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Befaco BF-22 build problems. (Solved)
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Befaco BF-22 build problems. (Solved)
erocfx
I built a BF-22 from a PCB and panel. I sourced the parts myself.

It is not working. It does not pass any audio at all on either channel.

Things I checked:

I have +12volts and -12 volts on the PCB. I check at the ICs.
Nothing is getting hot.
I double checked all polarity of diodes and capacitors.
I check for accidental solder bridges and found none.
I checked the audio in HP mode and signal drops off after R21.

Any ideas what else to check?

I am attaching photos of my build. On the daughter board I mounted the large electrolytic capacitors on the back for mounting purposes.

Any help would be greatly appreciated.



creativechaoscom
Some of the Befaco PCBs seem to have inconsistent through hole plating. Looking at some of your resistors for example (R19, R45) it could be that
the contact is simply not made on both sides. I'd check if both sides are good.
OIP
i've had one in the cupboard for a while, was never able to get one side working and since then have another MS20 filter build. but one thing i read and tried was to check the trimmer calibration - there's a pretty decent sweep where you will get nothing out, so have to dial it in first.
erocfx
creativechaoscom, super good suggestion. I reheated all the solder points and made sure they went through. It is still not working.

OIP, I did a double check of the trim pots and swept through them end to end.

Still nothing very frustrating

Thanks for the suggestions!
erocfx
I check the signal path with an oscilloscope and don't even see signal at the first 5532 OpAmp IC1A. On both channels.

The input signal comes in at the LO_PASS_In_1 or HI_PASS_IN1.

erocfx
I suspected the 2N3819s, which I bought of eBay. I sourced them thru Amazon and replaced them. It is working fine now!

Semiconductors from eBay can be a bit dodgy.
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