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Old 12-27-2007, 04:06 PM   #1
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Default Victor Engineering 12V Power Supply Repair

Hi everyone. A good friend of mine who is heavily into racing RC has asked me to help fix his Hi-IQ power supply. It is made by Victor Engineering which is now gone.
The problem it is having is that it blows fuses immediately with any load. I have troubleshot it down to a couple of shorted power transistors. The problem is that I'm not having any luck finding the part #'s for the transistors. The writing on them is SK C2307 050. Anyone have an idea what the replacement part # would be.

I'm not a pro at fixing electronics, I just fiddle. This repair is not for money, just a favour to a friend.

Any help would be appreciated. Thanks.
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Old 12-28-2007, 08:13 AM   #2
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I did a quick search on your number on Mouser Electronics website and came up with what looks like an answer.

Here's a direct link to the result:

http://www.mouser.com/search/refine....t=SK+C2307+050

Hope that helps...
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Old 01-06-2008, 07:23 AM   #3
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Not sure, what you mean? When I click on the link there is no result found for the part. Are you seeing something different than no result found?
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Old 01-06-2008, 03:49 PM   #4
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I did repair a lot of the Victor PS including mine about 10 years ago. All of them did show the same behaviour as yours. Problem was these power transistors were underrated for the 230V mains voltage as used in Europe. I found not only that SK (Sanken) C2307 were shorted but also some other parts in all of the PS.
I remember it wasnīt that easy getting replacement parts but after that I never heard the PS went bad again. My own Victor PS is still working until today.
I have to look if I have any informations left at home. I think Iīm used transistors from Philips Semiconductors and Valvo but anyway the problem was the original Sanken transistors used an isolated case (as a lot of Japanese high voltage transistors) but not the replacement parts. The other question is if those replacement parts are still available today.
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Old 01-07-2008, 05:33 AM   #5
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I'm not having any luck finding a replacement for the c2307. Every search I've done has come up empty. Someone on another forum has mentioned NTE2308 as a replacement but I have not been able to verify this. The datasheet for the NTE2308 is here:

http://www.nteinc.com/specs/2300to2399/pdf/nte2308.pdf

Since I have no info on the C2307 I have nothing to compare to. Any info would be appreciated.

By the way I did also find a couple of diodes shorted around the two C2307. If you remember what other parts I should pay attention to, I'd appreciate it. Thank you.
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Old 01-07-2008, 08:48 AM   #6
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The exact name of the original transistors is 2SC2307 but they just printed C2307 on the case. This is a typical code for japanese transistors where C means NPN transistor. So the NTE2308 is a NPN as well and if I remember right specs are very similar to the 2SC2307.
Donīt know where you are living but if your mains voltage is in the 110V range these could work. For 230-240V mains voltage these are not good enough, I used different ones rated for 800-1000V.
Just didnīt find my repair notes until now. Anyway you should replace both of the highvoltage transistors even when only one seems shorted. The powerdiode near the transistors usually is OK but you should check.
Sometimes the bridge rectifier at the voltage input is shorted too, you should check again. Regarding the other diodes which are used in the area driving the power transistors, some of them are shorted usually always. You should replace all of them.
Donīt know your degree of electronic knowledge, but a word of warning here. The voltage generated in some area of the powersupply is very dangerous, please be carefully here. You should remove the powerwire (mains voltage) always and deadshort the big capacitators using an isolated tool or wire before working on the unit.
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Old 01-07-2008, 01:27 PM   #7
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I've replaced all the diodes already. Also found the big 1/2 watt resistor (100M ohm) that goes across the main 12VDC output shorted as well. The part # that you gave me, 2sc2307, works at Newark Electronics and I've ordered 2 of them. The bridge rectifier seems to be fine. I've removed and checked it and it is not shorted. With the 2sc2307 transistors removed, I am measuring 330 VDC output from the bridge rectifier.

I'm usually very careful with power supplies, but this morning I did manage to get shocked, LOL. I had worked all night and was tired so I made a silly mistake and got shocked.

Thanks so much for sharing your information. I will keep this thread alive with any other findings and I'll let you know if it works when I get my transistors. Take care.
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Old 01-07-2008, 02:54 PM   #8
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So when you can get the transistors your Victor PS should work again.

But wait, there is one mistake. That big resistor isnīt shorted and itīs not 100 MOhm but 0.01 Ohm. I hope you didnīt throw this one away or replace it. The colourcode on low ohm resistors is a little crazy and you can go wrong easily here.
If you analyze the output circuit you will find that resistor doesnīt go across the 12VDC output but is in series to the negative output terminal. The PCB and wiring is a little misleading here. The function of that 0.01 Ohm resistor is currentlimiting. Sometimes there is a big resistor used across the output as a load, but not here.

Hmm, 330 VDC output from the bridge rectifier? Where do you live, is your mains voltage 115V or 230V? If your mains voltage is 230V the transistors can go defective again. Under certain conditions the voltage at the switching part of the PS will go beyond what the original transistors could handle. So itīs better using different type of transistors then.
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Old 01-07-2008, 09:18 PM   #9
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I'm in Canada so I'm using 115VAC. You are right the resistor is not across the output. Thanks for pointing that out.

The bridge rectifier has 18VAC across the the input and 330VDC at the output. The transistors are not installed right now. So you suspect the bridge rectifier is no good as well?

Sorry if these questions seem trivial. I'm still learning. Thanks for your help.
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Old 01-08-2008, 10:16 AM   #10
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I never did measure voltages around the bridge rectifier. But we have 230VAC so you canīt compare anyway. I think it also doesnīt work out measuring here as long as you doesnīt have any reference values, as there is a very special circuitry used with this PS. Also itīs a no-load condition when the transistors are removed.
Best is removing the bridge rectifier from the PCB and testing on a component-tester or diode-tester as used with some DVM.
Sometimes one of the diodes is shorted but itīs not always.
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Old 01-09-2008, 03:47 PM   #11
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I am awaiting the arrival of the transistors from the supplier. In the mean time, a local electronic store carries a bridge rectifier that is equivalent to the original KBL404. It is a KBL04. Measuring with a multimeter, I could not fault the original so I bought a new one only because it was cheap. With the transistors removed the output of the new bridge rectifier has not changed at 330VDC. The input of the new bridge rectifier has changed, it is 12VAC, the original was 18VAC.

I wanted to ask another question. I did find one of the diodes around one of the transistors bad. The diodes are all the same around the transistors. I was planning on replacing all of them. The problem is that the part # printed on the diode is not recognized in any of my searches. It is PXPR1004. Measuring a good diode they have a forward bias of .5V and resistance of ~300 KOHM. Do you happen to know what a common replacement would be?

I'm determined to fix this thing. Thanks again.

Last edited by Degull; 01-09-2008 at 04:24 PM.
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Old 01-09-2008, 04:31 PM   #12
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Degull,

I can't explain that... when I first posted that the link did produce results, and the part WAS shown to be in stock... I have no idea why it's not working now.

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Old 01-09-2008, 04:34 PM   #13
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Trips, no problem, I figured something happened. V12 was kind enough to help with a good # that worked at Newark Electronics. Thanks for your help.
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Old 01-10-2008, 04:14 PM   #14
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The link also didnīt work for me but I think it canīt work as C2307 isnīt the full code/name of that transistor.

The PXPR1004 diodes are the ones I meant, 4 pieces overall. At the PCB these are marked as D8,D9,D10,D11. If one of these are shorted you really should replace all of them.

The problem is I also didnīt find specs or replacement parts for them so I just used common 1N4007. Maybe these arenīt the perfect replacement, but itīs difficult if you have no specs. At least the 1N4007 do work and from the Victor PS I repaired no one ever went bad again.
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Old 01-11-2008, 06:17 PM   #15
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Hi there. I will replace all the diodes with 1n4007's. I'm awaiting the arrival of the transistors. Thanks for your input. I'll let you know what happens once I replace everything. Take care.
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