(Topic ID: 254399)

Hollywood Heat - Stopped booting after NVRAM

By MaxAsh

8 months ago

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  • 107 posts
  • 18 Pinsiders participating
  • Latest reply 7 months ago by pincity
  • Topic is favorited by 1 Pinsider


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#29 8 months ago

System 80B games will boot up with no 5101 (NV)RAM installed. Remove the NVRAM module and try to boot the board. If the board now boots up the NVRAM likely needs replaced. If the MPU is still locked up something went wrong during the socket install or the daughter board cracked solder during the nvram socket install.

The FM16W08 works down to 3.3v. The CE combining chip is a 74HCT00D. I haven't run into any situations where the v drop from the battery block diode causes issues.

#33 8 months ago
Quoted from MaxAsh:

Thanks @barakandl That's good to know, I had no idea. Just checked with nothing in the socket, same issue, so the NVRAM is good (no surprise since the other old RAM chips didn't help either I guess).
So is the next step to pull the board again, and reflow solder to the daughter board connections where they go to the main board? Or should I desolder the daughter board completely from the main board, reflow the underside of the daughter board, then reattach it to the main board? I haven't had daughter board issues with the 80B games I've owned.

Double check around the IC socket install if it stopped working after putting that in. Make sure not traces or holes got torn out and make sure nothing is shorted together that shouldnt be. Like where a trace passes between two IC socket pads.

The daughter board is a pain to rework. You can try to reflow solder but you dont have access to all of the solder joints without removing it entirely which is not the easiest thing to desolder.

#37 8 months ago
Quoted from MaxAsh:

Okay thanks, I'll check everything again. I didn't think about checking where traces pass by other socket pads, they do sneak between them. Worth checking for shorts on non-adjacent stuff as well.
I guess I need to do my best to try and desolder that daughter board. I have a feeling it will be a huge pain, but if I'm pulling the board again to test, I might as well try. I have a feeling it will be a tough one.
barakandl In terms of trying to fix this... is the replacement board on your site a better option for my situation? Or is the Piggy Deux a better choice? I've never needed a replacement or work around on any System 80B before.

The one I make is a much smaller footprint of the same original circuit. It has posts that will mate with an IC socket if you want. The much smaller foot print should resist cracking more than the original. Whether or not using a dip24 socket is better than hard soldering the daughter board in is probably up to debate.

The Piggy Deux one plugs into the test socket if I remember right. Advantage with that may be you can cut out the original daughter board or maybe even leave it on the board with no EPROM installed and not have to do solder rework that area.

#43 8 months ago
Quoted from G-P-E:

74HCT00 parts are rated for 4.5 to 5.5V operation. At his 4.5V, he's at the very bottom edge of the parts rated VCC range. I would think shorting CR34 would bring the VCC back into proper operating voltage range. Running at the voltage extremes (either high or low) is never a good idea.
74HC00 parts will run at the lower voltage range (2V to 6V) with no problems. And since the two CE inputs are driven by 4000 series CMOS operating from the same Vbat voltage - the 74HC00 would be a much better choice. Food for thought - two FET's and a pullup resistor would have been a good choice as well.
As to the mention of not running without the reset board. Some boards refuse to operate properly without the DIP plug installed regardless of whether or not the reset board is connected. This is due to the addition of a pullup resistor that Gottlieb added during 80A days.
When this resistor is added - some of the boards come back to life.[quoted image]

74HC00 actually caused me problems at times in gottlieb sys 80b where HCT00 worked fine. Testing with a HC00 in my 80B game occasionally the RAM gets scrambled and the high scores would show junk, if you go to ram test it would still pass. I did not have pullup but it should work with 74HC00D. Something odd happens probably power up or down where the RAM corrupts. Tons of 5101 modules all with 74HCT00D and never had any reports about trouble from V drop of the diode. Granted I sell them towards a few specific 5101 systems that I know work but maybe not every possible 5101 application outside of pinball. I guess adding pads for 0805 pullup resistors on the next time I order PCBs wont hurt. Then I can try again with HC00

I did have to put a 10K pullup resistor for /CE on 6116 NVRAM modules destined for Bally Midway arcade games. Without the /CE pullup those games will fail to boot and scramble the RAM at times.

1 week later
#57 8 months ago

If it stopped booting after NVRAM install figures that most likely the problem is there. Check continuity from 5101 to the 6502 and to the piggyback's chip socket. A trace or plated hole might have been ripped out when the IC socket got installed breaking continuity of an address or data back to the CPU. A connection may go to the 5101 before going out to the ROMs so even if the 5101 is fully connected if the trace is ripped as it leaves the 5101 everything past there would be open circuit and if the ROM is missing an address or data it probably will not boot up.

With no ROMs installed the CPU should run through all the address looking for program and in this state you can poke around with a logic probe to see if any address or data is dead at say a ROM chip that is pulsing at the CPU chip. Then that indicates there is an open circuit.
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#60 8 months ago
Quoted from gdonovan:

While I agree in principle (look in the area where you last worked), System 80B will boot up and run without a 5101 even being installed.

A trace run may go in order 6502 to 5101 to EPROM. If the trace is ripped out at the 5101 it also disconnects everything downstream from it and if a ROM has an open data/address it will lock the CPU.

Quoted from MaxAsh:

barakandl thank you for that info, I'm game to run through what you said, but I'll be honest, I got a little lost in there. It sounds like you were suggesting two things:
1) Check continuity between the 5101 and the 6502 / Piggyback chip. I was trying to figure out where from the schematic section, but I'll be honest, it's a little confusing.
For example, I see A0 - A7 on the 5101 as pins 4, 3, 2, 1, 21, 5, 6, 7. They seem to be labeled as a group "A", which goes over to AB0-AB10, BAB11? Which then heads over to the 6502 A0 - A11, pins 9-20? I'm a little confused there, my apologies. I'm pretty good with schematics usually, but chip-to-chip stuff and the logic involved isn't as in my wheelhouse sometimes. I'm sure I'm just missing something simple.
2) Remove ROMs (not sure which), turn the game on, and poke around with a logic probe? I'm a little unsure of what to do there. I have a probe, but I've only used it a handful of times on arcade games in the past. Happy to perform whatever testing you suggest, just a little more explanation/guidance would be awesome, if you have time.

I am saying check continuity from the CPU chip to the most likely problems which is 5101 since you just reworked there and the usually problematic piggyback. I think the B thrown in stands for "bus". Its a bit confusing they used multiple designations for things that are electrically connected but AB0 = A0 and etc.

D0 = 6502 P33 = 5101 P9&P10 = PIGGYBACK's 2764 socket P11
A0 = 6502 P9 = 5191 P4 = PIGGYBACK's 2764 socket P10

The BAB10 through BAB13 for upper address piggypack socket is shown on the PROM selection section and connect back to Z10 or Z12.

#76 8 months ago

A picture shows the reset board is not installed, so its not an issue with that. In the same picture I do see an EPROM without a cover on it. The fluorescent lamp used in the head may be able to erase bits over a long period of time. I have noticed in some EPROMs you can crash the CPU just by shining a bright light into an uncovered erase window. After exhausting continuity and short problems it may be time to verify the ROM content and if good try test a ROM.

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