Can Germaniums Be Saved?

[thorpy6]

I'm using the test rig as shown in the "Technology of the Fuzz Face". Reading the voltage drop across a resistor. When no voltage is applied to the base they read 100 mic amps or so. When voltage is applied to the base they start climing and don't stop or they roller coaster. With this test rig I think the limit in terms of reading approx hfe is when the transistor passes votage as it is shorted = 9v or 900 mic amps of drop across the resistor. Sounds like the transistors are trash which is too bad, hundreds of beautiful OC75s and none worth a damn. Well, I didn't get taken by someone passing crap stock, just unlucky I guess, the same place gave me great testing OC44s, OC76s, OC71s, 2N527s, and the SFT337s that ended up in David's 1966s pedals. Sound like the Atlas might be an easier and more consistent way of testing my Ge stock. The rig served me well: http://www.youtube.com/watch?v=SG8CjsJsnOA -that's how I've been testing transistors for 5+ years with good results.

i did it your way for a while but found inconsistencies, which is why i got the atlas. It is excellent for getting those gain matched pairs together and has saved me so much time its untrue, cannot recommend it enough.

[simonm]

Is the Atlas you're talking about the DCA55 Componenet Analyzer?

yep - http://www.peakelec.co.uk/acatalog/jz_dca55.html

[John Lyons]

Even is the transistor measures unuseable you can use it as a germanium diode.
Better than nothing.

Does the Peak meter calculate the leakage into the Hfe measurement?

john

[thorpy6]

The leakage is given in mA the gain is shown on a separate screen (scrolling readout of the characteristics of the transistor) and is shown as hfe.

[sir h c]

Some of those early ones are glass cased, could be light getting in and freaking the measurements, try covering the transistors and testing.

[PlumCrazy]

That component analyzer kinda rock, just got one.

[thorpy6]

That component analyzer kinda rock, just got one.

Glad you took the leap, how do your oc75's read now. Are they leaky, stable and what are the gain ranges like. And...................Do you have any for sale?

[noelgrassy]

I'm pulling the trigger on one of these today.

I thought another positive aspect with these was it's ability to identify the component
whilst in the circuit.

I found only one dealer in the US with it in stock.

[PlumCrazy]

I tested a few of the OC75s and some are really high (300+) while others seem to be testing well. The only thing that worrys me is that the test on the DCA55 seems to be a point-in-time measurement and doesn't track specs. We all know that germanium gain goes up when heated and the DCA55 locks in a measurement that doesn't change once locked, even if you grab it with a finger to heat it up. I also have some Philips OC44s that show no leakage on the DCA55 but do the blowing into a microphone sound when put into my "The Squawk" Rangemaster-style pedal test rig, so there's leakage there. All in all, it's better than the rig I was using but still has a few quirks that I have to beware of when testing. So it'll be good for a first round test but throwing it into a test pedal for a sound test will be the final test. As for having OC75s for sale, I'm sorry but I've got to scrounge everything I've got as I'm currently working on adding a MKII-based pedal to my line-up of pedals I sell. The DCA55 did, however, just pay for itself this weekend as it helped me identify 700 NPN Germaniums (old house-numbered RCAs and TI) that test 70-170 with good leakage at an electronics junk shop that I got for about $.08 a peice.

[JimiB]

Im sure any of us that have an atlas would be glad to test some of them for you, just to see If thay test any different.