JENSAMP-51X (Germanium Mic-Pre by Darius Kubarth)

[andre tchmil]

finished mine , sounds good , but I have loud clicks on every gain step.

Did you install C7 as recommended?

OK, will try first thing in the morning.



By the way, C13. Is it me or do I see that one leg on the PCB is open ?
I have REV03 boards.

 

[[silent:arts]]

finished mine , sounds good , but I have loud clicks on every gain step.

Did you install C7 as recommended?

OK, will try first thing in the morning.

should fix it

By the way, C13. Is it me or do I see that one leg on the PCB is open ?
I have REV03 boards.

look closer 
one side is connected to the top layer ground plane

 

[andre tchmil]

By the way, C13. Is it me or do I see that one leg on the PCB is open ?
I have REV03 boards.

look closer 
one side is connected to the top layer ground plane
[/quote]

Yeah , found out myself :-[
Was a bit late at night

 

[zmgwg]

Hey Volker, what would be the first thing you'd check for a unit passing no sound at all? I got a little click when I hit the XLR->HI-Z switch, thats it. Lights work. Thats about it. I have one unit working beautifully. I've checked the parts, all looking right. I re-flowed all the solder joints. Next I think I'm looking at a bad part or two. Any suggestions?

same problem here - no signal.. led's on all the switches work [I didn't do polarity switch, jumpers in place of relay are correct].
I did use different transformer on output. any ideas?

Winetree, you said you got signal after switching C7, you meant for the first time from the original polarization or second time around?

 

[Winetree]

I had sound both ways and times. It didn't fix the posted problems.
I shelved this project as of my last post Dec 2010
However SILENT Arts did sent me those new transistors that I haven't installed.
I'll try to get these back on the bench next week. Good luck to us.

 

[canidoit]

Do these sound like the Chandler Germanium pres?

Can these easily be converted to normal 16volts power for a lunchbox?

 

[zmgwg]

I had sound both ways and times. It didn't fix the posted problems.
I shelved this project as of my last post Dec 2010
However SILENT Arts did sent me those new transistors that I haven't installed.
I'll try to get these back on the bench next week. Good luck to us.

maybe It's some bad parts. when i tap around the output meters move a bit but nothing when i do the same with input.
I used some resistors values that were close enough in my opinion, but it can't be the reason of unit not passing sound right?

Do these sound like the Chandler Germanium pres?

Can these easily be converted to normal 16volts power for a lunchbox?

I think chandler is based on something else, and I have no idea if the fact both use germanium transistor will make them similar
you can convert from +/- 16 to +24 but theres no room for that.

 

[[silent:arts]]

Can these easily be converted to normal 16volts power for a lunchbox?

no

 

[[silent:arts]]

maybe It's some bad parts. when i tap around the output meters move a bit but nothing when i do the same with input.
I used some resistors values that were close enough in my opinion, but it can't be the reason of unit not passing sound right?

do you have a scope to look where the signal disappears?
no sound at all (even no noise?) isn't one bad part.
you substituted the output transformer with which model?
are you really sure your jumpers for the polarity relay are correct?

 

[zmgwg]

maybe It's some bad parts. when i tap around the output meters move a bit but nothing when i do the same with input.
I used some resistors values that were close enough in my opinion, but it can't be the reason of unit not passing sound right?

do you have a scope to look where the signal disappears?
no sound at all (even no noise?) isn't one bad part.
you substituted the output transformer with which model?
are you really sure your jumpers for the polarity relay are correct?

I have used ed's 1166-500 [no zobel yet, but it should pass signal], there is output starting from transformer output [so polarity jumpers are ok] also starting from transformer input [ so transformer is ok]. It doesn't matter if it DI or Mic [so it's not input transformer]. taping gain resistors or switch contacts also gives some noise so I guess there is signal flow there and switch is ok.
I use rev2 and I got it with traces cut, could it be that cuts are not deep enough?
I have +24 and +48 and those read correct values coming in to pcb. LEDs light up.
All the caps have right polarity.
Gain switch at max and there is not even noise coming out.
unfortunately I don't have a scope ... :/  <ashamed>

 

[3nity]

Didnt know one can use a 1166 type transformer on this JEnsamp...???

 

[shabtek]

what if you remove the transformer and probe for signal after c11...that would eliminate the chance that the transformer is wired incorrectly

 

[zmgwg]

that was my next guess to maybe change transformer for a diferent type, but maybe I'll just remove it and see what happens.

 

[3nity]

Yeah you could use a any 600:600 transformer.
Thanks.

 

[[silent:arts]]

Yeah you could use a any 600:600 transformer.

no

 

[zmgwg]

so I disconnected output transformer [also tired a different transformer] it still doesn't work even when trx bypassed.I figured out wiring after lundahl footprint: in pin1 pin4 out pin7 pin 11 -is that correct?
when it's off output xlr connections are responsive, when it's on not. power supply [jlm trex] is ok.
can it be bad gain switch? [grayhill ].
all transistor cases read some voltage except for asy26, is this normal? resistors around it: r13 doesn't show voltage, r2 and r10 no voltage on one side.  so I've checked grounding - it seems to be ok. [bad resistors or something else around it? I've chcecked and soldering is ok]

edit: now Q4 and Q6 also don't read any voltage, could there be a problem with grounding?

 

[3nity]

Isnt the LL1717 a 1:1 transformer 600R to 600R?
Thanks.

 

[[silent:arts]]

Isnt the LL1717 a 1:1 transformer 600R to 600R?

It is 1+1:1+1
In the Jensamp it is wired:
- primaries parallel
- secondaries serial

 

[zmgwg]

@[silent:arts] in 1517.pdf there is drawing of lundahl "Suggested use" is this is how it's connected on pcb?
if so connecting 1166 primaries to said 1517 pins and secondaries to according 1517 pins should work? [with other 1166 series connections done externally]
I still have no signal...

 

[zmgwg]

...it was bad gain trimmer