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I'm impressed by the number of electronics wizards in this forum. Maybe you can help me identify a source or equivalent for this transistor.
It is a T0-3 type power transistor, manufactured by RCA.
The numbers read: 7 0100 7628
It is one of eight output transistors in a "Kustom Stereo-X" PA system.
Back when I used to work on amps regularly (about 25 years ago!) I could run down to the electronics parts store and get these over the counter. Whic is something I had to do regularly with Kustom amps, as they liked to blow their power transistors. But I don't think RCA makes them anymore and I can't find anything on the web. Kustom amps has long changed hands and I don't think they have info on their old stuff anymore.
They appear to be NPN transistors, but I don't have the schematic. This is the only one that is shorted. The amp blows a fuse the moment you turn it on.
This is a very solid looking 250 watt PA. I hope to make it work again.
It is a T0-3 type power transistor, manufactured by RCA.
The numbers read: 7 0100 7628
It is one of eight output transistors in a "Kustom Stereo-X" PA system.
Back when I used to work on amps regularly (about 25 years ago!) I could run down to the electronics parts store and get these over the counter. Whic is something I had to do regularly with Kustom amps, as they liked to blow their power transistors. But I don't think RCA makes them anymore and I can't find anything on the web. Kustom amps has long changed hands and I don't think they have info on their old stuff anymore.
They appear to be NPN transistors, but I don't have the schematic. This is the only one that is shorted. The amp blows a fuse the moment you turn it on.
This is a very solid looking 250 watt PA. I hope to make it work again.
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Re: Mystery transistor
Sun, July 2, 2006 - 3:59 PMHmmm...I wouldn't rate myself as much of an electronics wiz or much of a web geek either (others who know me might disagree, but hey it's all relative). Anyhoo, a couple of Google searches and a little bit of intuitive reasoning yields the following:
www.vintagekustom.com/frame.html (source for vintage Kustom schematics)
www.goldmine-elec-products.com/pr...asp (source for power transitors once you find a part number
Dunno if this is what you were looking for, but it was a momentarily interesting research project for me.
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Unsu...
Re: Mystery transistor
Sun, July 2, 2006 - 5:29 PMThanks.
Unfortunately, none of the amps they list are the same model.
I suspect Kustom used the same power transistor in all their amps.
But I have my doubts that the schematics identify it any differently than what is on the case.
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Re: Mystery transistor
Sun, July 2, 2006 - 4:14 PMOh and there appears to be another vintage Kustom fan site that claims to have a schematic for your amp:
www.broadwaymusicco.com/Kustom10.htm -
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Re: Mystery transistor
Wed, July 5, 2006 - 8:22 PMMy best guess is 2N3055. I've repaired a few guitar amps in the past and they all used the 2N3055 finals. Sometimes several. The 2N are dirty cheap and it may be worth to try if it works.
There is usually a high wattage/low ohm resistor that dies with the finals, you should probably replace that as well. -
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Unsu...
Re: Mystery transistor
Wed, July 5, 2006 - 11:10 PMThanks. I'll bet you are right.
I fixed a lot of these old Kustom amps back in my day as a tech at the guitar store, and that transistor number seem right. It's just been so long, I could not quite remember anymore.
Used to be, you could just grab a transistor book that had all the equivalents. Now you have to outbid someone on ebay to get your hands on one of those books. ugh. -
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Re: Mystery transistor
Wed, July 5, 2006 - 11:29 PM> I'll bet you are right.
I wouldn't be sure about that :-)
Anyway, the 2N3055 was introduced by RCA. I've tried to download this paper:
ieeexplore.ieee.org/search/wrapper.jsp
but access to this journal is not included with my subscription.
If you want to do an extra test, for peace of mind, you can try to cut the metal top with a dremel and expose the die. Do the same with a 2N3055 of the same vintage and they should look the same. Problem is that if they don't, you still have no answer since the two could be two different generations.
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Re: Mystery transistor
Wed, July 5, 2006 - 11:46 PMThe exposed die should look like this:
tesladownunder.iinet.net.au/LEDT...r.jpg
Transistors manufactured in a different period might look different; this picture is claimed to be of a 2N3055 as well:
www.fieldlines.com/story/20...5028/6819
From what I remember (I've opened a few in the past, dead 2N3055 = poor man's solar cell :-) ) the die should look like the first one.
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Unsu...
Re: Mystery transistor
Thu, July 6, 2006 - 12:32 AMI think I'll just pop one in and see what happens.
Remember, this amp blows a fuse the moment you throw the switch. There could be a lot wrong with it, but a shorted power transistor like I have on this amp is the mostly culrpit on a Kustom.
If I can't fix it, I've still got $50 to $100 worth of good project parts to salvage from it. Paid $15 at a garage sale. You ougtha see the transformer on this thing. There is some serious iron. -
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Re: Mystery transistor
Thu, July 6, 2006 - 11:59 AMGood luck and keep us posted.
At worst, it sounds like a perfect candidate for an Ebay auction :-) -
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Unsu...
Re: Mystery transistor
Thu, July 6, 2006 - 4:13 PMEbay, no way.
I'm keeping it. The cabinet would make a great housing for a guitar ube amp I am meaning to build, and the parts will come in handy for that and other projects.
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