Home » VintageKustom.com » Repairing Kustom Amps » K100-2 Hiss but no other output (Need help troubleshooting)
Re: K100-2 Hiss but no other output [message #21219 is a reply to message #21198] Tue, 19 August 2014 12:04 Go to previous messageGo to previous message
Jerrybass1955 is currently offline  Jerrybass1955
Messages: 45
Registered: August 2014
Location: NC
Member
An update:

I re-soldered the broken reverb wire and technically it works, but is very very sensitive. I think the springs may be too saggy to give good results. That said, there is a post suggesting increasing the value of R170 rather drastically and I may try that and see what happens. Maybe a trim pot there. But a new pan may be in my future.

I noted that the PS caps are allowing some hum to ride on the supply so I replaced them with 10,000uF caps and the supply is quite solid now and the amp is noticeably quieter.

But ..... since changing out the PS caps, I find that the amp oscillates when you switch it off until it is completely off!!! Very strange!!!

The tremolo still has a tick/thump when turned all the way down. and still goes unstable with speed above about 8. I am going to try upping R152 to 15K and check the remainder of the circuit out more carefully.

In probing and scoping around at random, I noted that there is an oscillation at Q122, but the + and - 8V power supplies are rock solid and if I recall, read 8.4 and 8.5. Gotta look into this further. Maybe a degraded cap in the neighborhood and maybe that is the source of the oscillation when I turn off the amp?

I also checked the value of 8 or 10 resistors and found none that were out of spec. Most were within 5%, so perhaps this amp hasn't seen hard use. Will continue checking as I go.

Any comments or thoughts on any or all of the above will be appreciated. Thanks for helping me get this far.

Jerry

Report message to a moderator

[Message index]
 
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Read Message
Previous Topic: trem-vib distortion on my k150-8 and k100-8
Next Topic: Do I actually have a Frankenstein??
Goto Forum:
  

[ Syndicate this forum (XML) ] [ RSS ] [ PDF ]

Current Time: Mon Jun 03 04:27:10 EDT 2024
.:: Contact :: Home ::.

Powered by: FUDforum 3.1.3.