HP 8563A Spectrum Analyser - display itensity problems

[charlyd]

i spended an other few hours on my display problem again. First of all, the following post i found on Keysight forum, keeps me away from the thought my CRT is the problem.
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Q: I have an 8563A that powers up OK but the display stays blank. It shows a green flash when powering down indicating a normal field collapse.
I have checked all the DC power supplies and also the signal levels on J201 202. Also the ext video out produces some output on a scope.
HV module substituted and A17 driver with no effect.
I suspect it is the CRT, is there any way to confirm this?
A: If you saw the green flash when turning the power off then your CRT is probably OK. I'd suspect the A2 controller (especially since your HV and driver assemblies seem alright)
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I also see the green bright flash/spot in my CRT when powering off so that answer sound reasonable enough for me to continue and when i poke arround U210 with my probe i see my text boxt on the right and bottom side light up as they should. So there is hope i would say...

In the following weeks, i decided to take out U207,U210 & U211 and put them in (high quality) round-pin IC-sockets for easy probing. I also took out the R250(3M16) resistor and R266(1M47) but that checked ok. 

Shorting the switch U207 pins 2 and 3 my picture looks ok. So i decided to pull pin 1 out of the socket and traced down the switching line from 74HCT377-> DEF1.
the line was high where i suspected a low to enable the U207 switch.

Meanwhile some part came in which i ordered over a month ago. A Harris HI-> U207 and two MC34084B -> U210 and U211. I did a quick swap but without any succes.
i checked my +15VF supply voltages, but they are just +14.92  and -14.91. quit on the low site if you ask me. Normally i would suspect a few .1 over the printed values in the Manual but these are below.. not much but.

And my DEF1 line is high which open the U207 1,2,3 switch.  strange..

suggestions? 
i am also curious what exactly to be expected on the line (-U207B/P7- U207A/P3 - U210D/P13 see marked in picture.) 



 

[charlyd]

This is the result of pulling the U207 pin 1 out of the socket or pin 8   -DEF1 line. then the picture on the tube looks very ok.

[Closed the other topic] https://www.eevblog.com/forum/repair/hp8563e-repair/msg2989588/#msg2989588

[charlyd]

hello anybody who can probe arround and tell me the voltages arround the U207B switch  and the DEF1 line.
for example is the +14.92 ok or should it be like 15.03v or what ever.

and what about the DEF1 line when should it be high?  when i would have had Option 7 in the unit then DEF1 would be ok the manual states,

i am also curious what exactly to be expected on the line (-U207B/P7- U207A/P3 - U210D/P13 see marked in picture.)

[dxl]

Hi Charly,

have you fixed that problem?

I would check the Display RAMs U201/U202 - what makes me suspect them is that the lines in the background grid are not really connected - is that only in the pictures? And the horizontal line in the test picture should be one line, but in your picture it looks like two diagonal lines crossing each other.

The intensity information is encoded with some commands in Bits 14,13 and 12 of the Display RAM.I would check whether the Address and Data lines on the RAMs are looking good, and maybe swap U101 and U102 and see whether something changes.

[charlyd]

Hi thanks for the info. I will check this as soon as i ended my TDS7404 project which is al over the bench now...  very happy with the tip!  great.

...will comment back here.

[charlyd]

@dxl i did a replace of my both U201/U202 or U101 and U102
video ram chips, now socketted.
but that didn t fix the display issue. any other suggesties?

[charlyd]

Hi i want to re-open or refresh this topic because it was never fixed yet.


can someone do some measuring arround U207 (or the Y or Z output board) or the +15VF
for me on a unit with a good working display?

thanks in advance