Mrs. Pacman help

[John's Arcade]

Tube manufacture has nothing to do with anything when doing a tube swap.

It's about the tube angle in relation to the neck (if doing a YOKE swap), socket size, and Yoke impedance.

Here's a list of suitable TV tubes for popular chassis:

http://junknet.net/donor-tvs

Measure the YOKE to see if it's compatible.

[P-feif]

Thanks John. I looked all through that list and I don't see anything about what tubes will fit the WG K4900 monitor. I may just try to rejuvinate this tube. I don't have the equiptment to do it but the shop that was giving away the free monitors (I drove by today and didn't see them sitting out there so I'm guessing they are gone now), said that they could rejuvinate it for me. So I may just pay them to do it. I have everything done on the monitor board except that thermistor at th501.

Every company I've called about buying a thermistor says that they can't cross referance the Wells Gardner part number and so I don't know what other part number to give them. I can't give them the specs on the thermistor because the WG manual doesn't list the specs. I did find an article on KLOV that talked about a few differant parts that could work and who to buy them from but when I called the company they had since disscontinued those parts and no longer make or sell them. If we can just figure out the specs on this thing I'm confident that we can find a suitable replacement for it. Everyplace I search on the net I find people that want replacements for it too. GRRRRRR!

How does John say it? ARRGGGGGG!  ;)

[P-feif]

o.k. just got off the phone with a place called Mouser Electronics. They have lots of thermistors. What they need to know are the specs (same as I've been hearing) but this guy talked to me about what specs which is more then any other place has done so far. So let's work together here and see if we can figure this thing out. They need the risitance at room temp, is it an NTC or PTC (resistance increases or decreases as temp goes up), the temp range (upper temp limit) and maybe the volts and amps that it operates at?

If you have any of this information post it here.

[P-feif]

I found some more. I was lookint at the schematic and I noticed some numbers associated with the thermistor at th501. So I called back the tech at Mouser and talked with him some more. These are the numbers that I had noticed PH631-138F and PTC-070. From that we were able to fiqure out that it is a PTC thermistor and NOT and NTC. We speculated that it might be a 70 deg to 138 deg F range part and so he looked up some more based on this information and found this. http://www.mouser.com/Search/Refine.aspx?Keyword=b59750b0120a070  These are two possible candidates. What we need to know at this point is what is the resistance at room temp. Hopefully in the next few days I can de-solder one leg on this thing and measure the room temp resistance. That just might give us a good enough spec to get a really close part that will work as a suitable replacement. Anyone happen to know the resistance at room temp on one of these???

Closer... We're getting closer. 

[alby13]

continue updating.

[P-feif]

O.k. finally got a little time to unsolder one leg of this thermistor and get a room temp resistance value. 7.2 ohms is what I got (assuming it's still a good part). Just got off the phone with Dan at Mouser, we came up with a list of about 7 or 8 posible thermistors but it's still somewhat of a guess. I'm thinking of sending a note to Bob Roberts to see if he has any input on this. Hey if anyone knows what will work wouldn't it be Bob?

Here's a link to the "possible" thermistors for this monitor degause circuite.

http://www.mouser.com/Circuit-Protection/Thermistors/Thermistors-PTC/_/N-axfwr?P=1z0x71qZ1z0s0adZ1z0z7l5

Any input you guys have would be greatly appreciated.

Useing ohms law, 7.2 ohms and 120 volts would be roughly 16 amps (16.667 amps). So that's at room temp anyhow. It's headway but still frusturating to fiqure out.

And if anyone would like to see the schematic here's a link (provided by another John's Arcade Forum member) http://www.vernimark.com/arcade/archive/monitor/mon_rc__wg-19k-4901-06-51-56.pdf

[P-feif]

So I just got home from work a short bit ago and just for fun I checked the resistance on this thing one more time. This time I got 6.6 ohms. I walked away and did it again.... 6.6 ohms. So did I goof up the measurement the first time? I think I may have been just barely letting the leg come in contact with the solder pad the first time. So now that I have a reading of 6.6 ohms I went back to Mousers web page and found that this is the only one with a 6.6 ohm rating. So did I find it? I need to somehow confirm it.

http://www.mouser.com/ProductDetail/Vishay/PTCCL17H401HBE/?qs=vB0g00R0fR%2fBNM6bWcpDMw%3d%3d

I guess the big question is the amp rating because it's not what I calculated but that doesn't mean that I was right to begin with.

[VertexGuy]

Thanks John. I looked all through that list and I don't see anything about what tubes will fit the WG K4900 monitor. I may just try to rejuvinate this tube. I don't have the equiptment to do it but the shop that was giving away the free monitors (I drove by today and didn't see them sitting out there so I'm guessing they are gone now), said that they could rejuvinate it for me. So I may just pay them to do it. I have everything done on the monitor board except that thermistor at th501.

Every company I've called about buying a thermistor says that they can't cross referance the Wells Gardner part number and so I don't know what other part number to give them. I can't give them the specs on the thermistor because the WG manual doesn't list the specs. I did find an article on KLOV that talked about a few differant parts that could work and who to buy them from but when I called the company they had since disscontinued those parts and no longer make or sell them. If we can just figure out the specs on this thing I'm confident that we can find a suitable replacement for it. Everyplace I search on the net I find people that want replacements for it too. GRRRRRR!

How does John say it? ARRGGGGGG!  ;)

1995 RCA tv

[P-feif]

Really? Interesting! Thanks, I just might look for one!


And for the record I got word back from Mr. Roberts today. He has no idea if that thermistor that I found at Mouser will work. Crap.....

[P-feif]

Never did find a thermistor to replace that one so I decided to put it back together and see what I've got. All I can say is the game worked and played before I took the monitor out. Now all I get is this.



Maybe when I vacuumed it out I caused an issue with the PCB or one of the fuse blocks??? Not sure where to go with this but I'm determined to figure it out. Well anyone seen this before???

Also I noticed that it does not go through the boot up sequence. No blocks of colors on the screen or the white test pattern, nothing. I tried the test switch and it did nothing.

[P-feif]

Yay!!!! I have THE COLOR RED now! Notice how the red is shifted WAAAAAY low on the screen??? I think it just a convergence adjustment. Like everything else I've done on this thing, never done it before, but I'll figure it out. Even with the convergence way out of wack I still played my first game on this thing since last February... until the game reset. Need to figure out why it's reseting. Most likely a loose wire on the main PCB connector or on the self test switch. But hey this is real progress. It's the best it's been since I bought it.

From the last post with only blue on the monitor, it just took some adjustment to get more colors to show up. Still needs a bunch but I'm getting there.




John you got any good tips, especially for getting the convergence right? Is it possible that the drive on the fly back is turned up too high???

You know I was thinking about this and looking at the above picture I noticed that most of the red that is not converged is just skewed to the bottom of the screen, but I noticed something strange. If you look closely there are a few spots in the picture where the red is not skewed to the lower part of the screen but instead, it mirrors the maze. I'm thinking that a convergence issue will not mirror the maze so I'm wonder what is going on here and what to do next. I'm going to research this but "as always" I will be more then happy to take your advice.

[mrdude]

Does this now come the trial and error part of adjusting those convergence rings?? Glad you have the red!

[P-feif]

Well after talking with a guy I work with that used to work on monitors for a living he thinks that I might just have the flyback set too high. I agree, it looks way too bright. It might just get a whole lot better if I turn it down a bit. Still need to get the colors set right too. ...................... As soon as I get a little more time to mess with it.

[P-feif]

Last night I did some adjustment on this thing. Got some really great color out of it, except I can't get enough red to show up. If I really crank up the red cutoff then I can see the red features on the screen but I also get all kinds of other things showing in red that shouldn't be there, red bars down both sides of the screen, red shadows of every object on the screen. If I turn the red down enough that you don't see that stuff then you loose things like the red dots that the 6th game board has. Also in the attrack screen some of the red lettering gets hard to see. Also after it's be on for 5 or 10 minutes I starting getting a hum bar accross the screen too. So it's got some issues to work out. I'm betting the hum bar is some sort of power supply issue (power supply or transformer). I "THINK" the red issue might be a weak red gun but I don't have enough expieriance to really know for sure. If I crank up the green or blue cut off I can get the entire screen to turn green or blue, but I can only get red bars on the sides of the screen if I crank up the red. I'm going to try to check the voltages (need to look up how on this thing) and get any power issues straightened out so I know that a power issue is not influancing this thing, but my best guess is a week red gun. So if that's the case I need to find a way to rejuvinate the tube because I don't have the equiptment to do it.

Thoughts?

[P-feif]

O.k. I'm trying to find time to get back to this thing but I have a question for you guys. Take a look at the picture above. Notice how the red shadows are only on part of the maze? Notice how some of the shadows are mirror images of only some of the maze shapes? Notice how the ghosts and Mr. Pacman DON'T have any red shadows? I would think that if this were a convergance issue or a back tracing issue that the red shadows would be everywhere and not just in certain select spots. I'm wondering if this is possibly a board issue? 

Anyone???