Uher 4000 Report Monitor

[diapason]

I have a Uher which has a blown transistor on the motor control board. A radio engineer friend has looked at the machine, but can't identify the transistor as it is too badly cooked Does anyone know where I can get sight of a circuit diagram to enable us to identlfy the transistor, or, alternatively, buy a motor control board from a scrap machine.

Nigel

[Skywave]

Originally Posted by diapason

I have a Uher which has a blown transistor on the motor control board. A radio engineer friend has looked at the machine, but can't identify the transistor as it is too badly cooked Does anyone know where I can get sight of a circuit diagram to enable us to identlfy the transistor, or, alternatively, buy a motor control board from a scrap machine.

Nigel

Yes - I know that machine - I used to use one regularly - but I can't help you directly with your need.
However, I have come across problems like this myself, and my approach - although not guaranteed to get the item working - gives you a fighting chance.

Trace out some of the circuitry: establish if it is an NPN or PNP. The vintage of this item makes a power FET extremely unlikely. Also have a check if there are any diodes in parallel with the collector-emitter junction - they may have blown - ditto, diodes across the motor.
What type of case is it? TO-3, TO-126, etc. For obvious reasons, you want to replace it with one of the same case style.
This narrows the possibilities of a suitable replacement. If the PSU rail is of the order of 25v or so, and a TO-3 is required, a good starting point would be to try the ubiquitos 2N3055. If a TO-126 case - or similar - a check of transistor specs. in the TIP range should suggest something worth trying. If the PSU rail is of the order or 50v or more, choose a transistor with a high Vce and a Ic max. of about 5 Amps.

For test purposes, hang the transistor off the board on wires - the pcb will only take so many "attempts" - and besides, it's much more convenient to tackle this problem using this "experimental" method by doing this.

Don't overlook the possibility that you might need a Darlington - albeit unlikely. If the motor seems sluggish to respond, this could be the cause (inadequate current gain in this application).

Finally, there is the Q. of why did the transistor fail? A faulty motor winding is what obviously springs to mind. A quick check of its resistance plus a "visual" of it will help here.

And good luck with it!

Al / Skywave

[igranic]

There is probably a good chance that the motor control board is similar to that used in the Uher 2000 Report L; the motor and chassis seem identical in the models I have seen.

In which case, the transistors could be either AC151, AC153, or BC108/BFY39.

On my circuit diagram (which seems impossible to scan effectively due to the background colour):

T10, T12, and T14 are AC151

T11, T13, and T15 are AC153

T16 and T17 are either BC108 or BFY 39

HTH

[roffe]

Your 4000 Monitor(a later model than the Report) probably has Si transistors.The circuit is essentially the same,but the transistors have all been replaced by modern silicon types.You'll find three BC212A(npn),three BC369(pnp) and two BC238B(npn)in the same locations as the old ones.

[diapason]

Very many thanks to you all. I'm not a technician, so will pass your advice on to my friend who is, and, hopefully he will be able to fix my recorder. I've got, and use regularly, and older Report-L which I have used recently for Broadcast work. Until such time as I win the Lotto and can get a Nagra, my Uhers will remain invaluable, so I'll be pleased to get this one (given to me as a dud) working.

Regards,

Nigel

[mitajohn]

Hi,

The attached image, I believe, it would be very helpful.

[diapason]

Many thanks, John.

I'll get a copy to my friend who's working on the machine. The support and information on this forum is amazing!

Regards,

Nigel

[James B]

And to resurrect an old thread... I need circuit info for this machine too! In particular I need to know the pinouts of all the DIN connectors, so that we can connect line and mic inputs and line/headphone outputs to one!

Can anyone help out?

Thanks,

J

[Tom_I]

Originally Posted by James B

I need circuit info for this machine too! In particular I need to know the pinouts of all the DIN connectors, so that we can connect line and mic inputs and line/headphone outputs to one!

DIN connectors were (supposedly) wired to a standard, so unless this machine has any "quirks", the normal pinouts should be OK. Here's a link which shows the pinouts for a 5-pin 180-degree plug, which is the one normally used for audio connections.

Tom

[mitajohn]

Hi all,

Here are scans from an old schematic, but you have to translate the pin's assignment from the circuit.

[James B]

Yes, it's the unusual 8-pin ones we were wondering about. I expect the mic socket carries power on the extra pins for electret mics. Thanks guys!