Scope help

[nosamiam]

There doesn't seem to be much of a DIY community out there in the field of oscilloscope use/repair. So once again, I fall back on the DIY stompbox community.

I just bought an old scope on ebay and am trying to get it all calibrated and running nicely. I'm doing well for the most part but I'm stumped. I can get it to detect a sine wave using a freeware tone generator on my macbook.  It looks like this on my scope:


(Note the stack of Post-its under the left front of the unit. It's the only way the thing will work. Can you imagine the headscratching this caused?)

Anyways, if I scale it vertically smaller it smoothes out to a nicer sine wave, not perfect but close. If I try to scale it larger it looks like this:



Anybody have experience with scopes who can tell me what to look for? I've had the hood open and made some adjustments, but nothing seems to give me more amplitude. The more I crank the volts/div knob, the more square the waveform gets. And I have the service manual, but the calibration procedure doesn't mention this as a potential problem as far as I can tell.

[ClinchFX]

The first thing you need to do is locate and repair the fault that stops it working without the post-its under the left front.  This may well be a dry joint, possibly in the power supply, but it could be anywhere.  There's no point in trying to calibrate anything until that one is sorted out.

It also looks as if there is a problem with the vertical amplifier in that channel, although it could also be the result of a power supply fault.

Peter.

[nosamiam]

Yeah, that problem with tilting the unit is gonna drive me crazy, but you're right. I need to find it.

I'll go back to the schem and start getting voltage readings. Sucks because it's tough to get to the board because of its orientation. But that's life!

Thanks for the tips!