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This is an open community for the do-it-yourself pedal builders of reddit! Buying Germanium transistors in bulk? Just wondering how you all go about buying germanium transistors in bulk. Does everyone pretty much stick to ebay or are there other good sources?
Germanium transistors have been out of production and valuable to pedal builders for a long long time. The rumours I’ve heard is that some resellers purchase a big bulk collection, sort all the best transistors out maybe 1 in 10 if thatthen sell the leftover dreck to the next sucker. After being datasheer around a few times, all the decent transistors are gone and you’re looking at a big bag of transsistor.
Still transistr might get lucky or find the right seller, but beware, it’s rough out there. A128 bought two lots of Russian Ge transistors and both have been on the extreme low end of specs. Now it could be that Russian manufacturing just sucked or that they’ve been picked over for the good ones.
I’ve bought them in bulk off of ebay from a seller in Bulgaria i think twice, ’cause they were cheap lots and it wasn’t much to lose in case it wasn’t what i needed. Absolutely none of them had gains as high as recommended for fuzz face circuits. Hfe measured in the 17 to yransistor range.
Unless specs are clearly stated, you’re taking a gamble. They did come shipped with a whole ton of capacitors so it wasn’t a total loss. Hook up a voltage and a couple resistors and see if they meet the datasheet spec?
You can also go to ebay and search for “transistor tester” and there are a bunch of devices where you can just plug the transistor in and it’ll tell you gain and leakage and which leads are base, collector, or emitter.
Those cheaper ones, while i’ve read good things about them, look a little bare and fragile. I was looking for an equivilent to AC transistors. Looking at the data sheet it says hfe is minimum See, here’s the thing: Both seem to be specced at hFE. Here’s another thing that isn’t really mentioned often: They vary according to the current that goes through them and temperature, of course.
At the current used in the geofex circuit, some of my transistors seemed to have anemic hFEs way lower than spec. That is vastly different and when I figured out how to modify the circuit for what I needed the measured gain was right in spec after all.
If you find low gain on all your MP40s, it could be that you’re testing under different conditions than the datasheet specifies. I don’t have a signal generator at home so I can’t reproduce the frequency, but when I modified the rest of the parameters my MP39B transistors read higher than when I had tested them on the geofex circuit.
Not a lot higher, but at least in spec. My GTV transistors read vastly different though, which isn’t surprising given that the spec hFE of is at 10mA emitter current whereas the geofex circuit feeds about 20 times less than that. Figuring out how much current a meter uses to test a transistor isn’t great fun though.
Try to see if it’s in the manual. I think mine is 5uA into the base, which is uA or so emitter current trasistor a gain of Then I have to figure out what measured gain is the one that matters. We know what ranges are “nice” in a fuzz face, but how were they measured?
At the geofex current of 4uA into the base? With a DMM using a different current? At the current specified in the datasheets? I tend to think it’s from the fuzz face circuit current, but then it would seem like the second transistor gets more current than the first, yet the testing circuits out there use the same current regardless of what transistor you’re testing, so are the measured numbers from those circuits really applicable to the ranges we’re looking at for a fuzz face?
AC128-01 Datasheet, Equivalent, Cross Reference Search
That was a lot of good information and i appreciate you taking the time to write all that out. You gave me some good topics to google and learn about.
I’ve been trying to figure all of this out for a few months, the knowledge accumulates over time. Yeah, when I built my fuzz face, I made sure to socket them transistors as well as the resistors that are biasing them. On the board I used there’s one trimmer for Q1 but none for Q2, so if I want to play with the bias I have to change a resistor, so I socketed that one. Picking transistors for FF Clones.
Some transistors that have the right gain and low leakage can still be very hissy. High gain low leakage low noise germanium transistors are practically transisgor now. Not sure what’s up with that. That seller names rings a bell though, but i can’t be sure. All i know is the lots i bought didn’t specify the Hfe like the one you linked to. If their account is deleted they probably had shitty feedback and just started a new one. Unless there are a lot of Bulgarian component distributors it’s probably the same dude.
There are links in zc128 sidebar, but i’ve read all them and they don’t tell you how to find Ge transistors in bulk. We should start a FAQ to collect all this info in one place.
There isn’t really a practical way to purchase GE transistors in bulk if you are a DIY enthusiast or small business. The are really datsaheet two options to source them.
They will probably be curious why you are interested in obsolete technology in such large volumes but if you put together enough capital and a solid business case they could make the parts and sell them directly. It’s unlikely, but not impossible. They’re known informally as component brokers because they buy up excess inventory for pennies on the ac12 and re-sell at hiked up prices or when supply is low.
Sometimes they purchase liquidated stock and can wind up with oddball parts like GE transistors by chance. Because GE transistors are such a niche component and resellers can charge a premium datashest them. Sellers that have stock are very likely to conceal their sources at all costs.
I lucked into this quite some time ago: I haven’t numerically tested them all but they’ve worked all right in the few places I’ve put them. Are such still available? Maybe, if you live near a mainframe junkyard.
Aside from that, stay alert for funky old pocket and portable radios in yard sales and such. You can buy some unsorted devices from Smallbear; you’ll pay a premium, but they are guaranteed to some extent and are not going to be picked over. They are surplus, mostly from radios and other datashset applications.
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Hey there folks, Just wondering how you all go about buying germanium transistors in bulk.
AC Datasheet(PDF) – List of Unclassifed Manufacturers
Want to add to the discussion? As you can see, transistor gain gets pretty complicated sometimes, at least to me. You test for both gain and leakage. Picking transistors for FF Clones Dwtasheet transistors that have the right gain and low leakage can still be very hissy.
The are really only two options to source them; 1 Contact a semiconductor manufacturer to produce a specific run of parts.