Preamplifier's universal input board building info/support

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trancedental

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Igor said:
OOPS... Anyway, refer to CBE printed on PCB, it is right.

There's no CBE on my PCB board but I'm assuming (wrongly) that for the PN222A  the Emitter  is fitted at the top towards the Mic i/o as per the "half moon" transistor  shape marked on the PCB? It's going to the 100K resistor & 24V supply? 

I know I'm just a newbie (plus my brain is starting to hurt)  but the schematic says the emitter goes to the relay & D2? Or have I lost the plot? LOL!  :mad:

Disclaimer the attachment to this post is wrong but that is what I originally used, do not refer to this layout!!!! Use layout link at start of thread!!!!
 

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alexc

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I had a problem here too. Can't remember exactly what it was, being some time ago.
I blew some PN222 until I figured the problem out. Then perfect.

I seem to recall there being a problem with the pinout

Suggest check and recheck PN222 placement.

I'll have a look at it again and see if I can remember the exact issue.


 

trancedental

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Hi alexc,

So the collector goes to the 24V voltage & the emitter goes to the relay & D2 junction, thats what the schematic says?

The PCB I received has the T4 "half moon" shape around the wrong way so the PN222 needs to be upside down, collector towards the 24V voltage / mic i/o side of the board.

The layout link posted at the start of the thread also has the T4 shape around the wrong way but the EBC appears to be the right way around as per the schematic. The collector is towards the top of the PCB / mic i/o going to the 24VDC voltage & the emitter goes to the D2 & relay junction. So the PN222 goes upside down compared to the T4 "half moon" shape!  ;D

I had an old layout saved which had the EBC opposite to the layout linked at the start of the thread  which has confused me even further see my previous post (& attached file  :()



 

alexc

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Yep - the PN2222A transistor on the relay coil has a datasheet pinout different on the pcb


It should be mounted upside-down

ie. with the crescent shape in the opposite direction to that on the silkscreen.

My pcbs don't have a revision that I can see, so check yourself on your pcb
The emitter pin goes to the relay coil, and the base pin (middle) goes to both R12 and R13
The remaining collector pin goes only to R12.

I found out the hard way : built up a few before testing!
 

Igor

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The c-b-e printed on PCB is correct; you're right, too; I used 2n2222 in metal package, as seen on photos.
 

alexc

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I've been using my Igor Preamp Universal Input pcb with my acoustic guitar+piezo  a lot lately  ...

Sounds fabulous!

It goes to the mic input transformer (Jensen) I added to a Noetek channel which I racked up along with a JLM opto compressor.

My favourite acoustic guitar direct channel by far !


Cheers
 

duantro

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Ditto 3, I could use some of these for sure. Has anyone heard back? I know Igor has been enduring a huge move.
 

Nele

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I mailed him a while back and if we would need more than 6 he would do another run. I think that shouldn't be a problem...
 

alexc

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I have 2 of these I'm not going to use.

They are the 'parts kits' from igor. One is unpopulated, one is partially populated.

PM me if you are interested

Thx
Alex
 

duantro

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I picked up a couple of these and wanted to double check. It seems like I remember Igor labeling things differently. The values on c1 and c2 are 100uf, correct?
Thanks.
Edit: Thanks AlexC for confirming them as 100uf.
 

andre tchmil

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I'm assembling one of these boards , works fairly good but I have a high pitched sound in the background.
I used a BC560 instead of the BC214.
Any idea ?
 

hape

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Dec 4, 2008
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I got two of these kits from Igor about ten years ago and finally managed to get them to good use in my two channel EZ1290 project. Everything works fine except for phantom and phase reverse, they both just cut the signal. 48v from the power supply to the input board is fine. Since both channels have the same problem I thought maybe there is a mistake in the schematic of the revision I have or something. I got the pcbs and parts all from Igor so they should be fine. I tried to email Igor but his email didn't exist anymore; some googling lead to a facebook post telling he had died last summer :(

Any ideas anybody?
 

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