About
Sometimes, you can get a little lucky. While walking about the neighborhood one night, I spotted this amp on a curb tucked in with some other waste. A paper sign was taped to the amp that read “broken” on it. I figured this was quite the find and thought I’d take it back with me to see how broken it really is – and worst case, if there was anything worth salvaging in it.
I wasn’t very familiar with these amps. After some digging around, these seemed like reliable, affordable, 2000’s-era gigging amps for acoustic-electric guitars. It packs two 40 watt power amp sections that drive two 8 inch drivers and a high-frequency tweeter horn. It has an instrument and a mic channel that can be used independently and also comes loaded with a bunch of on-board DSP effects.
I plugged it in as soon as I could and noticed that nothing seemed to power up. Further investigation showed that the fuses were gone, so I replaced those, but the LED never came on. The amp did ‘thump’ to life however, so I knew it was on. For about 5 minutes of noodling around it seemed like nothing was too out of the ordinary until a deep hum started to overtake any instrument signal in the amp. The volume knob didn’t seem to have any effect on the hum once it started so it seemed like there may have been some issues in the power amp.
Luckily for me, this amplifier is solid-state and incorporated familiar parts. After poking around, I noticed a few red flags. Some capacitors could use replacing and it seemed like there was a short where it looks like some liquid got into the amp. After some closer testing, I noticed some voltages were off at a couple test points based on a repair manual I found online. I decided to replace the mosfets in the power section as well as some capacitors, the LED, a couple of faulty potentiometers, and the chips responsible for the power amplifier’s output – just to be safe.
Once everything tested green, I decided to upgrade the 8 inch drivers to some Celestion TF0818’s I grabbed on sale and I also upgraded the little tweeter horn with a TPT-DH150 horn. I don’t know much about acoustic amps, but this thing sounds awesome and the digital effects really make it stand out. I’m glad I grabbed this weird little amp.
Process Documentation
