Beta Matching!

[Tom C]

the G version and the non G are the same... all the same specs.

Tom C

[Lman]

hello lman

just a snap question for future development
here in europe the MJL21194 is no longer available. so i suppose it will be a problem in america in the future
here they offer now the MJL21194G as other option
i believe the only manufacturer is ON semiconductors

its not exactly the same but do they react the same way?

kind regards
stephan and serge

Hi wild weasel,

The G letter shows that it is a Pb free or in other words there is no Lead used. More environment friendly as electronics is a big pollution factor worldwide.
I have seen some Motorola MJLs but I do not know if they still produce them.

Lman

P.S. Heh Tom C has been quicker on the answer

[peth]

Hi,

I am trying to match transistors I am using MJL21194 I have built the device as per the manual using a 500ma meter as recommended but the most deflection I can get is 80 to 90 ma. there is a sweet spot with the pot that gives that. Is there any adjustment in the circuit that will give m e more deflection on the meter?

Peth

[peth]

Hi,

I have had no feedback on this yet the only thing I can think of is to replace the 500ma meter with a 100ma meter. How does this effect the overall matching of the transistors?

Peth

[James_Somewhere_In_Idaho]

Hi peth

I have not built that circuit. However, they say one needs to go through their transistors, once to find the lowest value one (making that the benchmark transistor), and then marking the rest based on the higher values. They do not say that there will be a large variation in readings. I imagine, after not having seen the circuit diagram you are using, that one can simply change out a resistor and/or capacitor value to achieve what you are looking for--though I do not know that for sure.

That being said, I went a simpler route using one of the many cheap transistor testers out on the market. Those typically display two numbers: hFE (current gain or amplification factor)--which mine were typically between 41-54, and VF (forward voltage)--which mine were typically between 541-551. Most people only match forward voltage. I matched for both in my builds.

Hope that helps

[peth]

Hi,

Thanks for the feedback I think I will go the way you did but may need a little guidance, here is what I have found on e bay http://www.ebay.com.au/itm/2014-Mega...AAAOSwstxVA693 will this do the job

Peth

[James_Somewhere_In_Idaho]

Here is the one I purchased:

http://www.ebay.com.au/itm/Small-128...UAAOSwLVZVu3ms

I purchased this one, because I could test for inductance in coils. One modification you should do...solder 3 micro-hook test leads to the 1, 2, and 3 positions (found under the circuit) for ease of testing, as the quick release IC hook-up is non-durable, plus the addition of the micro-hook test leads, allows for testing components in a circuit. There are only 3 positions the quick release connects to on the PCB. It will be more apparent when you get yours.