This amp came to me to be repaired and if possible modified to sound nicer.
Problems it had included popping noises and hum. Opening it up revealed a nicely laid out eyelet board with through-hole components which was a bit surprising (this amp is made in China and costs way under 200€!).
First I took out old tubes and re-soldered all tube socket connections. Many times these have cold solder joints or just loose wires. Next I cleaned all jacks and pots. Re-tubed it with Tung-sol 12ax7 (+tube cover) and JJ 6V6S and tried it out; no pops or hum. Sound was a bit muddy (as before) but had more punch than before.
Decided to modify the tone stack and use better components for increased articulation. I used Mallory 150’s and silver mica caps and 1W carbon film resistors. This amp uses similar tone stack as in Fender Blackface amps.
Here are the values I used:
C6 Silver Mica 250pF/500V
C9 Mallory 150’s 100nf/600V
C10 Mallory 150’s 47nf/600V
C14 Mallory 150’s 22nf/600V
(less mud, more articulate)
(mid scoop from 800hz->500hz)
Much better :) The guy who owns this amp says it compares very well to his Fender Princeton! For the price this amp is a bargain and there is also an “Ultra” version available with more features (effects loop, more gain, etc.). Very mod-friendly amp so you could transform this into something else if you want to :)