Joust power supply

tendril

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Bought this game broken. The +5V led was out on the power supply board so I bought and installed the Bob Roberts repair kit. +5V led is still out. Probing deeper if I disconnect the power line to the ROM board (? The one with the alphanumeric output on it) the +5V led illuminates. With the ROM board connected the +5V line reads at +1V.

Does this mean a short on the ROM board is likely? Or the PSU can't supply the load the ROM board needs?

Ideas? :)
 
did you do all the caps too even the big axial cap? that runs the +5.

BTW: i have a complete cap kit and a mega deluxe kit available for the williams power supplies. the cap kit is 100% 105c caps even the axial no screwing around trying to put radial in and wiring them up. my mega deluxe rebuild kit has more/higher rated/better parts then any out there i have seen.
 
reseat the upper transistor on the black heatsink. the 6057.

Mecha - thanks - but no improvement.

security0001 - I replaced all caps except the really (really) big one. From the schems it seems involved in the +12 part only though, not really any of the +5 circuit.
 
Pete, thanks for putting these together i just put my order in.
Chris.


did you do all the caps too even the big axial cap? that runs the +5.

BTW: i have a complete cap kit and a mega deluxe kit available for the williams power supplies. the cap kit is 100% 105c caps even the axial no screwing around trying to put radial in and wiring them up. my mega deluxe rebuild kit has more/higher rated/better parts then any out there i have seen.
 
Mecha - thanks - but no improvement.

security0001 - I replaced all caps except the really (really) big one. From the schems it seems involved in the +12 part only though, not really any of the +5 circuit.

i would have to pull the schematic but i thought it affected the +5 side too. i am sure someone will confirm either way.

if you need that big axial cap i have them in stock now. 18,000uf 25v
 
Ok, KLOV help me out, I don't know much about this analog stuff... Should I be able to test the bridge rectifier in circuit with a DMM?

br1_zpsji83niuk.jpg


On the part BR1, pin 3 to 4 tests good (diode setting on DMM). Pin 3 to 2 tests good.

Pin 2 to 1 shows open circuit (as does 2 to 1 direction).
Pin 4 to 1 shows open circuit (as does 1 to 4)

Pin 3 to 1 also shows open circuit (as you'd expect if 2/1 and 4/1 are bad right?)

D2 & D3 also test good.

Can I conclude the BR1 part is bad? Do you carry this security0001?

Thanks!
 
yes i carry ALL the bridge rectifiers 35a1000v with wire leads for newer p/s and the spade terminal for the older p/s.
 
tendril BR1 sounds kinda pooched to me from what you are describing but... LOL!!! a bridge rectifier is just a bunch of diodes and we usually have to test those out of circuit. i would lift leg 1,2,4 to test just to rule it out, if its done it has to come out anyway. what did 3 to 2 test? that looks like it feeds to C16 to D2 to the 27.4vdc into pin 11 & 12 of the vreg IC2, and out on pin 3 of IC2. check for +5 on pin 3 . after IC2 the only other stuff i can see on the schematic that could possibly effect +5 maybe if C4,C5,C7 , Q1,Q4 or zener ZR1 had short to ground, and you already ruled out 6057 .
 
Thanks, I can understand testing in-circuit could give a false positive, but the opposite seems unlikely (if its dead it's dead). But I don't know much about these things, that's why I asked :)

I ordered a new one anyway, so I'll compare them both when it arrives.
 
im learning also, I have two deluxe kits coming from security next few days and am going to go through mine asap. I have a low +5 issue also but not as low as yours .these kind of threads I really enjoy in this forum they engage my mind much better than the pinball forums do.
 
There are a couple resistors you can switch to adjust 5V. Don't know offhand exactly which ones, but it's in the manual if you download it. Can try that after rebuild if it's still a tad low.
 
There are a couple resistors you can switch to adjust 5V. Don't know offhand exactly which ones, but it's in the manual if you download it. Can try that after rebuild if it's still a tad low.

yup you can put a pot in there and i will have that in my kits in a few weeks when i get a great fitting and proper rated one for it in stock. that can be done to the D8784 and also the older D8359 both.
 
Thanks to security001 for some fast shipping! Parts arrived Saturday afternoon, new BR and I got the big cap too as shipping was the same. +5V restored when under load. Futzed with the board inter-connects a bit to get it to boot, replaced 1 RAM chip reported bad by the self test and it works 100%! Seller told me it had been home use since late 80's and a board had gone bad around 2001 and it hadn't been turned on since. I had a cap kit for the monitor ready to go too but in fact it was damn near perfect as it was. (Photo taken before a slight horiz pos adjustment to center up those title screen bars :))

E9BC695F-DADF-40CA-A096-BB552E522F69_zpsvhyvntu4.jpg
 
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