Oscilloscope problem

[Alien8]

Hi

I think I've managed to 'hurt' my tektronix 485 scope. The symptom that is showing is whatever is present on one channel, also shows up on the other one. So channelseparation would be zero (?)

At first I thought it could be just a mechanical problem with the switches for the vertical mode. After all this piece is over 30 yrs old !

So I opened it up and tried to see if I could get to those switches, unfortunately they are buried under the input dividers. And I can't get to them.

Upon inspection of the other pcb's I noticed an overheated resistor (showing burn marks) and a broken capacitor next to it on the power supply board, next to one of the connectors that connect to the vertical divider boards. I would think that that resistor is for PSU decoupling of a +15V line.

When I started thinking what might have caused this, it is possible that I had both probe grounds connected to a differential voltage point of 6V, unfortunately by a high current battery in between. Or, connected to the ground input of my spectrum analyzer ???

Can somebody point me in the right direction ? I sure would like to have this problem fixed if possible. Any one knows somebody in Belgium that can still service these tektronix scopes ?

TIA

[Netlist]

This is about the only info I have for the Benelux:
I'm not sure its accurate but worth a try.

TEKTRONIX HOLLAND BV
POSTBUS 226
2130 AE HOOFDDORP
+312503-13300

TEKTRONIX
POSTBUS 406
2130 AC HOOFDDORP
+3123-5695555

/Hugo