Use for the Tesla Switch

[nvisser]

Data sheet for 2N108 from American Microsemiconductor, Inc. in Transistors on GlobalSpec

[linesrg]

A 2N108 looks like this!!

Good Evening,

A 2N108 looks like this. I have built the circuits shown on JB's web pages on a PCB I had made but have only used 2N3906's as the 2N108's were quite expensive.

Regards

Richard

[Matthew Jones]

Yes, I confirmed this with JB. They were used in IBM high speed printers that were made in the late '60s and '70s. They were used to drive the hammers, each printer would have had 60-100 of them.

And yes, they really are the size of a hockey puck.


John K.

I bet ya there is a land fill out there full of them. I have seen a few for sale so I gotta go back and look. See if I can find them.

There is this page on them
http://ed-thelen.org/1401Project/GermaniumAlloy.html

Matt

[linesrg]

Hockey Puck's?

Good Morning,

I don't know where this reference to hockey pucks comes from. The text under the schematic on JB's old web page described them as 'old top hat' which is what I sourced.

I haven't run the circuit I built up on the PCB's I had made for very long but it has run for over 30 minutes and the 2N3906's I actually used didn't burn up or get hot so for this size I don't think you need large 'power' transistors.

Regards

Richard

[Matthew Jones]

I think your right. The 2n108 is not a power transistor but if it was the IBM 108 it was big. About an inch diameter. Picture is in the link in my last post.

I read the article again and the IBM was also a dual emitter transistor. Either the base or the emitter could be used for the base or the emitter.
That might have something to do with it.

Good Night
Matt

[Bit's-n-Bytes]

I bet ya there is a land fill out there full of them. I have seen a few for sale so I gotta go back and look. See if I can find them.

There is this page on them
http://ed-thelen.org/1401Project/GermaniumAlloy.html

Matt

Hi Matt, they are availble at http://www.surplussales.com/Semicond...rs-SCR-1.html;

(STR) 2N1302 NPN, 150mw, 300ma, 3 MHz, TO-5 2.50

Thanks
Jeff

[Matthew Jones]

I don't know Jeff thats a NPN. The 108 was different.

I like that link though.

Matt

[John_K]

Good Morning,

I don't know where this reference to hockey pucks comes from. The text under the schematic on JB's old web page described them as 'old top hat' which is what I sourced.

I haven't run the circuit I built up on the PCB's I had made for very long but it has run for over 30 minutes and the 2N3906's I actually used didn't burn up or get hot so for this size I don't think you need large 'power' transistors.

Regards

Richard

Hi Richard,

The reference to hockey pucks comes from JB. I have no reason to doubt him, since he has stated the same publicly and also privately. He has also seen Bill & Ray's machine after they brought it onto the Bill Jenkins show, "Open Mind" in the '80s with his own eyes.

I'm not sure where "2N108" appeared from as this was never mentioned and is not what Bill & Ray used. The "IBM 108" was developed especially for print hammer drivers, which IMO would probably pull a few amps so a power transistor would be required. IBM always has their own unique way of identifying their own parts which does not usually conform to any other "standard".

Anyhow, I hope that clears up this misunderstanding. It looks like you have a good build there and I hope you have some success with it as well.


John K.

[Matthew Jones]

.....I'm not sure where "2N108" appeared from as this was never mentioned and is not what Bill & Ray used.....
John K.

Thats just one I was looking at. I didn't remember anything being said about the IBM 108. I have been looking at anything that was a top hat germanium PNP.
I grew suspicious about the 2n108 because I couldn't find anything (specs) on it.

Matt

[John_K]

Thats just one I was looking at. I didn't remember anything being said about the IBM 108. I have been looking at anything that was a top hat germanium PNP.
I grew suspicious about the 2n108 because I couldn't find anything (specs) on it.

Matt

Thanks Matt,

Rick Dill's article kind of proves that IBM usually gave their early transistors a 3 digit number to identify them. (One theory I was told was so people that serviced them HAD to buy genuine IBM parts as no one could identify a substitute) I worked for IBM some years ago and they always made up generic names for their parts and you could only get those parts from IBM.

I'd be very surprised if you can find any specs on the "IBM 108" as not even people within IBM could get the specs. Even if you worked for IBM it was on a "need to know" basis only.

The IBM 1403 printer is a pretty old device. I never worked on that model, but I remember seeing similar models where there were usually banks of 8 or so hammer drive transistors sitting behind the hammers. I recall that they were all common collector (hence the thread on the collector in the picture of the IBM 108) and the emitter and base wires were soldered on. Best bet would be to try and find an old IBM "band" printer from somewhere and see if there are any "IBM 108" transistors in there.

I have to recall my statement about "hockey puck" size as the picture says they were 1" diameter "TO-5" case. We don't play ice hockey here but from what I know (which ain't much) a hockey puck is bigger...yes?

I hope this helps....


John K.

[Matthew Jones]

Ya i was looking to see if I could find a 1403. I contacted a couple of people on ebay who sell ribbons for them.
I am trying to get an answer if they sold any ribbons lately.

We'll its worth a try.

Matt

[John_K]

Google is my friend...

Ya i was looking to see if I could find a 1403. I contacted a couple of people on ebay who sell ribbons for them.
I am trying to get an answer if they sold any ribbons lately.

We'll its worth a try.

Matt

Hi Matt,

I did a bit of Googling and came up with some interesting bits that might help you..

"Delco developed the high-voltage germanium power transistors for the 1403 hammer drivers."

Below link is for substitute transistors... (look in the list for IBM Type 108, then Google the datasheets)
http://ibm-1401.info/BobEricksonIBM-...stitution.html

IBM 1403 Maintenance Manual... (shows some pics of the hammer unit but I couldn't find anything on the 108's)
http://ibm-1401.info/1403FieldEngine...anceManual.pdf

IBM 1403 Parts Catalog...(doesn't list the transistor part numbers, but shows on page 1403-5, ref G & H - transistor card assembly. This leads me to assume that the transistors were mounted on a card which was in the blower section at the rear of the unit)
http://www.ibm-1401.info/IBM1403PartsCatalog.pdf

Hope it helps. Happy digging!


John K.

[John_K]

One more thing...

Matt,

I found a site with some pictures of 108's. Looks like they were also used in IBM System/360 power supplies, which should be easier to source (???)

The System/360 Power suppy restoration project

Good luck!


John K.

[nvisser]

Wow John K. This is amazing
http://members.optushome.com.au/intaretro/T108A-S.jpg
http://members.optushome.com.au/intaretro/T108A-L.jpg
http://members.optushome.com.au/intaretro/T108B-L.jpg
This guy put such a lot of effort into that supply. I see it was already in 2001

[nvisser]

check this out
Google Translate

or try it in german
Aluminium Kühlkörper mit 3 Leistungstransistoren RT (aukcja 270593011461) - aukcje eBay.pl | Zakupy bez granic!

http://cgi.ebay.at/Aluminium-Kuehlko...-/270572339992

I see it has ended but was not sold.