R.G. Keen Rransistors Tester

[peps1]

Soooooo..........

Just about to put a R.G. Keen Transistors Tester together in an enclosure, but was wondering if there have been any revised/improved versions in the last 10 years.

And sure I will have more question about the maths once built (I know anything with 10 to the power of minus 6 in the example will give me headaches  )

[Joe Hart]

I believe it's still good!
-Joe Hart

[newfish]

Not aware of any updates.

If it works (and it does), it's good to go.

[MikeH]

If it ain't broke....

[peps1]

Having a little trouble even getting a reading.....

Put a AC128 in, and switch the DMM to 2000m and it just starts counting down from 500ish, and the button dose nothing!

anyone spot my %^&*-up?

[Brymus]

Wheres your 1m resistor?
And did you wire it for PNP or NPN ? or is that what the switch does ?
I need to make one of these instead of leaving it on my breadboard in one corner...
Along with his quick n dirty signal generator,Vibe baby,EQ,ect,ect...

[peps1]

At the moment I THINK its wired up for PNP (Thats what the switch will be for, but right now its just wired in as a power on/off)

1M? Iv used a 2.2M resistor to the base.....is that wrong?


this is how my layout is at the mo

[MetalGod]

The voltage going down is due to leakage current in the transistor - if I recall correctly, you really don't want any more than 100mA of leakage current if you want a solid, reliable and good sounding device.

Here's my notes on this from last time I was testing Ge transistors...

* 0.021v with the switch open
* 0.324v with the switch closed

To get the leakage current, you use I=V/R where V is the voltage (with the switch open) across the collector resistor R

* 0.021V / 2.4k = 8.75uA

To get the gain,  subtract the voltage with the switch open from the voltage with the switch closed; then multiply the result by 100.

* (0.324 - 0.021) x 100 = 30.1

So in this example, the transistor had low leakage of just 8.75uA, but the gain was also low at 30.  Unsurprisingly, you'll find that most higher gain devices also have higher leakage - leakage above 100mA I would be wary of as a usable transistor (it will probably test with crazy high gain too).

[Brymus]

No Peps your right I didnt realize you were using a pot for one resistor...
If I get a chance I will check mine later,I have some Ge Qs that I need to sort as well.
Yours looks alot nicer though,sorry I was no help.