Tinkling transistor!

Maybe it's like those Chinese musical balls.

A multimeter on "diode check" range and see if you see the E-B and C-B junctions (usually reads something like 650 on the meter) and that they block in the reverse direction (overrange). If it passes that, you can check the hFE if your multimeter has that function (almost all inexpensive meters seem to have it these days).

Best regards,

Best regards, Spehro Pefhany

I seem to have a vague memory of germanium power transistors that had a bit of silica gel or some other humidity absorbing stuff inside the case that rattled around. But I can't be sure this is not a fake memory produced by suggestion. If your transistor has low junction forward drops (less than .4 volts) and is PNP, it is germanium. If it isn't I don't have a clue of what is in there.

The 2N456A is a Germanium PNP, rated at 40V, 7A and 0.5 C/W in its TO-3 package (it must have had a large die). In recent history it was made by GPD (Germanium Power Devices Corp), Semitronics and Advanced Semiconductor, Inc. (who may still offer it). Asa, I'd try replacing it with a large silicon PNP transistor, like a TIP34 or TIP36. These have TO-218 cases, but will mount properly in place of your TO-3 part.

After you do this you can open up the 2n456 and tell us what you find.

I'll add to that.

Different era but around 1980 I came across some *wickedly * well specced Sanken power transistors.

Indeed Sanken still make excellent transistors for audio output stages.

I had some trouble understanding how they made them so well with Isb figures that trounced Motorola or RCA's devices..

So I took a hacksaw to one and lifted the lid off a TO-3 device with a view to examining the die.

It contained a large amount of a 'thermal compound'.

It might have been alumina - it might have been beryllia : see

I ditched the part in the trash very fast.

Modern semis don't use that trick. They also don't 'rattle'.

Graham

"Asa Cannell" wrote

I suggest pro-forma replacement of all tinkling transistors. Something's broke. It may or may not be what is causing the problems you are seeing but dollars to doughnuts they are/will cause problems.

When in doubt, throw it out.

"Asa Cannell" wrote

I just googled, the 2N456 is a power PNP Germanium.

From the days of my youth PNP Ge power transistors were not very (at all) reliable, at least in teen-ager driven Hi-Fi gear. Try a modern silicon unit -- ge is (normally) only needed for battery powered equipment. Common in old car radios.

Is Oliver Germanium still around?

A lock-in amplifier is NOT an audio power amplifier. All the signals are at low or very low power levels, including the output, which is +/-10V into a 10k load. Therefore it's most likely the 2N456A TO-3 transistor was in the power-supply regulator. It's also likely the regulator has sufficient voltage overhead to work with 0.65V base- emitter drops instead of 250mV in its control feedback loop.

We will see.

Looks like a good source, I didn't know about them.

Perhaps we won't see.

Too young to remember joly old Oliver, a bear of a man?

Date: 04 Aug 2004 18:12:53 From: Spehro Pefhany Subject: Re: Unusual Characteristic [LOL]

Anyone know if that Oliver dude from the ad campaign of the ties is still kicking?

Best regards, Spehro Pefhany

Date: 04 Aug 2004 19:39:28 From: John Larkin

Oh, Oliver Germanium. Dunno. I'll ask next time I contact them.

Nowadays they mostly make GaAs photodiodes. Last time I bought a TD from them, some years ago, it was about $80.

John

What about it John?

I kept waiting for him to announce germanium devices passivated with germanium nitride and doped with ion implantation. I would love to see what .5 volt germanium CMOS would look like. Still waiting.

He would have to re-bias the amplifer to use a silicon device in the output. May not be trivial.

Why not suggest a TO-3 can device btw ?

MJ2955 would do nicely.

- can buy online

Better still, replace it with the same part and no re-biasing should be required other than setup.

Graham

I recall the ads featuring him !

Graham

That may be because the GPD devices had very large dies, and thus very low thermal resistance. OTH, one was supposed to keep their junction temps lower than for silicon, right? I don't recall.

GPD's power trannies would have been well suited for low-voltage high-current linear regulators. They had 100A transistors with beta = 125 (min, 25A), and Vce(sat) = 0.3V at 100A, beta = 10.

That diode drop test will also tell you if it is Germanium (i call it flower power from "geranium"), or Silicon (i call it sand power); prolly Germanium. You may be able to get away with using sand power replacement.

I remember these also, fairly clearly. Power transistors that tinkled when shaken or moved did exist!

- Don Klipstein ( snipped-for-privacy@misty.com)

Actually, i had designed and built a 3V 100A regulated DC power supply using two power Germanium transistors for the pass; never had problems. Ran from 1K load to full load for years. I found that used properly, they were more reliable that tne "replacement" silicon power transistors (same power level).

I thought beryllia was harmless in chunk form. (Powder from machining is very nasty.)

I have an equivalent P type Ge high power transistor. The 2N2079 Motorola part ought to do the trick.

I have a collection of electronics materials for auction, as well. let me know if you need these GE power transistors...

Marc

Link to auction site

Good luck

Marco

The "older" germaniums had problems at "high" temperatures, due to the use of Indium for doping. However, the "newer" germanium transistors withstood high temperature better than silicon transistors (do not remember what was used for doping). What that meant was one could dissipate more power at heatsink temp approaching 100C and not have reliability problems.