Donkey Kong Sanyo (20EZ?) B+ problem

hindered

Well-known member

Donor 2015
Joined
Jun 4, 2009
Messages
1,796
Reaction score
32
Location
Kalamazoo, Michigan
Hi all. Time for yet another Sanyo 20EZ thread.

I have not yet capped this monitor, but I'm planning to. My DK has a wavy screen with white/fading at the top, which is almost certainly a B+ issue. I measured my B+ and it's about 78VDC. Ok, figure I need to recap the monitor and replace the filter cap while I'm at it. However, the B+ adjustment pot looks weird to me, almost as if the pot itself is broken. I couldn't find a picture of what the pot is supposed to look like, so can someone please tell me: Does this look like your B+ adjustment pot? Does mine look broken?
 

Attachments

  • DSC06438.jpg
    DSC06438.jpg
    88.9 KB · Views: 158
It looks "normal" to me. They covered them in glue from the factory....that's what that white stuff is. I find it very difficult to adjust them without breaking it. That glue is pretty tough. You can always replace it with a new pot.

Edward
 
Do you know where I could get a replacement pot? I'm assuming the venerable Bob Roberts has them available.
 
That looks like all the ones I've seen. It's easiest to break the glue when you have the chassis out for reacapping. I use a small pick tool and scrape the glue off until the pot can be turned easily. After the cap kit I center the pot and fire it up to test B+, then adjust if needed. I have had the paint be a real pain to break a couple times but of the 10 or so ez's I've done, I have yet to break or replace a pot. - Barry
 
Ok, I'm getting the filter cap + a replacement pot just in case. If the monitor appears 100% fine besides the waviness, which cap kit should I get?

20EZ 13"/19" - Standard Industry Kit [20-Z2AW] $5.00
20EZ 13"/19" - Plus Kit with 9 more chassis caps $7.00
20EZ 13"/19" - Deluxe Kit [Plus & Audio Bd Kit] $12.00

I'm of two minds here. The $5 one is cheaper and will probably cover everything I actually need. However, since I'm going to the trouble to take the montior/chassis out, I might as well get the $12 one and replace everything and be trouble-free (knock on wood) for the forseeable future.

Any opinions?
 
The cheap one is NOT the way to go here, the Deluxe as Timberterror has stated is going to be what you will want to go with.
 
Get the deluxe kit. No sense of pulling the monitor out _several_ more times to fix additional problems.

Agreed! I have no idea why Bob still sells the "standard" kit. I'm always finding bad caps that are NOT in the standard kit.

Edward
 
Ok everyone, got the cap kit, replaced all caps. I also replaced all caps on the audio board, the filter cap (C606 I believe) and the B+ pot. Buttoned it all back together, put it back in the machine, and set the B+ to 107.9.

Screen won't sync and picture is super garbled. Fiddling with the pots on the control board didn't help. Come search KLOV, find a thread that mentions the horizontal sync pot on the board. I tweak that and am able to at least get visible text, although the screen still won't sync. Pressing on the pot makes the screen freak out. I've got the monitor back out and have reinspected my caps, all are the correct polarity, and I fixed any potential cold solder joints I see.

Another weird symptom is the sound card makes a weird "woop woop woop" sound similar to the noise in Pac Man.. if I turn down the sound volume all the way, or disconnect the cable that connects the PCB to the audio board, the sound goes away. May be related to the monitor issues but is probably a separate issue.

Recap: Before the cap kit/replacing the filter cap, the game displayed and synced fine with the B+ at about 78vdc. However, it had the flag-waviness and the B+ couldn't be adjusted. After cap kit, B+ is fine at 108vdc but monitor won't sync.

Any ideas of how to proceed? Pics attached. First pic is prior to adjusting the sync pot on the main chassis, second is after.

Edited to remove misinformation about capkit.
 

Attachments

  • DSC06472.jpg
    DSC06472.jpg
    96.5 KB · Views: 38
  • DSC06473.jpg
    DSC06473.jpg
    89.4 KB · Views: 36
Last edited:
Test the H hold pot through it's range with the power off to verify the pot is good. Also wouldn't hurt to reflow the solder on the H hold pot.
 
Test the H hold pot through it's range with the power off to verify the pot is good. Also wouldn't hurt to reflow the solder on the H hold pot.

Can you explain how to test it? I already reflowed the solder just to be sure. I'm skeptical that this pot is the issue though, as the sync was fine pre-cap-kit, and the screen gets super garbled on either side of the "sweet spot" in the middle. Still, the fact that the screen flips out when I press the pot with my finger does point to this pot...

Also, the hold pot has a resistor soldered to the middle leg on the solder side (R462). I don't know what resistance it is but the bands are brown black yellow gold (or maybe gold yellow black brown). Is this supposed to be here? Was it a hack to get it to work with the lower B+ maybe

Edit: Testing end to end on the pot at 20k gives 2.65. Testing the resistor out of circuit at 200k gives 85. I looked it up and I think the brown black yellow gold resistor should be 100kohms with 5% tolerance. Doesn't seem to be resisting there... the pot doesn't seem to be resisting at 3kohms either.
 
Last edited:
Can you explain how to test it? I already reflowed the solder just to be sure. I'm skeptical that this pot is the issue though, as the sync was fine pre-cap-kit, and the screen gets super garbled on either side of the "sweet spot" in the middle. Still, the fact that the screen flips out when I press the pot with my finger does point to this pot...

Also, the hold pot has a resistor soldered to the middle leg on the solder side (R462). I don't know what resistance it is but the bands are brown black yellow gold (or maybe gold yellow black brown). Is this supposed to be here? Was it a hack to get it to work with the lower B+ maybe

Edit: Testing end to end on the pot at 20k gives 2.65. Testing the resistor out of circuit at 200k gives 85. I looked it up and I think the brown black yellow gold resistor should be 100kohms with 5% tolerance. Doesn't seem to be resisting there... the pot doesn't seem to be resisting at 3kohms either.

VR451 (H. Hold) is a 3K pot, and should NOT have a resistor attached to it. Pull the resistor off and try it again.

It is very common to have to adjust the H Hold after a cap kit.

Attach one lead to the center leg, and one lead to either end. Rotate it through it's full range. It should go from 0 to 3K.
 
VR451 (H. Hold) is a 3K pot, and should NOT have a resistor attached to it. Pull the resistor off and try it again.

It is very common to have to adjust the H Hold after a cap kit.

Attach one lead to the center leg, and one lead to either end. Rotate it through it's full range. It should go from 0 to 3K.

Great minds think alike. I just got done testing the monitor after removing the resistor (impatient). I turned the brightness up all the way, set B+ at 107.9, although I accidentally set it too high at first and it shut down the monitor.

Powered down monitor, got B+ back to ~108vdc and the monitor's squealing pretty bad. Turn the brightness down, and started to tweak the horizontal hold pot.. must have turned it too high because the monitor shut down again. I turned the machine off and came here for further advice. Ideas?
 
Do you have a copy of the flow chart yet? http://forums.arcade-museum.com/showthread.php?t=111041

Big box on the right hand side of the page in the middle.

Yep, just got back from trying that. I centered everything, powered up, and if I go above 105vdc or so B+ the monitor shuts down. If I leave the B+ at 105vdc and go to tweak the horizontal hold, the monitor shuts down.

I'm starting to think that resistor was there for a reason. The 20ez manual does indeed list a resistor at that position, although it's a different value than the one that was attached on my chassis.. R462 18kohm 1/4 w. The chassis had a 100kohm resistor there which registers at 75kohm resistance, if I'm reading the bands and my measurements properly.

P.S. Thanks for the flow chart. I found it and the ones Ken Layton provided on searches earlier this evening.
 
Last edited:
Just verified, R462 is 18k on the parts side. The 100k resistor was in parallel on the solder side. It doesn't connect VR362 though, and it doesn't seem to connect to the flyback (directly, anyway) unless I'm misunderstanding. On my chassis, R462 comes off of the center leg of VR451 (H Hold pot) and I'm not sure what it goes to.

What is VR362? I see 3 pots, the B+, the brightness, and the horizontal hold. None of these are VR362.
 
Last edited:
Back
Top Bottom