Gorf issues

dmbj

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So i am working on this almost DOA but near mint Gorf. at first all i got was some screen raster, no sounds, would not coin up.

I check the power supply and notice the center large 2000uf 16v cap has fallen off of the board. with the power supply not connected to anything and 12v was about 20, 5v was about 13. I put in a known good power board and by 12v is now 13.X and my 5v was 5.02.

Hook up the game board set and still nothing has changed. 5v is not 4.75 under load at the board set.

I pull out a good board set and it boots up but the k4600 monitor will not sync, the best i can get is scrolling horizontal and vertical at the same time. so its scrolling on a diagonal.
I cap the monitor and reflow all solder on the small board connecting pins, 18 caps as per bob roberts site, this input board did not have a c202 and i did not have a vr201 on hand. and I am still geeing the same scrolling. but the colours look way better now.

I pull the monitor from the machine for easy adjustment (no more walking from the front of the machine to the back 1000 times) monitor is on the ground behind the cabinet hooked up and i fire it up. i get nothing on the screen.

I now hook the monitor on my test bench(us classic jamma) and adjust the vert, horiz, and that other one that you need a plastic screw driver to get to on the h/v board. now its got a perfect pic. go back to the gorf and get no game again, but the monitor is working fine.

sometimes when i boot up the game i get proper 5 and 12 volts. sometimes i get very low volts. but even when they are proper i get no game on the screen and it will not coin up. i hope i did not fry out something on the 2nd game board stack. i even turned up 5v to about 5.2 at the board set under load, with the boardset not hooked up this was about 5.45v or so

If i flip the service switch and boot it i still get the same thing.

Earlier when it would play with the sync off, I tried all of the original boards in the board stack one at a time in the good cage, one ram card worked fine, one would bring up strange sprites, and every other board would cause the game not to boot, so the only good board out of the original set was the very last ram board.

Any ideas guys
 
I would also check the little RGB Board. All video signals run through it before entering the monitor. If you have a good Gorf (or Wizard Of Wor, or Robby Roto) to swap the unknown into....the better.

Edward
 
I would also check the little RGB Board. All video signals run through it before entering the monitor. If you have a good Gorf (or Wizard Of Wor, or Robby Roto) to swap the unknown into....the better.

Edward

Will do, at first with the sync problems i wast thinking that board may have a problem, then after hooking the monitor up to the test bench and still having issues i forgot about that little board. i have one and will put it in but at this point it should at least coin up and play blind, and it is not doing that again.

Before starting this i had a working POS water soaked, gouged up gorf for parts. I had pulled the monitor a wile back so that was the only thing not there on the nasty gorf.
 
Will do, at first with the sync problems i wast thinking that board may have a problem, then after hooking the monitor up to the test bench and still having issues i forgot about that little board. i have one and will put it in but at this point it should at least coin up and play blind, and it is not doing that again.

Before starting this i had a working POS water soaked, gouged up gorf for parts. I had pulled the monitor a wile back so that was the only thing not there on the nasty gorf.

Yes, if the RGB Board is the issue....the game should still coin up and play. Your previous post mentioned the power fluctuating....I would look for cracked header pins/cold solder joints, and/or bad connectors/pins.

Edward
 
I'll look at the power supply board again tonight. and resolder everything on it. i did check the main caps on the thought to be good power supply and they all had good esr. of course i was checking them on the top of the board, not at the solder points because it was mounted in the cab.

Anyone have any recommendations on exactly what voltages should be set at measured at the game board set under load? other than my current 5.2 and about 13.3 or 13.4 (i forget now exactly where it was)
 
...I would look for cracked header pins/cold solder joints, and/or bad connectors/pins.
I agree with this.
I shotgunned the P.S. with a Bob Roberts kit & replaced all of the connectors on my Gorf before it would play consistently.
I also took the cage apart & cleaned the connectors that each board sits in.
 
A few notes from the 2 Gorfs I just stitched together. Keep in mind I'm in the middle of moving so....brain is mush...specifics may be lacking.

On the PS board. I would freshen it up if your values are moving around on you. Reading wise I set mine at a hair over the stated values (IE..for 5 go 5.10) measured at the .156 header on the card cage.

Watch the lower connector on the Power Supply board....as it mounted to the cab wall. That is the input side of the PS from the transformer assembly. The lowest wire, on the lowest connector, seems to like to burn up. Its like 14v unreg???? If the connector is burned replace it, replace the header, and re-pin the bad positions. Look at the schematic. Electrically the unpopulated pin next to said wire/pin is the same. I snip the pin, attach 2 tails, crimp a pin to each, and populate both holes to help spread the load.

You said that at one time you had the game running with a 2nd board set but it would not lock sync. That is where Edward turned you on to the RGB board. Once you have that sorted out leave your working set in place then swap cards, one at a time, from the suspect set to see what card(s) are good/bad.

When you get this far...there are 2 versions of the ROMs the early (I guess) and a later. The early will not strobe the rank board. The later will strobe through each of the ranks. Beside burned out lamps I have had to replace 3 or 4 of the TIP110's on the rank board to get all of my ranks working on both that I had. One of the TIP110's drive the bulbs in the flight stick. PAY NO ATTENTION to the schematic for the rank board. It's wrong as to which TIP drives what lamp...at least the copy I have was.
 
I got busy last night (The local garbage picker/recycler as he likes to call himself, dropped of a few lcd monitors for repair) and did not have time to even look at this game, Thanks for the input. And yes i noticed the board sets are different, at least the one card with a bunch of roms was. one has (as i recall) a fully loaded top row and i think nothing in the 2nd row. and the other had every other socket filled. I hate to wire in a switcher but maybe i will, just to eliminate the transformer and regulator board out of the equation.
 
If it were me, I would just keep the original PS. There is not much to it, easy to rebuild and repair. Keep in mind how long it survived and how long it can go once fixed, if it even needs to be fixed. As I recall you had a working board set in there correct?

If you do go switcher Mark makes a plug an play adapter for an ATX power supply. I would be interested in the old PS board as well.

good luck either way!
 
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