Thermaltake PurePower 420w W0052

[ipman]

Re: Thermaltake PurePower 420w W0052

Cannot find anything else than Jamicon here. Until I can find a better replacement, I hope it will do the job. It is a test PS, so it will not have much uptime.
Anyway, now I have 5.1V, way less than 5.6V of the zener diode. I'd say it's OK now.
Again, thank you all.

[everell]

Re: Thermaltake PurePower 420w W0052

Now............lift one leg of that new zener, and measure the 5vsb. If the voltage is greater than the zener voltage, you still have a problem, and the zener is protecting the mother board.......until it burns up! Make sure that the 5vsb voltage is correct, then reinsert the zener diode.

[c_hegge]

Re: Thermaltake PurePower 420w W0052

Nice job fixing it, but I REALLY wouldn't use a jamicon there. The are even worse than teapo for PSUs. If the teapo failed you, the jamicon will fail sooner and you'll be having the same problem again.

[ipman]

Re: Thermaltake PurePower 420w W0052

Yesterday had enough time to work on it.
Replaced that Teapo 4.7uF/50V cap with a Jamicon 4.7uF/63V same can size. Also replaced the unknown diode with a 5v6 1.3watt Zener on secondary.
Afther rewiring everything, it went on without any problems.
Filtering caps for 3v3 and 5v are Teapo and 12V is G-Luxon, but they are all just fine, with ESR around 0.02-0.03 ohms, so I did not replace them.
Thank you all for the sucessful repair!

[everell]

Re: Thermaltake PurePower 420w W0052

Yes. A shorted transistor measures zero ohms. Replace the capacitor and fire it up!

[ipman]

Re: Thermaltake PurePower 420w W0052

I've measured 31ohms base to emmiter on the SMT transistor. Between the base of the small transistor and the base of the big one there is a 30ohm SMT resistor.
From these measurements can we conclude that the transistor is fine?

[ipman]

Re: Thermaltake PurePower 420w W0052

I did not yet remove it (lack of time to do it).
Found a BCW66H transistor yesterday and the replacement for the damaged capacitor. It seems to fit the specs of the original transistor. Found in fact two kinds of caps for replacement: a miniature 4.7uF/50V from Jamicon rated for 85 degrees celsius and 4.7uF/63V also from Jamicon but rated for 105 degrees celsius. Also did not had enoughe time to check the specs.
Hopefully today I will have more time to measure again the resistance between the base and the emitter of the SMT transistor to be sure before removing it (which is not impossible, but not too easy for me). The Fluke DMM beeps as a short on diode check scale, but I did not measure the effective resistance.
@Toasty: sorry, if I take a full picture of the board, you can't see the small SMT transistor. If I take a closer picture to see the SMT components, you can't see the whole board

[everell]

Re: Thermaltake PurePower 420w W0052

The smt transistor may not be shorted. There is usually a 39 ohm resistor between the base of the smt transistor and the emitter of the big TO-220 transistor. From emitter of the big TO-220 transistor is usually a 2 ohm or less resistor to common. The emitter of the smt transistor goes to common. So between base and emitter of the smt transistor you should measure about 40 ohms each direction which can be confused with a short. The only way to check that smt transistor is to remove it, and then test it outside the circuit.

But...............if you go to the trouble of removing the smt transistor, you might as well replace it with a new transistor. I would leave that transistor alone and replace just the capacitor which is definitely bad. Then test the circuit. If the capacitor doesn't fix it, then go for the smt transistor. If it is shorted, the low ohms resistor between the emitter of the TO-220 big transistor and common is probably open. And maybe some other parts bad!

[Toasty]

Re: Thermaltake PurePower 420w W0052

?? What ??

Anyway... "the 2222 or BCW71??? I am totally confused ..."

are both the same. As I said, it's such a common transistor, especially in SOT23, that it's literally everywhere you go. If you have some junk electronics about, you'll likely find half a dozen on each board.

I still have no idea from your pics (too close), but that's not important.

Toast

[ipman]

Re: Thermaltake PurePower 420w W0052

That's the best i can do, really. The big transistor is behind the heatsink which is also above it, the big rectifier bridge in front ... so on.

[Toasty]

Re: Thermaltake PurePower 420w W0052

I should tape some to a postcard and mail it to you. Could be like playing "Cold War" with micro-dots and such! LOL

[ipman]

Re: Thermaltake PurePower 420w W0052

Here are the pics of the PS board: first one, the TO220 transistor is on the other side of the heatsink, and in the vacant place was the 4.7uF blown cap.
On the other pics are the SMD components on the other side of the board.

[ipman]

Re: Thermaltake PurePower 420w W0052

Yes, indeed it is a very common transistor, I can find it in TO92 capsule, but not in SOT23 ...
I will take some pictures when I'll be home. I've read your mail in the morning and had to go to work instead of pictures (shortened the breakfast to read forum).

The main problem is that the TTH components around this SMD transistors are on the other side, underneath an aluminium heatsink. The 4.7uF cap was removed with a tweezer and a lot of patience ...

Later edit: Found a SMD catalog which states that the device marke K1P on SOT23 capsule is a BCW71 produced by Philips.
Which seems more apropriate: the 2222 or BCW71??? I am totally confused ...

[Toasty]

Re: Thermaltake PurePower 420w W0052

I've got a whole pile of them in different manufacturer's.
Got to be some out there, it's a *VERY* common transistor.



.............still no pics.............. :|

[ipman]

Re: Thermaltake PurePower 420w W0052

Can't find a 2222 in a SOT23 package
Can somebody tell me if there are equivalents? Maybe BC-style?

[ipman]

Re: Thermaltake PurePower 420w W0052

All diodes, including Zener ones are marked with just D. Found another ones marked only as D.
The switching diode is before this, a big one in a black capsule which I found to be just fine afteher removing one leg and measuring it.
Yes, the 2 transistor circuit is complete, one big transistor in a TO220 capsule on a heatsink marked SSP 2N60P and one SMD one marked K1P which seems to be MMBT2222A SMD transistor shorted base to emitter.
The emitter of the MMBT22222 SMD transistor is tied to the stand-by transformer.
The picture of the are is quite hard to understand, there is a mix of through the board and SMD components, but in the first post there is a schematics of what's afther the transformer.

[c_hegge]

Re: Thermaltake PurePower 420w W0052

... I found 5.6V, 6.2 and 6.V rated 1.3watts. Should I get 5.6 or 6.2?

I would go 5.6v. Any higher than that and it wouldn't short in time to save the motherboard in case of another overshoot.

[Toasty]

Re: Thermaltake PurePower 420w W0052

Looking at your picture more closely now. I see the burned diode has a designation of D583. Is that correct? Zeners are -usually- marked ZD### or Z###.

Look around the board and see if there are any marked that way. If so, then I expect this to be a switching diode, not a Zener.

Can we get a larger overall shot of this area? Where is the 5vsb transformer?

The 2 transistor circuit is usually (as mentioned by others) one mounted to the heatsink [mains HOT] and the other is a TO-92 type, 3-legged package, mounted nearby. Perhaps they used an SMD, but without a better overall shot, it's tough to tell.

Toast

[ipman]

Re: Thermaltake PurePower 420w W0052

Indeed, I've found the second transistor. It was a SMD one on the other part of PCB covered in some white stuff. Both transistors are OK, but a 4.7uF/50V Teapo was blown up, electrolyte leaked, etc.
I will go tomorrow to find a replacemnt cap (did not found another one rated more than 35V on my junk) and a replacement Zener diode. I found 5.6V, 6.2 and 6.V rated 1.3watts. Should I get 5.6 or 6.2?

[Toasty]

Re: Thermaltake PurePower 420w W0052

@Toasty: Do you mean the small failed cap should be on the high-voltage part of the power supply? Before the transformer?
Or to put it in another form, those two transistors are the main transistors on a heatsink on the high-voltage side?
I ask about this because the voltage of this cap is too low to be in the high-voltage side.

Indeed, this diode was shorted, but I need to find out why.

c_hegge answered your question.

You can have ~320v or better [mains HOT] on the primary side of the 5vsb transformer that is controlled by the 2 transistor circuit which gets feedback from the output side of the transformer via the optocoupler. If the cap in the 2 transistor circuit fails, it will allow the 5vsb to rise, sometimes as high as 20 volts, frying the motherboard. The Zener (OV protection) diode shorted in this case, likely preventing damage to the motherboard. They are typically not 5v, but more like 6v or so as there is some tolerance built in to allow for load changes. I'd look for a 5.7v to 6.1v, 2A unit to replace it with and call it a day. Replace all the caps in that area, even the tiny ones.

Toast