Schematics

[normt04072]

I recently got a Kustom KLA100 from E-Bay. With it came a Quantum 25R amp head. The guy told me that it worked when he put it in his closet but when he pulled it out and tried it several years later it didn't make any sound. I had the electronics instructor here at the college look at it for me and he says that the power transistor is missing. Must have had some gremlins living in his closet that ate transistors. Any way, this little Quantum doesn't owe me anything but it might be a fun little amp to play around with. I'd like to get a transistor for it. Hence, my dilemma. I cannot find a schematic for it anywhere. I've had little success in just finding anyone who's even heard of them. Any suggestions? Anyone know where I can find one? Thanks for any help!

[cynical1]

norm -

Well, you're right, there aren't a lot of resources out there. I didn't find anything on the free sites, but I did find one site that sells them for $7.00:

www.broadwaymusicco.com/Kustom10.htm

I've never used the guy, so let your own judgment prevail.

You might try the newsgroups and see if anyone has anything, like alt.guitar.amp. Haven't used newsgroups in a long time, but they have been helpful in the past.

Good luck

Cynical1

[cynical1]

norm -

You now, I really should put my glasses on when I read these posts...

Disregard the post for the KLA100 amp schematic.

And you're still right, there's nothing on Quantum heads that I could find.

I'd still hit the newsgroups...you might get lucky

Happy Trails

Cynical1

(...soon to be selling pencils at the ballpark...)

[sumgai]

Acoustic Sounds International - that's the name of the Korean manufacturer of Quantum amplifiers. Gone, and apparently, highly lamented.

One reviewer for Harmony-Central said that he got a schematic (for a different model), but the company folded more than 2 decades ago, so that avenue is probably a lost cause. Other fora are your only possible sources now, sorry.

HTH



sumgai

[normt04072]

Thanks Cynical1, I've already been to that site and ordered a schmatic for the Kustom. It has a hum to it when the reverb is turned up. I figure a bad cap or something like that. The amp also came with a Peavy Ultraverb II. It appears to work OK, I've just got no idea how to use it. Maybe thats why he had it. He used the Peavy for reverb instead of the built in one. I downloaded the manual for it but it's all Greek to me. Anyway Thanks again!!!

[normt04072]

Sumgai, Thanks for that info, Maybe I can run with that and come up with something.

[RJB]

norm
take a pic of where the transistor(s) are missing.

I would assume the circuit would use 2 power transistors not 1. If only one is missing the part number on the other would be helpful. But a complete blind guess is that the transistor would be a 2N3055, the work horse device of the 70's and 80's. Used in amps from 20-200W

[normt04072]

Hey RJB,
I was going to send a pic but I don't know how to post one here. If you want me to email it shoot me a line to [e-mail]. Thanks

[newey]

Norm-

How to post pix

That way we can all see it.

[normt04072]

OK I'll try. Let's see what happens. The area circled in red are 5 connections arranged in 3 over 2 much like the keys on a keyboard. The ones in blue are what appear to be metal mount points that were broken off rather tan take the screws out from the back side.

[normt04072]

Well that didn't work try this

ctech.smccme.edu/~norm/quantum.jpg










(Edited by sumgai to make the image show up, instead of just a link)

(Edited again by sumgai to restore the link, after discovering that most people on most monitors have to do the shimmy-shimmy-shake to see the whole thing.

Note to normt - could you please reduce the image size about 25%, please? Thanks.)

[RJB]

What is missing isn't exactly a transistor, instead it's a power amplifier IC or module (slang - Power Brick). So the amp is newer than I expected. The 2 items circled in blue were part of the heatsink for the device which is also missing. The 3 holes in the chassis with the white residue is where the rest of the heatsink mounted.

So the bad news is that without the schematic I can't tell you exactly which part went in there. I can guess as to the "family" of parts, but without knowing additional information about the circuit. i.e. power supply voltage, audio signal levels, .. A usable match would be difficult. Plus a new heatsink would be needed.

What you need is a savvy electronics tech who would be willing to tinker and research a bit, but then there goes the cost of repair. If you want to do some experimenting on your own (depending on your level of expertise) my 2 minute search shows a likely candidate to be an National Semiconductor Overture series LM1875. But no warranties or guarantees apply ;D. Don't forget the heatsink, heatsink grease, and insulators (if needed).

Good luck

[normt04072]

Well, I ordered up one of those LM1875 IC's. Figure whats the worst that could happen. It doesn't work now. Won't work later!I'll keep you all posted as to what happens.
Thanks for all the help!

[normt04072]

Got the IC the other day and installed it. I can get just a hint of sound out of the speaker a full volumn. I have to assume the IC was the wrong one. Hey, it was worth a try right!! I'm not sure what I'm going to do with it at this point. My gut say's to just place it in the trash. Any suggestions???