The Sanyo 20EZ from hell.

RetroHacker

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Well, I've been round and round with this monitor. I'm really getting sick of looking at it...

You may remember my previous thread about the HV shutdown - that one got derailed with another user's problem, so I'm starting a new thread about this monitor.

Previously, I could get a raster on the screen, but I couldn't dial the B+ up over 95v, any higher and the monitor went into shutdown. I just received the new IC 601 from Bob Roberts, and I installed it. Now, the problem is even worse - it goes into shutdown immediately, regardless of how the B+ pot is set - just a quick burst of HV, then shutdown.

Some history on this monitor:

As found, it was totally dead. Quickly checking with my meter revealed that the 300ma fuse was not blown. I recapped it. Still dead. Notice that the large 180ohm 20W resistor gets REALLY hot - and it was cracked down the middle. Further investigations revealed that the HOT was shorted, and closer inspection of the 300ma fuse revealed why it had not blown - some joker had replaced it with a 7A fuse at some point. (I never even knew that they made 7A fuses that small). Carefully inspect flyback and see some evidence of seepage along the seam at the top. Replace the HOT and the flyback with new parts from ArcadeCup, and replace the 180ohm resistor with a 25w one scavenged from another chassis. After that, I can get a raster, but adjusting the B+ results in shutdown. Replace flakey B+ pot. Find that it shuts down at right around 95v. Replace the current limiting transistor as IC601 was still on order. No change. Replace IC601 - now monitor goes immediately into shutdown regardless of B+ pot setting (quick flash of HV). Replace C606 for the heck of it - no change.

So... I've gone over the board looking carefully for shorts, cracked traces or cold joints, and I can't find anything. All the caps are installed the right direction, etc. I've already changed all the parts I've ever seen fail on these monitors. Now what?

-Ian
 
Hey RetroHacker,
I apologize for derailing your last thread about this topic. But go back and read the banter that Dokert and I had. I found that even after I found that broken solder joint mine was still shutting down. I ended up dialing the B+ pot all the way counter clock-wise, and also VR451 all the way counter clockwise, turned it on, and bingo I had a picture for the first time in about a month. It was completley washed out, but I was then able to dial up VR451 close to where it should be, then was able to dial my B+ right to 108v.
Your problem seem very similar to the one I was having.....
If that doesn't work, might be worth testing the resistance on that VR451? Make sure it is where it should be.
 
Well, I had forgotten about VR451, as I had dialed it all the way counter-clockwise earlier. I dialed it back to the middle, and fired the chassis back up - and it stayed on! Best I can get for B+ is 103v or so, with the B+ control all the way clockwise.

As for the picture, I hooked it up to my test rig, and was able to get a wobbly picture. Fiddling with the B+ control, I was actually able to get it to 105v for thirty seconds or so - but with lots of noise and lines through the picture. Then it shut down. Dialing back the B+, and I could get the picture back, but it's still too wobbly to be useful. It looks like a monitor with a bad B+ cap - which isn't possible, I just put a new one in tonight.

So, sorta there. I am beginning to wonder if that IC601 regulator I got from Bob is good...

I'm looking forward to the next time I get to rebuild a G07.

-Ian
 
The traces on IC601 are pretty small and some of the other traces have some really sharp angles. Look very closely for any kind of solder splash in the 600 area.

Keep in mind that VR451 is only the sub-brightness. The main brightness control is on the fly and may need to be adjusted too.

Give this a try... Center the brightness on the fly, center VR451, center the brightness control on the frame, and finally center the B+ pot and fire it up.
 
Give this a try... Center the brightness on the fly, center VR451, center the brightness control on the frame, and finally center the B+ pot and fire it up.

Yup - that's how I got it to come up at all. I had accidentally left VR451 all the way counter-clockwise, and Zork2 reminded me of it. I can get a picture, but it shakes, and no matter what I do, I can't get the B+ over 103v and be stable. Even if I dial the screen control on the flyback all the way down.

I've been over the area around IC601 very carefully - no solder splashes, no cold joints. I even ohmed out from each pin on IC601 out to the components the trace connects to - no breaks.

-Ian
 
have you changed Q901(2sd1090)

I think you emailed me on this I didnt have any to supply you with. Im working on a solution for this. locating subs / or originals.
 
lets try desoldering pin 9 of the LA1464 ic.. that is your x-ray shutdown pin..
if it now holds for awhile that is being triggerd.
But why is being triggerd?. bad ic?. crossed cap legs from the cap out?
 
Definitely no cap legs crossed, I always mount the caps right against the board.

Actually, it stays on now, now that I rememberd the VR451 contol. I get a shakey picture, but even with the B+ pot turned up all the way, the B+ only gets to 105v. And while it's at 105v, the picture gets lines through it and the thing shuts down after thirty seconds or so.

I can try disconnecting the x-ray shutdown pin and see if that changes anything, but still, something is definitely not right, I should be able to get the B+ up to 108v.

-Ian
 
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