CombiScope PM3384

[david69]

Hi, I would like to repair this fault on PM3384 scope,
when I switch them in digital mode, chanel 1 and 3 are out of range, beam is outside display, where I should look into? Thanks for any idea, David

[HighVoltage]

This is a typical problem on the Philips / FLUKE PM33xx Series of these scopes including the "A" and the "B" versions.
I have several of the PM3394B with all options and this problem even happened to those high end scopes.

On your 4 Channel version, it either happens to Channel 1+3 or 2+4 or all off them.
There are two hybrid chips responsible for this problem, one of them is for Channel 1-3 and the other for Channel 2-4
They are a pain to exchange, because they are soldered on to the PCB
The Problem is, that nobody has these hybrid chips anymore.

I have the full schematics and service manuals for these scopes, if you need them.

[david69]

I see two hybrids on main processor board. I have opened
signal board with amplifiers, but now I don`t have focused track and text :-( I think that is not easy to soldered this hybrids :-( The focus pot beeps without any
changes on screen... The nice evening David

[david69]

Hybrids are OK, I changed them in position. Calibration for
chanel 1-3 writes "calibration error 102" which I don`t know How continue??

[david69]

hybrid has  in bad position  pin1 -2,5VDC, pin2 0V, pin3 -2,5VDC,  and in good positon has pin1 -0,5VDC pin2 -0,5VDC and pin3 -0,5VDC ... I change hybrids in position
and it has same parameters
The sources 4,5V -6,5V, 17,5V are in both positions...

[david69]

first I will change BF579 in oscillator, and look at clock signals again...

[david69]

the part of MASPU-A which sources buffer with clock,
is broken :-( PIN61 ClockA is destroyed ...
It needs replace older IC OQ0233WP ....