Forums

Transistor Checker

Started by Unknown July 9, 2014
OK, I pretty much never used one. When the circuit would come alive, the sc=
ope tells you if a transistor is bad. If not, the DVM or ohmmeter will. (yu=
p, that old, I know others are older and actually want to query them so I c=
an make sure not to do what they did)

At any rate, the boredom does set in once in a while and go looking for tro=
uble. In the B&K 520B transoistor tester, I may have found it. That is unle=
ss an answer comes too quiclky... ...

%he print is here :


http://elektrotanya.com/bk-precision_dynascan_520b_transistor_tester_sm.zip=
/download.html

Any trouble with it and I'll rip it and throw it in Dropbox, whatever. You =
might not need it for my question though.=20

The question : How the hell does it tell the collector from the emitter ? M=
ost bipolar transistors (and that's it when it comes to this) will amplifiy=
 i connected with the collector and emitter leads reversed. At low voltages=
 of course. Most B-E junctions Zener out on you at five or six volts, but t=
easting that way cannot reallt be called non-destructive because the transi=
stor REALLY doesn't like it.=20

That tester has to work with DUTs from what, 50 volts to twelve hunder ? Ga=
ins from 40 to 1,000 ? Well 400.=20

It is p[robably reasonable to assume a bipolar has more gain when the termi=
nals are used according to Hoyle, 100 the right way, reverse collector and =
emitter and get what, 5 ? But the tester has no way to figure that out beca=
use it has nbo idea what it is testing. What coul tell the difference in a =
vertical or horizontal output in a reactive scanning CRT system, would fry =
most small signal transistors. just to find out what it is.=20

The way the thing works is it figures out if it IS. If it IS it figures it =
is good, and IDs the leads. You know, it might be worth keeping around just=
 to IS the leads of old ass surplus components that are unmarked or marked =
with somehithng from Mars or Venus or whatever. You know like from 1980 or =
something.=20

But anyway, y'all engineers in here, some of you know alot about the actual=
 construction of transistors. I find the subject fascinating but really, it=
 was never in my interest to spend alot of tine on it because I just wasn't=
 going for that kind of job and probably never would. Plus I suck at chemis=
try so...

Anyway, it's not so muh that I want to know how THIS unit tells the collect=
or from the emitter, it's also that I ask, how would YOU do it ?=20

It is not a really important thing. Take care of business first. But when y=
ou want to break off thre mule team, the race, the game and all that shit, =
just WHAT tells them ?=20

I am sure that with enough time (and eyesight) I could figure it out eventu=
ally. But that - well, maybe I should.=20

To fix the freq counter recently, I had to print out the print. Eight pages=
 I taped together. Then it made sense.=20

Maybe I should do that with this, but I don't have it in that format. I wou=
ld have to cut it up on the PCC and then print it, and I ain't doing screen=
 captures because it is too hard to get the sizes right. Unless I , well of=
 course if I get the right software.=20

But the thing is, this has bothered me for a long time. Tnen, now, matters =
not. With such a wide range of possible devices, how can this thing non-des=
tructively determine those pins ?=20

You hook up the three leads. You run the switch through all its ppositions =
which makes an audio signal when a good transistor is detected. Seems to me=
, most transistors should check good at two positions.=20

On Wednesday, July 9, 2014 12:36:47 AM UTC-4, jurb...@gmail.com wrote:
> OK, I pretty much never used one. When the circuit would come alive, the =
scope tells you if a transistor is bad. If not, the DVM or ohmmeter will. (= yup, that old, I know others are older and actually want to query them so I= can make sure not to do what they did)
>=20 >=20 >=20 > At any rate, the boredom does set in once in a while and go looking for t=
rouble. In the B&K 520B transoistor tester, I may have found it. That is un= less an answer comes too quiclky... ...
>=20 >=20 >=20 > %he print is here : >=20 >=20 >=20 >=20 >=20 > http://elektrotanya.com/bk-precision_dynascan_520b_transistor_tester_sm.z=
ip/download.html
>=20 >=20 >=20 > Any trouble with it and I'll rip it and throw it in Dropbox, whatever. Yo=
u might not need it for my question though.=20
>=20 >=20 >=20 > The question : How the hell does it tell the collector from the emitter ?=
Most bipolar transistors (and that's it when it comes to this) will amplif= iy i connected with the collector and emitter leads reversed. At low voltag= es of course. Most B-E junctions Zener out on you at five or six volts, but= teasting that way cannot reallt be called non-destructive because the tran= sistor REALLY doesn't like it.=20
>=20 >=20 >=20 > That tester has to work with DUTs from what, 50 volts to twelve hunder ? =
Gains from 40 to 1,000 ? Well 400.=20
>=20 >=20 >=20 > It is p[robably reasonable to assume a bipolar has more gain when the ter=
minals are used according to Hoyle, 100 the right way, reverse collector an= d emitter and get what, 5 ? But the tester has no way to figure that out be= cause it has nbo idea what it is testing. What coul tell the difference in = a vertical or horizontal output in a reactive scanning CRT system, would fr= y most small signal transistors. just to find out what it is.=20
>=20 >=20 >=20 > The way the thing works is it figures out if it IS. If it IS it figures i=
t is good, and IDs the leads. You know, it might be worth keeping around ju= st to IS the leads of old ass surplus components that are unmarked or marke= d with somehithng from Mars or Venus or whatever. You know like from 1980 o= r something.=20
>=20 >=20 >=20 > But anyway, y'all engineers in here, some of you know alot about the actu=
al construction of transistors. I find the subject fascinating but really, = it was never in my interest to spend alot of tine on it because I just wasn= 't going for that kind of job and probably never would. Plus I suck at chem= istry so...
>=20 >=20 >=20 > Anyway, it's not so muh that I want to know how THIS unit tells the colle=
ctor from the emitter, it's also that I ask, how would YOU do it ?=20
>=20 >=20 >=20 > It is not a really important thing. Take care of business first. But when=
you want to break off thre mule team, the race, the game and all that shit= , just WHAT tells them ?=20
>=20 >=20 >=20 > I am sure that with enough time (and eyesight) I could figure it out even=
tually. But that - well, maybe I should.=20
>=20 >=20 >=20 > To fix the freq counter recently, I had to print out the print. Eight pag=
es I taped together. Then it made sense.=20
>=20 >=20 >=20 > Maybe I should do that with this, but I don't have it in that format. I w=
ould have to cut it up on the PCC and then print it, and I ain't doing scre= en captures because it is too hard to get the sizes right. Unless I , well = of course if I get the right software.=20
>=20 >=20 >=20 > But the thing is, this has bothered me for a long time. Tnen, now, matter=
s not. With such a wide range of possible devices, how can this thing non-d= estructively determine those pins ?=20
>=20 >=20 >=20 > You hook up the three leads. You run the switch through all its pposition=
s which makes an audio signal when a good transistor is detected. Seems to = me, most transistors should check good at two positions. Hello, A good/reliable transistor checker would give=20 you the same I-V curves as seen in a devices textbook, thereby ensuring a working device. We use a bit old transistor checker from HP, and so far it has been very reliable.
On 09/07/2014 05:36, jurb6006@gmail.com wrote:
> The question : How the hell does it tell the collector from the emitter ?
It doesn't - it will give a tone either way round. To distinguish between the two positions you have to insert resistance in the base connection then it becomes obvious which. piglet
>"It doesn't - it will give a tone either way round"
It does. I got the thing and it only goes off in one position on damnear an= y transistor it is connected to. See the oscillators in the print, the spea= ker puts out the 1 kHz interuppted by the 10 Hz. I gues they wanted it to s= ound like a ringing bell. . or something.
>"A good/reliable transistor checker would give
you the same I-V curves as seen " I got this free. I never wanted it as I said I know if a transistor is bad or good fro how it acts in the cuircuit. But I do not have to identify the collector from the emitter. It was intended for the repair businees and was a tool for those less competent. What i am really asking here is what other parameters could be used to tell if the transistor is not " upside down " so to speak, let's say if you don;t have the pinout. A DVM or ohmmmeter only really identifies the base.
On Wednesday, July 9, 2014 7:56:34 AM UTC+1, jurb...@gmail.com wrote:
> >"It doesn't - it will give a tone either way round" >=20 >=20 >=20 > It does. I got the thing and it only goes off in one position on damnear =
any transistor it is connected to. See the oscillators in the print, the sp= eaker puts out the 1 kHz interuppted by the 10 Hz. I gues they wanted it to= sound like a ringing bell. . or something. The classic tr tester simply looks for hfe, and if enough is found it says = its good. Presumably the threshold is set so that upside down most trs dont= give enough. Assuming a gain of at least 40 is a bit optimistic, there are trs out there= that only get ya a gain of 3 or so. NT
On 2014-07-09, jurb6006@gmail.com <jurb6006@gmail.com> wrote:
> OK, I pretty much never used one. When the circuit would come alive, the scope tells you if a transistor is bad. If not, the DVM or ohmmeter will. (yup, that old, I know others are older and actually want to query them so I can make sure not to do what they did) > > At any rate, the boredom does set in once in a while and go looking for trouble. In the B&K 520B transoistor tester, I may have found it. That is unless an answer comes too quiclky... ... > > %he print is here : > > > http://elektrotanya.com/bk-precision_dynascan_520b_transistor_tester_sm.zip/download.html > > Any trouble with it and I'll rip it and throw it in Dropbox, whatever. You might not need it for my question though.
> The question : How the hell does it tell the collector from the > emitter ?
If you get it the right way round there will be more gain. presumably the sider switch for pin asignment has each pair of C-E substitutions adjacent so that performing comparison is easy.
> That tester has to work with DUTs from what, 50 volts to twelve hunder ? Gains from 40 to 1,000 ? Well 400.
it seesm to run a dual rail supply +5v and -5V with the emitter of the device under test grounded.
> But the thing is, this has bothered me for a long time. Tnen, now, matters not. With such a wide range of possible devices, how can this thing non-destructively determine those pins ?
it doesn;t. theres some transistors that can't handle 5V those would probably be damaged. 500V transistors will work kind-of at 5V, well enough that youu can tell it's a transistor.
> You hook up the three leads. You run the switch through all its > ppositions which makes an audio signal when a good transistor is > detected. Seems to me, most transistors should check good at two > positions.
most transistors have a reverse beta of less than 10 and a forwards beta of more than 10, so if the threshold for the buzzer is at a current gain of 10 you's only get a buzz in one position. -- umop apisdn --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
<jurb6006@gmail.com>
> > > What i am really asking here is what other parameters > could be used to tell if the transistor is not " upside down " > so to speak, let's say if you don;t have the pinout. > A DVM or ohmmmeter only really identifies the base.
** Method one: A DVM used on the "diode check" range will give a B-E and B-C conduction voltage (while out of circuit) at a fixed current. The slightly lower reading is the B-C junction long as the device is OK. Method two: A "beta" or Hfe checker will normally give a much higher reading when the C and E are connected with correct polarity. However, most are intended for small signal devices and will not test many power transistors or power Darlingtons reliably - I have a dedicated tester for them that operates at a much higher, fixed collector current. Method three: Use Google to find a data sheet for the device, which ought to contain pin-out information. ..... Phil
In article <cda98dae-6373-47e6-b2ea-3020560dd5b3@googlegroups.com>,
 <jurb6006@gmail.com> wrote:

>What i am really asking here is what other parameters could be used to tell if the transistor is not " upside down " so to speak, let's say if you don;t >have the pinout. A DVM or ohmmmeter only really identifies the base.
If I recall correctly, there are several difference between the B-E and B-C junctions which can be used to distinguish them. (1) The forward voltage drop (at low current levels) is different, due to different doping profiles in the junctions. (2) As you note, DC gain is typically a lot lower if you run the transistor "upside down". (3) I believe I recall that the C-E saturation voltage is different than the (E-C) upside-down saturation voltage. I'd guess that automated transistor testers probably look at all of these factors in order to make a decision and analysis. There are some pretty sophisticated little automated semiconductor testers available these days, for cheap (look on eBay). They do all of this and more. They can distinguish bipolar transistors, FETs (depletion and enhancement), diodes, LEDs, and more... some of them can tell you things like "This is a bipolar LED, green in this direction, red in that direction".