Need help repairing couple 'scopes (different faults)

[fezder]

well this current one is this megure, model mso-1270. seemed ''easy'' due PSU fault, and so small psu, but so far i'we encountered 4 S/C's due screws......i abandoned that kikusui for now, seemed such puzzle, but so does each of these

 

[fezder]

managed to repair it little bit, current consumption dropped ALOT, now it's in much better levels. HOWEVER, still something cooks lm317, gets really hot...that's enought for this day

 

[fezder]

back again, made some progress with testing. at least something works, calibration pin for probes gives ok signal.

another note, as it tries to draw signal, when it disappears, it always shoots up vertically before disappearing, never down. it doesnt try draw anyhthing on x-y setting, so could this hint there is something wrong in horizontal section?

 

[fezder]

any clues? i know it's hard to help via internet, especially when no service manuals/schematics are in hand.....I made HV probe for multimeter in case repairs need checking of crt voltage. No worries, i'll buy prober probe some day near future for DMM, but perhaps i'll need better DMM too, i'll have just cheap victor b88.

 

[tvtech]

Fez...

One at a time.

What you need to do is decide what you want to fix. Give as much info as you can on that particular scope you are busy with. The one you have chosen for the Day....and stay with it until it is tossed or repaired...

Trying to fix Six things at the same time will end up in....nothing fixed. And everybody confused.

Little bit of sense maybe

Regards,
tvtech

 

[fezder]

yeah, good point, i'we tried to do this like concentrating, but i'we changed target, to see if that specific would have service manual or such in web.
and due the fact i have so little experiecne, it's pretty hard too to study same time on different faults. Oh man what i would give to be apprentice of some sort.

 

[tvtech]

Hi Fez

I am a simple Guy that knows "stuff".
What works well for me is order. Otherwise....I get confused too

Business environment....I tackle ONE job at a time. Either complete it properly...or toss it. And never come back to it.

Done and dusted. Out of the system........different for you..

Same principle though.....one at a time..fix it of toss it

Regards,
tvtech

 

[fezder]

yeah, well perhaps ill dump this meguro for now and focus to kikusui, as kik has at least schematics and perhaps the most worthwhile to repair atm...

 

[tvtech]

yeah, well perhaps ill dump this meguro for now and focus to kikusui, as kik has at least schematics and perhaps the most worthwhile to repair atm...

Dump nothing. You will get to the others.

Sorry for being hard on you and you are new to repairs and all....it's your Hobby.
Mine is my means of eating. And staying alive


Regards,
tvtech

 

[fezder]

oh no, you were not hard at all. hearing other's opinions and way of learning/doing is part of learning.

 

[fezder]

i read this thread and i see what you mean by confusion thanks for pointing that out...

 

[tvtech]

OK... I know are here ...

What did you try to fix today?

Sorry if I sound harsh..and full of Crap. My star backup..has decided to drop me for a while....LOL.
I will get through it though...

Here is my story : A CLEAN bench is a problem free area to work in/on or whatever..finish a job and throw away blown stuff...throw away. Don't wander..uhm..was it blown or not???
Blown = Toss.

Every new Job has a clean bench...FFS...so easy. Now I am going to shout Fez..Not at you but at people that like to fix things with blown/faulty/rubbish lying around the bench.....

End of the day...they do not know what the fulck is working or not....

Hobbyist maybe fine...working in a Professional environment = WRONG..

I remember a memorable post when the late Jim Williams from National Semiconductor had a picture taken of him and and the mess he worked in....
Man, was I shot down or what from Members that agreed that a Genius should work that way...I disagreed. And still do.

The photo is here somewhere still...thing is for me: CLEAN BENCH = NO MISTAKES.

Sorry Fez you had to bear the brunt of this......all in good faith

Regards,
tvtech

 

[fezder]

haha, i know what you mean tech, i too have one bad habit, should clean desk more often.
i have also some sort of electrical problems with my car also. the button that opens back trunk, gets stuck sometimes, and causes solenoid which unlocks trunk, to latch open, so it doesn't shut down. also due same problem my trunk has been opened couple time on highway! the other problem is idle-running motor-thingy that seems to malfunctioning, again, causing throttle to wiggle around 1000-1500rpm. but that's another story.

i had to make small improvement to my isolation transformer to reduce 400 amp startup peak, fuses don't like it, already blown fuse couple times due that. now i'we almost, only thing left to make are some final wirings and stuff. inrush current limiter is pretty simple: but works: time relay controls power relay that shorts out power resistor that reduces current spike. of course one possible flaw is that if relay gets faulty and doesn't short resistor, transformer doesnt run in full power....but at least doesn't blow fuse.

as for the scopes, 'been pretty occupied with other stuff, as you can see. but i should be able to return to this topic soon, and better be before i forget what is fault in scopes....

 

[fezder]

okay guys, time to get back to repair-attempts, if anyone of you have aknowledge and patience (is this resurrecting dead-thread? hopefully not....)
oh, and i do have schematics for that kikusui cos5040, it's pdf, so how can i attach it?

 

[KeepItSimpleStupid]

If it's not too big, then under "Go advanced". You can also get a free Microsoft One drive account and post it there,

 

[fezder]

hopefully i made it right, here's link to that one drive account
https://onedrive.live.com/redir?resid=477358247C3BC88D!158&authkey=!AN5j82bO6mixGCw&ithint=folder,

edit: seems it doesnt work just yet...

edit again, now it works, schematics are found under that link!

 

[KeepItSimpleStupid]

Your schematics work. Now, explain your issue again.

 

[fezder]

ok, issue with that kikusui (for which those schematics are for) works fine at first, then, after some time (around 3-5 minutes or so, could be even less) signal disappears in such way, as it would try to draw it on screen, only disappearing before reaching the end of x-axis. also, time-knob does take some effect, it streches/thinners the signal itself (more/less time/div) but overall speed of drawing stays the same, dunno if this makes any sense!. it's like it draws signal on background normally, but with lowered time/div (around 20ms) and it disappears around middle screen. i would take video, but cinda hard (probadly only lack of skill)

 

[alec_t]

Is the Y-axis (vertical deflection) circuitry working correctly?

 

[KeepItSimpleStupid]

First things first, look at the +-12, 5 and +140 supplies before and after the fault.