Kalamazoo bass 30

[Hipnote]

Hi everybody,

I was having so much fun fixing a KC roland amp I broke in a horrible ice slip and fall. ( thanks to you guys was an easy fix) I thought I would try something else? It's good therapy for me since I had a severe concussion, lost my sight the whole awful bit. It's been over a year now, sight slowly came back, but still having some difficulty. Always been a tinkerer so to speak, and want to keep learning at my advanced years lol.
So here it goes:
Kalamazoo bass 30
Has sound but weak sound level.
Noticed preamp tubes cool to touch and not much light.
Speakers test good
Appears to be lots of new parts inside. I am going through a schematic and checking for correct values and connection.
Would really like to learn some diagnostics on this old amp.
Any guidance will be treated with utmost respect.

Thanks so much!

Without music I would be blind still.

[52 Bill]

There are many things that can cause a loss of volume, so you need to start by trying to figure out what section of the amp is causing the problem.

The most common problem would be the tubes. My recollection of that amp is that it has a few odder tubes than the typical Fender amp. If you have the schematic, post it here and we can all refer to the same things.

Unless you have access to another set of tubes, you might want to start with the power supply. If you feel that you can safely measure voltages, start by reading the main dc power supply voltages and the ac filament voltages.

What sorts of equipment do you have access to? If you want instructions on how to do these tests, just ask and we can give you specifics.

[Chuck H]

I didn't see anything that looked like an official schematic but I grabbed this one which seems decent if it's accurate.

[g1]

If the tubes are not well lit and cool, start by checking the heater voltage.