Sanyo 20EZ: acceptable voltage range ~100v

Teknotoyz

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I have a 20EZ which was working GREAT after a cap job for months....
Then it goes dark.... Tube is not firing up at all now (no neck glow).
No fuses are blown, but the machine also wasn't grounded either.

Checking the B+, I got 140v... :(
Checking the isolation transformer plug.... I'm running at 108v.
The transformer is tapped as high as it can be at 120v on the primary side.
Sooo, is 108v acceptable for the 20EZ to run on?
If not, how do I lower it, no taps for a higher primary voltage.

I got a new regulator, current limiter, and B+ pot in hand now.
Planning to check diodes first, the machine wasn't grounded, so I'm not sure if the fuse would blow on a bad diode or not.
I'm trying to make sure I have my plan or repair in mind before I start so I don't damage anything more....
 
100vac +/- 10%

Most likely your B+ pot has failed, which is common after a cap kit on a Sanyo.

Well, I FINALLY pulled the monitor chassis last night and checked diodes (good) and the B+ pot, which measured as essentially open. They put that dang epoxy on it and I'd guess that ruins it as you do tend to have to adjust after a cap kit. I'm really surprised it worked as long as it did after the cap kit!
Thanks Dokert! You nailed the cause! 140v dropped to 108v with no issue with the new pot.

Pics for fun!


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I am really liking this DK Jr. Nintendo table, it can run Donkey Kong, DK Jr., and Popeye upright boards with no wiring changes! Plug and play (except Popeye needs the monitor rotated!). Power supply and harness works fine for all boards.
 
ARGHHH!!
So, it works for a little while, got a few games of Popeye in at least, then I turn it on last night and it comes on for about 30 seconds then turns off, HV Shutdown again with a B+ of 137v. Newly installed POT does nothing to help.

In one way I'm not surprised, the original POT was bad, but I'm thinking that me turning it full range to see if I could bring down the voltage is what got epoxy under the wiper. In any case, a few questions for those that know better than I:
1.) Is it possible for a bad regulator to "come back" if set for a couple of months?
2.) Wondering if bad solder is the culprit, maybe it worked again after I had moved the board or whatever.
3.) If the 300mA fuse has bad contacts, would voltage rise or fall?
4.) If I replace the regulator and not the current limiter, is it possible to damage a new regulator if current limiter is bad? (I can replace the regulator without removing the chassis pretty easily.

Thoughts?

Current plan is to check the new POT, then look for bad solder joints, check B+ voltage, then replace the regulator, check B+, then replace the current limiter. Hopefully all will be good once I get B+ back to 108v.




Man that cocktail has some rust on them thar legs.

It's a cosmetic mess right now, sat in storage near a river for years.
I'll be doing a complete teardown this summer when I have some nice warm painting weather! :D
 
I am stumped now,
I took the plunge and replaced both the regulator and the limiter and I still get the 140v!!
Adjustment pot is still measuring OK.
NEW VR601
NEW IC601
NEW Q901
Cleaned DC 0.3 amp fuse holder - measures good now.

SO, what next?


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Still can't seem to find any new problems. Decided to check the voltage out of the ISO transformer. Hell, I'm up to 112v now. Would the excess voltage cause a HV shutdown??
 
Still can't seem to find any new problems. Decided to check the voltage out of the ISO transformer. Hell, I'm up to 112v now. Would the excess voltage cause a HV shutdown??

that's not good.

see if you can lower that voltage below 110v.

Peace
Buffett

112vac out of the iso is NOT a factor. 100vac +/- 10% the extra 2vac is not your problem.
 
So I'm still brainstorming on this.

The pot replacement fixed an issue with the original pot I created when I tried to adjust it down the first time. The epoxy looked to have gotten into the wiper.
So, in all my glee when the monitor fired up after that replacement, I sorta knew the fix wasn't likely the root issue.

A quick history of the monitor:
-It sat for many years in a damp environment, caps blew up as soon as it was powered the first time.
-I bought it at this stage, pulled the monitor and it was COVERED in cap paper and foil. I blew off all the debris and the board really looked good underneath the mess.
-Installed a cap kit, many of the caps looked like leaky batteries! The monitor powered up and looked great after the cap kit was done.
-This worked for a while, wasn't heavily played, but one day I installed the Popeye board, moved the monitor to the horizontal position.
-Then after maybe 3 power cycles, the monitor powered on, then the tube shut down with 140v on the B+ (maybe within 5 seconds of power on).
-I basically walked away for 2 months, too many things going on. I did buy the IC601 and Q901 and the pot at this time.
-To install the pot, I removed the tube from the frame for chassis access. I thought when I saw the neck pins that they looked in poor shape.
-But the monitor powered on fine after this.
-Worked for a few days, then upon power up it again died.
-Looking over the chassis, checking resistors, I checked the 0.3amp fuse and it measured in the Kohms installed! Checked the fuse and it was good. There was a pretty good amount of tarnish on the copper fuse holder, cleaned that off and the fuse is now maybe 2 ohms resistance installed. (monitor still didn't work)
-So I installed the new IC601 and Q901 and got nowhere. I did this WITHOUT removing the tube this time.

So I'm wondering, why would the monitor work if I didn't replace the cause of the fault. Regulators, flybacks, HOT's and so on don't usually "come back to life" that I know of.

I'm seriosly wondering if a poor neckboard connection to the tube could cause a 140v B+?
I haven't pulled the neckboard since I replaced the pot. (gonna try tonight!)
Any ideas on other such items?

The only think I can possibly think is that a bad connection is getting hot and causing the shutdown. Evidently it would have to be poor enough to not restart when it is cool. I can't see something "getting good" over 2 months, vs overnight. Resistors seem to measure out fine, VR601 is still measuring good as is the small DC fuse.
 
Temp of the storage area could be a factor. You may have a bad solder joint or a cracked trace that doesn't open up until power is applied or the deflection board is flexed. Rotating the monitor in some cases could flex the board causing this problem too.
 
Temp of the storage area could be a factor. You may have a bad solder joint or a cracked trace that doesn't open up until power is applied or the deflection board is flexed. Rotating the monitor in some cases could flex the board causing this problem too.

I really appreciate your following this Dokert! The help is great moral boost. :D

Some progress tonight, I pulled the neck board and reinstalled, did nothing else, and the 140v dropped to 112v and the picture looks great again.
I still have to do a full inspection of the neck board for bad solder, but at least I'm moving again.

Real pain in the arse is I can't get the voltage below 112v, doesn't range (as it did after the POT install) when I turn the POT.
I am worried if the new IC601 is OK as it was bought from Bob Roberts which may be an issue as I am reading other threads. Or it could be due to the neck board as I have yet to confirm the issue.

3 questions:
1.) Does this sound like the IC601 may be an issue?
2.) Is a B+ at 112v OK or too far off 108v?
3.) How can I clean the tube pins safely?

Hopefully these are a final set of questions.... I feel much better at least seeing a nice picture again!

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1. No, not really
2. Do you have a new flyback installed or is it original?
3. 90% or better isopropyl alcohol and Q-tips

Try to adjust the brightness in the following manner and then check the B+ afterward.
1. Center the brightness pot VR351
2. Center the Sub-Brightness pot VR301
3. Adjust the Brightness pot on the flyback for best looking picture
4. Fine tune the brightness with VR301 and finally VR351
5. Retest B+

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2. Do you have a new flyback installed or is it original?

It is an original Flyback.
I'm not 100% sure a 20EZ flyback would fit, this is a 18-z2ab model
(18" version of a 20EZ)

Just to confirm, no sanding, buffing or anything else on the pins, just alcohol?
(idiot confirmation!!) ;)
 
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Well, took some pics of the neck board.
I didn't spot any visible bad solder, but the neck socket sure looks like it's been repaired to me. I'm thinking that it is possibly the socket, the tube pins did not look so bad when I took a closer look at them.

Does the socket look to be patched??


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