Small wave in my Pacman Jr screen

[2PacMan]

I bought this game and the monitor had a wavy line scrolling across the screen.  I thought it was the classic "pacman humbar".  But i noticed the board was grounded to the transformer.  Once i removed the ground and relocated it to another screw inside the cabinet, 98% of the wavy dissapeared.  Now there is a small, barely noticeable wave.  I'd like to get it completely gone, but i'm not sure where to go from here.  Also, the board seems to be running pretty hot, in the areas I have circled on the pic, it's extremely hot to the touch, and i noticed some burning on the edge connector.  The metal was pitted and almost gone in a few areas.  I flowed some solder over the pitted edge connector to make the clean and shiny again, but it didn't seem to do anything.  Any ideas?

[D_Zoot]

Besides edge connector/grounding issues, another common cause of hum in the picture of these machines is tarnished fuse holders.

Sometimes they look ok, but develop resistance where the fuses make contact with the clips.   Often you can diagnose this by letting the machine run a while, UNPLUG it from the wall and then touch each fuse to see if it's hot.  But be carefull, one could be hot enough to burn!

If any of the fuses are quite warm to hot, replace the fuse holder and fuse. 

Actually, given the problems caused by the cheezy factory fuse holders, it's a good idea to upgrade them anyway.


D

[2PacMan]

Thanks for the information.  I did notice the 1.5 amp slo blo fuse (on the fuse block containing 2 fuses) was getting very hot, i replaced it with a 2 amp one, and it is fine now.  Also, the 5 amp ones (on the fuse block containing 4 fuses) were warm, not hot, but warm. 

I think i will replace these to be on the safe side.  Can I just use generic fuse holder from radio shack, or do they need to be special ones ordered from the net?

Any idea why the board would be getting so hot in that particular area?

[D_Zoot]

Thanks for the information.  I did notice the 1.5 amp slo blo fuse (on the fuse block containing 2 fuses) was getting very hot, i replaced it with a 2 amp one, and it is fine now.  Also, the 5 amp ones (on the fuse block containing 4 fuses) were warm, not hot, but warm. 

I think i will replace these to be on the safe side.  Can I just use generic fuse holder from radio shack, or do they need to be special ones ordered from the net?

Any idea why the board would be getting so hot in that particular area?

Radio Shack fuse holders would be fine.

They get hot because over the years the fuse clips get tarnished.  The tarnish isn't conductive and creates resistance.  As current is drawn across this resistance it becomes heat.  What was a fuse holder is now a resistor, or if you prefer, a Pac Cab warmer!  Keeps those pacs nice and warm in the cold winter months!   



D

[D_Zoot]

Also, I was just taking a closer look at your pics,   since your edge terminals on the board are less than pristine, the terminals in the plastic connector are probably tarnished as well and/or have lost tension.

You may want to consider replacing those terminals.   Same problem happens there, tarnished terminals or loose fitting terminals create resistance and heat, things start to burn up.   Cleaning up the edge on the board was a great idea, but to complete the job new terminals in the connector housing would be the ticket.     You would have to order those from Bob Roberts or one of the other vendors, RS doesn't carry them.


D

[2PacMan]

Thank you for the reply.  You are correct, the 2 pins on the edge connector terminal that corresponds to the burned board connector pins are a darker bronze color, while the rest of the connector is shiny brass color.  Looks like those 2 pins are tarnished.  I tried to get a small piece of sandpaper in there to sand the tarnish off, but no luck.  Is there a way to clean the tarnish off?  Other than those 2 pins, the rest of the connector looks great.

Also, i'm having trouble finding exactly what fuses should be in the fuse blocks.  It was originally a galaxian conversion, so I have values based on the galaxian manual.  But then the little typed up labels next to each fuse in the bottom of the cabinet have different values.  And the fuses that were originally in the game have different values than the manual or the labels.  Finally, the Pac Jr board says it can be plugged into a pacman game (since it is the field kit), and the pacman game has different fuse values than the galaxian.  What should I do?

Also, does the PCB even need to be grounded with that yellow grounding strap?  I don't think any of the PCBs are grounded on my other pacman games.

[D_Zoot]

Thank you for the reply.  You are correct, the 2 pins on the edge connector terminal that corresponds to the burned board connector pins are a darker bronze color, while the rest of the connector is shiny brass color.  Looks like those 2 pins are tarnished.  I tried to get a small piece of sandpaper in there to sand the tarnish off, but no luck.  Is there a way to clean the tarnish off?  Other than those 2 pins, the rest of the connector looks great.

The color of the terminals isn't directly from tarnish, but excessive heat (from tarnishing)  causing the terminals to discolor.  Impossible to clean, aren't they?  Sandpaper will take the plating off the terminals anyway, so if it was me I'd just replace them.  If the rest of the connector looks good, I'd do just the first 5 on each side, that will cover your power and grounds and ensure it's all fresh and minty.

Also, i'm having trouble finding exactly what fuses should be in the fuse blocks.  It was originally a galaxian conversion, so I have values based on the galaxian manual.  But then the little typed up labels next to each fuse in the bottom of the cabinet have different values.  And the fuses that were originally in the game have different values than the manual or the labels.  Finally, the Pac Jr board says it can be plugged into a pacman game (since it is the field kit), and the pacman game has different fuse values than the galaxian.  What should I do?

If it's running a Pac board, I'd use the fuse specs for the Pac, but only on the supply fuses to the board.   For the monitor, marquee, etc. go with what's indicated on the cab label.     There's probably only minor variations in what's called for in all of the documentation anyway, honestly go by any of the specs and you'd likely be fine.

Also, does the PCB even need to be grounded with that yellow grounding strap?  I don't think any of the PCBs are grounded on my other pacman games.

The yellow ground strap would have originally gone to the filter board, which is probably missing (they usually are).  Most of the Midway games I get of that vintage are missing the filter board and the ground strap is just hanging. The game board gets ground via the edge connector anyway, so  I wouldn't worry about it.    For safety sake, you probably should make sure the coin door, CP and monitor are all hooked to the ground strap.

[2PacMan]

Well, i replaced the fuse blocks and cleaned the edge connector as well as the connector pins real well. Still no difference. It is still generating a good amount of heat near the first 2 pins and towards the heat sink. The good news is that the rest of the board and the fuses now remain very cool. Maybe these boards just run hot near the heat sink? Anyone know? The ripple is still there, but it is very minor...i might just leave it, it seems like a grounding issue. There is only one yellow grounding strap in the entire cabinet and it goes from the PCB to a screw in the bottom of the cabinet. There are no additional grounding straps going from the monitor/control panel, or coin door, although there are the green grounding wires present, and they are grounded to the monitor frame.

[D_Zoot]

That edge connector shouldn't be hot,  warm maybe, but not hot.  If it's still getting hot then you really need to replace the power and ground terminals in it.   Heat in connections comes from resistance, if the connector is hot, there is excessive resistance in it.


The only other possible cause for your hum bar would be a ground floating,  this generally comes back to connection issues as well. 


D

[fredster]

Some of those hums come from the sync caps in the monitor too.

What kind of monitor was it?  The one I had was a WG 4600 series.  There are some caps on it that cause leaking.  If you want to keep that system 4600's are a pain to re-cap, but they are pretty good.

The ground wire helps to discharge the monitor too.  If you don't ground the monitor it strains the caps.  They put it there for a reason. 

Engineers do stuff for a reason.  I know, I'm one of 'em, and there is nothing I hate more than somebody telling me that they didn't need that support or they didn't want to put that block back.

Like I put it there and picked up my pencil for no reason whatsoever.

[2PacMan]

Well, curiosity got the best of me and I pulled out my Galaxian and my Pacman games, and both of them run pretty warm along the two end connectors as well, so i'm laying the heat issue to rest, as it must be normal i guess.

While i had the machines out, I pulled the pac jr board and put it in the galaxian and got a nice clear ripple free picture.  I put the galaxian board in the pac jr cabinet and it had the ripple.  Now i'm thinking it must be the monitor.  The guy i bought it from said he did a cap kit on it but it doesn't look like he replaced all the caps, just some of them.  I'm not a monitor guy, so i'm probably just going to leave it as is....it's not really noticeable once the game starts and the pacman starts moving around.

[Kevin Mullins]

but it doesn't look like he replaced all the caps

Without knowing exactly which monitor you have..... I'd bet the main filter cap in the power supply section wasn't replaced. (usually the biggest one)
Some call it a smoothing cap.
They generally don't come with a standard cap kit.
You might be seeing a bit of AC ripple type effect.

[2PacMan]

I believe it's a G07 monitor.  Whatever the standard monitor is that came in all the pac/galaxian cabs.  It's gotta be some kind of monitor issue.