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Author Topic: Improving Gefell UM92  (Read 22572 times)

D9sus4

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Re: Improving Gefell UM92
« Reply #30 on: March 27, 2008, 10:15:24 pm »

I would also love to hear an answer to that question regarding finding a replacement PSU for the UM92. Where do I find one, considering Oliver thinks the Gefell OEM PSU is "crummy"? How about a good schematic and a parts list.

Also, the schematic that Oliver posted is for a 6-pin connection, wheras the UM92 and UM92.1 have seven pin connectors.

-Dave

P.S. I have a copy of the schematic, sent to me by Gefell, for the UM92S (not the UM92.1). If anyone needs it, email me. I can also email some photos I took of my UM92S after the first "simple" mod suggested by Oliver (direct wiring the transformer to pin 3).  
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Oliver Archut

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Re: Improving Gefell UM92
« Reply #31 on: March 28, 2008, 08:59:55 am »

Here are two pics, the first one the UM92 stock, the 2nd one is modified with reference to the schematic. For any owner that wants to do it please be aware
!!!!!You will void you warranty and you need a good tech!!!!!.
The head assembly needs to me mechanical changed as well as the PCB.
PSU there is currently no aftermarket PSU that I could recommend.

index.php/fa/8316/0/
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Oliver Archut
www.tab-funkenwerk.com

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Oliver Archut

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Re: Improving Gefell UM92
« Reply #32 on: March 28, 2008, 09:03:54 am »

 The schematic posted was drawn over the CMV one, the UM92(.1) uses a seven pin and you need to change the pin hookup to 92 specs.
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Oliver Archut
www.tab-funkenwerk.com

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D9sus4

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Re: Improving Gefell UM92
« Reply #33 on: March 28, 2008, 09:21:59 am »

[quote title=Oliver Archut wrote on Fri, 28 March 2008 12:59]Here are two pics, the first one the UM92 stock, the 2nd one is modified with reference to the schematic. For any owner that wants to do it please be aware
!!!!!You will void you warranty and you need a good tech!!!!!.
The head assembly needs to me mechanical changed as well as the PCB.
PSU there is currently no aftermarket PSU that I could recommend.[end quote]


Oliver, thanks for the photos

Can you clarify what you mean by "head assembly needs to be mechanically changed as well as the PCB"?

Lastly, if there is no aftermarket PSU that you can recommend for the UM92, then why do you suggest that we replace it? Replace it with what?

Thanks, Dave
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Oliver Archut

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Re: Improving Gefell UM92
« Reply #34 on: March 28, 2008, 10:36:04 am »

Gefell uses a three post quick connection hookup for the head, the front capsule is grounded, so in order to change it over to a better working M49 style remote, you have to disconnect the ground lug, and hard solder the head assembly in order to make it work.

PSU? I replaced the one I did with custom made ones, not commercially available. Sorry....

Best regards,
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Oliver Archut
www.tab-funkenwerk.com

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Klokkern

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Re: Improving Gefell UM92
« Reply #35 on: April 13, 2008, 07:27:29 am »

Hi again

I haven´t changed the transformer yet, but the Telefunken tube is in place, and I have tried it on several sources since I swapped. All I can say is that the difference between the original tube and the Telefunken NOS tube was beyond expectations. The mic sounds more open, more defined, simply put a lot better!!

So to anyone out there with a UM92, swap the tube! The difference is well worth the $100...

Best regards,
LarsK
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Sredna

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Re: Improving Gefell UM92
« Reply #36 on: October 13, 2010, 04:37:37 pm »

Oliver Archut wrote on Mon, 03 March 2008 04:21

The UM92 was build upon request of the former Gefell US distributor G-Prime. However it was nothing else than a slightly modified UM57, only difference was the output x-former that was taken from the MV amplifiers. Aside the low grade metal composition, the core was/is not able to get any resolution an M7 requires.



Do you mean that UM92 has an x-former from MV691/692 (BV130)?
The BV130 is considerably smaller than Bv
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Klaus Heyne

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Re: Improving Gefell UM92
« Reply #37 on: October 13, 2010, 04:47:44 pm »

Transformers may have been changes out, but the circuit is virtually identical to that of the UM57.
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Klaus Heyne
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Sredna

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Re: Improving Gefell UM92
« Reply #38 on: October 13, 2010, 05:06:24 pm »

Yes, that I understood.

What interests me is if they used a x-former meant for transistor output and what consequences it has for the sound.

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