红灯记 发表于 2020-2-27 19:24
$ O! E" F' I7 S& N* c4 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: X. a ~- l( r1 q" O
...
https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/750/
0 N' n( Z7 X/ K
3 Z- G4 R G' A8 m
/ n! V6 V, u' x. O" R E
! W. o& T! L3 H6 t+ J, H# Z I5 J. E# |7 p& M% B
/ {6 w/ x5 B. _1 I, `0 ?/ B# u; e, T2 u
4 f* n! @- f- t' y$ `
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. " k) F A. ]7 T8 `- A
& P- `) K n' n9 X( |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.
3 f1 H0 Z+ k9 M( m% i# u$ o1 g1 r+ \' l3 c. a1 N5 V
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.; i r" [- R1 F* w
8 o b q( p! P) k) x7 v/ D8 k8 o1 G
% Q& C+ K5 y3 G# B$ K6 @- F
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.; }& s" u$ V, x" D7 }9 Q3 s9 e
9 F+ e. z2 d) |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.' Y- B/ `' c8 E o1 E4 {
3 v6 Z$ c( K: \0 ~9 r( z
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).
% H4 r( P5 T# D* w. n$ {9 i" F; o5 |9 w+ c# Y z" E2 t* z
4 M5 y! w p& y* }8 y: A
L$ V! Z2 `& b* n0 {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.& u0 J5 ~- |; x9 l6 |" f0 ^
& J& m- Y: S/ U4 P4 s! z
* n8 m" m! G; l
& {7 `: j0 z9 D4 ~
# o0 C3 i0 B4 F- r' K. L3 t7 s# A- K9 i8 X2 h
你有沒有A26板?
7 U3 Y6 q+ ^+ }5 x1 ]+ [! \/ L5 O/ `( N$ }
8 v" A% D7 `- R$ F6 d4 u |
[复制链接]
公安部备 45010302002201
客服：18077773618
楼主
发表于 2020-2-26 12:09:28
