| Attempting to repair a Kustom 100 (k 100b-5) I think?? [message #8101] |
Thu, 25 January 2007 19:47  |
washburnkc70v
Messages: 2
Registered: January 2007
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Junior Member |
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Hi everyone, this my first post here.
To get to the point, my brother recently gave me an old Kustom 100 PA head, its missing the labels on the back that would have the model number, but I found one on ebay that looked just like it so I'm assuming its a 100b-5. I would love to get this thing running.
The problem with it is it seems to be powering up, but has no output. I'm getting 40v dc on the filter caps if I remember correctly. I checked the output transistors and the voltages I'm getting seem a bit funny but I really don't have any experience with these and I couldn't find a data sheet on them(RCA 36892). I'm leaning towards thinking they are bad, but thats just a guess.
I know I probably won't be lucky enough to get a schematic, but if anyone has it and are feeling generous... I was hoping maybe someone could give me some tips, like if these have some typical things that fail or known issues. Most of my previous experience is with Fender tube amps and effects pedals. Any help would be much appreciated.
[Updated on: Thu, 25 January 2007 20:53] Report message to a moderator |
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| Re: Attempting to repair a Kustom 100 (k 100b-5) I think?? [message #8102 is a reply to message #8101] |
Thu, 25 January 2007 20:51  |
washburnkc70v
Messages: 2
Registered: January 2007
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Junior Member |
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I think I've got the pinout for those output transistors.
collector=red wire
base=blue wire
emitter=yellow wire
Here's the voltages I'm getting on those-
on the left one
c 39.4V
b .594V
e 49.6 mV
on the right one
c -39.5mV
b 38.9V
E 39.5V
I searched on the forum and found where someone listed NTE130's as replacements, so I'm looking at the the data sheet for those for the pinout. It's strange to me that the outer case is the collector, but like I said I've never worked with these.
Either way those voltages seem very wrong to me. Also, checking the transistors with my meter in "diode check mode" I get a reading with every combination, but I am checking them while in the circuit.
[Updated on: Thu, 25 January 2007 20:52] Report message to a moderator |
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| Re: Attempting to repair a Kustom 100 (k 100b-5) I think?? [message #8107 is a reply to message #8104] |
Fri, 26 January 2007 09:53 |
C4ster
Messages: 686
Registered: June 2001
Location: Mukwonago, WI (Milwaukee...
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Senior Member |
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Wow, it's nice being quoted, but I don't remember that one! I really prefer Motorola if you can find them. Now Motorola is ON Semiconductors. The part numbers I would recommend are MJ15001G, MJ15015, and MJ15022. I have used these quite often and are virtually indestructable. They have higher ratings than the NTE181. These are available from Digikey and Mouser but Mouser is quite a bit higher. A MJ15015G is $2.55 and an MJ15022G is $4.73 from Digikey. Pretty cheap if you ask me.
Conrad
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| Re: Attempting to repair a Kustom 100 (k 100b-5) I think?? [message #8109 is a reply to message #8108] |
Fri, 26 January 2007 13:29 |
C4ster
Messages: 686
Registered: June 2001
Location: Mukwonago, WI (Milwaukee...
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Senior Member |
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No big deal. Actually, I found the Motorola's while being a service tech for Sunn 20 years ago. They use the MJ15022's and MJ150023's for matched pairs in their 600 watt SA21 power amps. They crossover to just about any application. It really takes a lot to destroy them. They have a 25 amp collector current at 140 volts. Where Kustom was getting 100 watts at 4 ohms out of a quad set of transistors, Sunn was getting 200 into 4 and 300 into 2 ohms. All night long! 600 bridged into 4. That was 25 years ago. Technology advances steadily.
Conrad
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