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New Mystery Amp Kustom Project [message #29727]

Thu, 07 May 2026 10:04

Furthurdown
Messages: 4
Registered: May 2026

Junior Member

I have taken stwewardship of a Kustom amp to be repaired for a friend of a friend. He acquired it in the early 90s to play bass after his father purchased it sometime in the 60s. I also live in KCMO, so my geographical connection to Kustom is pretty strong (RIP Holy Cow Market). The amp model is a mystery to me as there's no markings anywhere on this guy. I think it's a J495/595/695 because it's got the offset knobs as well as reverb/tremolo. It's one of the J lines as it has 15" EM1500s in it. It only has 2 circuit boards in it, with what appears to be the output transformer and power amp section connected to the back part of the chassis. There are only 5 transistors on the back (as opposed to 6), and there doesn't appear to be a matching set of 4 transistors like I'd expect in the power amp section.

The bad: The guitar section of the amp doesn't have any input. If I turn up the reverb, I can hear the spring when I hit the top of it. One of the 15 inch speakers doesn't produce sound, but that may be a wiring issue after opening up the cab. There's a missing power lamp, missing cab handles, and missing cab wheels.

The good: None of the solder looks like it's ever been touched. I may be the first person to open it. I'm definitely the first person to open it in a very long time.The head, outside of a weird pink color on the top, is in great shape.

My first step is to ID what amp model this is, then begin digging into what's wrong with the guitar section of the amp. A re-cap will come once I get the thing working. Pictures for reference.

I can't post links until I have 10 posts, so you may have to copy the link below to see pictures.

imgur.com/gallery/kustom-mystery-amp-H8Yv4Bf

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Re: New Mystery Amp Kustom Project [message #29728 is a reply to message #29727]

Thu, 07 May 2026 12:59

stevem
Messages: 4902
Registered: June 2004
Location: NY

Senior Member

Hello and welcome.

You have the guitar amp version and this is the second version of a Kustom with close to a 100 watts of clean output as opposed to the earlier 25 watts.

That amp should have 6 transistor all the same on the rear of the amp, 4 of them on the center of the amp and two more stacked to the right as you view from the rear .

Of the two on the right one is a driver feeding that driver transformer mounted on the inside rear next to the PC201 board which is the driver / voltage regulator board.

At this point in time with the age of these amps you should plan on changing all the electrolytic type caps on all 3 boards.

The two big power supply rail filters mounted on the floor of the chassis may not be bad.
When they go fully bad the red plug on its top will pop up.

You can find the schematic on this site .

It’s under the A serise amp listing which will bring up two different sets of schematics.

Yours has PC101 main board, a PC301 reverb/ tremolo board and a PC201 driver/ regulator board.

While you’re working on the amp I would derate the speaker fuse to 2 amps along with the main fuse.

You can send photos to my email if you like smsg25ra5@yahoo.com.

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