JFETS, matching etc.

[Chuck D. Bones]

Follow-up on the transistor tester...
It measures germanium transistors correctly - it accounts for leakage (Iceo) when measuring and calculating current gain (hFE). I checked a few Ge transistors using the tester and the "Bare Bones" method and they correlate. To quote Steve Daniels of Small Bear Electronics: "The temperature sensitivity of older germanium transistors has to be seen to be believed..." This is no exaggeration. Whatever method you use for measuring Ge transistors, they have to temperature stabilize before you can get a useful reading. The heat from your fingers can drive the leakage up 4x or more with some transistors. It can take several minutes for the device to cool down and stabilize after handling.

The diode test current is fairly high, causing some diodes (the ones with higher resistance) to read an abnormally high Vf. Those I test with a DMM.

 

[Nostradoomus]

Yeah I’ve done a just for fun experiment of rubbing GEs between my fingers before testing them and it’s ridiculous

 

[JetFixxxer]

My transistor tester arrived yesterday.
View attachment 1470
What a cool device! Measures wah inductors no problem. I tried measuring a guitar pickup, but the winding resistance is so high that the tester thinks it's a resistor and can't measure the inductance. Try testing 2-color LEDs in a darkened room... it's a mini light show!
Only complaint is that it doesn't measure Idss & Vp on JFETs. I still have to do that manually until I can find my Heathkit curve tracer. Assembling the case is tricky, it's like building a house of cards. I wasn't going to cheat & use tape.
Warning: don't try to use a guitar pedal power supply to power this up because this thing is wired for a positive center pin. When I'm not using a 9V battery, I'm powering it with a 12VDC power supply left over from an old router.

Since I wind my pickups I picked up a cheap LCR MS8269 from Amazon to measure pickups. Not sure how accurate it is since I don't have anything to compare it to. Even then people still think that DCR is the way to measure pickup output and really don't care about the inductence.

 

[Chuck D. Bones]

I think the reason most people measure pickup resistance is a) it's an easy measurement to make and b) they don't know what inductance is. If you want a good idea of how the pickup will sound before you install it, you need to measure the impedance as a function of frequency. I do it the hard way with a functions generator and an oscilloscope. That method is good enough to tell if a pickup's cover is brass or nickel-silver. The hard-core guys use a pickup driver and a network analyzer. An LCR meter will measure the impedance at one frequency and not know anything about resonance. If the measurement freq is low enough (1KHz or lower), then it's measuring mostly inductance and resistance.

 

[JetFixxxer]

Dave of Sigil Pickups helped me a lot when I first go into winding and he suggested the Syscomp CGM-101. Was never in stock and always unavailable so I got myself a Hantek 6022be and eventually two other Oscilloscope. Now I haven't wound pickups over a year as pedals have taken my over my spare time