Home » VintageKustom.com » Repairing Kustom Amps » Kustom 100 blowing fuse (Kustom 100 )
Kustom 100 blowing fuse [message #18016] Tue, 08 January 2013 05:45 Go to next message
imsteinrecording is currently offline  imsteinrecording
Messages: 7
Registered: January 2013
Location: California
Junior Member
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
Re: Kustom 100 blowing fuse [message #18017 is a reply to message #18016] Tue, 08 January 2013 10:39 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4207
Registered: June 2004
Location: NY
Senior Member
Welcome!
Yes, your problem is likly to be the same and likly to be a blown output transistor( TO3 type mounted on chassis heat sink) which sometimes also takes out its driver transistor(TO5 type in heat sink box on driver board)when it pops.
Also likly to be bad would be the 5 watt resistor associtaed with that side of the output stage.
Your rectifier bridge diode may also be bad, this is the round case 4 terminal item bolted down to the chassis near the power transformer.
A good way to check that is to unhook the red and green wires that come from it from there termination point on each power supply filter.
When unhooked and place out of the way from shorting, replace the fuse and turn on the amp, if the fuse holds them you know that the power supply is ok and the problem resides in the output stage/driver section of the amp.
You could also disconnect the output side of each power supply filter(red and green wire) and do the same test.
Do not hook up a test speaker to the amp until you have it fixed and the steady state DC reads less than 1 volt on the amps speaker output other wise the 40 volts of DC output can blow your speakers.
Inform us on your progress, or if you need more help.
Re: Kustom 100 blowing fuse [message #18019 is a reply to message #18016] Tue, 08 January 2013 12:03 Go to previous messageGo to next message
chicagobill
Messages: 1932
Registered: April 2003
Senior Member
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.
Re: Kustom 100 blowing fuse [message #18020 is a reply to message #18017] Tue, 08 January 2013 16:16 Go to previous messageGo to next message
imsteinrecording is currently offline  imsteinrecording
Messages: 7
Registered: January 2013
Location: California
Junior Member
Hi Steve,

Thank you very much for the advice. Happy New Year!

Sincerely,

Mark
Re: Kustom 100 blowing fuse [message #18021 is a reply to message #18019] Tue, 08 January 2013 16:17 Go to previous messageGo to next message
imsteinrecording is currently offline  imsteinrecording
Messages: 7
Registered: January 2013
Location: California
Junior Member
Hi Bill,

Thank you for the warning. I'll be very careful. Happy New Year!

Sincerely,

Mark
Re: Kustom 100 blowing fuse [message #27233 is a reply to message #18017] Wed, 10 April 2019 17:58 Go to previous messageGo to next message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member
I have the same problem blowing fuse when powered on. I checked and replaced as needed parts listed above and still same problem. If i disconnect the preamp the fuse doesnt blow. I checked the diodes on the preamp circuits and they are working. ANy other suggestions?
Re: Kustom 100 blowing fuse [message #27234 is a reply to message #18016] Thu, 11 April 2019 15:15 Go to previous messageGo to next message
chicagobill
Messages: 1932
Registered: April 2003
Senior Member
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.
Re: Kustom 100 blowing fuse [message #27235 is a reply to message #18016] Fri, 12 April 2019 06:10 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4207
Registered: June 2004
Location: NY
Senior Member
To help you better we atleast need to know if the K100 model you have is a combo type, or a piggiy back model?
Both the K100-1 and K100-2 are piggy back models and have but one main circuit board mounted to the front of the amp.

If you have replaced both output transistors and the driver Transistors you may still have a bad Tantaum type cap that is shorted, but I would think that a fully bad cap like that would be showing signs of being burned and black if not blown near apart to be taking the fuse out like that !
If you disconnect the red wire on each of the output Transistors on the chassis does the fuse still blow?
Re: Kustom 100 blowing fuse [message #27236 is a reply to message #27234] Fri, 12 April 2019 09:55 Go to previous messageGo to next message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member
THis is the 24-L model it has 3 circuit boards the PC5033 is power the PC5068 for tremolo and PC5066 for EQ there is a quick-connect jumper between the power and preamp boards when i disconnect this jumper it stops blowing fuses. I was going to start testing resistors but seems like might take awhile. THere is one Cap that has what looks like dried silicone caulk around it, I'm assuming this was to stop vibrations or something.

replaced so far: 2 driver transistors and 1 output transistor

Test: removed red wires from filter caps and fuse does not blow

checked bridge rectifier

checked diodes

checked for cold solder joints and shorts on board
Re: Kustom 100 blowing fuse [message #27237 is a reply to message #18016] Fri, 12 April 2019 12:32 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4207
Registered: June 2004
Location: NY
Senior Member
This is a differential output stage and preamp , meaning they run on and need a positive and negative supply voltage .
Your act of unhooking just the red wire (positive supply) may have done damage to the amp on its own.
Re: Kustom 100 blowing fuse [message #27238 is a reply to message #18016] Fri, 12 April 2019 13:31 Go to previous messageGo to next message
chicagobill
Messages: 1932
Registered: April 2003
Senior Member
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.
Re: Kustom 100 blowing fuse [message #27239 is a reply to message #18016] Fri, 12 April 2019 21:02 Go to previous messageGo to next message
JDinPA17603 is currently offline  JDinPA17603
Messages: 40
Registered: May 2018
Location: Lancaster, PA
Member
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

Re: Kustom 100 blowing fuse [message #27240 is a reply to message #18016] Sat, 13 April 2019 06:24 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4207
Registered: June 2004
Location: NY
Senior Member
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

Re: Kustom 100 blowing fuse [message #27243 is a reply to message #27239] Sat, 13 April 2019 12:08 Go to previous messageGo to next message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member
john

The the red and green wires WERE connected to all of the boards and the fuse did not blow when the molex was unplugged

I had disconnected both green and red from filters previously (not just the red as stated in previous post),

Ill be checking the caps next

Re: Kustom 100 blowing fuse [message #27244 is a reply to message #27240] Sat, 13 April 2019 14:07 Go to previous messageGo to next message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member
ok i checked the caps in the 5033 board they all checkout within tolerance. the model is a hustler
Re: Kustom 100 blowing fuse [message #27245 is a reply to message #27240] Sat, 13 April 2019 14:14 Go to previous messageGo to next message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member
the pilot light has been out all along.
Re: Kustom 100 blowing fuse [message #27246 is a reply to message #18016] Sun, 14 April 2019 06:13 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4207
Registered: June 2004
Location: NY
Senior Member
Well it seem like your back to where Bill posted, that being testing the 2 output and the driver Transistors and the string of 3 bias diodes..
Be very careful with the leads of that metal cased diode in the clip between the output Transistors as they are very fagile!
Re: Kustom 100 blowing fuse [message #27247 is a reply to message #18016] Sun, 14 April 2019 11:01 Go to previous messageGo to next message
JDinPA17603 is currently offline  JDinPA17603
Messages: 40
Registered: May 2018
Location: Lancaster, PA
Member
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.
Re: Kustom 100 blowing fuse [message #27248 is a reply to message #27247] Sun, 14 April 2019 19:05 Go to previous messageGo to next message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member
Retested output transistors and one was blown. I replaced with a new transistor and turned on =blew a fuse again. Rechecked newly installed transistor and it is blown. I'm thinking I somehow managed to switch the yellow and blue leads around or is there something else that would cause the transistor to blow.
Re: Kustom 100 blowing fuse [message #27249 is a reply to message #18016] Mon, 15 April 2019 06:12 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4207
Registered: June 2004
Location: NY
Senior Member
Just unhook all the connections to the output Transistors and see if the fuse still blows.

The yellow wire of the slip on connector goes to the Emitter of the transistor.
If your Transistors are mot marked on the bottom then if you look at them up side down with the slip on terminals closest to your left, the Emitter will be the top terminal.
At this point to not harm the power transformer with all this blowing fuses stuff I would derate the fuse just for now by 1/2 amp or like Bill posted for all of 20 bucks build yourself a light bulb limiter!
Re: Kustom 100 blowing fuse [message #27250 is a reply to message #18016] Mon, 15 April 2019 12:23 Go to previous messageGo to next message
chicagobill
Messages: 1932
Registered: April 2003
Senior Member
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.
Re: Kustom 100 blowing fuse [message #27267 is a reply to message #27250] Mon, 22 April 2019 17:02 Go to previous messageGo to next message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member
thanks for all the help. Right now im trying to replace a resistor but going from the 5033 hustler diagram the lower diagram says its r24 but the top diagram says r24 is a 5w .51 resistor and i know thats not right the resistor is burned so i cant read the stripes
Re: Kustom 100 blowing fuse [message #27268 is a reply to message #27267] Mon, 22 April 2019 19:12 Go to previous messageGo to next message
JDinPA17603 is currently offline  JDinPA17603
Messages: 40
Registered: May 2018
Location: Lancaster, PA
Member
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.
Re: Kustom 100 blowing fuse [message #27271 is a reply to message #27268] Tue, 23 April 2019 10:42 Go to previous messageGo to next message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member


according to the schematic the r23 and r25 are supposed to be 150 ohm 1% the ones in my board now are 150 ohm 10% and not measuring to 1% so replacing those along with r26 ... waiting on the parts. meanwhile gonna recheck transistors to see if they got screwed up because i turned on with resistors out of tolerance.
Re: Kustom 100 blowing fuse [message #27272 is a reply to message #27271] Tue, 23 April 2019 12:12 Go to previous messageGo to next message
JDinPA17603 is currently offline  JDinPA17603
Messages: 40
Registered: May 2018
Location: Lancaster, PA
Member
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.
Re: Kustom 100 blowing fuse [message #27273 is a reply to message #18016] Tue, 23 April 2019 12:13 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4207
Registered: June 2004
Location: NY
Senior Member
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

Re: Kustom 100 blowing fuse [message #27274 is a reply to message #18016] Tue, 23 April 2019 12:30 Go to previous messageGo to next message
chicagobill
Messages: 1932
Registered: April 2003
Senior Member
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.
Re: Kustom 100 blowing fuse [message #27275 is a reply to message #18016] Tue, 23 April 2019 12:35 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4207
Registered: June 2004
Location: NY
Senior Member
I have always felt that the protection circuit and its close tolerance resistors was a great idea, but since Kustom did not use matched drivers it's a strange deal in my book!

I
Re: Kustom 100 blowing fuse [message #27276 is a reply to message #27275] Tue, 23 April 2019 13:19 Go to previous messageGo to next message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member
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

Re: Kustom 100 blowing fuse [message #27277 is a reply to message #27276] Tue, 23 April 2019 18:00 Go to previous messageGo to next message
JDinPA17603 is currently offline  JDinPA17603
Messages: 40
Registered: May 2018
Location: Lancaster, PA
Member
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

Re: Kustom 100 blowing fuse [message #27278 is a reply to message #18016] Wed, 24 April 2019 07:40 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4207
Registered: June 2004
Location: NY
Senior Member
There's no need to use anything better in these amps then good old ( cheap these days ) 2N3055!
In fact the higher gain of the nte181 might cause oscillation problems due to the way some amps are layed out!
Re: Kustom 100 blowing fuse [message #27279 is a reply to message #27277] Wed, 24 April 2019 08:33 Go to previous messageGo to next message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member
that might be the problem i replaced Q5 with a nte128 when it should be a nte 129
Re: Kustom 100 blowing fuse [message #27283 is a reply to message #27279] Thu, 25 April 2019 13:20 Go to previous messageGo to next message
chicagobill
Messages: 1932
Registered: April 2003
Senior Member
Yes, that would be a big problem. Follow the parts listing that John posted for you and you should be able to get it sorted out.
Re: Kustom 100 blowing fuse [message #27303 is a reply to message #27283] Thu, 09 May 2019 14:19 Go to previous messageGo to next message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member
OK replaced the nte 129 and still blew the fuse. However, i disconnected the output transistors and it does NOT blow fuse when turned on
Re: Kustom 100 blowing fuse [message #27304 is a reply to message #27303] Thu, 09 May 2019 16:33 Go to previous messageGo to next message
JDinPA17603 is currently offline  JDinPA17603
Messages: 40
Registered: May 2018
Location: Lancaster, PA
Member
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.
Re: Kustom 100 blowing fuse [message #27316 is a reply to message #27304] Fri, 17 May 2019 11:43 Go to previous messageGo to next message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member
Just to double check what is the replacement part for Q3 transistor? part number is 007-0002-00
Re: Kustom 100 blowing fuse [message #27317 is a reply to message #18016] Fri, 17 May 2019 12:21 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4207
Registered: June 2004
Location: NY
Senior Member
Q3 on the pc5066 board is a FET, it crosses to a nte221 or a ecg221.
You need to follow strict anti static techniques when handling and installing new one?
Re: Kustom 100 blowing fuse [message #27318 is a reply to message #27317] Fri, 17 May 2019 12:51 Go to previous messageGo to next message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member
rca 38135 is what is in it now on the 5033 circuit board. rechecked the transistors and diodes one diode CR-2 was facing the wrong direction. reconnected everything and tested still some problem (fuse blows and Q8 output transistor gets blown)
Re: Kustom 100 blowing fuse [message #27319 is a reply to message #18016] Fri, 17 May 2019 13:40 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4207
Registered: June 2004
Location: NY
Senior Member
Sorry, Q3 on the 5033 board crosses to a nte128 NPN type.

It's original RCA number is 38735.

[Updated on: Fri, 17 May 2019 13:41]

Report message to a moderator

Re: Kustom 100 blowing fuse [message #27327 is a reply to message #27304] Sun, 19 May 2019 08:48 Go to previous messageGo to previous message
timetraveler is currently offline  timetraveler
Messages: 25
Registered: April 2019
Junior Member
the .5 ohm 5 watt resistors are reading .7 ohms which is outside of the 10% tolerance range would that cause the fuse to blow?
Previous Topic: K200A-1 Power Amp Rescue Needed
Next Topic: Kustom III lead pc board 5065 rev2
Goto Forum:
  


Current Time: Fri Sep #d 20:43:03 EDT 2019
.:: Contact :: Home ::.

Powered by: FUDforum 3.0.9.