Hung Chang 20Mhz CRO Dual trace. First fire-up in twenty+ years. - Page 1
Forum section: electronics / repair

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: May 17, 2015, 01:42:06 am
content: 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?

author: Grapsus
author_rank: Regular Contributor
timestamp: May 17, 2015, 02:42:59 am
content: 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.

author: waytec
author_rank: Newbie
timestamp: March 10, 2021, 02:19:25 am
content: 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:ThanksWayne

author: bateau020
author_rank: Frequent Contributor
timestamp: March 12, 2021, 06:54:28 am
content: 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.

author: waytec
author_rank: Newbie
timestamp: March 16, 2021, 01:30:29 am
content: Thanks for your reply.....It is a little different but close......Not a bad Analog CRO really....seen a lot worse.....Wayne

author: floobydust
author_rank: Super Contributor
timestamp: March 16, 2021, 01:38:31 am
content: Look at this thread for more info:https://www.eevblog.com/forum/repair/meguro-mo-1252a-25mhz-analog-oscilloscope-nothing-on-crt/msg1529113/#msg1529113

author: beanflying
author_rank: Super Contributor
timestamp: March 16, 2021, 02:22:22 am
content: I uploaded what I have to my Google drive herehttps://drive.google.com/drive/folders/1vQjYoeBmy6Jp73LG8ZAUAJXCZEs_mxru?usp=sharingI 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.

author: waytec
author_rank: Newbie
timestamp: March 18, 2021, 02:37:54 am
content: 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