Ok when you replaced transistors TR19 & 20 did you replace them at the same time? I am wondering if you replaced say tr20, with tr19 being faulty then tr19 with the now tr20 faulty etc...

Other than disconnect the motor and make sure there is no short at the emitters of tr20 and 22 and as Mika says check motor with psu or batteries. Also diodes and transistors could act differently under load...

BTW regards C1 & 2 are they under the motor PCB?

Step1:

Ok when you replaced transistors TR19 & 20 did you replace them at the same time?

At first no. I should have taken Martin's advice (of course).

But then yes! All eight. With the same references.

I insist on the fact that the motor works fine. What else could cause the top left BC142 to fail?

The top-right one (for right-bound carriage movement) continues working fine (replaced for nothing): the arm moves back to the right when I press stop (fast return) or slowly when I press >.

Anyway, after changing the transistors and spending several hours on the problem, the problem remains.

Jacques

The transistors work together in sets of four. If one fails, the remaining three will see an overload.
I suggest you replace them all eight in one go.

There is a H-bridge transistor kit for the Beogram 4000 to repair faults like this, which seems to be more common in the Beogram 4000.
I haven't had time to check if the same transistors are used in your machine but I think so.
However, if you have already sourced suitable transistors locally, you won' t need a kit.

Having a servo motor that works fine one way but shorts the other way is not very likely.

Martin

Perhaps it would be useful to replace the motor with a resistor that is clearly larger than the motor load? Hopefully the transistors would survive, and you could measure if the operation voltages make any sense after that.

I'm waiting for yet another batch of transistors.

The number on my PCB is 80-5016E if that means something. Made in 1980? One of the last ones then surely.

Jacques.

Martin, what's your kit worth?

I paid 5€ for the whole lot.

Dear all,

Success!

Thanks to all who helped me, from the bottom of my heart.

The only thing which is a bit scary really is that I'll never know what happened the first time around... will it happen again?

The arm, after shutter alignment (I had some experience with my 6006 and 8000!), tracks perfectly. Automatic speed change works too.

My remaining problems are:

- the arm which doesn't go up quickly enough (even after lubrication),

- the manual movements which are too slow (this shouldn't be too difficult, there are trimmers).

Let's have a look at the other posts now: homework time!

Jacques

Glad all is sorted :)

Have you cleaned and lubed the angled arm that transfers the solonoid motion to the picup arm? Easy to miss this one I think! The pivot is under the the sensor arm and might be a little stiff...

Oh yes the trimmers are R56 and R57. I highly recomend the manuals for these decks and it is worth joining up for!

Step1:

Have you cleaned and lubed the angled arm that transfers the solonoid motion to the picup arm? 

Well it didn't need to be lubed. 

The deck is in good condition and lubrication was no disaster, except for the main bearing (dry sintered bronze).

Anyway it plays records now, no rumble or hum, just music!

I just think there must be some problem with the damper cylinder, the stylus lifting veeery slowly but the descent being just within tolerance (1 sec.). Insufficient solenoid power an option?

Any further advice appreciated of course!

Jacques

Step1, what name can we call you? After all we are flesh and blood creatures, aren't we?

Jaques you need to remove the platter and press start to watch everything working - Only then will you determine exactly where the slow down is. It is almost certainly down to lubrication at a pivot point. Of course make sure the springs are intact and not stretched especially the main spring between solenoid and damper. However you should see that the damper retracts very quickly with the vertical lever I mentioned above following it!

Also don't be afraid to manually manipulate parts to see things a bit clearer!

Step1:

[...]you should see that the damper retracts very quickly with the vertical lever I mentioned above following it!

That's my point, the damper retracts very slowly when it is free!

Everything is intact, and I do manipulate, and love it! 

The mechanism is lubricated and everything moves freely, except for the damper. Is there a valve that could be obstructed?

Also, I am not afraid putting everything into bits and pieces!

Jacques

Ah ok have you ever had the piston out of the damper? I would do that and clean up then relube..

No, no. The thing is, you just can't relube with ordinary grease, can you?

I have arm damper fluid (polydimethylsiloxane, 600,000 cst) in stock which could be used.

Have you done it yourself?

If so, could you tell me how you (or anybody else here!) did it please?

Many thanks,

Jacques

There is an adjustment screw on top of the cylinder to adjust the air in/outlet rate.
It's usually locked with a bit of locktite or similar.
It's quite sensitive and you will find that the adjustment should be done in
very small increments.

Martin

Hello,

Right then.

After a dozen records, the dreaded BC142 kicked the bucket again! Same symptoms, except that this time it went short-circuit. I say it again, all eight transistors in the H-bridge were renewed, even though the BC 142 (top-left on diagram,  top-right on the PCB) only was tested bad.

After a new replacement, the deck worked again... For one LP!

There is something I don't get here.

The deck was set on 220V, and with 238V on tap, I thought it could be a problem but I doubt it. If anything the transformer will hum a bit more but that should be it.

What do you think?

I am in relation with Martin and Tim Jarman on this, still waiting for some hints to explore.

Jacques

Hello, Me again.

Well I had a clue from Tim who thinks the motor might be the problem. It's a Swiss Maxton DC motor with ball bearings —the spindle turns for ages!

It seemed sealed, but then I saw a small cap at the centre of the red side which, once removed gives access to the brushes!

I cleaned them because they were very dirty. The motor draws 9mA with 9V.

It seems better now but I'd like your opinions before sending yet another BC142 to transistors' heaven!

Jacques

I happen to have a spare motor (admittedly I haven't actually seen it working a Beogram, but it seems to run fine) and it takes 10/11 mA when run with a 9V battery.

BTW with that mains voltage, I'd set the deck to 240V. It sees almost 10% more than specified now. I don't believe that affects this problem, but the power supply probably heats more than normal now.

EDIT: sorry for messing with your post Jacques - I deleted your double post at the same time you edited yours! I restored the content.

Thanks Mika.

You have a private mail!

Jacques

Answered.

The motor has been cleaned, mounted back (be careful, the black wire goes to the + polarity of the motor!) and now playing some record.

To be continued [...]

Isn't that exciting?

Edit: still working after 5 records. No, not 45 RPM !

A dozen LPs later...

The Beogram is still working!

I'm not sure what did the trick but I noticed that changing over to 240v made the transformer hum disappear completely. Anyway, cleaning the motor brushes actually made it noisier!

Keep your fingers crossed!

Jacques

I hope it will stay that way, but keep us posted, the power supply is important, here in Mex. my power goes up and down between 90 and 135 volts, should be 117 V, so I have to work with line stabilizer and nobreaks to all my computers and audio equipment.

Good thread Jaques, thank you

Olà!

Well the 4002 keeps working.

I too hope it will keep that way... keep your fingers crossed! Lots of 'keeps', eh?

Jacques

The servo motor is still reserved for you in case you need to try it later - hopefully not! I've had it in a drawer for more than a year, so it's not like I'm going to need it myself for another week or two