红灯记 发表于 2020-2-27 19:24) p& x9 p. \5 s
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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" e8 a/ b/ e# T6 ehttps://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/750/) L$ d6 S5 c5 z" h/ q, p
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) d5 I. W" Z0 }% c0 O) yMark, 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. $ q2 G2 J3 F7 D: h8 L
' x* \* G4 W' l2nd, 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.3 N# ]7 t1 S7 g5 H
' V5 I- I4 f- pI 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.
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, ^# r/ R% c4 X* VYou 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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4 Q. z1 m) d; |( y' DOn 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.( |1 }' `5 r" D8 L0 r3 K/ O1 V# d
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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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My 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.4 T* |8 D$ G* ^! y
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" m: W/ F: N- C你有沒有A26板?
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