Gorf - converting back from switcher to linear PS

westal_sage

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I would like to get away from the switcher PS that someone had already installed in my Gorf upright, and go back to the linear PS. I was hoping some folks out here could help me. My main reasons for wanting to do this are these 2:

1) Knowledge and the satisfaction of doing it and understanding what is happening. This is the hobbyist in me. As I'm starting to look at this task, on the one hand it logically seems like...well...not too terribly complicated of a thing. But wow I sure do have some questions.

2) Originality or having it running like it was designed to. This is the purist in me. I just like the idea of having the original linear PS up and running again.

And I actually am having a minor problem with audio interfering with the monitor image, have noticed that diff switchers cause a diff in the intensity of this problem, and am wondering if the linear PS would do away with it altogether. But this is minor and I don't want to dwell on that right now. It's the above 2 reasons that I would like to focus on.

So with that said, I would really appreciate any help/feedback from the KLOV community. I'm gonna work right now on some obervations and some compare/conrast notes between the switcher and the linear. I will post this soon in this thread and hope to hear from you. Thanks much!!

Oh and my Gorf does look to have the linear components still in there. i.e. the big xformer and the power supply pcb. But, I would bet something is wrong somewhere with it, since the conversion to a switcher was done in the first place.

- Wes
 
I don't know if I'm going to be much help, but I totally understand what you are saying about the linear power supply. My opinion has always been, repair the machine the way it was built with as many of the original parts as you can.

I would rather have a game with a rebuilt original power supply then all the switchers in the world. I would rather have a CPO with a couple of cigarette burns and a few cracks than a brand new one. That worn CPO tells me that this machine has been around and survived.

The first thing your going to need is a wiring diagram. The KLOV entry for Gorf has links to the manuals. http://www.arcade-museum.com/game_detail.php?game_id=7983

Then you need to make sure that all the original wires are there and hooked up. They don't have to be hooked to the game board yet. Just make sure any bare wires are insulated. You are going to need to power up that big transformer and check to make sure all the voltages are there.

If they are, you are probably going to need to rebuild the linear power supply before you test it. You'll probably need something like the Bob Robert's Gorf & others OEM PS (90411) Repair Parts Kit $21 at his site. http://www.therealbobroberts.net/parts.html#bridge

Hopefully this will get you started.
 
Awesome info Robotron - thanks! Yes my plan is to have the xformer and the pcb completely outta the game and on the bench. I do have the manuals and diagrams - looking at them now and composing my next post. :)
 
The Switcher

OK so this looks to be pretty super straightforward. Almost too much so - like how could it really be this simple. I'm gonna say "pins" here when it's really "terminals", but I would think that a terminal on the switcher pretty much corresponds to a pin on the linear - but in concept only - obviously not a 1-1 mapping. So here what I'm seeing:

Input:
3 input pins - AC household - I would call the pins:
* hot
* neutral
* earth ground

Output: 3 DC voltages
* +12V
* +5V
* -5V

And then 2 ground pins. I would call these logic ground as opposed to earth ground. I would guess that these are internally hardwired together, and really the only reason there's 2 and not just 1 is simply for convenience.

Then there's a single pot to adjust the +5VDC output. I think this pot adjusts only that voltage, and has no effect on the other 2 output voltages.

Seem right so far?
 
Original Linear PS - The Transformer

OK so here's what I see here, and do have some questions. First off, is it correct to say that ALL of the voltages for this thing (both in and out) are AC voltages?

Input:
* 115V hot
* 115V neutral

Output:
* 14.5V
* 9V
* center tap
* 9V
* 14.5V
---
* 0V (???)
* 12V (???)

This all seems pretty straightforward to me except for the last 2 terminals (0, 12). Is this just basically a totally separate 12VAC output?
 
Original Linear PS - Input Side

Whereas the switcher's input is super simple (just the 3 wires of the power cord), the linear's input gets more complicated. The input side of the linear PS doesn't "see" the 3 lines of the power cord at all, but rather it sees the outputs of the big transformer.

So here's what I have for the input pins:
1 - center tap

2 - hmm well it looks like no wire actually comes "in" to this pin, but rather it is tied to the center tap on the back end - seem right?

3/4 - 9V line, #1 of 2
5/6 - 9V line, #2 of 2

7 - key, not connected

8 - 12V line, after a fuse
9 - nothing coming in to this pin?

10 - 14.5V line, #1 of 2
11 - 14.5V line, #2 of 2

12 - 0V line, just not sure what this whole 12VAC line is. Is it a dedicated line just for the "display lites"? What exactly are the display lites?

Comment on this section?
 
Original Linear PS - The Transformer

OK so here's what I see here, and do have some questions. First off, is it correct to say that ALL of the voltages for this thing (both in and out) are AC voltages?

Input:
* 115V hot
* 115V neutral

Output:
* 14.5V
* 9V
* center tap
* 9V
* 14.5V
---
* 0V (???)
* 12V (???)

This all seems pretty straightforward to me except for the last 2 terminals (0, 12). Is this just basically a totally separate 12VAC output?

The voltages would be AC. They don't become DC until they go though a set of diodes or a bridge rectifier.

The last two wires off the transformer are "8" and "12". The wiring diagram doesn't say what the voltages are. It does show a display light and that the circuit is fused with a 2 amp slow blow.

OK, on the next diagram drawing no. M051-00789-A011, it shows the voltage as 12 volts AC, then it runs through four diodes changing it to DC. It comes out the other side as +voltage IND 10v and +voltage audio 13v. And -voltage audio and -voltage ind.

Those voltages won't be exact. Without a load they might be higher.
 
Thanks Robotron! OK yep that A011 diagram is the one I've been looking at for awhile now. And ah yes you pointed out something I wasn't seeing - the fact that we're getting those negative voltages on the output side from that 12V line coming in.

But the output side of the linear is where my questions really start to stack up. I'm about to work on my little writeup of that output section and the questions I have. Right off the bat, bam what you pointed out - we have these "weird" voltages (13V, 10V) that don't even exist on the switcher, so how can that work.....

Well - I'm gonna go ahead and do my little notes on the linear's output and post that. I've got more questions on that for sure, lol. Thanks again! -Wes
 
Original Linear PS - Output Side

OK so yep this is where my questions really start coming up. I guess that makes sense, since it's the final output and that's what we now have to work with to start powering things up. Proof's in the pudding. Well, I'll start with what I'm understanding to be the pinout - actually I'll start with the big question that just kinda pops in my head looking at the linear's output connector:

Since the switcher could handle *everything* with just 3 output pins (well, 3 output voltages), then why does the linear have to have so many pins?? This is just a "thinking out loud" question to myself - I'll get more specific with the pinout as I understand it:

1) +13VDC - so then how can we expect a switcher to work when it doesn't even have a 13V output? Is it just that +12VDC is "close enough" so we can just use that?

2) -5VDC - no problem to understand this, we had that on the switcher

3) +10VDC - same question as on pin 1

4) Reset line - major confused here. What is this? What is the voltage, and what is it used for? My guess is that it *must be* either +5V, -5V, or +12V (or pretty close to that), and that's why the switcher works for us.

5) I don't see this at all on the diagram - so....not used?

6) key - not used

7) +12VDC - easy enough

8) +12VDC - but why is this even there since pin 7 is +12V - just to carry more current, or convenient that we don't have to split off later?

9) Sense line - same question as on pin 4

10) same as pin 5?

11) -V.IND - what is this? Maybe -10VDC? Same question as on pin 1.

12) -V.AUDIO - Is this -13VDC? Same question as on pin 1

13-16) COM - logic ground - easy, we had this on the switcher

17) coin counter - What is this voltage?

18-19) +5VDC - 2 pins just for convenience? (switcher only had 1 terminal for +5V)


Any feedback would be greatly appreciated here. I'm gonna start looking at the big xformer and seeing if the voltages are there. Thanks!! -Wes
 
1 and 3 are the positive for the ind and audio.

12 and 11 are the negative for the same thing (at this point I'm not sure which indicator lights they are talking about)

5 and 6 not used.

17 Coin counter is probably 9 volt pulsing dc. Only one diode in line.

When most people put in a switching power supply. They tend to find all the 12 volt wires and tie them together. Same for all the +5 and -5. So to undo it you have to find all the connections they made and undo them. Trace the wires back to where they came from and reconnect them to the linear power supply on the correct pins.

You're going to need someone a lot smarter than me to explain the Reset and Sense lines. My guess is they are not connected with the switching power supply.
 
Thanks Robotron! Well I just checked the big transformer and all the voltages are there - woohoo! They're all running a little hot - maybe about 1.3V or so higher than stated. But I'm thinking that's OK.

Also, the input side connector looks to be intact - although pin 1 (center tap) is burned all to hell. I'll just be redoing that connector.

And the Bob Roberts kit you pointed me to is awesome! Along with the connector housings and pins I'm hoping he carries for the linear PS, I'm starting to think this gonna be somewhat of a snap to get going. Things are starting to fall into place. :)
 
Oh ya know what I think the IND indicator lights might be the rank lights. Those pinball-style (SCR controlled even?) lights that show what rank you are thru the game (warrior, avenger, etc.)
 
Just a quick update to this thread. Everything is up and running fantastic with the original linear power supply - woohoo! I did a rebuild with the kit from Bob Roberts, redid the connectors to molex and put some new header pins on.

As I suspected, the problem I was having with audio interfering with the video is 100% gone now - everything is awesome! It just feels good to be back to original from the switcher someone had put in there.

Many thanks to Robotron for some awesomely useful info!! -Wes
 
That's great! I'm glad you got it all working. It really feels good when you restore a power supply to working condition. Switchers are OK, but I really prefer the original power supply, especially for Williams games.

Remember when you said the power readings on the transformer were a little high? They have to be, when you go though a diode, it drops the voltage .6 volts. Two diodes or a bridge rectifier drops the voltage by 1.3 volts. So 13.5 volts AC comes out 12+ volts DC.

Not to mention the circuits pull the voltage down a little more. Just a little info FYI.

In any case congratulations.
 
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