Kustom K6320 PA head

[johnhoef]

Hi,
I own a Kustom model K6320 PA head with a noisy reverb. I suspect a noisy transistor in that circuit. I have searched the internet for a schematic, and come up with nothing! Can any of you supply me with a schematic? Thanks.
John

[Enzo]

I would start by calling the company and asking if they can provide it.

https://www.kustom.com/contact-us

[g1]

Get the board number and check here: https://music-electronics-forum.com/...ad.php?t=34637

[Enzo]

I could be wrong, but I think this is latter day Kustom, the reborn company, not from the old tuck-n-roll days.

[J M Fahey]

I guess only link between new and old Kustom is the logo ... and not much of that either.

And modern one is not much American designed, they are "very korean", including car stereo and minicomponent style "graphic EQ in a single chip", Sanken/Sanyo power modules, KA**** ICs, etc.

[Enzo]

They resurrected the Kustom name, product has nothing to do with the original stuff.

WHen they came along, I signed on as a warranty station, but in the five years before renewal of status, I never got so much as a single customer from it. I guess they did not have strong sales in my area of the country. They hired James Brown away from Peavey to design some guitar amps, don't recall the results of that. He has moved on since then.

[johnhoef]

Thanks for your thoughts. I have owned and gigged with this amp for many years, and has served me very well. For my purposes, six channels has always been more than sufficient, and I like to simplicity if this PA head. Anyone in the band can walk up to it, and use it within a minute, so easy to use. I may just end up trying to fix the reverb without a schematic, using a can of freeze spray to pinpoint the faulty transistor......however, a schematic is something I have always had a desire to obtain for any future repairs.

[johnhoef]

Another thought....as you can see in the photo, I have cables plugged into the pre out / main in jacks. They go to an external digital reverb unit. So, for now I do have reverb, but I have never found a digital reverb unit that sounds right. The internal spring unit is far superior, in my opinion, so there is a strong desire to get that working again. A schematic, anyone???

[Enzo]

Seriously, did you call Kustom and ask?

[johnhoef]

Enzo, Yes, I did contact Kustom. They have little if any documentation dating back as far as this unit, so no help there.

[J M Fahey]

Ok, now we only have Plan B left.

Go to reverb return jack (is it connected through RCA jacks or straight plugged into PCB?) and follow the track leaving it, it should lead you to a coupling capacitor which will then lead to a transistor base or an IC leg.

Please identify such active element and take a closeup picture showing its surroundings.

If an IC, which I suspect, which pin is used as input?

Almost forgot: define "noisy reverb" , even better upload some MP3 or video.

suspect a noisy transistor

is pulled out of the blue and does not mean much.

[Enzo]

I dug my new-era Kustom files out of storage tonight. I have docs on the KPM6160, which is like yours but mono. That is from about 1999. But nothing on your model. I suspect yours is somewhat newer than 1999.


meanwhile, if you want to FIX it, isolate the problem. Is the noise on the return side or the drive side? Does the noise turn up and down with the reverb control? UNplug the drive cable from the reverb unit. Still noisy?

[johnhoef]

Enzo, JM, Thanks for your continued thoughts. I have decided to simply recap the main board which includes all the reverb circuitry. As old as this unit is, I figured why not, and it may solve my problem. There aren't that many caps, and new caps are cheap enough. It shouldn't take but an hour or so. I'll let you all know the result. By the way, at this point, the situation has gotten worse...the reverb is now completely dead...all other functions work. Caps are on order, and I should have them any day now.

[johnhoef]

Oh my!! I had forgotten to get back to you all! I suppose since I have not been here in a while, you all assumed I had solved my problem. Indeed, I did. I went ahead and replaced all the caps on the main board, as well as all the op amps. Problem solved. The caps and op amps were cheap, so I figured as long as I had the unit disassembled, may as well do this. It solved the problem, and I now have reverb again!! Generally I like to figure out the problem rather than blindly do a mass component replacement. In this case, the time required to do the work may well have been less than trying to figure out the circuit without a schematic! In other repair jobs of vintage equipment, I find more times than not, a recap fixes a lot of problems.....particularly if I am having difficulty zeroing in on a particular problem. Further, I feel it's a good idea to recap anyway, considering we really don't know how much more life is in those old caps, or how far they have drifted off their values. Anyway, thank you all again for your thoughts.