Re: Tech: Old Bally Star Trek - HV display Power - Rebuilt, R52 Smokes

Out of curiosity -- are there any manufacturer ID's or symbols and date
codes on these 2N3440 transistors?




"BarryMinnesota13" <theowlnose@xxxxxxxxx> wrote in message
news:4596bcf7-4fc7-4273-86ca-61571e54d811@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Mar 20, 12:07 am, Klickit <klickit_2...@xxxxxxxxxxx> wrote:
On Mar 19, 10:10 pm, BarryMinnesota13 <theowln...@xxxxxxxxx> wrote:

Thank you to you all for your help. While there was an net
interruption on my server, I pulled the Driver board and replaced the
smoked resister R52 and also since it was close, also Q22. I also
pulled the CR21 diode and tested it out of circuit and it was good. I
reinstalled the board with the HV fuse pulled, and there was no HV.
TP4 measures 260VDC. The base of Q22 measures 7.6 VDC. The base of
Q21 measures around 7V. TP2 measures around 8V. The resistors all
look and measure at proper values. I hope Q21 is OK. I have one more
2N3440 but do not have another 2N3564. What do you think?
Barry

Replace VR1 the Zener.

Thanks for the help. The root cause of this problem was a bad new
part Q22 2N3440 which also took out Q21. I pulled all transistors off
the board, and found that the replaced Q22 was good, but Q21 was bad.
The 2N3584 was good but I replaced it anyway. Upgraded the small form
resistors and the board HV is adjusted and working fine. Last week I
just was again bit by two out of five new 6821 PIAs failing out the
box. In my mind I thought that the transistors likely had a high
quality rate, but now I am not so sure.

Thanks again,

Barry

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2N3440's are usually of pretty good quality as they are still widely
availble from several manufacturers. Out of curiosity -- are there any
manufacturer ID's or logo's and/or date codes on these bad 2N3440
transistor?

The 6821's -- it's getting harder and harder to find good NOS parts for
these (which is why I have been sold out for about 6 months). Luckily,
there is still one manufacturer for these but the new ones are quite costly
at $7.50 each.

Ed


.

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