gefell UMT711s PCB pics

hi Gus, Here are the pics....

www.geocities.com/pepperplace/gef

www.geocities.com/pepperplace/long

www.geocities.com/pepperplace/gefback

As I said before , the circuit is the same as the UMT71 except for the
1/2" round inductor replaces the LP11 section of the circuit.

http://www.gyraf.dk/schematics/Gefell%20MT71S.gif

cheers,
Lance

I get a

The web site you are trying to access has exceeded its allocated data transfer

I will try later.

hey Gus, Are you able to view these or is there a problem?

Lance

I would guess the fet is the noise problem. The circuit has plastic inserts for the High Z points.

I would measure the IDSS of the FET and then find a replacement that has the same IDSS.

I would also change the ceramic cap that is connected to the gate with a polystryene.

hi Gus,

thanks for the advice. I'll be sure to get polystrene in there . I wonder why Gefell discontinued this version and went back to the MT71? In my
spec sheet they claimed the MT711 was an improvement on noise performance over the MT71.

Lance

hitchhiker,

do you have any advice on how to open the mic (and put it together again) without damage? I've got a M71K (precursor, transformer based version) and would like to have a look inside and maybe change a cap or two.

Thanks!

Gregor

Gregor,

There is a tiny set screw that removes the cone shaped piece at the base of the grill. Then a pair of set screws that allows the body to pull away from the grill. And now the unfortunate thing is you have to desolder the wires from the capsule mount pins.It's tight because the wires are very short. After the body is removed from the grill there is another set screw at the XLR end that allows the tube to slide off the end that the grill was.

I'm curious, is your mic a tad dull in the hi end? I was so surprised to hear the extended hi end the capsule produced when I attached it to a G7 circuit.

Lance

Lance,

Thanks! It's a fine sounding mic, but I agree, it is rather dull, too. Maybe replacing a few of the stock caps might just do the trick. At least using a higher quality capsule-to-FET cap should have some impact.

BTW, what happend to the capsule's "midrange magic" in your G7?


Now I have to decide whether I'm attempting to pull it apart... Is it tricky to solder the wires back on? As of now, I haven't even figured out how to remove the small rubber things that cover the screws without destroying them...


Gregor

Gregor,

My attempts to cause changes that I like into preamp circuits have been dissapointing. So I would probably just use it as is. YMMV.

The M7 mid range magic is still very much there when used with a G7 .

That rubber almost seemed like a maluble compound IIRC?

I never put mine back together so I'm not sure how easy it would be to solder the wires back in. With a small solder iron that's able to go into tight spaces would make it doable for sure.

Cheers!
Lance