Joust Power supply issue

What is your +5VDC reading.

Here's a snippet from the manual.

+5v DC ADJUSTMENT (R10 & R24)
Before adjusting the voltage output, always check the output at the supply for AC hum. This hum should never rise above 0.005v on the +5v DC supply.
This is measured with the AC setting on your Meter.

If it does, consult your schematic drawing set for proper DC voltages throughout the circuit. Test for these with the DC setting of your multimeter.

Make a second check using the AC setting. Pay particular attention to readings at TP5 (top of capacitor C10). If the voltage here is too low (less than +11v DC) or you
find excessive ripple (more than 700mv rms), replace the capacitor.

There are instructions on how to decrease, or increase voltage on page 7 of the instruction manual. It's really quite easy. I'm interested in what the +5VDC is, and what the AC ripple is.
 
Power Supply Option

Another option to consider is upgrading your power supply to a Jamma style power supply.

I am currently restoring a Robotron and I plan to use a Jamma power supply (higher reliability).

PM me if you need more info.....

Regards and Happy NEW YEAR!!!
 
Rampart35 said:
Another option to consider is upgrading your power supply to a Jamma style power supply.

I am currently restoring a Robotron and I plan to use a Jamma power supply (higher reliability).
Click to expand...

You mean Downgrading to a Jamma Power Supply with a higher failure rate, not to mention the problems you will have with your high scores continually resetting.
 
Rampart35 said:
Another option to consider is upgrading your power supply to a Jamma style power supply.

I am currently restoring a Robotron and I plan to use a Jamma power supply (higher reliability).

PM me if you need more info.....

Regards and Happy NEW YEAR!!!
Click to expand...

I'm too lazy to find any of the threads, but the short version is that the original Williams boards (and any close knockoffs, but apparently not the JROK board (unless I've just been real lucky)) rely on the +5V lasting a few milliseconds longer than the +12V. The 6809 CPU has an annoying habit of writing random values to random locations in memory (including the CMOS high score and settings) while it is being powered down (a leftover from the 6800 series). The Williams designers recognized this and added a much larger than necessary capacitor on the +5V to power the CPU and added a circuit that trips the CMOS write protect circuit when the +12V goes down.

Switchers don't have this. Both +5V and +12V go down at the same time and the CPU sprays the memory space. Because it is random, the CMOS may only get hit once in a while or it may get hit every time. The worst case is when the CMOS gets set to funny (but valid) settings and suddenly your game is no longer on freeplay or you start with 0 men (very short games) or you are set to impossibly high levels of difficulty to start.

There is a good reason for rebuilding/replacing your existing linear power supply with an original one, unless you don't mind losing your high scores and settings periodically.

ken
 
Thanks for the info Ken!

I may reconsider using the original power supply instead....

By the way your Robotron ROMs work great!
 
Gettin a multimeter

Hey guys. I wanted to thank you all for the info. I hope to get my hands on a multimeter in the next few days and try to do the testes prescribed in yellowdog's post above.

I will let you know what it turns up.

Thanks again.
 
Talon2000 said:
What is your +5VDC reading.

Here's a snippet from the manual.

+5v DC ADJUSTMENT (R10 & R24)
Before adjusting the voltage output, always check the output at the supply for AC hum. This hum should never rise above 0.005v on the +5v DC supply.
This is measured with the AC setting on your Meter.

If it does, consult your schematic drawing set for proper DC voltages throughout the circuit. Test for these with the DC setting of your multimeter.

Make a second check using the AC setting. Pay particular attention to readings at TP5 (top of capacitor C10). If the voltage here is too low (less than +11v DC) or you
find excessive ripple (more than 700mv rms), replace the capacitor.

There are instructions on how to decrease, or increase voltage on page 7 of the instruction manual. It's really quite easy. I'm interested in what the +5VDC is, and what the AC ripple is.
Click to expand...

ok, i must be retarded then! i can't find an adjustment pot anywhere on an original Joust PS???

i think i remember it on a Defender but this is a totally different PS.
 
There isn't an adjustment pot on either Defender or the later Williams PS boards, unless somebody hacked one in. The "official" way to adjust the power supply is to make minor modifications to the resistor network comprising the feedback part of the voltage regulator circuit. This normally involves removing R10 to slightly increase the voltage or adding a larger value resistor to replace one of the other resistor (can't think which one right now. It is documented in the schematics.).

ken
 
YellowDog said:
There isn't an adjustment pot on either Defender or the later Williams PS boards, unless somebody hacked one in. The "official" way to adjust the power supply is to make minor modifications to the resistor network comprising the feedback part of the voltage regulator circuit. This normally involves removing R10 to slightly increase the voltage or adding a larger value resistor to replace one of the other resistor (can't think which one right now. It is documented in the schematics.).

ken
Click to expand...

ahh...ok! i have a Joust that will not let you put in 1st player initials but will 2nd player. i read a post from someone here saying that he had about 4.8 and adjusted to 5.1 and all was good! he obviously has a switcher then i guess. i didn't know where to ck 5v so i assume mine has low voltage also!

i'll try removing R10(nothing goes in its place?) on power supply pcb then and see if it works cause like you guys said, i want to keep original without all the switcher probs!!!
 
kray37 said:
i read a post from someone here saying that he had about 4.8 and adjusted to 5.1 and all was good! he obviously has a switcher then i guess. i didn't know where to ck 5v so i assume mine has low voltage also!

i'll try removing R10(nothing goes in its place?) on power supply pcb then and see if it works cause like you guys said, i want to keep original without all the switcher probs!!!
Click to expand...

Not a switcher for sure. I am guilty of the "hack" that Ken speaks of for making you original linear power supply adjustable.

Defender style ps is a 5k pot at R2.
Joust style ps is a 5k pot at R25.
 
kray37 said:
ahh...ok! i have a Joust that will not let you put in 1st player initials but will 2nd player. i read a post from someone here saying that he had about 4.8 and adjusted to 5.1 and all was good! he obviously has a switcher then i guess. i didn't know where to ck 5v so i assume mine has low voltage also!

i'll try removing R10(nothing goes in its place?) on power supply pcb then and see if it works cause like you guys said, i want to keep original without all the switcher probs!!!
Click to expand...

Check the voltage with a DMM before you mess with it. Check the voltage at the ps board and then again at the CPU board, best place is to test at the RAM. It is likely that you are losing voltage over the connectors and the wiring. I have seen several cases where the ps board is putting out 5.0V and the CPU board is seeing 4.7V because of corrosion on the connectors.

If the voltage on the board is lower than 4.9V then it is probably worth spending the money to get it rebuilt. That usually means that the caps are starting to dry out or the voltage regulators are starting to drift. THis can happen even if the 3 LEDs are lit. They are a good warning sign that the PS needs help, but they are not fool proof.

ken
 
YellowDog said:
Check the voltage with a DMM before you mess with it. Check the voltage at the ps board and then again at the CPU board, best place is to test at the RAM. It is likely that you are losing voltage over the connectors and the wiring. I have seen several cases where the ps board is putting out 5.0V and the CPU board is seeing 4.7V because of corrosion on the connectors.

If the voltage on the board is lower than 4.9V then it is probably worth spending the money to get it rebuilt. That usually means that the caps are starting to dry out or the voltage regulators are starting to drift. THis can happen even if the 3 LEDs are lit. They are a good warning sign that the PS needs help, but they are not fool proof.

ken
Click to expand...

good explaination! i'll ck at ram and at ps!
 
kray37 said:
so how is that done with a wiper on the pot(3 pin pot)? can you explain or is there a 2 pin pot that i'm not aware of?

i will do this for adj also!!!

thanks
Click to expand...

You take a circuit board mount pot and bend the wiper and either of the legs to fit the holes. The best one I've seen used one of these:

853775.jpg


and had a small value resistor soldered in line to prevent accidentally running the value to zero and frying something.

Most just jam one of these in:

94714.jpg


ken
 
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