Williams Power Supply Woes

[VidyaGamez]

For my Defender/Multi-Williams restore, I rebuilt the original PS with the big kit from arcadepartsandrepair, as well as added the heatsink to BR1 and the 5v adjustment pot mod. I initially put the big 18000uf cap in backwards, causing it to blow the 2 7A fuses. Once I figured that out, I replaced it and checked BR1 and the bottlecap transistor on the larger heatsink to make sure they were good.

Now when plugging in the connection from the transformer, I get the 3 lights on the PCB, but the 5v light is dimmer than the rest, and even with the 5v adjustment pot cranked all the way, I'm only getting ~4.9. Can anybody help me out?

 

[taitovoxkids]

Gotta get Mecha in here - he helped me dial mine in when I was having issues after a rebuild. If I can find any info I will pm you.

Good luck. It is possible to bring one back from the dead and get it almost bulletproof.

 

[mecha]

lose the adjustment pot. you don't need it. I don't know how many times I have to stress this. I'm sure security can still make money selling other things than this completely unnecessary mod. Defender doesn't even require that much voltage to operate and the power supplies are set for 5.0V.

also, oops. the giant axial cap is the filter cap for the bridge rectifier. specifically unregulated +12V.

oops.

 

[VidyaGamez]

lose the adjustment pot. you don't need it. I don't know how many times I have to stress this. I'm sure security can still make money selling other things than this completely unnecessary mod. Defender doesn't even require that much voltage to operate and the power supplies are set for 5.0V.

also, oops. the giant axial cap is the filter cap for the bridge rectifier. specifically unregulated +12V.

oops.

Yeahhhh I did a boo boo on that axial cap. I tested the BR in circuit though and it was within spec though. I will buy the resistor I got rid of for the 5v mod. I didn't do much research on it, it just sounded like a good idea. You think the low 5v is caused by the pot?

 

[jacklick]

Yeahhhh I did a boo boo on that axial cap. I tested the BR in circuit though and it was within spec though. I will buy the resistor I got rid of for the 5v mod. I didn't do much research on it, it just sounded like a good idea. You think the low 5v is caused by the pot?

I don't want to speak for Mecha but I would say the adjustment pot is not needed if you have good connectors. It is basically making up for voltage drop.

I have done the VR adjustment and even made a bad video describing the "correct" Mark Spaeth way but have since also done videos clearly showing it is not needed and a .3v improvement in voltage drop by just replacing pins and connectors.

>edit> if you are not careful, the VR mod can actually put like +7v on the 5v line which is impossible with the stock setup.

 

[ElectricDreamz]

as someone rebuilding a Moon Patrol power supply for the first time, this thread is causing me to tread a bit more lightly. OP, your sacrifice is not in vain

 

[VidyaGamez]

I don't want to speak for Mecha but I would say the adjustment pot is not needed if you have good connectors. It is basically making up for voltage drop.

I have done the VR adjustment and even made a bad video describing the "correct" Mark Spaeth way but have since also done videos clearly showing it is not needed and a .3v improvement in voltage drop by just replacing pins and connectors.

>edit> if you are not careful, the VR mod can actually put like +7v on the 5v line which is impossible with the stock setup.

I did replace the male connectors, but as I don't have the tool to crimp the new female connectors to the wires (and I don't have a harness yet), I'm holding off. By chance, could anybody tell me what the value of the resistor is that goes where I installed the 5v pot? I can't seem to find it

as someone rebuilding a Moon Patrol power supply for the first time, this thread is causing me to tread a bit more lightly. OP, your sacrifice is not in vain

Glad I could be of assistance, even if it is in an indirect way.

 

[jacklick]

... By chance, could anybody tell me what the value of the resistor is that goes where I installed the 5v pot? I can't seem to find it

Did you use the method documented on Peter's website? It is a defender PS correct/ If so, it was probably R2 and ikely 2.15k but would double check on schematic.

 

[mecha]

for totally ironic posterity, my Defender power supply does have an adjustment mod on it, and I wound up having to do it on Defender (since decommissioned with a switcher) and Stargate at my work because they were both missing those resistors in spots, so I just copied how mine was done. that said, I don't remember which ones I replaced as that was 5 years ago.

if you go here: https://www.robotron-2084.co.uk/manuals/defender/defender_cocktail_drawing_set.pdf

look at the drawing and compare that to where you installed the pot. on the right side of the page is the parts listing by location, that's how you can find your resistor values.

 

[KPW66]

You're only getting 4.9v max with a load or no load? If the former., perhaps it's PCB and not the PS causing an issue.

 

[mecha]

sometimes the 6057 transistor needs to be removed and reinstalled. worth noting, with voltage adjustment mods, it will be capable of reaching 6.xV. I don't remember the peak, but it can be monumentally dangerous. especially considering Defender will have a Burger King freakout above 5.10V. this is notably why I don't condone the voltage adjustment mod.

the Defender manual has no documentation I know of for which resistor to remove in stock trim to give it a .10V boost. you remove R10 on Robotron and later. I've only ever seen these run at 4.9-5.0V. 4.9V is actually extremely sufficient.

the only component that's really voltage sensitive are the rams, if you go super low (like 4.2V or below) it will start to throw intermittent ram errors. it will be even worse with 4164 ram, which is a particularly overrated mod that doesn't really fix anything if you have other underlying issues... that I incidentally was once a heavy proponent of years ago.

on all my repair boards I replace, mandatory, the power headers to the MPU and rom boards along with their bypass caps. the skinny round headers Williams used during this era will not be compatible with trifurcon pins if you replace the plugs due to the reduced surface contact area. hasn't happened to me too much, but I know of one Defender at a location I overhauled where it would randomly crap out and it was not caused by logic, but the MPU power plug was diminishing the voltage down to 3.7V.

the location subsequently wussed out and wasted a JROK on the game later.

is your AC plug to the power supply from the transformer burned up? the unregulated +/-12 voltages off BR1 are powered by the 22.5V wiring (cited as 10.5V on Defender if I recall) and the high current draw there will cause the pins there to burn up. this will result in increased resistance, which results in more heat, which results in more damage. there's a wiring mod you can do there to double the wires, which I'll need to find visual aids of.

 

[jacklick]

not suggesting you do it but if you want to read about the voltage mod...

here is an archive of Mark's Williams Power Supply +5V Adjustment
https://web.archive.org/web/20170603044126/http://cambridgearcade.dyndns.org/?q=node/76

 

[ElectricDreamz]

if i may take the thread on a slight detour ... speaking of Williams power supplies ...

how the hell do i remove this bottlecap and heatsink?? i wasn't gonna replace it, but the heatsink is loosely sliding across the surface of the PCB, and the thermal compound is only dust, so i figured i'd at least clean it up and apply some new compound.

is there some secret trick to removing that assembly??

 

[joeycuda]

if i may take the thread on a slight detour ... speaking of Williams power supplies ...

how the hell do i remove this bottlecap and heatsink?? i wasn't gonna replace it, but the heatsink is loosely sliding across the surface of the PCB, and the thermal compound is only dust, so i figured i'd at least clean it up and apply some new compound.

is there some secret trick to removing that assembly??

Just remove it from the top. You took the nuts off the topside, so the bolts are no longer holding it. Heat up the leads and wiggle, probably a speck of solder holding it in.

 

[ElectricDreamz]

so ... let me tell you how corrosive and adhesive decades of mouse piss can be ...

is it going to require some kind of Level 84 arcade wizardry to address this?

i don't mind replacing that bottlecap, etc but curious with that metal ring lifted out if that trace is dun goofed.

Just remove it from the top. You took the nuts off the topside, so the bolts are no longer holding it. Heat up the leads and wiggle, probably a speck of solder holding it in.

 

[VidyaGamez]

for totally ironic posterity, my Defender power supply does have an adjustment mod on it, and I wound up having to do it on Defender (since decommissioned with a switcher) and Stargate at my work because they were both missing those resistors in spots, so I just copied how mine was done. that said, I don't remember which ones I replaced as that was 5 years ago.

if you go here: https://www.robotron-2084.co.uk/manuals/defender/defender_cocktail_drawing_set.pdf

look at the drawing and compare that to where you installed the pot. on the right side of the page is the parts listing by location, that's how you can find your resistor values.

Did you use the method documented on Peter's website? It is a defender PS correct/ If so, it was probably R2 and ikely 2.15k but would double check on schematic.

It was R2, which is 2.15k, thanks guys. I was trying to find something like what you linked, and I did find that website, but I didn't look at the cocktail documentation because I figured it would be different than the upright lol.

You're only getting 4.9v max with a load or no load? If the former., perhaps it's PCB and not the PS causing an issue.

This is all with nothing plugged in. I don't even have a Defender wiring harness yet, I wanted to get the PS and monitor squared away before I started dealing with removing the Yie Ar Kung Fu board that currently is installed from the conversion.

 

[VidyaGamez]

*pain and suffering*

I would imagine you could just run a jumper wire or use the leg of a cap on the solder side wrapped around the leg of the bottlecap transistor in order to resolder the connection? I'm not sure if that ring is anything more than a pad, and there's nothing on the parts side it's connected to.

Attached is what I had to do for one of the BRs that burned my board up something fierce. Clearly no pads left here haha, but I think it should be fine since I soldered the legs where they need to go. Maybe this repair job is why my board's fucked though, so take my advice with a grain of salt lol

is your AC plug to the power supply from the transformer burned up? the unregulated +/-12 voltages off BR1 are powered by the 22.5V wiring (cited as 10.5V on Defender if I recall) and the high current draw there will cause the pins there to burn up. this will result in increased resistance, which results in more heat, which results in more damage. there's a wiring mod you can do there to double the wires, which I'll need to find visual aids of.

I will get you a pic later, but someone bypassed the AC plug inside the cabinet. This bypass isn't the problem though I don't think, as the Yie Ar Kung Fu board inside booted up before I decided I couldn't leave well enough alone and decided to rebuild the PS.

 

[crayzkirk]

For the resistor values, you can look up the datasheet for the voltage regulator IC. The power supply is based upon a standard circuit for the 723 regulator. Just find the section which shows the +5vdc regulator with pass transistor.

A lot of the scans available are hard to read for Defender; I've had good luck with the cocktail schematic scan. Stargate uses the same supply however most scans of that are worse than Defender.

The molex crimper is fairly cheap. There are also ones which crimp the conductor and insulator at the same time which will make it faster.

If you don't take the time to do it right, when will you find the time to do it over? Do it once now or do it over later.

You can get replacement thru hole rivets. From the looks of it, the only conductor is on the bottom so you can simply solder the transistor in. You might be able to remove that one and put it back.

 

[G-P-E]

is it going to require some kind of Level 84 arcade wizardry to address this?

i don't mind replacing that bottlecap, etc but curious with that metal ring lifted out if that trace is dun goofed.

That is a 2 layer board. The main traces to the device are on the bottom where the device solders to. The plated via (metal ring) is used to connect bottom of board to top of board but since there is no trace on the top of the board then the plated via is not required. You have nothing to worry about here.

 

[mecha]

that BR2 I've never seen go bad. they're also a nuisance to remove even with proper tools (that I recall... maybe I was shack bulbing still then when I didn't know how these worked yet. LOL) I don't know if it's the same exact part on the sound board but I did have one of those bad recently when fixing my stock and with my fatter Hakko tip it actually was easy to remove. (YMMV, I suppose)

you have thus learned the hard way that, you know, you should just leave well enough alone. if the bridge rectifier were bad it would blow the fuse for it. that wasn't happening, you shouldn't have replaced it. I don't know why security even includes that part. BR1 you should absolutely replace, and as Dokert says, you need to make sure it's soldered thoroughly top and bottom. I always mount those high off the board as I can, so you can do that. the old BR1 you go to replace, you cut it at the legs, then you won't need like 8000 degrees of heat to desolder the old part out.