Hi Anatech, actually they were used in a very old industrial regulator within a same heatsink with the lower gain one
driving the four others wich were parraleled, and when i mean paraleled that s not even with emitter resistances
to evenly distribute the output currents, that s why they needed four matched devices.
This leave me wondering about the low gain devices you and wg-ski got at the time, possibly that the manufacturers
unloaded most of their rubbish in the consumer market while pro users got the best parts, be it for DC regulators.
Edit : I ll add that testing condition was at 9V VCE and 25°C since they still are on their original big heatsink.
driving the four others wich were parraleled, and when i mean paraleled that s not even with emitter resistances
to evenly distribute the output currents, that s why they needed four matched devices.
This leave me wondering about the low gain devices you and wg-ski got at the time, possibly that the manufacturers
unloaded most of their rubbish in the consumer market while pro users got the best parts, be it for DC regulators.
Edit : I ll add that testing condition was at 9V VCE and 25°C since they still are on their original big heatsink.
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Hi wahab,
No, we buy from industrial suppliers. I did industrial and consumer work and they did not differentiate for end use, plus bought direct at times when quantities were high enough. Fly-by-night shops would buy from anywhere that had them cheap, including surplus that may have had rejects. TV service shops were famous around here for using junk. I only bought from distributors, and sometimes shops I knew well and knew they bought from the same suppliers. Plus I (still) tested each part before using it. It's a habit I got into at the beginning.
Your power supply transistors were certainly matched by the manufacturer, of that I have zero doubt! However, even matched parts require emitter resistance as they will hog current as they get warmer. We used matched parts for consumer (including PA and MI) applications, and also industrial power supplies. The main concern was reliability, and if it comes back, I'm fixing it for free!!!
No, we buy from industrial suppliers. I did industrial and consumer work and they did not differentiate for end use, plus bought direct at times when quantities were high enough. Fly-by-night shops would buy from anywhere that had them cheap, including surplus that may have had rejects. TV service shops were famous around here for using junk. I only bought from distributors, and sometimes shops I knew well and knew they bought from the same suppliers. Plus I (still) tested each part before using it. It's a habit I got into at the beginning.
Your power supply transistors were certainly matched by the manufacturer, of that I have zero doubt! However, even matched parts require emitter resistance as they will hog current as they get warmer. We used matched parts for consumer (including PA and MI) applications, and also industrial power supplies. The main concern was reliability, and if it comes back, I'm fixing it for free!!!