Need help finding an LF Power Amp for my load tester

[jonnyGURU]

I've been looking all over for a Hitachi 1031(K) low frequency power amplifier for the ol' Sun Moon SM-268. It burned out and now the thing pops any PSU you plug into it. Stupid little $2 part and I can't find one.

Any help would be appreciated, alternate part numbers, source even if it's in China, etc.

Here's pics of a burnt one and a functioning one:

[etnietering]

Re: Need help finding an LF Power Amp for my load tester

Here's the datasheet, hopefully that'll help you find something equivalent:
https://cdn.badcaps-static.com/pdfs/...4e5ba85a27.pdf

[jonnyGURU]

Re: Need help finding an LF Power Amp for my load tester

Yeah... Thanks. I've got the datasheet and I'm afraid it doesn't help me find an equivalent. Maybe it can help someone else find an equivalent for me though. I'll offer up a free PSU in exchange for a good lead.

[370forlife]

Re: Need help finding an LF Power Amp for my load tester

http://www.chinaicmart.com/series-B10/B1031.html

They only seem to have TI and ST branded one's

http://www.ic-trade.com/eparts/B1031.html

Theres some, all in china though, don't really know how reliable those sites are either..

[kc8adu]

Re: Need help finding an LF Power Amp for my load tester

http://www.ceitron.com/semi/nte$$.phtml?part=NTE2542
i get a lot of tough parts from this guy.lots of old stock.

[Khron]

Re: Need help finding an LF Power Amp for my load tester

I did a quick search on Farnell with some "similar and above" ratings to the transistor that's blown, and i got THESE RESULTS .

I've searched for both PNP's and NPN's; if i were you, i'd replace both, in case they're in pairs. Check the datasheets to see which model is complementary to which.

Good luck on the repair

[stj]

Re: Need help finding an LF Power Amp for my load tester

it's just a 2sb1031 transistor - there must be equivilents.

[jonnyGURU]

Re: Need help finding an LF Power Amp for my load tester

it's just a 2sb1031 transistor - there must be equivilents.

Agreed. There must be. Any ideas?

[hardwareguy]

Re: Need help finding an LF Power Amp for my load tester

The high Hfe gave it away before the equivalent circuit did...its a Darlington transistor.

Ill look for something. Is this in the PSU?

[hardwareguy]

Re: Need help finding an LF Power Amp for my load tester

Parameters that matter:

Hfe a.k.a gain doesn't matter that much usually as it drifts wildly from transistor to transistor even of the same type! The original Hfe is 1000 with a max of 20000 spec'ed in the datasheet!

Base-collector voltage must be 100V or greater
Base emitter voltage must be 100V or greater
Collector current must be 15A or greater with a 20A peak rating or greater.
Emitter-base voltage: 7V. I doubt this will be too much of an issue.

Im not finding much in TO3P packages....most of the suitable substitutes are in TO3 metal can.

[hardwareguy]

Re: Need help finding an LF Power Amp for my load tester

Im looking on Mouser and there is only one thing in a plastic package that comes close, the ON Semiconductor MJH6287. Package is SOT93/TO-218

Higher collector current than the original. (20A vs 15A)

Same collector voltages, 100V.

Maximum emitter - base voltage of the old was 7V, this one is 5V. Max base current of the original is 3A, this one is 0.5A.
If the circuit was designed well, ie, not really pushing the base hard, it should work.

Hfe is lower at 750, max is 18,000. This will not likely cause issues unless the circuit is VERY picky.

There's a databook online showing 2SB1317 as a substitute....its NOT! (2SB1317 is not even Darlington!)

[hardwareguy]

Re: Need help finding an LF Power Amp for my load tester

ST Microelectronics BDW84C may also work. TO-247 plastic package. Similar to TO3P but slightly larger. As with the other substitute I mentioned in the TO-218 package, you WILL need a new mounting insulator!

Same collector voltages and same collector current as the original but with a peak current of 40A instead of 20. Hfe is 750 instead of 1000, the base-emitter voltage is 5V instead of 7v and the base current is 0.5A instead of 3A.

[hardwareguy]

Re: Need help finding an LF Power Amp for my load tester

kc8adu has suggested using an NTE 2542. This is in the same package and is a little closer electrically as well to either of my previous suggestions. Its a huge durability upgrade, much like the ON Semi device I suggested.

25A continuous current, 40A peak instead of 15A, 20A peak

NTE2541 (NPN) is the complementary to the 2542 (PNP).

If its used in a complementary pair I would replace the pair. Pairs are obvious if you look for them....sometimes they come in black and green, especially with the Japanese types. Otherwise, just look for an equal number of two different numbers in the circuit. For example; if you have as many 2SD1435 as you do 2SD1031 in the circuit; it's VERY likely to be in complementary NPN and PNP pairs.

Look into changing all of them because when one blows, the rest may not be far behind. Test the ones that aren't obviously burnt, they may be bad as well.

[jonnyGURU]

Re: Need help finding an LF Power Amp for my load tester

Wow! Thanks hardwareguy!

I actually found a couple pieces in Taiwan that are exact matches, so I have someone over there trying to figure out who's actually reputable enough to buy from.

Funny thing is that the data sheet says this transistor pairs up with the 2SD1435K. Maybe in typical applications, but in this load tester I can't find any 2SD1435K's!!

[hardwareguy]

Re: Need help finding an LF Power Amp for my load tester

In a common push-pull configuration amplifier, it would pair up with the 2SD1435. The lack of 2SD1435s is a clear indication that this is not push pull.

Who knows, it may not be an amplifier at all. Id have to examine the circuit to be sure. Darlington transistors certainly wouldn't be my first choice for a switching power supply. MOSFETs make way more sense there.

[370forlife]

Re: Need help finding an LF Power Amp for my load tester

It's in a power supply tester.

[stj]

Re: Need help finding an LF Power Amp for my load tester

so the transistors are directly across the test-supply i assume and you vary the base-drive to convert more current into heat!

well 15a wont do it, so i also assume there are several of these in parallel with current balancing resistors.

[hardwareguy]

Re: Need help finding an LF Power Amp for my load tester

It's in a power supply tester.

I know that....that doesn't mean the tester cant have some sort of PSU or amplifier circuit inside it.

I'm guessing it works as stj has described...and in that case, it would be a funky amplifier.