Quick question... Pinout for OC140?

[vanessa]

The search engine seems to be down.

Does anyone know the pinouts for the OC140? Is the red dot the collector or the emitter?

[MartyMart]

I have around ten sucessful builds with red dot as emitter.
Ritchie was asking me recently about this and after "swopping" some
around, I got very similar results !!
The "tone" of the Fuzz/Octave is all that changed, but I'm sticking with
Red Dot --- Emitter 
This is of course for the CV7112 which is a "similar" millitary spec OC140 !
A real Mullard "OC140" may well be different ....

MM.

[vanessa]

Mine are the CV7112. I just read that for the OC140 the red dot is the collector???

This is strange...

I bought a few back when they were up on eBay cheap. I tested a few at the time (my guess using red dot = emitter) and they all came out to perfect hfe's. Today I went back and tested the rest and all the hfe's were off the scale being way too high. This time I used the red dot as the collector like the OC140. After you said that Marty, I switched it around and for example with C = red dot = hfe 165, and with  E= red dot = hfe, 94.

What's the verdict?

[MartyMart]

For the ones that I've tested ... dot as emitter .... hfe's were between 70 and 150.
This seems about right and they also "sound right" to me this way  FWIW

MM.

[vanessa]

Interesting...

I thought up a test just to see if you could tell for sure. I put several NPN si transistors of different types into a DMM hfe counter. Knowing their correct pinouts I reversed them to see what the difference would be in hfe values (this may sound stupid, but what the hey I'm on a roll). All silicon transistors displayed higher hfe's when their collector's were in the DMM hfe counter's collector slot, than if the transistor was reversed and the emitter was in the DMM hfe counter's slot.

Almost the same readings were obtained when I put a CV7112 into the DMM hfe counter. I also compared these to my proper leakage gains (using the GEO test) to see if I was in the park on this and they were close on both positions.

I am convinced that the red dot on the CV7112 is the collector...

That would leave me with a bunch of transistors that are too high in gain for some of the projects I'm working on...

[nelson]

I have always used the red dot as the collector.

Thats with 6 successful builds using CV7112.

[MartyMart]

Well, that could be correct ... all I can say is that I have tried "reversing" them in
three circuits and I didn't like the sound as much .... !
( FF/RM & Tycho Octavia )
So they must be "working" for me backwards .... what the heck and who cares
if it sounds good 

MM.

[vanessa]

It should work right???

I mean if you flip them around you'll just get a lower gain...

Hummmmmm, we might be on to something here!

[nelson]

Well, that could be correct ... all I can say is that I have tried "reversing" them in
three circuits and I didn't like the sound as much .... !
( FF/RM & Tycho Octavia )
So they must be "working" for me backwards .... what the heck and who cares
if it sounds good 

MM.

I demand you argue with me!

Collector! RED DOT!

I might try reversing them in a few circuits.

[aron]

The OC140 is a most unusual transistor. It is symmetrical. The collector and emitter are identical and can be interchanged. I have come across the OC140 in professional video equipment where its symmetrical construction make it useful for signal switching and clamping.

[MartyMart]

The OC140 is a most unusual transistor. It is symmetrical. The collector and emitter are identical and can be interchanged. I have come across the OC140 in professional video equipment where its symmetrical construction make it useful for signal switching and clamping.

Thanks for clearing that up aron .... I thought that I was going "nuts" there for a 'mo !

Marty.

[cab42]

Well, that could be correct ... all I can say is that I have tried "reversing" them in
three circuits and I didn't like the sound as much .... !
( FF/RM & Tycho Octavia )
So they must be "working" for me backwards .... what the heck and who cares
if it sounds good 

MM.

I demand you argue with me!

Collector! RED DOT!

I might try reversing them in a few circuits.

If you really want to argue, I'm with Marty on this 

This is great info, I just thought I was lucky when it worked at first try. I think I have to put the kids early to bed so I can turn some OC140's

Regards

Carsten

[vanessa]

Last night I found two CV7112 @ 70 and 100 to build into a 2 transistor tone bender. These were tested with red dot = E.

I finished it today and it sounds very different than one built with correct hfe and red dot = C. It sounds like its hard clipping. I've tried other transistors in there with verified pinouts and they all sound closer (smooth) to the CV7112 (OC140) with red dot = C.

I would conclude that the red dot on these things = collector.

[MartyMart]

Last night I found two CV7112 @ 70 and 100 to build into a 2 transistor tone bender. These were tested with red dot = E.

I finished it today and it sounds very different than one built with correct hfe and red dot = C. It sounds like its hard clipping. I've tried other transistors in there with verified pinouts and they all sound closer (smooth) to the CV7112 (OC140) with red dot = C.

I would conclude that the red dot on these things = collector.

Did you read Aron's post above about them being symetrical ...?

MM

[doctornorbert]

While we're at it, does anyone know the pinout on a Toshiba 2SB77? It has a triangle - not sure if this is C or E.

And do Ge transistors often work backwards?

[doctornorbert]

After some testing, the 2SB77 sounds better if the triangle is assumed to indicate the collector. So I think that's my answer.