PM3285A repair

[david69]

Hi, I could ask You, what I should measure on this VHF scope. I have trace down from screen
on both chanels, what I should have on delay line driver? because of text on crt is fine, readout
works well, focused OK. The final Y amplifier works? Voltage on position trace A and B, turned
front button, changes 1 to -2V on delay line driver OM547
Thank You David

[david69]

I removed POT cable from socket X1102, and I have both trace A,B on right down corner of screen,
when I conected calibrator, I saw partly signal on screen.
There was broken elektrolyticum capacitor C1121 +5VD digital 1000uF/10V on Intermediate unit.
I guess that something wrong on this unit. The capacitor was short circuited. The POT settings are
line to microproccesor unit... The reference voltage +10V uA723 is in tolerance. What should I do?

[david69]

I desoldered MUX HEF4053 D1101 from Intermediate unit, this switch position voltage on delay line
driver OM547 N5031 on Signal unit, I suppose that +5VA will be centre trace on screen, but when
I connect force +5VA on circuit POSA, POSB of OM547, supply goes down, 0V so MUX hasn`t
such current. When I disconnect +13V on OM547, I have trace on half of screen Do You think
that delay line driver is broken?? Than You for any idea.

[singapol]

Please put your country flag so we know where you are. I believe you are not native english speaker so it's hard for me to understand what you are trying to say. In general the delay line is seldom the problem. See the service manual for a clearer understanding of the scope's construction. Hope this can help you.

http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Philips/pm3285a_pm3286a.pdf