Hoffman Amplifiers Tube Amplifier Forum

Other Stuff => Solid State => Topic started by: dpm309 on November 20, 2021, 02:01:31 pm

Title: Washburn VGA30 Humming
Post by: dpm309 on November 20, 2021, 02:01:31 pm

Have a Washburn South Side VGA30 with a loud humming problem. Cleaned jacks and pots and getting a loud humming with nothing plugged in and all controls at 0. It seems to be coming from the PT. Getting sound and normal volume with a guitar plugged in. I have not worked on many solid state amps and am wondering where to begin?

Title: Re: Washburn VGA30 Humming
Post by: shooter on November 20, 2021, 05:05:27 pm

begin with a schematic


PS, whether tube or SS does basically the same thing, clean, regulated DC to the amp
knowing what the DC values compared to good, as designed, makes life easy.

Title: Re: Washburn VGA30 Humming
Post by: dpm309 on November 20, 2021, 11:04:34 pm

Have not been able to find a schematic for this or any Washburn amp. I'll start poking around and get some voltage readings in the power supply.

Title: Re: Washburn VGA30 Humming
Post by: PRR on November 21, 2021, 12:06:43 am

> schematic for this or any Washburn amp.

The SX30 is online: https://elektrotanya.com/washburn_sx12_guitar_amp_sch.pdf/download.html

This is a very basic chip-amp. Simple power supply. I do not know what a "VGA" is, but if similar +/- some frills, the SX12 plan will give a start.

Note that the main power supply is same-as most tube amps, just a fraction of the volts. If you understand how AC volts relate to DC volts, you can figure if the main cap is working or punked-out.

Title: Re: Washburn VGA30 Humming
Post by: dpm309 on November 21, 2021, 10:58:29 am

Thanks for the schematic. This gives me a starting point to determine where the excessive hum is coming from.