SOLVED: Brown Betty Issue. No sound.

Loxton

Member
Hi, I'm having an issue with no audio when engaged.
The volume pot and trim pot has a scratchy audio when turned.
Led4 lights up when the trim pot is fully counter-clockwise.
Led3 lights up when turned 1/4 turn - fully clockwise.
I have audio up to IC2 pin 2 and 7 then nothing after that.
R14 was removed and retested great but no audio on the left side of it. No audio at C9.
Replaced IC2 with same results.
I replaced the trim pot with the same results

I'll re clean the board and get some more info and pictures.

See IC readings in attachment 20220518_194855.jpg 20220518_200433.jpg
 
We still need to make sure there is no "extra" connection to IC2-2.

Power off. Remove IC2, set TRIM to minimum (full CCW) and then measure the resistance from pin 1 to pin 2 on IC2's socket.

I see cold solder joints on the BASS & GAIN pots. Pin 1 of the TRIM is also suspect.

First, INSPECT everything. Then reflow the suspect joints.
 
That's all good. It appears we do not have any missing connections to IC2.1, but we might have an extra connection to pin 2. Carefully inspect around IC2, R13, R14 & the TRIM pot. Look for conductive debris trapped under IC2's socket.
 
That's all good. It appears we do not have any missing connections to IC2.1, but we might have an extra connection to pin 2. Carefully inspect around IC2, R13, R14 & the TRIM pot. Look for conductive debris trapped under IC2's socket.
Yep, pull IC2 & do Continuity test between Pins 1 & 2, 2 & 3, 3 & 4, 5 & 6, 6 & 7, 7 & 8
 
If you can't see anything around R14 & C9, then you'll have to remove the trimmer to see if the short is hidden underneath. Exhaust all other possibilities before removing the trimmer. Do you have a spare in case the trimmer does not survive the removal process?
 
I had already removed the trim pot, R14 and C9, inspected and replaced them before I started asking for help. I'll remove them again, do some digging and report back later. Thanks a bunch for all your help.
 
Back
Top