Hung Chang 20Mhz CRO Dual trace. First fire-up in twenty+ years.

[Ed.Kloonk]

Bought this puppy from Jaycar in Sydney in 1989(?) 
 
 

Powered up yesterday after a twenty year neglect. The voltage zero positions on channel one are slightly off as I remembered, is near enough but now the scope hates to display two channels simultaneously. Bridging the two inputs sends the trigger into a spin. But connecting just one channel displays sort of OK.

Not sure if I want to waste too much time on this scope since I'll probably need a new DSO to properly diagnose it and (I hate to say) by then the new scope would surely supersede the CRO by a million miles. So I won't need the CRO. 

Have the manual. Has schematic. Full maintenance chapter. Except each vertical channel has two hybrid 15-pin ICs. Labeled only AX 1015. Whilst everything else bar the hybrids and switches are replaceable, I wonder what are the odds of one of those funky, mysterious hybrids being the culprit?

Does anyone know what this hybrid chip even does?

[Grapsus]

A CRO is always good to have.

If you active both channels in ALT mode, with the slowest timebase, it will take 10 seconds or more to sweep each channel, so in this way a diagnostic could be possible without another scope.

[waytec]

Hi Ed ...

My Hung Chang 20Mhz CRO has just developed no Horizontal Sweep.....

Having trouble finding the exact circuit diagram for mine...

Do you still have the manual etc:


Thanks

Wayne

[bateau020]

Having had a Hung Chang 20MHz CRO before, I used the manual attached below. Not sure of course, but could very well be applicable to the one you have. Yes, the brand in the manual is different, but this scope was sold under many brands.

[waytec]

Thanks for your reply.....

It is a little different but close......

Not a bad Analog CRO really....seen a lot worse.....


Wayne

[floobydust]

Look at this thread for more info: https://www.eevblog.com/forum/repair/meguro-mo-1252a-25mhz-analog-oscilloscope-nothing-on-crt/msg1529113/#msg1529113

[beanflying]

I uploaded what I have to my Google drive here https://drive.google.com/drive/folders/1vQjYoeBmy6Jp73LG8ZAUAJXCZEs_mxru?usp=sharing

I did a fairly good search when I got the beasty last year. Also known and marketed as Protek elsewhere in the world. I managed to get the info needed from this lot to run a Calibration check on it.

[waytec]

Thanks very much for all your replies......

Mine is different unfortunately but the circuit diagram is close....
Will upload a picture .....
On the Horizontal PCB all the transistors are labelled as TR while on all diagrams I have tried they are labelled as Q...
But what I have is better than nothing....

Wayne