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发表于 2020-2-29 22:29:49
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红灯记 发表于 2020-2-27 19:24
6 ?- R) m5 `- B. q/ [! ^' d _# [这个帖子不一定有多人看,但是错了一定要更正补上,否则会把对此有兴趣的人的认识带偏,我个人丢丑是小事
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https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/750/. I, d. V0 b8 L/ y j. c, h" V
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Mark, first....I want to publicly thank you for the prior assistance you've given me in getting this 2465 fully functional. It is greatly appreciated.
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2nd, I saw your post in the other thread concerning lowering the voltage to the EAROM and I did wonder if perhaps it would help with mine. So I did some checking but I found a discrepancy in what you did vs what is currently in place and perhaps your memory of what you did 20 years ago is a little fuzzy. X/ e; O2 T; [9 b0 p4 q {# @
a4 M/ T& h( `2 GI looked up A5 Board VR2003 and it's currently a 7.5 V Zener. You indicated that you lowered the voltage by 2 volts by installing a 9.1 V Zener. Isn't that actually RAISING the voltage by approx 2 volts? But you are correct. That line (OEA35) does supply the EAROM's on the both the A5 Board and the Buffer Board.- ?( P% D) ?( A& H9 {
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! {! S; H( B) U; J$ W5 fYou are most welcome! I enjoy working on this old equipment and I'm usually looking for excuses to pop the lid off and get out the service manuals. It's not something I get to do with more modern equipment I use on a daily basis for work.
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$ B9 x1 C2 ~# p& y1 W }% E, j) AOn VR2003, note that it and CR2004 are used as a dropper from the +42V rail to supply the EAROM. So, the end result to the EAROM is 42V - 9.1V - 0.7V = 32.2V. The spec on the ER1400 says 35V +/- 8%, so the minimum happens to also be 32.2V.
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I just verified the voltage on my EAROM (between pins 1 & 2) as 32.3V. With the original 7.5V zener, this would be higher by 1.6V ( = 33.9V).
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" q. i9 Y2 e! s, I* {" kMy EAROM had intermittent checksum errors and I was able to get it working by lowering the operating voltage 2V (replaced VR2003 with a 9.1V zener). It's been working fine with that modification for at least 20 years now.
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9 [- k& Z5 a+ {- l! q7 h2 ?/ I2 J你有沒有A26板?
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