Apple ][+ Astec power supply

[RJARRRPCGP]

Re: Apple ][+ Astec power supply

2N1136A: made in 1973 (as far as I can guess)
466 103-9: made in 1972 (same deal)

The 466-103-9 makes sense, I see the usual format on the bottom (international format)

And the 2N1136A looks like different type of format, without the usual four characters. Reminds me of Intel, where the year number is often just the last digit of the year manufactured in.

[eccerr0r]

Re: Apple ][+ Astec power supply

The reasons why I think 1973 is because:
1. Germanium power transistors have not been made for decades.
2. Bendix has been gone for decades.
3. I think 1963 is a bit too old for the transistor, but it's possible.

[BigTroll]

Re: Apple ][+ Astec power supply

heres a awful youtube video to celebrate the Rifa caps. https://www.youtube.com/watch?v=4hjnAc55lDQ

[eccerr0r]

Re: Apple ][+ Astec power supply

Too many burst RIFAs. Why haven't I seen any dead WIMAs...

Incidentally the BUW44 probably could work as a replacement for the PSU, it should switch at 200KHz, sustains 400V, 6A... This 200KHz is probably pretty close to the Ft though its gain is still apparently 5 at this given frequency test condition.

[stj]

Re: Apple ][+ Astec power supply

be interesting to put a frequency counter near one of those old designs.
just holding it over the transformer should be enough to lock on.

[PeteS in CA]

Re: Apple ][+ Astec power supply

be interesting to put a frequency counter near one of those old designs.
just holding it over the transformer should be enough to lock on.

I don't think they were fixed frequency. That said, they were normally above 20KHz, so they would not be audible, and bipolar transistors limited the practical maximum switch frequency to around 50KHz.

Not only are the turn-on and turn-off times of bipolar transistors slower than for MOSFETs, but there is also a turn-off delay called "Storage Time". If all those delay times are too great a % of the period, the useful on time (and range of control) is limited and the % of time when the device is dissipating power becomes too great.