红灯记 发表于 2020-2-27 19:247 ]* K3 |/ Z, b
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3 `7 M8 v# k! Z6 G7 }2 v
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0 h6 K9 ?: ]: h/ ^- Vhttps://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/750/% `" ]% S; V9 C# c
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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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0 n* u( ^/ }# w+ Q7 t& A6 {9 ~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.5 D+ B9 V( D' k1 U9 d M+ {4 `
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I 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./ e: `9 W3 W+ t) v r, p
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You 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.0 d- x/ q8 D7 Y( `
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On 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. ]) P% S1 i6 q' Y1 P
+ ]: a0 r* U6 G& G: W RI 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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# I3 ~& M1 n' r3 r2 XMy 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./ p0 n. b6 h5 {' G( j) c* X
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4 z; o" C6 k" L; t& o: ^1 _你有沒有A26板?
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发表于 2020-2-26 12:09:28
