Again a M15a with problems.

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Laurens487
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Again a M15a with problems.

Beitrag von Laurens487 »

Hello reel-to-reel friends,

I've read all the posts for this machine here on the forum but haven't found my answers yet so therefore a new topic.

Allthough I have wanted one for several years now, I recently got a M15a wich belonged to the Dutch broadcasting studios, but sadly with a few problems:

1) The capstan motor doesn't run properly or at all, and if it runs it's very unstable. When it doesn't run, it's like the axle is locked in position by two coils of the magnet because it's very hard to turn by hand. Also sometimes, it does nothing and it's also easy to turn by hand but when you turn it, the light wich indicates the tape speed dims and comes on again with every turn.

2)The counter doesn't work.

3)The stop function doesn't work.

All other functions seem to work normally, like spooling back and forth and when you put it in play mode the spoolmotors engage and everyting is put into place, but since the capstan doesn't run nothing happens.

I've got machine number 5286, so it's a late one as I understand, and I do have some schematics and experience repairing taperecorders, but I can use a little guidance as where to look.

I want to tackle the capstanmotor problem first so here is what I have checked so far:

- From the supply darlington MJ-3300 only come 19 V. even with adjusting the BC-TR11 card.
- When the motor runs the TIP130 darlingtons become very hot and something starts smelling awefully
- When the motor doesn't run the TIP130 darlingtons stay cold
- All fuses are the correct value and none are blown.

So all in all a very long openingpost and if something is not clear just ask!

Any help is appreciated and thanks in advance,

Laurens.
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cavemaen

Re: Again a M15a with problems.

Beitrag von cavemaen »

Hi Laurens!

You have the last Series from AEG Telefunken M15A. This Series has bad Power-Transformers, please look at all Voltages from Transformer comming!

The MJ300 makes +24V for Capstan, your Engine have 19V? Input 28-30V, out 24V.

I have two M15A from this Series (No. 4800 and more) with Transforker failure in 30V output!!

You want a Transformer from the better Series?

Rudy
Laurens487
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Re: Again a M15a with problems.

Beitrag von Laurens487 »

Hi Rudy,

Thanks for the quick reply! I will check the voltages and get back to you about the transformer, so thanks for the offer!
Laurens487
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Re: Again a M15a with problems.

Beitrag von Laurens487 »

Hi Rudy,

I measured all voltages coming from the transformer and they are all ok. So the transformer is not at fault. I did fix the problem of the non turning capstan motor though, it was the wire for the first winding of the motor (pin 12) that came loose from the printed ircuit board. Resoldering solved it. Now I haveto tackle the problem of the non counting counter: do you maybe have some tips on that?
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cavemaen

Re: Again a M15a with problems.

Beitrag von cavemaen »

Hi Laurens,

do you have found all Probrems in your M15A?

Rudy
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Laurens487
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Registriert: Sonntag 6. März 2011, 14:41

Re: Again a M15a with problems.

Beitrag von Laurens487 »

Hi Rudy,

Sorry for the late reply but I've been abroad a few weeks.

No I still have a ton of things to do. I had the capstan motor working but since the last time it now has a new problem: it doesn't start when you switch the machine on. You have to give it a swing with your hand and then it runs beautifully. I've changed two broken TIP130 darlingtons on the BC card and all the BC547 and BC557 transistors wich seemed faulty, but still this problem stays. All the voltages measure good, I've got the 24 Volts on the motor and can adjust with the pots on the card but I can't seem to get the motor starting upon power-up.

Then I have a problem that when the machine is in spooling mode, it doesn't go out of it with the stop button: you have to press the spooling button and the stop button, then release the spooling button and then it goes out of spooling mode.

Also the counter doesn't work at all, it only gives all zeroes and it doesn't count.

Apart from that ;-) , the play back and recording works, the spooling works, the heads are fine and the transformer still gave me no problems, but I don't have a proper manual so getting into all the logics of the machine is tricky.

That's it, I think there is something wrong with one of the sensing coils in the motor. because it doesn't start but I don't know what to measure.

I think all these problems are repairable but since it's the first time I work on one of these, work is a bit slow.
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cavemaen

Re: Again a M15a with problems.

Beitrag von cavemaen »

Now you want a Manual,

Without Manual no Repair.

Today I'm on Holyday, retourn at 11. /12. Mai.

Where do you living? I'm living southern from Kassel in the middle of Germany.

Best Regards,

Rudy
Laurens487
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Re: Again a M15a with problems.

Beitrag von Laurens487 »

I live in a small town in the Netherlands near Nijmegen, and I do have the schematics of the wiring inside the machine but none of the seperate cards so repairing individual cards is pretty hard.

Enjoy your holiday!
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cavemaen

Re: Again a M15a with problems.

Beitrag von cavemaen »

Today i have Holyday at North-See.

A Lot of Cards i have, 7 of M15A and many Parts.

Please send my your Cards after 11th May, I'm looking for it.

After change the Capstan-Card BC-CR11 / CR12 you must testing minimum Voltage at R27 for mininum Ampere of Capstanmotor!

The Power Suply is in order now? You tell me; you missing the 30V AC Power for 24V Stabilizer, is it in order?

Transformer I have!

Best Regards,

Rudy

(Radio-Producer & Engineer)
Laurens487
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Registriert: Sonntag 6. März 2011, 14:41

Re: Again a M15a with problems.

Beitrag von Laurens487 »

Hi Rudy thanks for the offer to exchange cards, but the cards are not the problem, I spent a day of testing and trying with a friend of mine who also has a M15a and we swapped my cards for his and tried my cards in his machine and the cards work, so it's the motor that's faulty.

The power supply is working perfectly, and also the regulator from 30 V to 24 V for the motor is ok. So if I need any new parts it would be a motor. But money is a bit tight richt now.
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cavemaen

Re: Again a M15a with problems.

Beitrag von cavemaen »

Hi Laurens,

your Capstanmotor have 18V or 24Volts?

Is the Wheel of your Motor free, or make he Problems? Look at the Bullet under the Motor-Screw and take a little fresh Grease.

Is the Frequenty-Generator from Capstan in order?? Please test it with Oszi.

Parts i have.

Next Days I'm coming home from Holyday...

Best Regards,

Rudy
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cavemaen

Re: Again a M15a with problems.

Beitrag von cavemaen »

Hi Laurens,

I'm (refreshed) in my Home.

In my 1st Answer I'm tell you, the 24V DC has an Failure.

Please test the Transformer-Output of 30V AC.

The Transformers of last Series of M15A has Problems, test your Voltage!


Rudy
Laurens487
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Registriert: Sonntag 6. März 2011, 14:41

Re: Again a M15a with problems.

Beitrag von Laurens487 »

Nice to see you have enjoyed your holiday! I will test the transformer and the synchro for the motor this weekend as I don't have the time right now but thanks for the hints.
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cavemaen

Re: Again a M15a with problems.

Beitrag von cavemaen »

Where do you come from?

Take your Machine in your Car to visite me...!

Rudy
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Laurens487
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Registriert: Sonntag 6. März 2011, 14:41

Re: Again a M15a with problems.

Beitrag von Laurens487 »

Hi Rudy, I checked the voltages and the are allright I get 30 V from the transformer and 24 V after the regulator. Also the tacho on the flywheel sends its signal to the card but I have to leave it for a while, because I don't have the money to invest in the machine a lot. Thanks for inviting me to come over but I live to far away for a days visit so that's not doable at the moment.
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cavemaen

Re: Again a M15a with problems.

Beitrag von cavemaen »

... and you testef all Cards in a other Machine??

Please test all Fuses and look at Dirty Connects! Old Fuses are o.k. by Messuring, but no Funktion by Power!

I have 7 Machines with a lot of Parts...

Rudy
Laurens487
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Registriert: Sonntag 6. März 2011, 14:41

Re: Again a M15a with problems.

Beitrag von Laurens487 »

Yes, I tested every card, and resoldered the whole motherboard wich you stick the cards into. Still no luck. I haven't had the time to check the motor for signal output back to the card.
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cavemaen

Re: Again a M15a with problems.

Beitrag von cavemaen »

Hi Laurens!

Now, you have a Machine over # 5000 No. This new M15A has Problems in the Power Transformer, he missing 30V AC for 24V DC !

Please check it or send the Machine to me in Germany by Truck!

Look at the Manual left under the Page; you see the Power Transformer. Please test all Transformer outputs!

Where do you come from?

My City: www.borken-hessen.de


Rudy
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