Vintage Amp Repair

14/05/2023

Laney VH100 Modification to reduce Hum noise

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

05/03/2023

Orange AD30 Twin channel blowing up fuses due to intermitent tube rectifier GZ34 and the output power tubes (EL84) being unbalanced. In the thermal image you can notice one of the tubes running cooler than the others.

05/03/2022

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

09/11/2021

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 high voltage electrolytic capacitors had problems causing not just the damage of the power tube, but additionally tremolo malfunction and noisy signal.

05/09/2021

Scratchy Master Volumen due to contamination/corrosion in potentiometer.

24/07/2021

Laney CUB12r for service with intermittent problem - If your amp is noisy it's time for a service. Signal from Laney Amp with a constant input of 1 KHz "jumping" due to faulty high voltage and bad JST crimping contacts.

15/06/2021

Marshall valvestate VS267 for repair:

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

25/03/2021

Frequency response of a Guitar Amp vs HiFi Amp

Have you ever wondered what the frquency 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:

29/01/2021

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).

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 (s…

02/01/2021

Fender Paul Rivera Concert 1984 for service:
- After 36 year was time to change all electrolytic capacitors.
- Broken capacitor.
- Broken high voltage tag.
- Broken Reverb connector

22/11/2020

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 resistor overheated due to short circuit between Grid 1....

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…