Home » VintageKustom.com » Repairing Kustom Amps » K200B (Lost output)
K200B [message #26029] Wed, 05 April 2017 08:18 Go to next message
stevem is currently offline  stevem
Messages: 4284
Registered: June 2004
Location: NY
Senior Member
Irish77960 had contacted me by pm about a issue with his amp.
He had installed a brite switch in one of the preamp boards that I provided him and things where fine.
While playing the amp he turned it up louder , played more and then heard a loud pop and lost output, but the strange thing is that the pilot lamp was still responding normal to his playing by dimming which is something I have never seen before!

So far in trouble shooting this issue I had him check the output from the amps RCA jack where he said that there is a screaming loud sound coming out if the jack.

My guess at this point is that one of the preamps is oscillating.

Irish77960 , at this point we neeed to pin down what's going on , and I would say that the thing to do is to unhook the Blue audio output wire from each preamp one at a time to see if atleast one channel is working normal and report back.

[Updated on: Wed, 05 April 2017 08:20]

Report message to a moderator

Re: K200B [message #26032 is a reply to message #26029] Mon, 10 April 2017 17:06 Go to previous messageGo to next message
irish77060 is currently offline  irish77060
Messages: 48
Registered: January 2017
Location: Atlanta, GA
Member
Steve,
Sorry it took me a minute to get this done. So, I plugged it in and turned it on before performing any of the tests. Dang. It worked. Plugged in a bass and sound from all channels. The light still dims a little when a note is hit, bit I could not recreate the same scenario I wrote you about. I'm baffled. There is a good amount of hum, more than my other K200b, but all channels, all tone adjustments, and bride switches working. This amp, along with another that Bill has helped me with are possessed.


Keep On Truckin'
Re: K200B [message #26033 is a reply to message #26029] Tue, 11 April 2017 06:03 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4284
Registered: June 2004
Location: NY
Senior Member
The input jacks on all Kustom amps have a built in shorting switch such that when nothing is plugged into the jack, but yet the volume on the channel is up there will be no added hum from the amp picking up its own power transformer hum, or the same from Floresent lighting .
When you plug a cable end into the jack the switch opens up and signal can then pass into the preamp.
Your should clean + lube this switch section of each jack.
I do this by wetting up a a thin scrap of plain card board like from a new Shirt package ( no coloring on it) with contact cleaner and drag it back and forth thru the closed switch.

Next with a wetted up Q tip clean up the ID of each jack and where the tip of the cable makes connection in the jack.

Many times you will be stunned at how much dirt and crap gets removed from the ID section of the jack.
On jacks that have been used a lot it also is good to bend the tip connection back out more because it's the side load on the tip connection that forces the ground portion of the jsck onto the ID of the jack.

If this side loading does not take then you get intermittent conduction, loud crackling and hum out of the amp.

Oh , and yes the amp May need new msin can filters, but report back on this first and then I will tell you how to check the filters out.
Re: K200B [message #26035 is a reply to message #26033] Wed, 12 April 2017 11:02 Go to previous messageGo to next message
irish77060 is currently offline  irish77060
Messages: 48
Registered: January 2017
Location: Atlanta, GA
Member
Black QTips. Lots of crap. Turned it on and the static was gone, just a very low audible hum. Hit a note, was good. Then blew a fuse. A new one in tonight. Luckily I bought a few before starting on these amps!

Keep On Truckin'
Re: K200B [message #26036 is a reply to message #26029] Wed, 12 April 2017 12:27 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4284
Registered: June 2004
Location: NY
Senior Member
Fuses in these amps are soldered in and for a reason, is yours still that way?

If not that's a sign that the amp has issues that likely have not been corrected seing as you blew the fuse, this of course assumes that the fuse that blew on you is the right 3 amp fast blow type.

[Updated on: Wed, 12 April 2017 12:30]

Report message to a moderator

Re: K200B [message #26037 is a reply to message #26036] Wed, 12 April 2017 15:52 Go to previous messageGo to next message
irish77060 is currently offline  irish77060
Messages: 48
Registered: January 2017
Location: Atlanta, GA
Member
Yes, soldered in. And it is/was the correct one. 3.0 fast blow.

Keep On Truckin'
Re: K200B [message #26038 is a reply to message #26037] Wed, 12 April 2017 21:00 Go to previous messageGo to next message
irish77060 is currently offline  irish77060
Messages: 48
Registered: January 2017
Location: Atlanta, GA
Member
Ok, in 40 years of playing through Kustoms, there's a first time for everything. When I desoldered the fuse, the end fell off the glass tube. Just slipped off. Never seen that before. May keep it just to prove it to someone.

Fuse in, all ports jacks and pots squeaky clean. Silent. No hum or buzz. Nothing but guitar sounds.

The lamp situation is just a little weird. It's steady illumination until the volume hits 90%. Then it dims slightly when a note is hit. My guess is the old caps. Although they are working very well now.


Keep On Truckin'

[Updated on: Wed, 12 April 2017 21:02]

Report message to a moderator

Re: K200B [message #26039 is a reply to message #26029] Thu, 13 April 2017 06:11 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4284
Registered: June 2004
Location: NY
Senior Member
I have had that same issue with new fuses and old one, so don't fret!
It's quite normal for the pilot lamp to dim a lot during playing, even when new this is what happens and is considered normal.
The louder you play the amp , the more the lamp will dim out!
I would say that now your amp has a clean bill of heath, enjoy!!
Re: K200B [message #26040 is a reply to message #26039] Thu, 13 April 2017 14:31 Go to previous message
irish77060 is currently offline  irish77060
Messages: 48
Registered: January 2017
Location: Atlanta, GA
Member
Thanks for all your help!

Keep On Truckin'
Previous Topic: K-250-4 head
Next Topic: K150-8 Loud Thump
Goto Forum:
  


Current Time: Wed Jul #d 17:22:17 EDT 2020
.:: Contact :: Home ::.

Powered by: FUDforum 3.0.9.