Missing components ok, checked pictures from the Internet and compared to Bass 20.

Could someone comment BC184 transistors. There is multiple different variants available mostly with C or B etc. It's harder to get original BC184. What alternatives I can use? Is BC184L identical enough with different pin order?

http://www.mouser.com/ds/2/149/BC184-310135.pdf
http://www.mouser.com/ds/2/149/bc184l-291988.pdf

- Volume pot change did not help
- Every soldering dots, heated once, not help
- C8 ok
- C9 ok
- What about those BC184 transistors?
- I think I will test BC184's and opamp next
- Any Lead 20 owners with inside picture? It would be nice to compare is there same missing ones..

Hi,

Could someone please help I have fully functional Lead 20 with small hum issue.

This is only appears on when volume is between 0 and a bit over 1. Opening volume more, hum is gone. With full gain comes op amp hiss but this is not the case. Gain between 0-9 does not change the hum character. I do not have oscilloscope but I guess that the hum is 50Hz AC hum. It is solid hum without any fequency change. Bass, Mid or Treble does not affect to the hum character.

I like to also know is it normal that R7 is missing and also C7. If this is mod, can you say what kind of?

Already changed or tested:

- New power caps 2200uF/50V
- Tested also with additional 2200uF in paraller with both power caps, the hum does not change
- All small electrolytic capacitors changed
- Bad pots changed
- W005 silicon bridge rectifier changed
- Speaker wiring moved away from AC section
- All components touched multiple times, no changes on humming
- Same situation using low input, hi input or no guitar on input
- Opening or closing guitar volume does not affect to the hum amount or frequency

So what next? Op amp? Those small transistors? Power transistors? Ceramic caps? And could you please comment missing R7 and C7.

What about 50Hz vs 60Hz. This is USA model, there is 60Hz AC? In my country 230V/50Hz.

Thanks!