Sanyo EZ left side droop/H-Synch acting up

JamBurglar

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I've got a Donkey Kong that has the typical left side droop. I keep two PCBs in this cabinet, DK and DK Jr. This just started acting up a few weeks ago.

Importantly, the droop occurs with both my DK and my DK Jr. boards. Adjusting the Vertical pots on the PCBs (i.e. the ones that move the screen left and right) will temporarily fix the problem but as soon as I power down and back up again the problem comes back. I never get a smooth left to right when I adjust the V pot. Instead, the screen repeatedly falls in and out of synch as I turn the pot through its spectrum. I'm getting the EXACT same symptoms on both the DK and DK Jr. PCB. I replaced the pots on the DK Jr. board and this failed to change anything. Based on the above I'm thinking the pots are good and not the problem.

I checked the B+ which was initially a little high at 111v but it adjusted down to 108.2v just fine. This had no visible effect on the problem or the image and the syptoms are still there.

I have also tried adjusting the H-Hold pot in the center of the chasis. This will also temporarily "fix" the droop problem until I power down and power back up. I get a good 10-15 degrees of turn radius where the screen is locked in, other than the droop. Outside of those 10-15 degrees I get a scrambled image like you'd expect when the H-sycnch is off. Also, once I get the droop mostly adjusted out, the very left side of the image still flares up or down just the slightest bit and I can never get the image truely flat/stable.

The monitor was capped in April 2010 and the monitor has been rock solid since that time.

Anybody got any ideas? I'm thinking about replacing the H-Hold pot, however, the pot looks like it's already been replaced in the past. It's got a plastic dial on it, not the crappy flat metal one that would have originally been on the monitor. Otherwise the monitor is great and I'd rather not mindless recap it if I can avoid it.
 
the H-Hold pot was never a crappy metal POS they all had the plastic tops.

i would replace or clean it and see.

Peace
Buffett
 
I will. FYI cleaning the H-hold pot didn't help. I'm going to replace that pot and, while I'm at it, give the chasis a visual inspection.
 
Okay,

I've replaced the 2 pots on my DK Jr. Board,

I've also replaced the H-Hold pot on my Sanyo chasis

The problem remains

Here's what I typically get on power up
picture.php


I can adjust this out either by using the H-Hold pot OR the vertical position pot on the game PCB to get this
picture.php


Here's a shot of it adjusted about as good as I can get it
picture.php


Here's shots of my DK board just to illustrate it's not the game PCBs
picture.php


Note the uptick curve where circled (it's hard to see I know)
picture.php


Anybody have any further suggestions other than a full capkit? I've done some searching of old threads and I've never seen anybody say a capkit fixes this sort of issue. I'm not saying it's not possible but I'm thinking this has something to do with the parts of the chasis that control H synch because adjusting the H-Hold pot and Vertical PCB pot directly affect this symptom. Buffett mentioned the resistors in line with the H-Hold pot. Does anyone have any tips on checking them?
 
R491 or R467 or R460 i seem to recall one of them fixed an issue with a chassis i had similar to yours.

i have also had broken traces in that area do a similar problem as you are seeing.

pull one leg and test them.

Peace
Buffett
 
R491 or R467 or R460 i seem to recall one of them fixed an issue with a chassis i had similar to yours.

i have also had broken traces in that area do a similar problem as you are seeing.

pull one leg and test them.

Peace
Buffett

Testing without power to the chasis I get:

R460 reads 15.07 kOhms (good)

R467 reads 5.65 kOhms (5640 ohms) (good)

R491 is only reading 15.33 kOhms. Going by the schematic it should be reading 100 kOhms. I tested from both the top and the bottom of the board (but didn't pull the leg because I could get to both ends from the chasis)

Is this enough info to merit pulling that resistor and replacing?
 
Testing without power to the chasis I get:

R460 reads 15.07 kOhms (good)

R467 reads 5.65 kOhms (5640 ohms) (good)

R491 is only reading 15.33 kOhms. Going by the schematic it should be reading 100 kOhms. I tested from both the top and the bottom of the board (but didn't pull the leg because I could get to both ends from the chasis)

Is this enough info to merit pulling that resistor and replacing?

Damn, I pulled the leg and it's a solid 100.9 kOhms. I was hoping I was on to something there.
 
Where did you get the capkit from? Not all of them include the non-polarized electrolytics that are going bad now from old age.

Don't forget that even new electrolytics can go bad.
 
Where did you get the capkit from? Not all of them include the non-polarized electrolytics that are going bad now from old age.

Don't forget that even new electrolytics can go bad.

I actually did not do the cap kit. The monitor came from TNT, who did the kit and re-solder in April of 2010. It's been running really well for the two or so years I've had it and just started doing this out of the blue. Most of the caps are dark blue (JH). There are a few black ones with blue writing and a few black with grey writing (which could possibly be original C453, C454, C202, and the big one C606). I've never done a cap kit so I'm just spouting off what I see here. There is one light blue (C479) but it looks newer.

I tested R462 as well since it was in the area, pulled a leg and it tests okay.

I'm pretty much just randomly testing resistors in the area of the H-Hold on the schematics at this point.
 
look at all the caps.

do any of the black caps say Sanyo on them.

if they do, they are original and need to be replaced.

i have the bipolar caps if you want to replace them to see if they correct your issue.

there are two of them on the chassis.

or a complete kit if you want one. PM me.

Peace
Buffett
 
This turned out to be cap 454. I replaced that cap, and only that cap, and the left side of the screen is straight and stable now. When I adjust the V pos pot on the PCB I get a nice smooth left to right pan. Turns out the last cap kit was only a "get well" kit and 454 was one of the original sanyo caps left on there. I'll likely replace the rest of those originals and leave well enough alone.

Many thanks to Buffett for guiding me through the fix and providing me with parts!
 
no prob happy to help.

at the very least replace all the original caps and the filter cap.

if it were me i would do them all.
but it is your call.

Peace
Buffett
 
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