MJE13005 vs STP13007 in SMPS

[Dannyx]

Good day folks. I'd like some advice on this little PSU I'm working on: it's out of a DVD player and I managed to only partly fix it.

When I got it, the transistor was shorted and the fuse was blown. Simple job, I though, I'll just replace the transistor and I'll be back in business. Now because I don't have new replacement parts readily available at this "professional" shop of mine, I dug through some ATX supplies and found one which used STP13007 as the main transistors. I removed one and installed it. The PSU works, but the regulation is rather poor: when unloaded it overshoots, so instead of 12v I get around 14-15. When loaded, the -12v bus drops to around -10v, while the 12v bus goes to a more normal 11v. Same goes for 5v. DVD still didn't power on though: initially, the blue backlight for the display came on but nothing else. Suddenly, as I was measuring the output connector, the PSU started making a faint whistling sound, so I unplugged it immediately. When I plugged it back in, funnily enough the display was showing nonsense on it: dashes and numbers and stuff....true, this could very well be a logic issue and not a PSU issue, however the reason I'm pushing on is because this is a very small and nasty device, yet my STP13007 got rather hot during the short time it was plugged in...

Point is: in the past, I successfully replaced the MJE13005 with MJE13007 or even 13009 and it worked. Could it be an issue here though ? Caps checked fine with my capacitance meter...should I bother to replace the transistor with a 13005 ? That would involve extra digging in the junk box...cheers and thanks.

[stj]

Re: MJE13005 vs STP13007 in SMPS

well i doubt nothing else was damaged,
and you may want to consider what killed it the first time.

start with the feedback - suspect the tl431, the opto and the small electrolytic that dampens it.
and check the snubber diode on the primary side - it looks cracked in the foto

[Dannyx]

Re: MJE13005 vs STP13007 in SMPS

Probably a bad logic board: I managed to get it more stable by changing some of the caps, including the one on the primary, so the TL431 is fine. Still, the -12v rail overshoots dramatically when unloaded - close to 20v ! The regulation is done by the 5v output, given that the 12v output is just a diode with a capacitor straight to the output connector, nothing between. Only the large connector is used - the other one isn't, it's for a different model presumably. No on/off command on this PSU, so it's a simple thing to troubleshoot.

Now it just went back to showing a blank display, so that instance where it displayed something was just a one-off or it was already on its way out. The overshoot could've killed it, for instance when it lost its regulation...just a hunch...either way that thing isn't worth more than 20 bucks on any auction site, so I don't think it's worth digging into the logic board to find out what is or is not working. It's like the thing is on all the time, just not doing anything.

[PeteS in CA]

Re: MJE13005 vs STP13007 in SMPS

MJE13005, MJE13007, and MJE13009 were part of Motorola's "Switchmode" series transistors, designed for use in switching power supplies. These three parts have the same voltage rating, but different current ratings (as listed above, lowest to highest). So the substitution you made should be safe, possibly improving the heat dissipation slightly (larger die, lower thermal resistance from junction to case).

That power supply looks like a self-oscillating flyback design. Probably the 5V output is regulated, and the +/-12V outputs are determined by the turns ratios and loading. Leaving one of the 12V outputs unloaded lets it peak-charge to whatever voltage spikes there are on that output.

[kaboom]

Re: MJE13005 vs STP13007 in SMPS

At least replace the output caps, preferably the bias and main filter cap on the line side also.
At least pull them and check for electrolyte leakage or corroded-off leads.

The first cap on +5 is either open or greatly decreased in value, causing low average voltage; duty cycle goes up to "compensate."
You see this as -12 running away.

Having recapped several of those "square" DVD players, I can tell you the caps were always trash.
This can sometimes damage components in the player.
Test it with a PC PSU before dealing with the units SMPS.

The snubber resistor won't get too warm if the caps are good.

[Dannyx]

Re: MJE13005 vs STP13007 in SMPS

I replaced just about every cap, except the main one and another small one on the output on the other -12v line, since there's two of them and that one is not connected....true, these "replacement" ones were not new, since this wonderful shop of mine doesn't keep a stock of basic parts - you have to pull them off donor boards which means they're going to have service hours behind them. This is the no.1 thing I hate about this place: recovering parts that should always be new...imagine paying like 100$ for a repair and discovering the parts aren't new...someone should really call consumer protection on these fellas, maybe then they'll get their sh!t together so I won't have to bring my own parts from home to fix stuff FOR the shop...:|

This introduces even more variables and frustrations, because you're not sure if the part you've replaced is good or not. True, the caps I put in were checked with my capacitance meter and they weren't out of whack, but still, not ideal.
Yeah, the DVD is a square one, how'd you guess ?

[stj]

Re: MJE13005 vs STP13007 in SMPS

does the shop use lead-free solder, or 60/40??

[Dannyx]

Re: MJE13005 vs STP13007 in SMPS

60/40, though this is the roll which I am currently using since it was given to me the first day...don't know about the other chaps around here...I might actually have a peek

[madan1]

Re: MJE13005 vs STP13007 in SMPS

Why do not you just hook up the logic board to an external, properly working PSU and see if it works?
Then you will know if there is any point in fixing its psu.

[Dannyx]

Re: MJE13005 vs STP13007 in SMPS

Yeah, that would've been the first thing I would've tried if I were at my old shop where I had everything I needed readily available...this place is pretty lacking in "features", so we don't exactly have functional ATX supplies around here, at least not without scavenging one from an old PC or something

[stj]

Re: MJE13005 vs STP13007 in SMPS

60/40, though this is the roll which I am currently using since it was given to me the first day...don't know about the other chaps around here...I might actually have a peek

well that's a breach of RoHS rules, the fine if they get caught is HUGE.

[Dannyx]

Re: MJE13005 vs STP13007 in SMPS

Not sure if that's actually possible, realistically speaking

[eccerr0r]

Re: MJE13005 vs STP13007 in SMPS

Speaking of ROHS rules, are companies required to mark their circuit boards that they use lead free solder? This pisses me off, I'd like to stick to using lead free solders on lead free boards but if it doesn't tell me, how would I know?

Is using melting point the only way to tell if a board is using lead free solder ahead of time?

Else I would MUCH rather use the easier to melt, leaded solders...

[stj]

Re: MJE13005 vs STP13007 in SMPS

it's easy from a repair standpoint,
if it used leadfree solder to begin with then you keep it that way - if not then it dont matter.
if your making stuff from scratch with the intention of passing it on then it's different.
you need to check on local laws/rules for your intended market.

in europe i dont think it needs to be marked, but it must be leadfree - not just the solder but the pcb and component plating.
and any final product must be CE compliant and marked "CE" to show it.
that wont cost you anything, it's a declararation that it complies with the rules - not a certification.

china RoHS is actually more strict than the EU btw, probably because they have so much polution already.

as for as your question, just go 100% lead-free.
there are very good solders around now, that totally wipe out the need for lead.
5 years ago that wasnt true, but the metal blends and fluxes are under constant evolution.

solder is complex, there is good solder and great solder and crap solder - you have to be selective when you buy it.
the main difference is the flux.

[momaka]

Re: MJE13005 vs STP13007 in SMPS

The 13007 in place of the 13005 isn't the issue.
As PeteS and kaboom mentioned, this is flyback design likely with regulation only on the 5V rail. So it's normal for the other rails to go a bit "wild" if they are not part of the flyback. Last month for example, I war recapping an LCD monitor PSU and thought I could get away with using 16V caps on the monitor's "13V" rail. The monitor originally had 25V caps. Well, I'm glad I decided to check the voltage on the caps before doing a recap with my 16V caps - it was close to 20-21V when fully unloaded.

That said, bad caps on the output and any "start-up" caps on the primary could cause the voltage on the unregulated rails to drift even further (higher), especially if the PSU is a 2-transistor design - which yours appears to be, at a quick glance.

this place is pretty lacking in "features", so we don't exactly have functional ATX supplies around here, at least not without scavenging one from an old PC or something

Bring you own in the future, then?

There are certain tools and supplies I just wouldn't work without. If the new place isn't providing them, it might as well be time to look elsewhere for a job. Nothing worse than working at a place that doesn't value your time and effort.

well that's a breach of RoHS rules, the fine if they get caught is HUGE.

Lol, sounds like you've never traveled to Eastern Europe.
Technically, they (the countries in the EU) have pretty much the same laws as the rest of Europe, but no one gives a rat's ass about following them and there's rarely any consequence for not doing so.
... and Romania is not even the worst when it comes to that.

So as Danny said... yeah, not gonna happen.

[Dannyx]

Re: MJE13005 vs STP13007 in SMPS

That said, bad caps on the output and any "start-up" caps on the primary could cause the voltage on the unregulated rails to drift even further (higher), especially if the PSU is a 2-transistor design - which yours appears to be, at a quick glance.

IS it a 2 transistor setup ? That is only if you count the small one in the TO-92 package which I believe drives the bigger one. Other than that, there's only one transistor there really.

Bring you own in the future, then?

There are certain tools and supplies I just wouldn't work without. If the new place isn't providing them, it might as well be time to look elsewhere for a job. Nothing worse than working at a place that doesn't value your time and effort.

Yes, most of...actually ALL the tools I work with are mine ATM and my toolbox is quite comprehensive - there isn't a job which I can't tackle with them so far. The only thing they were kind enough to offer was a soldering iron...what'd you expect ? My hot air station also arrived in the mail yesterday - one of those little 858Ds...decent enough. The airflow is a bit disappointing but it should get the job done. Better than nothing. Couldn't really dish out for a Quick, since it wouldn't pay for itself.
Moving somewhere else is not an option unfortunately because this is currently one of the biggest electronics service centers in the city from what I know, so you're not gonna get as good a salary as you do here, even if it means sacrificing some comfort and facilities. I constantly look for opportunities to pressure our boss to invest in better tools and equipment, but it's not really appropriate for a "greenhorn" to do so until they've proven worthy, otherwise why should anyone invest to buy you tools ? The biggest issue is replacement parts: working in what claims to be the best biggest and meanest center in town, I shouldn't have to struggle to find a screw, a cap or a resistor by salvaging them from old boards...can't get over this ! There should be a whole stockpile of parts readily available...anyway, what can you do...just carry on

[sam_sam_sam]

Re: MJE13005 vs STP13007 in SMPS

Moving somewhere else is not an option unfortunately because this is currently one of the biggest electronics service centers in the city from what I know, so you're not gonna get as good a salary as you do here, even if it means sacrificing some comfort and facilities. I constantly look for opportunities to pressure our boss to invest in better tools and equipment, but it's not really appropriate for a "greenhorn" to do so until they've proven worthy, otherwise why should anyone invest to buy you tools ? The biggest issue is replacement parts: working in what claims to be the best biggest and meanest center in town, I shouldn't have to struggle to find a screw, a cap or a resistor by salvaging them from old boards...can't get over this ! There should be a whole stockpile of parts readily available...anyway, what can you do...just carry on

Between a rock and a hard place not a good place to be

Very sad

One time I had worked for a company like that

Where I had to robbed Peter to pay Paul to fix anything especially when there was more than one of the same unit

Then I could request to order parts to fix all them really

Now do get me wrong about this concept if you do this to find out if what you think is problem with a piece of equipment this could be very helpful especially if the parts are very expensive and you want to make sure that this will fix the problem

[momaka]

Re: MJE13005 vs STP13007 in SMPS

IS it a 2 transistor setup ? That is only if you count the small one in the TO-92 package which I believe drives the bigger one. Other than that, there's only one transistor there really.

Well, you're right to wonder.

Technically, there really is only *one* main switching transistor (that drives the transformer). And that smaller TO-92 transistors simply drives the big transistor Off when needed. Nevertheless, with *flyback* (discontinuous) designs, this is known as a 2-transistor setup.

This is different from the 2-transistor forward topology you see for the main PS inside PSUs, where both transistors are involved in the switching of currents to the transformer.

And half-bridge also uses 2-transistors... but half-bridge is half-bridge.
Did I manage to confuse you now?

Moving somewhere else is not an option unfortunately because this is currently one of the biggest electronics service centers in the city from what I know, so you're not gonna get as good a salary as you do here, even if it means sacrificing some comfort and facilities.

Ah, I see. So you are getting paid a salary and not commission / per item fixed basis?

I constantly look for opportunities to pressure our boss to invest in better tools and equipment, but it's not really appropriate for a "greenhorn" to do so until they've proven worthy, otherwise why should anyone invest to buy you tools ?

LOL, that's completely backwards of what it should be.

A proper workplace is not an open field "proving grounds", where they just throw a bunch of people and "let the business grow". If they hired you, they did (or should have done so) based on the skills that you say you have. Then they simply give you a short "time trial" period, to see if you are the proper guy for the job... and after that, if you are, you become a permanent employee. Of course, in order to prove yourself, you should have all the necessary tools and supplies necessary for the job available to you.

Imagine I hire a bunch of construction workers, drive them to an empty lot of land, and tell them "build me a luxury house". Then I give them a shovel and tell them "feel free to use any of the resources around you to complete your job. Those of you who prove worthy, I'll hire for another job."
So in a case like that, what are those workers supposed to do? Build me a house out of rocks, mud, and sticks? Certainly one wouldn't expect them to go to the store and pay out of pocket to buy construction materials, tools, and anything else that is need. No, this should already be provided to them. And if it isn't, and I'm not the person adequate to do this task, then I hire someone else who specializes simply in that.

Anyways, I don't mean to rant about your workplace. All the reason I am mentioning this is because I've seen workplaces / repair shops like that simply go down / out of business overtime, because both the customer and the employees just end up being disappointed. And the owner loosing money. You have to invest in your business a little if you want it to do better.

Of course, I've also seen the reverse too: where the business would provide so much of everything that employees start mis-treating and wasting resources unnecessarily, because they are so abundant. The last place I worked was sort of like that... except the losses pretty much came out of our paychecks (that is, since I was working in a computer store, I could take any hardware off the shelf and use it for whatever was needed, if I had good justification. Of course, this costs money to the store. So naturally, our paychecks weren't that big either.)
Thus, I can completely understand you boss not wanting to waste money when it's not needed. But if he is a good boss, he should listen and get you fellas what is needed without question. Clearly, repair parts should be one of those things. Just have you document all repairs and all parts that were needed and why. Then keep everything on file and backed up. That way, if he finds out later on, for example, that the store is loosing money because employee X is purchasing some parts necessarily (and possibly for personal benefit), then finding out who it was shouldn't be too hard.

anyway, what can you do...just carry on

I agree with you to a point -sometimes you really just can't do much.
Just beware that this may only run on until the business starts suffering and boss lays everyone off (and it will suffer, eventually, with a policy like that.)

[Dannyx]

Re: MJE13005 vs STP13007 in SMPS

Ah, I see. So you are getting paid a salary and not commission / per item fixed basis?

Correct. The old shop used the commission system: I'd receive a "guaranteed minimum", to which 10% above each X $$$ was added as a "bonus", so even if I theoretically had no clients enter the shop at all one month, I'd still get something below which it never dropped...obviously

Certainly one wouldn't expect them to go to the store and pay out of pocket to buy construction materials, tools, and anything else that is need. No, this should already be provided to them.

As crazy as it may seem, I actually had to do that a couple of times because I absolutely needed a part or tool right there and then, including some very basic stuff which I still find absolutely inconceivable a "top-notch" (pfft) service center to be without: USB-SATA adapters, HDMI cable (only one in the entire 4 story building...), BNC adapters, HDMI-DVI adapters, 3.5mm jacks, just to name a few off the top of my head. True, not a fortune or anything, plus I get to flip off everybody who tries to touch this stuff. We each have our own toolboxes, that's....sort-of acceptable (though I walked into my former shop with absolutely NOTHING and I grew bit by bit - the company provides very little (unless you maybe request it, at which point it's likely coming out of your pay anyway ). You're taking quite a gamble asking for stuff, because behind an apparent kindness, BigBoss might come in one day and ask if you've put tool X to good use...not sure how he'd take it if I told him "no", especially since, again, I've been here just 3 months barely - no position to play smartass and "mr. Pro". So many things I'd do "right" just because I like doing stuff, but who would let you do that ? The boss might say "yeah, sure, go ahead", but others around you will immediately shut you down, so do you push on playing the "I spoke to the boss card" or do you oblige ? :| Network's a mess and barely works (no expert or anything, don't get me wrong: just stating the obvious), building needs some work, stuff is falling apart, doors are squeaky loose, sink is leaky...you get the idea: stuff which I'd love to tackle just to make things "right" (i.e. wouldn't even expect a tap on the back for doing it), but I can't do that....yet. Once this colleague of mine decides to finally retire, I shall be shopmaster and do as I please...patience....or not, just sabotage the old geezer just kiddin'

Anyways, I don't mean to rant about your workplace.

Go right ahead, I'm doing it myself because I'm not quite enjoying it, which is something I've always feared: not liking your job to me is the equivalent of having lead eyelids every morning