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kustom 150 woe... [message #22838]

Sun, 03 May 2015 11:33

pinkjimiphoton
Messages: 45
Registered: May 2015
Location: the dark side of the moon

Member

try 5. jesus.

bought a k150 head, the 3052 board is BURNED. the traces are still there, but the fiberglass is just carbon,

i DID pick this up strictly for spare parts, but do ya think it may be fixable?

i'm posting this NOW before it dumps my post for a 5th time... pix imminent.

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Re: kustom 150 woe... [message #22839 is a reply to message #22838]

Sun, 03 May 2015 11:37

pinkjimiphoton
Messages: 45
Registered: May 2015
Location: the dark side of the moon

Member

http://s605.photobucket.com/user/pinkjimiphoton/media/1_zps1 7hr0yib.jpg.html

http://s605.photobucket.com/user/pinkjimiphoton/media/1_zps1 7hr0yib.jpg.html

http://http://s605.photobucket.com/user/pinkjimiphoton/media /3_zpsb7itvm20.jpg.html

http://http://s605.photobucket.com/user/pinkjimiphoton/media /2_zpsihahuezu.jpg.html

[Updated on: Sun, 03 May 2015 11:44]

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Re: kustom 150 woe... [message #22841 is a reply to message #22838]

Sun, 03 May 2015 14:03

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

It's burnt pretty badly, but I've seen worse. I think that it could be fixed. You might have to run a trace or two away from the board just to be safe, but solid state amps don't run at voltage levels high enough to make carbonized board areas too much of a factor.

You need to grind away as much of the burned board as possible. Some of that black is just soot on the surface. The sections that are burned through the fiberglass are the real problem. I've sometimes made patches of pc board with the traces replicated and epoxied them together. Then all you have to do is to solder the traces together where they meet.

I did have one that had a board so badly burnt, that it was easier to just reproduce the entire board. I created an iron down resist pattern and etched a new board. Of course that was an extreme case.

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Re: kustom 150 woe... [message #22843 is a reply to message #22838]

Sun, 03 May 2015 22:26

pinkjimiphoton
Messages: 45
Registered: May 2015
Location: the dark side of the moon

Member

thanks for the advice bill,
i figured on carving away the damaged board, it seems to be carbon and conductive. i have no problem doing point to point repair if need be. gonna be curious to see if she'll fire up. i've seen amps that were smoked far worse that were resurrected.
i'm hoping when the other one comes in it's the same pcb so i can see what was there originally and try and repair it. Wink

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Re: kustom 150 woe... [message #22845 is a reply to message #22838]

Mon, 04 May 2015 06:18

stevem
Messages: 4772
Registered: June 2004
Location: NY

Senior Member

That's a good case for using flame proof resistors during the fix up!
Over the week end I just fixed a burned board issue on a new Fender deluxe III.
Fender when thru the needed trouble to have only the tubes on the bottom board and in the process of moving the other components onto the main board put the traces so close togethere that when one of the output tubes shorts out and just before the fuse goes out the board arcs over in a big way!
They just can't get it 100% right, it's too bad as now the amp comes with a 12 inch driver which it has needed for long time!

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Re: kustom 150 woe... [message #22848 is a reply to message #22845]

Mon, 04 May 2015 14:02

pinkjimiphoton
Messages: 45
Registered: May 2015
Location: the dark side of the moon

Member

i had a red knob showman someone brought me a couple years ago, the entire board (i forget which, i wanna say bias_) was GONE. like... looked like something that had been dug out of pompeii, just carbon that looked like ? and tended to crumble if touched. i didn't even mess with it, too much of a job. well, not too bad realy, but the guy wanted it done for like 50 bux. i'm a floozy and all, but not THAT cheap
Wink

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Re: kustom 150 woe... [message #22849 is a reply to message #22838]

Mon, 04 May 2015 14:04

pinkjimiphoton
Messages: 45
Registered: May 2015
Location: the dark side of the moon

Member

ps... the "other one" arrived today, looking forward to unboxing and trying shortly.

do you guys think it was a speaker impedance issue/ short that melted all those components? i'm just curious.
last time i saw something that seemed exactly like this was when i had taken some jbl 12's (out of some old guitar amp) and tried to drive them with a portable turntable/amp. smoked the resistors just before the speakers, replaced them and it fired right up Wink

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Re: kustom 150 woe... [message #22853 is a reply to message #22849]

Mon, 04 May 2015 16:39

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

The burnt board was caused by the bypassed fuse. The resistors burn because of a shorted transistor. The transistor shorted because of a shorted speaker output or because of a huge power surge or because the temp diode broke a lead or because it got too hot or because somebody sneezed in the clean room when the transistor substrate was being manufactured...

There are millions of reasons why these things fail some explainable and some not. The real problem was caused by the idiot that bypassed the fuse with a solid wire.

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Re: kustom 150 woe... [message #22856 is a reply to message #22838]

Mon, 04 May 2015 17:11

pinkjimiphoton
Messages: 45
Registered: May 2015
Location: the dark side of the moon

Member

agreed 100%. BUT trying to figure out what made it draw too much current can help me figure out what needs to be focused on for the repair, and what to compare to the other amp (which just came in, with the same board intact) so that hopefully i can fix it.

is there a preferred way to test the transistors?

the diode was still in it's heat sink with goo on it, unless the goo came OUT of it... again, newb here in a lot of ways, so i appreciate the info here from you guys who are more knowledgeable, and truly appreciate your patience with me thru my often dumb questions! Wink

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Re: kustom 150 woe... [message #22860 is a reply to message #22838]

Mon, 04 May 2015 17:41

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

I test transistors with a multimeter.

The Vaseline like goo is heat sink grease, used to help transfer heat to the diode case.

Every transistor and diode in the power amp section should be tested. Same thing for the resistors. The power supply diodes need to be tested as well. There's no way for you to figure out why it died, because there is no way to know what single part failed first.

In a lot of cases, one output transistor will short which causes the fuse to blow before any other part is damaged. When the fuse function is disabled, the shorted transistor draws too much current from the driver stage and power supply causing the driver transistor to short which causes the emitter resistors to burn, etc., etc., etc.

As long as the power supply can supply voltage to the circuit, parts will continue to burn or short until a resistor or pc trace burns open circuit and cuts off the voltage to the amp or the power transformer dies.

Have you tried powering up the amp yet? Do you have a light bulb limiter?

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Re: kustom 150 woe... [message #22866 is a reply to message #22838]

Mon, 04 May 2015 20:50

pinkjimiphoton
Messages: 45
Registered: May 2015
Location: the dark side of the moon

Member

nope, i was afraid of blowing something else up or compounding the damage.
years ago after being sick of moving milk crates full of transformers i gave away most of my tube gear, including my variac.

what's a light bulb limiter? never heard of that one.

i was thinking go thru test each part and do a point to point wiring on the pcb for the damaged parts that got smoked.

sad to hear about the transistors, i'm imagining some may be kinda hard to find. i do have a k 100 frankenstein head too that may have some of the same stuff in it.

that one got overly manhandled by the ups monkeys and arrived with both transformer and choke or whatever it was ripped right off the chassis. that was packed with peanuts in a box of peanuts floating in a second box of peanuts.

well done, ups, well done... in the end, they paid for the amp, so i got my money back and they didn't want it (the vendor) so it lives under my bench awaiting resurrection one day. Wink

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Re: kustom 150 woe... [message #22871 is a reply to message #22838]

Tue, 05 May 2015 05:49

stevem
Messages: 4772
Registered: June 2004
Location: NY

Senior Member

Actually none of the transistors used in these amps are hard to find and or sub out even now!
I think you ment to say Frank K200, as there where no K100 Frank type heads like you posted!

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Re: kustom 150 woe... [message #22873 is a reply to message #22871]

Tue, 05 May 2015 09:47

pinkjimiphoton
Messages: 45
Registered: May 2015
Location: the dark side of the moon

Member

hmmm, def a k 100, of course the guy i bought it from called it a frank. it was just the chassis. i didn't really care, i just wanted
a kustom at the time.

my girl brought me a beautiful minty k200 for christmas, the one with the transfomers ripped off is still under my bench awaiting resurrection.

i've got a head piece cab that was supposed to be for yet another one, but nothing i have will fit in it. just a little too short and not quite wide enough to fit aything i have.

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