hherazo

Laney VH100 Modification to reduce Hum noise

Replaced 6VAC heater power to a 5VDC power for first tube in preamp section Installed 100 Ohm 2w potentiometer with wiper to ground in transformer heater output Copper tape installed in cabinet (bottom & sides)

Orange AD30 Twin channel blowing up fuses

Blowing fuses during power up due to intermittent tube rectifier GX34 and the output tubes (EL84) being unbalanced. Also, looking at the thermal image, it can be seen that one of the tubes is running cooler that the others

Armstrong 621 with a dead channel and noisy output

Original problem point to a faulty transistor in the output stage but also found high leakage current in diodes

Japanese amplifier – Guyaton GA10500 from 1988 for service

Recently we serviced a Guyaton amplifier having an overheated output power tube 6L6GC and after extensive troubleshooting we found the problem was in the bias section of the power tube. The tube was running at approximately 300% of the recommended plate dissipation due to faulty decoupling capacitors. Later on, we realized that all the highContinue reading “Japanese amplifier – Guyaton GA10500 from 1988 for service”

Laney CUB12R for service with intermittent problem – If your amp is noisy it’s time for a service

Marshall valvestate VS267 for repair

Faulty -12 volts power supply due to broken PCB pads and poor soldering technique Incorrect resistor used in the +12 volts power supply (270 ohm instead of 180 ohm) Overdrive channel 1 and 2 not working due to faulty operational amplifier in Pre-Amp PCB board.

Frequency response of a Guitar Amp vs HiFi Amp

Have you ever wondered what the frequency response of your guitar amp is? I had the opportunity to fix a HiFi amp (Behringer-Ultratone K450) and recorded the response to a flat input between 20Hz to 20KHz. Later on, I compared it with a Fender Hot Rod Deluxe and here are the differences:

Noisy Fender Hot Rod Deluxe

American manufactured Hot Rod Deluxe received with high level of noise. After a complete service all high voltage capacitors were replaced with brand new F&T capacitors improving noise level (see attached photos).

Fender Paul Rivera 1984 for service

After 36 years it was time to change all electrolytic capacitors. Broken capacitor Broken high voltage tag Broken reverb connector

Fender Vibro Champ with burnt bias resistor

Original report for this Fender was only overheated bias resistor, but after a complete inspection we found so many things to improve an correct in the amp. Untwisted power transformer wiring going to the triode causing noise. Photo ref 1 Wirewound resistor used instead of carbon film or carbon composition. Photo ref 2. Bias resistorContinue reading “Fender Vibro Champ with burnt bias resistor”