repairing hameg 605 scope

[momin]

hay every body
i want to consult u about my hameg 605 scope i have since 1984
and it was working propably and suddnely it starts to show wierd signals even if the channel is set to ground and no probe is connected to it, the wierd signal is about 10kHz and u can only see it if u move the basic trace from the centre line then u will see a straight line and it has down levels to the center line this is continuted by about 10kHz and its not uniform
i have tried every thing: i replaced almost all the ic's and i check almost all the transistors nothing happened
please every body if any has suffer anything like that help me..

[gootee]

If you don't have the service manual for your scope, you should try to get one, ASAP.

The first things to check are the various power supply rails' DC voltages and AC waveforms. If one of them is more than a few percent off, I'd want to find out why.

If not much else is known about common failure modes for that model, the most-likely points of failure can probably be assumed to be electrolytic capacitors. After inspecting for leaking and bulging electrolytics (and for things like obviously-overheated components or PCB areas, loose or bad connectors, etc), you need to check the ESR (Equivalent Series Resistance) of each one, and compare it to the average ESR for caps with the same voltage and value. If you don't have an ESR meter, maybe you can use this simple method: http://www.fullnet.com/~tomg/esrscope.htm .

You might also want to search for your scope's make and model designation in the sci.electronics.repair group's archive, at http://groups.google.com .

Good luck.

Tom Gootee

http://www.fullnet.com/~tomg/index.html