DKjr sanyo ez 20

[Cothien]

picked up a dk jr machine that has a few problems.

The h hold (vr451) on the monitor when you turn it seems to wobble. In 3 different spots if you are turning it while its on the monitor will just shut off and will have to power it off and adjust the pot to turn it back on. I have a feeling that the pot is bad and needs to be replaced, but not sure what to replace it with. What are the specs for a replacement pot?

Was wondering in the may cap kits out there, what caps are the commonly replaced ones?

hopefully after the the caps and pot replacement it will stop it's scrolling to the right hehe

[qrz]

when the H hold ctl is turned, the frequency of the Hosc is changed .
when the Hosc is sync locked to an incoming signal , and the ctl is turned, there WILL be
some instability in the output frequency.  (some jitter is normal)
moving the Hosc frequency too far +/- normal operating parameters often results in HV shutdown

to adjust the Hosc, disable the Hsync to your monitor . this will allow the osc to "free run "
then adjust the H hold ctl for as close to a normal pic as possible ( may still scroll slightly )
reconnect Hsync and should be good .

note:
 in free run , frequency is too high if pic slants to the RIGHT , too low if to the LEFT
smooth frequency change indicates a good pot - replace if erratic 

[Cothien]

I have no idea how to do what you just said hehe. I am just starting to get in to fixing monitor issues. Normally I just send them out, but running out of money for more machines hehe.

with the H-hold almost turned all the way to the right, you can atleast see the game.

Here are 2 pics of what it is doing, granted you can see the scroll itself. I have a caps on the way, but always looking to find what to test before just randomly changing caps.

[lilshawn]

looks like the frequency is too high, you will most likely have to set it down to 15k ...   

[Cothien]

looks like the frequency is too high, you will most likely have to set it down to 15k ...   

how do you adjust the frequency? I haven't seen anything for that, but i could be just over looking it. took me about 20mins to find the H hold on the board. I am a complete noob on the monitors. I'm trying to learn. I am somewhat happy that after a hour of messing with the pots i found i was able to get the pics from the above reply and although the it scrolls the monitor looks really good.

I have plans to take the monitor out tomorrow or friday and clean it out. Everything around the fly back is cased in some thick dust and the air can wont move it lol.

[qrz]

i.e. the game is outputing a higher scan rate to which the monitor is set ( 2 or more pics displayed)

but, didn't think the orig game board had resolution settings...hmm ?

[lilshawn]

retracted....brb

there is another adjustment right behind the flyback towards the tube (depending on the monitor version) it's white. not sure if thats the one you found or not.

other than that check your sync wires to make sure they aren't broken. or you may be looking at replacing capacitors or as far as replacing the sync separator horizontal/vertical drive chip (IC401 LA1464) It performs sync timing functions and sync separation.

[Cothien]

i checked the wires they seem to be good, but will check them a bit better tomorrow when i get a chance

after that, I finally got brave and discharged the monitor (first time hehe) and pulled the monitor out and started cleaning.

I found this section and haven't touched it. It looks like something leaked onto the bored, maybe a cap, but i left that area alone. I was wondering what that part in the middle was that had "A700" printed on it. I had also thought about replacing everything in that area and cleaning it, but not sure if that might not be a good idea. would it be a good idea?

edit:

there is another adjustment right behind the flyback towards the tube (depending on the monitor version) it's white. not sure if thats the one you found or not.

this i think is the one in the pic and that is the one turned all the way one way to be able to see the game a little. other wise it scrolls so fast its just white lines on the screen.

Here is a pic.


bigger pic link, http://wolfpackcreations.com/miscimage/arcade/dkjmonlarge.jpg

[lilshawn]

the "A7007" (A700) part is a transformer. it looks a little funky because they used to dip them in wax to seal them up. over time the wax heats up and evaporates a little bit at a time leaving the little balls as it cools off. no big deal there.

your area there doesn't look like it has any real damage. it's just gotten a little warm there and burned up the board a bit. likely your green resistor and the diode there is likely the culprit(s). something may have been spilled and dripped on the one leg of the green resistor. it looks a little corroded. i don't think it the cap leaking, but i wouldn't rule it out. I would change that cap and test the resistor to be sure, but it may be just as easy for you to go ahead and replace the resistor too.

i would also check to make sure the B+ voltage is proper too as well, as if it's low, it can cause all sorts or wierdness to occur. a quick google search says 108 volts and 135 volt soooo, not sure of where you test it from, perhaps someone with more experience can shed some light?

[SirPeale]

Cap the monitor.  Get a kit that includes the main filter cap.  I've got them.

[Cothien]

Cap the monitor.  Get a kit that includes the main filter cap.  I've got them.

This is what i am planning on doing. Just been waiting for the parts to come in. hopefully they will be in tonight. although not sure if the kit has the filter cap in it.

...something may have been spilled and dripped on the one leg of the green resistor. it looks a little corroded.

i would also check to make sure the B+ voltage is proper too as well, as if it's low, it can cause all sorts or wierdness to occur. a quick google search says 108 volts and 135 volt soooo, not sure of where you test it from, perhaps someone with more experience can shed some light?

I pulled out that resistor and that one is messed up. getting no where near what it should be. For the B+ someone had a youtube video on here for that and I have that video linked and will be doing that after replacing the parts.

[Cothien]

got the cap kit a bit ago and started working on it, but ran into a small question.

C201 was a 10uf 25v and the kit has a 100uf 16v. is this correct or no?

[lilshawn]

short answer: install it.

long answer: it should be okay, it's just helping the power supply steady (filter cap) and even for when the circuit it's on, it's not a critical amount of difference.. besides they have since found all sorts of tweaks to keep the monitors running longer... this is likely one of them.

[Cothien]

well got everything done but one point and getting frustrated.

when trying to solder the last point of the 10K resister the solder pools up on the leg and doesn't make a good point on the board. I have tried removing the solder, cleaning the spot and putting flux on there and trying again, but get the same results. Even bought new flux and solder just because i needed to step back.

What am i doing wrong on this last spot? all the others went in great and no problems and I really want to test this today hehe

[qrz]

remove solder . clean pad AND resistor leg . burnish if needed .
parts MUST be free of contaminates for solder to properly adhere