| Blown 250 Bass Amp [message #11409] |
Sat, 11 July 2009 10:56  |
John Hylton
Messages: 18
Registered: July 2009
Location: Salem, Oregon
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Junior Member |
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I took my K250 - 1981 model - out of 4 or 5 year resting mode and was going to use it for a county fair gig. Turned it on at home and ran a few bass scales - worked fine - including the infamous Kustom hiss. Went to band job, setup with a DI box to run with house sound system, about 2 minutes into opening number, amp went dead and smoke poured out of the head. Opened up the amp head when I got home. There is a PC board mounted to the bottom of the amp, and has red and black wires feeding it from two large (what I think) are capacitors. This board has several transistor or resistors that are burned or burst open. From reading posts on this forum, it sounds like some of you are electronic experts and know how to repair these wonderful amps. Is there someone who works on these for a living or for hire? I really want this baby fixed if at all possible - I have owned it for 25 years and it is in almost brand new condition. To me, it's worth spending some $$ to get it going again. I might also mention, the lower channel..not the selectone one...has had almost no output for several years...you have to turn it almost full open to get any sound out of it...Just the top channel was fully functional.
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| Re: Blown 250 Bass Amp [message #11419 is a reply to message #11417] |
Mon, 13 July 2009 12:09  |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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John, welcome to the place.
My take on the situation is that your amp is repairable, and as Steve sez, any tech with good solid state skills can get it up and running again.
The usual problem is that a lot of young techs look at the power amp board and go "What the heck are those things?", referring to the driver transistors that have been out of production since the 80's. And so rather than figuring that this is just a solid state amp like any other Peavey or Fender or Crate, they may tell you that they can't or won't fix it because they can't get parts for it or some other excuse. I don't know what your tech situation is out there, but it might help if you find an older tech who has seen one of these before. Worst case, is that you could ship it out to have it repaired.
Pleat's idea of buying a donor amp is also a reasonable approach, as the basic 250 power amp board was used in a lot of Kustom amps. And if you do the work yourself, you can save some cash as well. The only down side I see to this is that the donor amp is still 30 years old and could also be nearing the end of its life cycle.
The pre-amp chip problem can be handled in a few different ways. You can find a NOS one or a used one or the board can be adapted to use a modern replacement chip. But before checking the chip, I'd do as Pleat suggested and check the plug on wires. That pre-amp board has a plug that connects the circuit to the Fuzz FX board. If you don't have the Fuzz FX in your amp, there is a jumper plug that must be installed or the signal will not pass through the circuit. From your description of the loss of signal, that would be the first thing that I would check.
As for dating your amp one of the members here, Les Strickland, has decoded the factory secret codes and has posted a serial number list. If you know the serial number of your amp, his list will give you an approximate date of manufacture.
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| Re: Blown 250 Bass Amp [message #11439 is a reply to message #11438] |
Sat, 18 July 2009 12:52 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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John, if you pm me your email address, I'll scan and send a pdf of the power amp board and if you need it the pre-amps as well.
To be safe, you should confirm the PC board numbers so that I can be sure to send the correct schematics. The power amp board in your amp should be a PC5065.
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| Re: Blown 250 Bass Amp [message #13093 is a reply to message #13092] |
Thu, 04 March 2010 15:37 |
John Hylton
Messages: 18
Registered: July 2009
Location: Salem, Oregon
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Junior Member |
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I know. Look at the size of some of the new Carvin and MarkBass heads...they weigh 5 or 6 pounds and are ridiculously small.. Is there a written chronicle of the old Kustom company anywhere? I've never read why they went out of business...was it change in business climate or poor sales, the economy ? I just never knew what happened to that product.
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