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K150 Repair Question [message #26453] Tue, 09 January 2018 18:28 Go to next message
mrchadsaylor is currently offline  mrchadsaylor
Messages: 1
Registered: January 2018
Location: Las Vegas, NV
Junior Member
Hello all! Just acquired my first Kustom and I'm very excited to get it up and running 100%. This is the 4x10 K150 with the built in Trem/Vibe and Reverb. The right side High and Low inputs work perfectly however, the left side High and Low have the same issue. When plugged in and turned on there is no output other than an annoying distorted buzz until I turn on the Intensity knob for the Trem/Vibe. Once I do this I have some output, not even half as loud as the right channel and the Treble, Bass, and the rest of the knobs, except the volume, work as they should. I have checked the PC1500 board and the pots are all testing fine as well as the resistors, diodes, and caps are testing normally. I was thinking it could be a transistor and testing ruled that out as well. Any ideas!? Thanks in advance!
Re: K150 Repair Question [message #26454 is a reply to message #26453] Tue, 09 January 2018 21:17 Go to previous messageGo to next message
Messages: 1843
Registered: April 2003
Senior Member
Welcome to the place.

If you turn off all of the effects Rev and Trem is there any sound? If you turn on the reverb and turn it all the way up and then shake the reverb tank do you get the sound of the springs rattling through the speakers?

The signal goes from the inputs to the preamp volume control, then the trem/vibrato and then the reverb and finally to the tone controls. Both of the effects are switched electronically, so if any of the switching transistors are bad it could cause the signal to drop out.

How did you test the transistors on the board? The first few input transistors all always the first thing to check.
Re: K150 Repair Question [message #26455 is a reply to message #26453] Wed, 10 January 2018 06:07 Go to previous message
stevem is currently offline  stevem
Messages: 4027
Registered: June 2004
Location: NY
Senior Member
Please note that this amp and the K100 4-10" model uses a lot of FET type semiconductors which can not be checked like a regular bipolar Transistor .
I had one fail in my own K100 4-10 model a few years ago on that same channel like yours'

If you find you need to replace any of these be sure to use the proper anti static procedures!

Post script.
The only place I have ever found bad resistors in a Kustom amp has been in the output or driver stage, never a preamp stage, this may save you some time on the repair work !

[Updated on: Wed, 10 January 2018 07:21]

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