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NFL Blitz 99 Seattle - Jumbled Text - -5V issue?

makattack98

makattack98

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Apologies, this is about to get messy...

I have an NFL Blitz 99 Seattle board that I'm "upcycling" (large converted cab was in a space it couldn't be removed from, I stripped what I could in a time crunch with limited tools) into a new cabinet and modern monitor (please don't crucify me). I do not have the test switches.
  • I purchased THIS Jamma harness which was actually meant for their in house multicade setups
    • This unit was a conversion kit and the original Jamma harness was an absolute rat's nest so I thought I'd start fresh
  • I could not get video to work and realized - from a 7 year old YouTube comment - this board needs -5V which the harness did not have wired up
  • After adding wires to the harness' -5V I was able to get the (original) HDD to fully spin up video and display everything on a modern ACER 144mhz monitor
  • I'm using an HD-VC990 for EGA>HDMI video output.
  • In getting this far, the board goes into attract mode but a lot of the "overlay" graphics (team logos, demo mode visuals) and text (insert coin, player 1) are a jumbled mess
    • The demo gameplay appears to be clean/working properly
The only way I was able to get everything stable - aka not caught in a reboot loop - was to increase voltage on the power supply. When "working" the +5 was reading 5.44, the 12V was at 12.5 and the -5V was at 4.48.

Those numbers feel much too high so I've unplugged everything and reduced the voltage to readings of 5.01 on the +5 and 12.2 on the 12V. This, however, takes the -5V down to 4.32

I guess I have three questions:
  1. Should the -5V reading also be close to an even 5 to reach stable video?
  2. If so, is there anything that might be cause my -5V readings to be so much lower than +5 (this happens on the OG power supply and a brand new one)
  3. Am I completely missing what's happening and focusing on the wrong thing?
TIA!
 
  1. Does the Jamma harness have all 4 pins for +5 and Gnd wired separately? Cheaper harnesses combine these pins, causing a power bottleneck.
  2. Ditch the HDD and get the CF mod (or whatever the tech is nowadays). It's been years since I dealt with Midway.
  3. Buy new power supply for piece of mind.
  4. Read voltage at the board, not the power supply.
 
streetfighterken said:
  1. Does the Jamma harness have all 4 pins for +5 and Gnd wired separately? Cheaper harnesses combine these pins, causing a power bottleneck.
  2. Ditch the HDD and get the CF mod (or whatever the tech is nowadays). It's been years since I dealt with Midway.
  3. Buy new power supply for piece of mind.
  4. Read voltage at the board, not the power supply.
Click to expand...
Thank you for responding!

1. Yes, thankfully. 4 pins for each.
2. I think that's my next move if I can't get this sorted. They aren't terribly expensive.
3. I do have a brand new one, it was having the same "off" readings for -5V.
4. Good call. The one thing I forgot to do was clean the connectors which I read could be a sneaky culprit.

For my own education, in an ideal setup, should both +5V and -5V read at 5 volts at the board?
 
streetfighterken said:
-5v is only for audio IIRC and doesn’t need to be as accurate as +5.
Click to expand...
Ah, interesting. I guess it was a red herring when I was testing the board and it was actually (potentially) the overall voltage was the culprit.

I took measurements at the board as you recommended. In order to get the HDD to spin, the voltage has to be adjusted (I think) and was reading 5.45. Does that seem high?

It's worth noting, prior to the removal from the cab which had the massive old school power supply/transformer (?), the game worked perfectly.
 
nem said:
Yes, very. Are you getting this measurement from the board itself?
Click to expand...
Yes. For whatever reason, the HDD doesn't "kick in" without an increase in voltage. Or that appears to be the correlation...

I'm going to clean the heads and see if that helps.
 
My recommendation is stop using that old HDD immediately and get the flash kit. It should be running between 5.0-5.1. If still not working, the board is damaged (possibly due to over-voltage).
 
streetfighterken said:
My recommendation is stop using that old HDD immediately and get the flash kit. It should be running between 5.0-5.1. If still not working, the board is damaged (possibly due to over-voltage).
Click to expand...
I might do that regardless but I increased my knob a bit more. I re-measured at the board after adjusting up at the power supply.

The +5 is hitting 5.01 and the jumbled words are gone. The demo/attract mode appears clear and stable.

After said adjustment, the 12V is at 12.48. Is that a concerning level?
 
mecha said:
go here: https://www.arcaderepair.net/mechas-essential-power-supply-guide-remastered/

I literally used a Blitz 99 at a point. ;)
Click to expand...
Amazing! Thank you for this. I realized I was focusing on the wrong thing entirely. -5V being for audio and lights.

I've been familiarizing myself with the wiring guide and checked the old harness which I have. On the old harness all 4 +5 jamma slots have individual 20 guage and go to the Power supply. On my harness it's 22 guage wire. And the 4 slots go into 1 wire. I think that's where a bottleneck is happening?
 
Last edited:
makattack98 said:
Amazing! Thank you for this. I realized I was focusing on the wrong thing entirely. -5V being for audio and lights.

I've been familiarizing myself with the wiring guide and checked the old harness which I have. On the old harness all 4 +5 jamma slots have individual 20 guage and go to the Power supply. On my harness it's 22 guage wire. And the 4 slots go into 1 wire. I think that's where a bottleneck is happening?
Click to expand...
Yeah that's what I meant by each pin should have its own wire to the power supply. That's why you've needed to crank up the power supply to get any useful power at the board -- which will burn out the power supply and possibly cause damage to board.
 
streetfighterken said:
Yeah that's what I meant by each pin should have its own wire to the power supply. That's why you've needed to crank up the power supply to get any useful power at the board -- which will burn out the power supply and possibly cause damage to board.
Click to expand...
Thank you for your help. I redirected a second wire (still +5V) that was used for a two pin connector (for EGA to VGA/HDMI). That helped a bit.
 
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