Home » VintageKustom.com » Repairing Kustom Amps » severe reverb problem on K100 model 2 (reverb way too sensitive: reverb "explosion" when touched...)
severe reverb problem on K100 model 2 [message #17645] Sun, 04 November 2012 16:52 Go to next message
UncleSpot is currently offline  UncleSpot
Messages: 2
Registered: November 2012
Location: Lodi, California
Junior Member
'been working on tube amps since 1968. 'seen most problems, never NOT been able to fix...
'have 11 Kustoms, and just acquired a K100, model 2 piggyback (2x12). The problem: the reverb is ON (sounds like it's turned up 1/2 way!) when the pot (R171) is all the way down. When you turn the reverb up it goes WAY past "surf music".
If the chassis is LIGHTLY touched it makes the "reverb explosion" like it was kicked (HARD).

Pulled EVERY xstr and put them on my curve tracer and they're all functioning like they're suppose to. Checked all caps to make sure the ESR is not high and they're within spec. Changed out the reverb tank with 3 others: NO change. WTH am I missing? I can NOT use this amp ANY where with this problem. I have a schematic, but it doesn't exactly match the PCB104 in the amp. I've never heard of this kind of problem...
TIA,
Ron
Re: severe reverb problem on K100 model 2 [message #17647 is a reply to message #17645] Sun, 04 November 2012 19:25 Go to previous messageGo to next message
pleat is currently offline  pleat
Messages: 1452
Registered: June 2004
Location: Belding, Mi
Senior Member
Kustom did a big revision on that amp to deal with the excess reverb problem. pm me and I can send you the revision.
pleat
Re: severe reverb problem on K100 model 2 [message #17649 is a reply to message #17645] Mon, 05 November 2012 07:07 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4728
Registered: June 2004
Location: NY
Senior Member
I will dive into my k100 tonight and post you some info and things to check, also what does the input and output of the other pans you tyred out check at resistance wise?
Re: severe reverb problem on K100 model 2 [message #17650 is a reply to message #17649] Mon, 05 November 2012 08:08 Go to previous messageGo to next message
UncleSpot is currently offline  UncleSpot
Messages: 2
Registered: November 2012
Location: Lodi, California
Junior Member
SteveM
the other tanks came out of a 2chan 100, and 2x 200s
...so I didn't even bother ohm-ing them out.
Ron
Re: severe reverb problem on K100 model 2 [message #17655 is a reply to message #17645] Tue, 06 November 2012 07:01 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4728
Registered: June 2004
Location: NY
Senior Member
Ok, they should have all worked out for you, check out the info Pleat ia sending on the after production factory mods that Kustom dealers where sent for a fix.
Let us know how you make out,if need be I will dive into one of mine and give you drive voltages and rcovery gain specs for the reverb stage.
Re: severe reverb problem on K100 model 2 [message #17659 is a reply to message #17645] Sat, 10 November 2012 06:43 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4728
Registered: June 2004
Location: NY
Senior Member
Hi, put my K100-2 on my test bench last night and heres what I found.
With the volume set on marking two(9:00) and the bass a treble set to full on I drove the input with a a 1k test tone at .116 mv.
This producded a input level to the pan of 5.30 volts.
This was measued between the tip of the RCA jack and CHASSIS ground,not the RCA sheild.

I then checked the output side of the pan between tip and chassis ground and it was at 5.30 volts also.

I then set out to drive the output end of the pan (recovery amp) and found it to be quite sensivtive, to the point that a -60 db input level would drive the amps output stage to a 17 volt level into a 8 ohm load.
Hope helps you out if you are still working on the problem!
Re: severe reverb problem on K100 model 2 [message #19040 is a reply to message #17659] Mon, 05 August 2013 12:38 Go to previous messageGo to next message
GaryLC is currently offline  GaryLC
Messages: 52
Registered: December 2012
Member
Hi folks!

I'm resurrecting this thread, I also have a Kustom 100 with that exact reverb problem! M techs say it appears that the ampand reverb are operating the way it was designed, although none of my other Kustoms do that. Can someone send me the "revision" of what Kustom did to correct this?

Thanks!!
Re: severe reverb problem on K100 model 2 [message #19081 is a reply to message #19040] Sat, 10 August 2013 13:19 Go to previous messageGo to next message
Haltone
Messages: 16
Registered: March 2000
Location: Syracuse NY
Junior Member
I also have this problem and would appreciate a copy of the revision. I was actually thinking of changing the pot to a different value.
Re: severe reverb problem on K100 model 2 [message #19096 is a reply to message #17645] Mon, 12 August 2013 06:54 Go to previous message
stevem is currently offline  stevem
Messages: 4728
Registered: June 2004
Location: NY
Senior Member
Is the reverb recovery transistor in the amp a factory one, if not it may have too high a gain factor to use a tube term?
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