use the propper voltage…I think its 60vdc

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