Home » VintageKustom.com » Repairing Kustom Amps » 1974 Kustom 1-b bass amp (fading notes are distorted)
1974 Kustom 1-b bass amp [message #26982] Thu, 20 September 2018 19:54 Go to next message
Hugh Andrews is currently offline  Hugh Andrews
Messages: 4
Registered: September 2018
Junior Member
Dug this amp out after many years of none use and it had 2 problems. 1) popping and crackling 2) and each note fades distorted (buzzing) at any volume. I replaced the electrolytic caps with 4700uf 50v caps instead of the 1900uf 40v caps as per suggestions from this forum and that solved problem #1. Notes are loud and strong, but as they decay it's distorted.I tried different guitars and cables. I disconnected the amp from the speaker and drove the speaker with another amp. It did not distort. So the problem is not in the speaker or cabinet. Does this sound like a a problem in the power section or the preamp? Or possibly the transformer? Also I cannot find a schematic. Any suggestions?
Re: 1974 Kustom 1-b bass amp [message #26984 is a reply to message #26982] Fri, 21 September 2018 05:56 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4272
Registered: June 2004
Location: NY
Senior Member
Hello and welcome!

Sorry that your post could not be loaded right onto the site, but we have been getting very heavy spam ( daily ) as of late and needed to make a change where new members first five post need to be approved first by a moderator.

What are the PC numbers on the circuit boards in the amp?

From what I have seen of pictures of this amp it looks like the preamp board might be a PC 5066, or 5067, as this is where I think your issue now is.

The power transformer has nothing to do with your issue at this point.

[Updated on: Fri, 21 September 2018 07:10]

Report message to a moderator

Re: 1974 Kustom 1-b bass amp [message #26985 is a reply to message #26984] Fri, 21 September 2018 09:01 Go to previous messageGo to next message
Hugh Andrews is currently offline  Hugh Andrews
Messages: 4
Registered: September 2018
Junior Member
Hey, totally understand the precaution. The preamp board is PC 5128 REV2. The power board is PC 5131 Rev 0.
Re: 1974 Kustom 1-b bass amp [message #26987 is a reply to message #26985] Fri, 21 September 2018 16:37 Go to previous messageGo to next message
Hugh Andrews is currently offline  Hugh Andrews
Messages: 4
Registered: September 2018
Junior Member
The PC5128 is indeed very similar to the PC 5066/67.
Re: 1974 Kustom 1-b bass amp [message #26994 is a reply to message #26987] Sat, 22 September 2018 16:38 Go to previous messageGo to next message
Hugh Andrews is currently offline  Hugh Andrews
Messages: 4
Registered: September 2018
Junior Member
This was way too easy! It was just a 100 ohm resistor way out of whack on the power board. Ordered an ESR meter to check the caps. Oh well, I'll probably need it on another project.
Re: 1974 Kustom 1-b bass amp [message #26996 is a reply to message #26982] Sun, 23 September 2018 06:16 Go to previous message
stevem is currently offline  stevem
Messages: 4272
Registered: June 2004
Location: NY
Senior Member
Good news to hear!
Previous Topic: Frankenstein L795 RV issues
Next Topic: K 100 8
Goto Forum:
  


Current Time: Sat Apr #d 17:27:55 EDT 2020
.:: Contact :: Home ::.

Powered by: FUDforum 3.0.9.