Old Kustom: Fix or forget

Discussion in 'Amps and Cabs [BG]' started by nashvillebill, Dec 5, 2003.

  1. Among my collection of "vintage" stuff(translation: old crap), I have an old Kustom K250 black tuck and roll, with matching 2x15 cab. I had gigged regularly with this rig, which I bought off the original owner a decade ago. Unfortunately, this 30 year old amp went kaput in the middle of a gig last year, an ouput transistor went and took out a handful of transistors in the power amp section.

    I had a backup head, so the gig was saved, and so I just threw the Kustom amp in the closet. But now I'm debating pulling it out and fixing it...Aside from my labor, the parts won't cost much...EXCEPT half the transistors have been discontinued and are a real pain to find.

    So I'm asking for opinions: worth a few weekends to fix, or forget it and move on? When I put it on the scope a while back, I measured a whopping 126 watts into 4 ohms. Whoopee. Parts are impossible to find (the cool looking blue pushbutton switches have been out of production for 20 years) and its reliability is now going to be really questionable....I mean, it's sorta cool, but.... :confused:
  2. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    getting warmer
    You never know, you might be able to find modern replacements for the blown transistors. Check www.mouser.com. As I recall they have a pretty extensive substitution table for a wide range of transistors.

    If you're never going to use the amp, I wouldn't bother. Spend the time playing instead. If you are going to use it though, it might be a fun project.

    BTW, once you replace the transistors, and the capacitors while you're at it, there is no reason the amp couldn't go for another 10 years.
  3. Actually, I had already replaced the filter caps to 10,000 mfd each...come to think of it, I had bought them from Mouser (great minds think alike).

    The main hassle is, the transistors have house numbers on them, I've had mixed luck in cross referencing the house numbers, some were easy but others haven't shown up anywhere. (The schematic just gives the Kustom part number, so I'm having to read the house numbers off of the components, to further complicate things)
  4. notanaggie

    notanaggie Guest

    Sep 30, 2003
    I always liked those for a sorta ugly 60's 'cool factor".

    Might be from using them back in the day, dunno. Mine got lost when a bar was padlocked by the bank with our equipment inside. Another reason besides poverty to get a day job.

    But it can't be that hard to locate replacement parts that will work. Those circuits are bone simple.

    I don't think I have worked on one for 10 years or more, and I don't even know if I have schematics anymore. But I seem to remember replacing the outputs with another type and having no problem. We were Crown certified, might have used their 2N3773, as I think the Kustom is quasi-comp output.

    If the tuck and roll covering is OK, I'd go for it. If its all torn up, I'd say forget it, the "cool" is gone away.
  5. The outputs are 2N3055's, no problem there of course, but everything else is weird--the 40409 drivers have the integral heat sink for example...and on the preamp stage there's a couple of IC's that are long obsolete.

    quasi-comp, yep.
  6. notanaggie

    notanaggie Guest

    Sep 30, 2003
    40409 and 40410, then, probably.

    they are 90 volt 0.7 amp 3 watt devices with beta 50 to 250

    I seem to remember using 2N3440 and 2N5415 in place of those, with a heatsink on them, of course.
    250V/200V 1A 10 watt (with sink) beta 40-160

    Close enough to work OK, even if minimum beta is a little lower for the 2N5415

    The ICs might be another issue, what numbers are they?
  7. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    Kinda like Danelectros? :p
  8. gfab333


    Mar 22, 2000
    Honolulu, Hawaii
    I used a Kustom 200 with a 2X15 JBL cab in high school. It was black tuck and roll. They have a special place in my heart.

    Keep the spirit alive! go for it. Refurbish that baby!
  9. I don't remember the IC's, the amp's still in the closet and it's been a year since I looked at it. I'm hoping the preamp boards are OK, though, so I shouldn't have to worry about the IC's.

    Philosphically, this is kinda like debating whether to fix up an early 70's station wagon.
    I've got so many other things to do, I've got to decide if I want to spend a lot of time on this. If it was a SVT, there would be no doubt about it.....

    Aw shucks I'll probably keep piddling with it, it'll give me good experience in solid-state troubleshooting. Hey notanaggie, I may be bugging you when I get further into this. As I recall, one of the input stage (curent source) transistors must've been cooked, from the voltage readings I took back then.