| Kustom 100 blowing fuse [message #18016] |
Tue, 08 January 2013 05:45  |
imsteinrecording
Messages: 7
Registered: January 2013
Location: California
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Junior Member |
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Hi,
I'm new to the group also. I have a similar problem to the other user who has an amp blowing fuses. Mine is a Kustom 100, model K100 2. It blows fuses immediately. I read the other threads and was wondering if the possible fixes are the same, ie. a driver or output transistor. I'm not sure what a driver is! Thank you in advance and Happy New Year!
Sincerely,
Mark
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| Re: Kustom 100 blowing fuse [message #18019 is a reply to message #18016] |
Tue, 08 January 2013 12:03  |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Please remember that working on amplifiers or anything electrical can kill you if you are not careful and well trained. If you don't know what a driver is, I doubt that you are qualified to do any real troubleshooting inside the amp.
I don't know you or what your skill set is, but if you are not up to it, please take the amp in for service.
With all of that being said, Kustom amps are very basic and most of the parts are either available or easily replaceable. They are standard designs that have been used for decades by many manufacturers, and any tech should have no problem in fixing your amp.
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| Re: Kustom 100 blowing fuse [message #27234 is a reply to message #18016] |
Thu, 11 April 2019 15:15 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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How are you disconnecting the preamp? What model amp do you have?
If the fuse blows when the preamp is unhooked, there must be short in the power supply somewhere. It's not likely that a shorted transistor would cause the fuse to blow, but there could be a bad cap or a shorted wire somewhere in there.
If we knew what amp you have, we could suggest a few specific things to look for.
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| Re: Kustom 100 blowing fuse [message #27238 is a reply to message #18016] |
Fri, 12 April 2019 13:31 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Not sure about that model, but if I remember correctly, that power amp board has a circuit ground that only connects with the three pin Molex plug.
If that is the case, then your problem may still be in the power amp, but it is being hidden by the fact that you are disconnecting the ground from the circuit.
I'd suggest that you go back to square one and retest all of the transistors and diodes on the power amp board. You might want to build or use a light bulb limiter on this one to save yourself a lot of trouble.
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| Re: Kustom 100 blowing fuse [message #27239 is a reply to message #18016] |
Fri, 12 April 2019 21:02 |
JDinPA17603
Messages: 69
Registered: May 2018
Location: Lancaster, PA
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Member |
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Time traveler
You stated that when you unplugged the three pin molex connector from the 5033 board that the fuse did not blow.
Question - were the red and green wires connected to all boards at the main capacitors at that time?
If so was the pilot light working at that time?
If the red and green wires were connected to all of the boards and the fuse did not blow when the molex was unplugged then I agree with Bill, the cause of the overload definitely points to the 5033.
Also agreeing with Steve bad idea to just unhook the red wire from the 5033 or any of the boards by itself.
From the board configuration and model it appears we are discussing a Kustom Commander with 2 12" speakers. If my model is off then a Kustom Hustler with 4 10" speakers.
I also noted you stated that the fuse did not blow with the red wires disconnected from the caps.
This is the reason for my question of were the red wires connected to the caps with the molex plug pulled.
Steve and Bill not trying to take over here, just trying to fully understand the situation.
John
Old Us Navy Vietnam Vet
Playing for my own enjoyment and irritation of the neighbors.
[Updated on: Fri, 12 April 2019 21:07] Report message to a moderator |
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| Re: Kustom 100 blowing fuse [message #27240 is a reply to message #18016] |
Sat, 13 April 2019 06:24 |
stevem
Messages: 4773
Registered: June 2004
Location: NY
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Senior Member |
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On the 5033 board there are 4 caps that could make for blowing fuses, these are c3,c4,c7 and c8.
You can find these on any of the 5033 schematics listed in this site's technical listing.
Yank them out and resistance test them for shorts, or if they are getting brown or splitting open from getting hot then just replace them.
C3 does not even need to be in circuit to have the amp work , but there will be a slight hum out of the speaker with that out if the driver's and the rest of the output stage are working.
[Updated on: Sat, 13 April 2019 06:24] Report message to a moderator |
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| Re: Kustom 100 blowing fuse [message #27247 is a reply to message #18016] |
Sun, 14 April 2019 11:01 |
JDinPA17603
Messages: 69
Registered: May 2018
Location: Lancaster, PA
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Member |
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One more test when checking the output transistors is to go from the case which is the collector to the chassis. They should read open. If the case is shorted to the chassis you will have instantaneous fuse blown. They are mounted to the chassis using insulating washers and a mica film with heat sink grease. This usually can happen if someone over tightens the mounting screws.
John
Old Us Navy Vietnam Vet
Playing for my own enjoyment and irritation of the neighbors.
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| Re: Kustom 100 blowing fuse [message #27250 is a reply to message #18016] |
Mon, 15 April 2019 12:23 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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A bad driver transistor can cause an output to blow, also open resistors, etc. You said that you replaced the drivers, what did you use as replacements, 40409 and 40410's?
You can just pull the black connector plugs from the outputs and that will remove them from the circuit for testing. The red Collector wires can stay connected unless you need to remove the transistor from the chassis.
Be sure to leave the speaker disconnected from the amp until you can power it up without blowing fuses.
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| Re: Kustom 100 blowing fuse [message #27268 is a reply to message #27267] |
Mon, 22 April 2019 19:12 |
JDinPA17603
Messages: 69
Registered: May 2018
Location: Lancaster, PA
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Member |
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time traveler
There are three versions of the 5033 board.
On two of them they have R24 listed as a 0.51 ohm 5 watt resistor
They also both have R26 listed as a 510 ohm 5% resistor and R25 listed as a 150 ohm 1% resistor.
The third version lists R24 as a 200 ohm 1% resistor R25 as a 510 ohm5% resistor and R23 as the 0.51 ohm 5 watt resistor. The 5 watt resistors are rectangular in shape.
Hope this helps.
John
Old Us Navy Vietnam Vet
Playing for my own enjoyment and irritation of the neighbors.
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| Re: Kustom 100 blowing fuse [message #27272 is a reply to message #27271] |
Tue, 23 April 2019 12:12 |
JDinPA17603
Messages: 69
Registered: May 2018
Location: Lancaster, PA
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Member |
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time traveler
If one of the two resistor R23/R25 you changed out was a 200 ohm resistor then you need to use the schematic labeled 5033(8/70) from the PC boards by number list. On that schematic R22 and R24 are 200 ohm 1/2 watt 1% resistors. R20 and R25 are 510 ohm 1/2 watt 5% and R21 and R23 are 0.51 ohm 5 watt ceramics.
If the good one you replaced (R23 or R25) with a 150 was already a 150 then R24 and R22 are 0.5 ohm 5 watt ceramic resistors, and R21 and R26 are 510 ohm 1/2 watt 5% resistors.
John
Old Us Navy Vietnam Vet
Playing for my own enjoyment and irritation of the neighbors.
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| Re: Kustom 100 blowing fuse [message #27273 is a reply to message #18016] |
Tue, 23 April 2019 12:13 |
stevem
Messages: 4773
Registered: June 2004
Location: NY
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Senior Member |
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Even 20% tolerance resistors in those two locations would not make the amp blow or not work.
The 5 watt resistors should be matched as close as possible .
I order 10 to 15 of them at a clip and test them resistance wise to match them with my ESR cap checker as it's far more accurate then the average multimeter.
[Updated on: Tue, 23 April 2019 12:15] Report message to a moderator |
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| Re: Kustom 100 blowing fuse [message #27274 is a reply to message #18016] |
Tue, 23 April 2019 12:30 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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The 1% resistors that you are talking about are part of the protection circuit. In a working amp, they read the voltage on the ballast resistors and when the voltage gets too high, they reduce the signal to the driver transistor to lower the output signal. Off values will cause the protection circuit to either trigger too early or too late.
The amp would work without the entire protection circuit if it was removed.
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| Re: Kustom 100 blowing fuse [message #27276 is a reply to message #27275] |
Tue, 23 April 2019 13:19 |
timetraveler
Messages: 25
Registered: April 2019
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Junior Member |
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R25 was a 150 R2 & r3 were also out of tolerance if replacing those wouldnt make a difference not sure what the problem is.
the 5w resistors read .7 ohms
i replaced the driver transistors with nte 128
and output transistors with MJ15001G one blew again so i replaced with nte 181npn
i think when i replaced the driver transistors the one legs got shorted to the heat sink box
[Updated on: Tue, 23 April 2019 13:22] Report message to a moderator |
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| Re: Kustom 100 blowing fuse [message #27277 is a reply to message #27276] |
Tue, 23 April 2019 18:00 |
JDinPA17603
Messages: 69
Registered: May 2018
Location: Lancaster, PA
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Member |
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timetraveler I am a little confused so I am offering this to you for reference. I know how confusing and frustrating this can be.
Driver transistors
Q4 is a NPN 40409 equivalent is NTE128
Q5 is a PNP 40410 equivalent is NTE129
They can be had as a matched pair by ordering NTE129MCP
NOTE: the correct transistor must be installed in the correct position
Both of the driver transistors must have a heat sink installed on it and care must be taken not to short the heat sink to any nearby components.
Protection circuit
Q6 is a NPN 2N3567 equivalent is a 2N3567 or a NTE123
Q7 is a PNP 2N3638 equivalent is a 2N3638 or a NTE129
Note as with the driver transistors these must be installed in the correct position.
Output circuit
Q8 and Q9 are NPN 36892 equivalent is 2N3055 or NTE130
I recommend a matched pair - order NTE130MP
THESE ARE INSTALLED with a mica washer between the transistor and the chassis with heat sink grease applied to both sides of the mica film washer ... between chassis and washer and between washer and transistor.
They also use nylon washers and bushings to isolate the case from the chassis.
Diodes and electrolytic capacitors must be installed in the proper orientation.
Resistors should be as close as possible to the correct values.
Check for accidental shorts between traces on the board.
With the 1N3754 make sure that the leads are not broken or shorted to the clip or each other And insure that the diode is securely fastened in the clip.
All voltage measurements are with no load (speakers disconnected), no signal input (all plugs unplugged from the inputs) and all controls full up.
Since you are having an issue with parts continuing to blow, as others have suggested, use a light bulb limiter (100 watt incandescent lightbulb) wired in series with the power cord) and decrease the amperage on the fuse until you get this straightened out.
Good luck with the amp.
John
Old Us Navy Vietnam Vet
Playing for my own enjoyment and irritation of the neighbors.
[Updated on: Tue, 23 April 2019 18:28] Report message to a moderator |
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| Re: Kustom 100 blowing fuse [message #27304 is a reply to message #27303] |
Thu, 09 May 2019 16:33 |
JDinPA17603
Messages: 69
Registered: May 2018
Location: Lancaster, PA
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Member |
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1. See my previous long note.
2. Use a light bulb limiter
3. Recheck all transistors / diodes.
4. The 5 watt 0.5 ohm transistors shoul match each other closely and the closer to the 0.5 (1/2) ohm they are the better.
5. Drivers must have heatsinks on and not shorting to anything else.
When you put the wrong transistor in you probably blew the output transistor. With it gone putting in the nte129 with the output still blown most likely damaged it.
Note 3 above and previous note.
Good luck.
John
Old Us Navy Vietnam Vet
Playing for my own enjoyment and irritation of the neighbors.
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