tube amplifier low volume

tube at low volume

I recently took my tube guitar amp to a repair shop. Whem I got it back the volume level now is a quarter of what it should be. What did this guy do to it?
I live in a rural area and there is nobody to take it to now. The guy that did the work originaly has died. Would the output transformer be the cause?

low volume tube amp repair

If there is no distortion, the transformer is the least likely problem. I suspect that the gain has been changed by replacing a resistor by one of different value.

One easy thing to try is to replace the valves(tubes) one at a time until the problem is fixed or they are eliminated as the cause.

For starters...Hows about providing the Brand and model of the amp...as well.. the tube lineup that it uses.
73's de Edd

It is quite possible that an incorrect tube replacement was made. Tubes are rated for gain with a parameter known as the amplification factor. There are tubes that are very similar but have different amplification factors. For example, the 12AX7 is a popular tube for low level amplifier applications such as audio preamplifiers. It has a relatively high amplification factor. The 12AT7 is similar but has a much lower amplification factor. Therefore, substituting a 12AT7 for a 12AX7 would result in a lower gain amplifier. You need to identify the correct tubes for your amplifier and then compare it with the actual installed tubes. Sometimes, there is a tube diagram inside the chassis. If not, you will need to get a parts list or a schematic.