Opinion: Wizard of Wor PSU

[level42]

Better replace those leaking cats ASAP !

[EvilCensor]

Uh-oh, a couple more questions.. before I replace caps etc. on the PSU PCB - and risk a known working gameboard set

I'm wondering if one of the transformers needs replacing (the one leading to the game boards - the "MT87").

As you can see in the following picture the posts are rated at (my readings to the right):

14.5 - reads at ~15.0
9 - reads at ~10.5
0
14.5 - reads at ~11.63
0
12 -reads at ~12.96

Q1: Are these readings reasonable/okay? (using a cheap multimeter atm -Innova 3320).
Q2: Are the two 0 posts interchangeable when taking readings?.. I'm guessing not
Q3: In the last picture down below you can see what it looks like, would this be considered in bad shape - or does visual appearance mean little with these?



The schematic shows:



Top view of the MT87 (looks a little rough - what do you think?):



Thanks for your patience

[Laszo]

It look perfectly normal and the reading are within specs. You should also check your outlet voltage if it is 230 volt and your primary wire is at 220 volt you should get slightly higher values. These trafo's are using oiled paper as a isolator... That always looks like this. The two zero's are, as you can see on different windings. so you should measure the relative voltage between the right lugs. So the 0 with the yellow green wire is paired with the white green wire. In between should be about 12 volt ac.

[EvilCensor]

Thanks for the reply - I'm in the US so the outlet should be ~120V.

[Laszo]

Thanks for the reply - I'm in the US so the outlet should be ~120V.

So if your secondairy output is to low go to 110 or 115 if it is to high go to 127.

Your wall outlet is 120? Which lug on the primairy side is connected, 115?


It is also good to realise that the power goes to the regulator board which can handle the tollerance and stil give a clean output for your gameboards.

[EvilCensor]

Thanks for the reply - it's connected to 115.

Hope I'm not irritating anyone asking so many questions - but yeah.. I have another.

Today I used the Kit Bob Roberts supplies to rebuild the 90411 PSU board.. and two "trimmer pots" were part replaced in the process (not sure why the third wasn't included. I tested the PSU and was pleased to say that not only did it fail to blow-up but it also seemed to yield the approximate correct voltages.

Readings I'm getting from the PSU (that would go to game boards) are:

On the -5 I'm getting -5.73
On the +12 I'm getting +12.23
On the +5 I'm getting +4.95
On the other +5 I'm getting +4.95

Q1. How close to -5, +5 and +12 should I be.. is slightly over better than under or dead on?
Q2. Also there is a yellow ground cable coming from the AC filter.. it's going nowhere but looks like it's supposed to be attached to something - I can't find any info on what though (maybe the game board cage?)



From the manual it looks like that GND cable attaches somewhere behind the game cage (to the right) - likely?

[Laszo]

No problem. Normally all metal parts in a device should be grounded. This is to make sure that for example coindoors and other metal parts are always save to handle. There should be a ground wire that is running through your cab and this  wire should be connected to al the metal parts. The yellow lug is the starting point. As long as the ground wire is running through your cab it is ok to connect this yellow ground lug anywhere in the chain.


The voltages look ok but I suppose that you have messured with the other boards not connected. It could be that some voltage go a bit lower under stress. Anyway they are within the limits so you can savely move on.

[Laszo]

Did you test the pots with no boards connected? You should see the voltages move up and down by turning the pots. Try to get al voltages within a 10% margin and then move on to connect the other boards.

[level42]

With all respect but you admitted at having a cheap multimeter so how reliable are these values ?

The +5V is a bit too low. You need to hook up the PCB and then find measuring points for +5V and GND. Measure between these two and adjust the 5V slowly and carefully to about 5,1 V.

[EvilCensor]

The PSU board was tested without the game boards connected - looking over the schematics I see that the ground cable is supposed to be connected to the game board cage.

The lines coming from the PSU and going to the game board are:

GND
GND
GND

-5V
RESET
+12V
+5V
+5V

The RESET is reading 5.05V - does anyone know if it should it be that high?

The meter doesn't seem too bad, have a replacement coming Friday however.

[Laszo]

Reset 5v in normal operation is correct, when connected to ground for an instant your cpu will reset.

[EvilCensor]

Thank you, appreciate all the help so far.

Well the game boards appear to be dead (which isn't a surprise) - and fault finding there isn't going to happen with my level of expertise lol.. still waiting for new working set to arrive.

[Laszo]

Thank you, appreciate all the help so far.

Well the game boards appear to be dead (which isn't a surprise) - and fault finding there isn't going to happen with my level of expertise lol.. still waiting for new working set to arrive.

Coaching that kind of repair over the forum will be a challenge 

[ajhippel]

Thank you, appreciate all the help so far.

Well the game boards appear to be dead (which isn't a surprise) - and fault finding there isn't going to happen with my level of expertise lol.. still waiting for new working set to arrive.

on the game  board there are only the 2 i/o customs and the sc-01 voice chip that can not repaired...
all the other chips are standard logical chips

try to swap the identical i / o chips... this might help.

if this does not, i can offer you repairing them (if the custom chips are ok)

(due programming the online-savekit for gorf or wizard of wor, i made a lot of experiences in repairing game-boards, ram-cards, pattern-boards etc)

Greetings
Jochen