Testing transistors for gain/leakage, help?

JVanDe7 · Post by **JVanDe7** » 07 Feb 2012, 15:03

I want to make some kind of device/kit that allows me to measure leakage and hFe. Anyone have any links/plans/advice?

Here's what Analog Mike uses... I'd love something like that... (although I must admit I don't know exactly what I'm looking at here)

I was going to get a cheap digital multimeter that has hFe capability but after reading some stuff on the web it seems that a cheap DMM won't take leakage into account. I'd like a reasonable degree of accuracy - and if leakage isn't taken into account, it seems the gain reading would be too high, thus unacceptably inaccurate.

So yeah, any help would be greatly appreciated. I'm just a novice builder with maybe 25 builds under my belt. 3 years of DIY pedal experience. I want something to help me sort Si and Ge transistors so I can order larger batches and pick the best ones for the job, rather than paying for a pair/set from SmallBear and just settling for what they give me.

JVanDe7 · Post by **JVanDe7** » 07 Feb 2012, 15:55

http://www.geofex.com/Article_Folders/ffselect.htm

I'm guessing I need to build the circuit at the above link. Simple enough. But I'll have to sit and think for a bit on what's the best way to box it up into something semi-permanent so it's solid/stable and protected.

jrod · Post by **jrod** » 07 Feb 2012, 17:39

There is also the method that Small Bear uses to test the germs they sell. You can find if here down towards the bottom of the page.

BTW, before I had any idea of what I was doing and didn't really understand circuits I rigged the above circuit up on a breadboard and ended up frying several perfectly good Mullard AC128 transistors.

Have you heard of the Peak Atlas? It's kind of expensive but well worth the money.

JVanDe7 · Post by **JVanDe7** » 07 Feb 2012, 18:27

Haha oh man, I'll have to be careful and test a couple cheap silicon trannies first, just in case.

But yeah that Atlas DCA55 looks slicker 'n snot on a doorknob. I'd actually pay the $70 if I could find a US seller... not too keen on ordering from overseas and waiting around for it to show up. $70 is a bit much to pay for such a device unless one is in "the business" but I wouldn't mind having a proper idiot-proof device like that. It may save money in the long run. I could order bundles of "rough sorted" Ge trannies instead of just looking for proper pairs/sets. Plus I could maybe sell off some of the surplus once they've been carefully measured and tested...

JVanDe7 · Post by **JVanDe7** » 07 Feb 2012, 18:35

BOOM. http://www.anatekcorp.com/atlasdca55.htm

Thanks!

I would just build a circuit and deal with all that... but for $67 I'd rather have the DCA55. You can connect the leads however you want and it tells you which is E, C, B. It tells you the leakage, gain and a whole bunch of other stuff too. I don't really see any downside other than the price, but thats close to what you might pay for a middle of the road multimeter - not bad at all.

UPDATE: out of stock. But Amascott may have them. It doesn't say out of stock, but it doesn't say in stock either.

culturejam · Post by **culturejam** » 07 Feb 2012, 18:44

You can order the DCA directly from Atlas in the UK. The price is the same and the shipping is surprisingly reasonable (and fast as well).

I have a DCA and the LCR. Both are great bench tools to have.

sinner · Post by **sinner** » 07 Feb 2012, 18:46

+1 to DCA55

It may look expensive, but honestly, it's well prized compared to what that can do.

I'm going to buy two more - LCR40 and ESR70 when my finances get better

phibes · Post by **phibes** » 07 Feb 2012, 19:47

Another plus to the Peak Atlas. I got two. Makes life sooo much easier.

jrod · Post by **jrod** » 07 Feb 2012, 19:54

Yeah the shipping is actually really quick and the customer service was top notch in my experience.

JVanDe7 · Post by **JVanDe7** » 07 Feb 2012, 20:50

Alright well damnit... now I have ot buy one. That's a heck of a lot of endorsement. Maybe I can sell one of my creations to help fund it.

I just bought $50 worth of tools (proper snippers [sick of using toenail clippers], klein wire strippers [sick of my bargain bin strippers], quality boxcutters [sick of my bargain bin cutter], some alligator leads and a capacitance meter kit) so it may not be the best thing to spend another $80 but I'm getting a nice tax return any day now and work gave me a small bonus this year so why not... gotta treat myself, right?

LucifersTrip · Post by **LucifersTrip** » 08 Feb 2012, 06:51

The DCA55 is very useful to differentiate between si & ge when you're looking at a bunch of unmarked or factory marked metal cans. It is also killer for idetifying which is E, B, C and anode / cathode for a diode.

Note that the results will not be exactly the same as using the RG method (mainly with leakages...the hfe's are close), but will give you a pretty good guideline. I believe the RG method is more accurate. I did A/B tests for leakage with a bunch and RG's method gave me a better indication of what the circuit should've sounded like with the measured leakage.

The DCA55 completely failed with vintage silicon. It was identifying all over the place... I posted this a while ago:

============
I just purchased it to analyze a bunch of vintage metal can silicons & germs, and the massive FAIL was with PNP silicon. For the last 30 minutes I went through a bunch (with hFe 15+) and the DCA55 reported mainly "darlington", some "common diode network", a few "digital transistor", and one "germanium".

These are the most recent failures: 2N3640, 2N2184, 2N2182, 2N493B, 2N2274, 2N2183, RCA34594, 2N2185, 2N2646, 2N2187

The Peak is much more accurate identifying germanium...Very few failures. The gains were pretty close to using R.G.'s method. It could go either way by approx 5% - 15%
============

still a great tool, but not the "end all"

JVanDe7 · Post by **JVanDe7** » 08 Feb 2012, 13:16

Thanks LucifersTrip, good to hear/know. That does make me slightly less excited to buy one. 15% is kind of a significant difference. Obviously if I have a 100hFe tranny going into Q3 of a tonebender or something, and the DCA55 tells me it's a 115hFe, that's not going to matter a whole hell of a lot, but still. I'm not crazy about paying $80+ for a less accurate device than what I can build for free (I have the parts and the DMM). It would be great to be able to hook the leads up however I want and find out which is E-C-B though. Maybe I'll build the GEO tester first and try my luck. If that doesn't go well, I'll drop the coin on the Atlas.

jrod · Post by **jrod** » 08 Feb 2012, 22:25

I found the two methods to be pretty close. But I have tested germs with the RG method one day and tested them again several days later with different readings due to temperature differences no doubt. I consider either testing method just a guideline to get in the general ballpark. RG's method is so easy and cheap to build or just throw together on a breadboard (that's how I had mine set up). It is a fun though sometimes time consuming way to measure ge transistors. You can really get a good idea of ge's temp sensitivity by watching the parameters change on the meter as they cool down from touching them, rm temp, etc.. I say build the RG tester and work with it a while. Can't beat the price!

DrNomis · Post by **DrNomis** » 09 Feb 2012, 02:23

My Semiconductor Component Analyzer recently stopped working, the battery in it was still good and installed correctly, but when I tried powering it up, I got no display on the LCD panel, so I'm debating to myself whether I should just buy a new one, have tried hooking it up to my power supply with same results, so it's deffinitely faulty, before it stopped working I noticed that the display would get barely readable (display fading) or would go all garbled....

The circuit board has surface mount components on it, if I had a circuit diagram I'd try and service it....

jrod · Post by **jrod** » 09 Feb 2012, 03:09

Have you tried a new battery? My Peak Atlas did the same thing. I tested the battery and it showed it was still good. I popped a new battery in just to try it and fired right up.

DrNomis · Post by **DrNomis** » 09 Feb 2012, 03:17

jrod wrote:Have you tried a new battery? My Peak Atlas did the same thing. I tested the battery and it showed it was still good. I popped a new battery in just to try it and fired right up.

Yep, tried a new battery, and I also tried connecting it up to my power supply set to the same voltage as the battery, I did that to eliminate the battery as a probable cause, and got the same results so I reckon my Component Analyser is deffinitely faulty in some way...

One thought though, there could be a cracked/dry solder joint on the circuit board somewhere cause I noticed that I could make the display come and go by gently twisting the case when the circuit board was installed in it, that was before the analyzer failed altogether....

culturejam · Post by **culturejam** » 09 Feb 2012, 04:01

LucifersTrip wrote:The DCA55 completely failed with vintage silicon.

I agree it's not the "end all" bit of gear. But it's so awesome!

I noticed that it uses the Base-Emitter voltage drop as the determination for what is silicon and what is germanium. And the cutoff is .39v. Anything over that it calls silicon, even if it's not. But I suppose short of some kind of metallurgical test, that's as good a method as any.

I've also noticed that if I a get a funky reading on any given tranny, MOST of the time that means the piece is bad/non-functional. If you're getting "darlington" readings from a transistor that isn't, it's likely that either there is some kind of internal short that looks like infinite gain, or it's an oddball internal setup that isn't taken into account by the DCA's algorithms.

I also highly recommend the LCR meter. It's really nice, and the only meter I can afford that measured inductance.

LucifersTrip · Post by **LucifersTrip** » 10 Feb 2012, 21:17

culturejam wrote:
LucifersTrip wrote:The DCA55 completely failed with vintage silicon.
I noticed that it uses the Base-Emitter voltage drop as the determination for what is silicon and what is germanium. And the cutoff is .39v. Anything over that it calls silicon, even if it's not.

that's good to know...i'll check that out next time it gives me the wrong info...

LucifersTrip · Post by **LucifersTrip** » 13 Feb 2012, 22:58

jrod wrote:RG's method is so easy and cheap to build or just throw together on a breadboard (that's how I had mine set up). It is a fun though sometimes time consuming way to measure ge transistors. You can really get a good idea of ge's temp sensitivity by watching the parameters change on the meter as they cool down from touching them, rm temp, etc.. I say build the RG tester and work with it a while. Can't beat the price!

here's my complicated build...hahaha

remember to handle em with gloves if you don't want to wait for em to cool down

culturejam · Post by **culturejam** » 13 Feb 2012, 23:27

The multi-turn pot is really smart.