Measuring 2sa733p gain

[evilxsystems]

I'm having a problem measuring the gain of the 2sa733p's on my multimeter. Those are PNP transitors right? What is the pin configuration? I'm either getting readings of zero or infinity when I test the hfe.

-thanks
jason

[moogah]

With the leads facing down and the flat side facing you the pins go: E C B

[subatomic]

With the leads facing down and the flat side facing you the pins go: E C B

when I test in the ECB holes of the multimeter in PNP mode I get readings like 3.01, 2.73, 2.65 (for 3 different 733's). It does appear to be a stable reading for each. the multimeter is a radioshack 22-181B. Is the meter maybe just off by a factor of 100? It doesn't mention this in the multimeter manual.

From the mods page:

Note that there are a few different ways to measure 'beta' and your meter may not be the same as another. Therefore, just pick the highest beta (test all of them) and mark those with wite-out or similar.

so maybe the meter i'm using uses a different scale for hfe than other meters... factor of 100. is this common?

Be sure to read the manual for your multimeter to see if it has transistor beta/hFE/gain testing.

I did, it has hfe.

Thanks for any tips.

[controlvoltage]

I have a similar (chinese POS) multimeter which I got only because it has a supposed hFE meter.

I tested it out first on two random 2906 transistors and got readings of "1" and "2" with no decimals or anything. I suppose it told me that the transistor was something other than a lump of silicon or a plain wire, but it wasn't nearly as informative as I was hoping...

So I rummaged up a TLC2272 and am working on this guy:



I should have it finished by tomorrow... mine is running off a 9V wall wart though instead of a 9V battery. I didn't have any batteries... I wonder though if I won't have to regulate the voltage beyond what the trimmer is doing already. There's not much of a load. I'll find out and post it here.
With this circuit and a decent multimeter I won't have to do nearly as much guesswork! It's almost enough to make me desolder all those trannys out of my own x0xb0x and measure them properly.

Edit: -- I had to share my mundane good fortune. I couldn't find any 1 megOhm 1% resistors, but I had a bin of 5%... I had only tested about 8 or so when I found one that measured 1.0000 M_(`)_ on my Fluke 'meter. W00t! [/nerd story]

[subatomic]

just measured all 100 733p's I got from mouser. here's the breakdown for those stats lovers out there...


the distribution looks like how i'd expect:
(my radioshak meter reads x.xx format, not sure why).
2.40 - 2.60 hfe: 31
2.60 - 2.80 hfe: 45
2.80 - 3:00 hfe: 17 (7 of these were 2.9x's)
3:00 - 3:20 hfe: 5 (3.13 is the highest, the rest are 3.0x's ...))
3:20 - 3:40 hfe: 1 (3.25!)


So out of 100, not too good. I was hoping for at least 3 or 4 3.20 or higher.

now, get this. I think I had one that was bad or something because one tested at 240.0, 100x the hfe of the others.

[evilxsystems]

cool thanks!

I had a 322 and a 304 that came with the kit. What's the best place to put them?

[Etaoin]

You all do realize that almost none of the meters out there are calibrated so comparing one person's gains to another's is meaningless. My 295 might be someone else's 325.

[zero01101]

that sucks.

going on relativity however, is it fairly safe to assume that if i have many in the 270-290 range and one at 342 that one's my good one?

[Etaoin]

That would be a safe bet.

[subatomic]

You all do realize that almost none of the meters out there are calibrated so comparing one person's gains to another's is meaningless. My 295 might be someone else's 325.

I figured. Maybe I need to build that circuit listed in the mods page. Do better quality meters read more consistently?

going on relativity however, is it fairly safe to assume that if i have many in the 270-290 range and one at 342 that one's my good one?

Unless it's too high.

So, Etaoin, In this project, would having a beta that is too high be a bad thing? (i've been reading the csa733k posts where that seems to be the case) Having these meters be inconsistent is useless - we don't know what is too low or too high.

[Etaoin]

Sadly I'm not the one to comment on which range of beta values goes where. I just wanted to observe that these are not absolute values. You'd have to measure the ones from a real 303 on YOUR meter to get it exactly right. I just picked the ones that had the highest reading on my meter for Q8-10 and it sounds ok to me. But I'm not a purist (I guess I'd have bought a real 303 if I was...)

[subatomic]

Sadly I'm not the one to comment on which range of beta values goes where. I just wanted to observe that these are not absolute values. You'd have to measure the ones from a real 303 on YOUR meter to get it exactly right. I just picked the ones that had the highest reading on my meter for Q8-10 and it sounds ok to me. But I'm not a purist (I guess I'd have bought a real 303 if I was...)

cool, thanks for pointing it out, I wouldn't have guessed meters wouldn't conform to some standard of measurement, that just seems crazy to me. Why buy a meter if you can't trust the readings... Maybe it's more of an issue of cheap meters vs good meters... even so, it's crazy. It's accurate for eveything else, why different for beta.

Posting results can be useful for people to see what the distribution was like, so they could know what to expect when they order. But you're right, for all I know my 3.25 transistor could be a 400beta...

[Etaoin]

By the way, I'm not stating this as established fact. It's just my understanding of these readings. It's possible for anyone to come in here and state that all meters offer you highly acurate beta readings. It's just that I have two meters over here which can't agree even on plain DC voltage, let alone on beta, so my guess is that it will differ.

[subatomic]

By the way, I'm not stating this as established fact. It's just my understanding of these readings. It's possible for anyone to come in here and state that all meters offer you highly acurate beta readings. It's just that I have two meters over here which can't agree even on plain DC voltage, let alone on beta, so my guess is that it will differ.

Thanks for the clarification Etaoin.

ok so I think it sounds fishy most meters would be off, or on purpose not read according to some standard. i'm guessing that maybe what's going on is one of your meters could be broken or cheap or something... especially if your voltage is also off. anyway, taking a wild guess: cheap meters could be inconsistent, and expensive meters should be much more consistant with some calibrated standard. that's just my unqualified idea of what I would expect from a measuring instrument, I really know nothing about meters since i've only had one. sorry, useless i know.

Searching around google I couldn't find mention of hfe inconsistency or calibration problems.

If someone has the definitive word on this, please post it...

[subatomic]

If someone has the definitive word on this, please post it...

not definitive, but certainly illustrative of Etaoin's point. Just tried a friend's $7 multimeter that has hfe measurement. all values were about 25 higher than my values (and mult'd by 100. note the $7 multimeter gives values in the 100's.. my $99 radioshack meter gives values like 3.xx).

so going by that logic I should have a 350, a 338, and a bunch of 326's I can use, out of a lot of 100 733p's. Not too bad - if I can trust the $7 multimeter over the $99 radioshack one!

I think I'm going to socket these when I solder the project in the event I find a better way to measure them in the future. But at this point I'm suspecting (hoping?) that i've got what I need and it's not going to matter...