Old Fluke&Philips PM3350 - broken Y-Axis

[THPallround]

Hey folks,
at the beginning of the year I bought a "propper functioning" oscilloscope on ebay.
When I turned it on, I see, that the menu shown on the CTR is completly moved to the upper corner, so I only can see the "button row" [pic1]
Whyle testing the CRT with the intern testsignal, it came out that everything has moved in +Y by ~7Div.

After downloading the Service Manual, i tried to adjust the Y-Axis like its given in manual. Unfortunately without success...
As you can see in [pic2] the line is out of view, just some light is shining in from the top corner.
I also replaced some explodet caps on the mainside of the PSU. But they are only there for EMV reasons. [pic2]

After throwing up the table, beeing sulk for some weeks while waching tons of YT-vids about faulty osc's I came up to write this forum entry.
So I hope you can help me out of my brain dead end.

I have uploaded some photos https://imgur.com/a/O2XCplO and the Service Manual https://elektrotanya.com/philips_pm3350_pm3352_sm.pdf/download.html so you can see what I have tryed to explain in my bad german mid scool english   
If you do need some more informations just ask, I hope that I can get this 80€ pice of copper work propper again 

Greetings Thomas

[pbarton]

Possibly a problem in the Final Vertical Amplifier? Diagram attached.
Check the power rails including those with a blue arrow +5, +12, +17, +48, -6.4 and -48V for DC level and AC ripple.
If you could reply with the following measurements….
Centre the front panel Vertical position control knob (Y) and measure the ‘red’ DC voltages (with a DMM) at X20, X21, X22, X23, also A, B, C and D.
No input signal is required.

[madao]

 I has repair  little brother (PM3335)  of PM3350.  But  analog part is same.

Same fail, but   mirrored (trace is with readout compressed to lower)   
Cause is  a failed  2N3866 in final stage of vertical amplifier.

I  would saying, check   vertical amplifier backwarts.

regards
matt

[THPallround]

Possibly a problem in the Final Vertical Amplifier? Diagram attached.

This was also a thought of me, but I had no plan which measurements I have to do exactly.

If you could reply with the following measurements….
Centre the front panel Vertical position control knob (Y) and measure the ‘red’ DC voltages (with a DMM) at X20, X21, X22, X23, also A, B, C and D.
No input signal is required.

I'll make the measurements tomorrow and will post them.

Thanks for quick reply!

[THPallround]

Hello there,

after I handled it to take the pcb's out of the oszi in one pice, I relized that this kind of flatcable ([pic5] on the same imgur https://imgur.com/a/O2XCplO) is  peeled of from it's insulation. What's the best way to replace/repare it? Just use some wires or a shielded cable? I don't want to make more problems than improfments 

So anyway I figured out all measurepoints you gave me. Tomorrow I hopefully can deliver some values.

[pbarton]

Repair using Duct, Gaffer or Gorilla tape?

[THPallround]

Repair using Duct, Gaffer or Gorilla tape?

That was my first thought, but than I remeber, its bend kompletly while mounting it and I don't want it to make a short circuit.
I think I will clean it up and pull a shrinking tube over each conductor.

[madao]

oh, rotten-cable.. 

2.54mm pitch flat cable is a option.  Hot glue is important supplement  to provided of realibilty.
 (or you can using  1,27mm cable,)

regards
matt

[THPallround]

Ohh man... After I wondering about the fact, that the output on the CRT gets more vaulty I and making all measurements I realize, that I switched up some wires from changing the rotten cable... This shows clearly: don't work until midnight    Hopefully, I don't make it worse... 

You hear from me in the next days. 

[THPallround]

So I found time today. Measurements are posted as [Pic6] on https://imgur.com/a/O2XCplO
There is some odd stuff going on at AC ripple as you can see. Hopefully, we can find the vault now.

[madao]

I have repair other Philips scope with  SMPS Power supply,  there is also rotten-eletrolytics  also cause for failure.

You can replacing eletrolytics of PSU. 

How removing of PSU. Yes, it is difficult, if you don't know, how about it is.

Left carry-handle  must be  pulled , while you're  pulling PSU-PCB   out of Philips. Otherwise, you couldn't pulled it out, because axle of carry-handle forces it down.   Yes, it is  mechanially nightmare.

regards
matt

[THPallround]

Yes, it's a nightmare to get the PSU out... After I managed it the first time I modified the clamps 

So you mean I should change all e-caps on the PSU-PCB?

[madao]

Sorry for late reply.

Only small  eletrolytics on secondary side is needed to replacing.

But i recommed, replace all on secondary side and little in primary ciruit.

[THPallround]

No problem, we all have a real life too 

Okay, I will order some new one for replacing. Any other parts that could be eventually faulty? I just want to try avoiding more shipping costs than needed