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Haunted House System 80 MPU boot issue

By stvns78

7 months ago

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#1 7 months ago

MRS

stvns78

Pinside member

Keller, TX

<1y 22,800 56 1 1

Problem description:
Haunted House System 80 MPU will not boot. Displays a "t" in the credit window.

Details:
MPU would boot reliably until I installed a 5v super cap for memory. MPU booted fine first time with super cap. On subsequent boots it would hang on boot, no sounds, and display the "t" in the credit window. Removed super cap but problem persisted. If I left the power off for a while it would then boot most of the times. Issue was 50/50 until I did the abetment work and installed new components now its permanent.

Resolutions attempted:

1. I abated previous alkaline damage. Removed all clock components (Z2,Z3, crystal, and associated resistors). I also performed the reset mod using the DS1811, verified pins on DS1811 are in correct location. Installed all new components for clock and reset. Reflowed some traces. Tested continuity. Exact same problem persists. Used the following components for new clock area per PinWiki

Crystal - https://www.digikey.com/en/products/detail/ecs-inc/ECS-35-17-4XDN/827601
Z2 - 74LS74 - https://www.marcospecialties.com/pinball-parts/74LS74
Z3 - 74LS04 - https://www.marcospecialties.com/pinball-parts/74LS04

2. Did diode test on U1-U6 and all seemed consistent except U1-5, U1-34, and U1-35 showed OL. Not sure if that is expected. Diode test on Z2 and Z3 seemed fine.

3. Some traces were broken and required jumpers. No shorts that I can find.

4. Removed EPROM but problem persists. I had previously installed the original EPROM backwards and nuked it but flashed an new one and it worked fine for quite a while before this issue appeared so I dont think its an EPROM issue. If I remove the EPROM it has the same behavior and does not flash like it did previously with no EPROM installed.

5. Attempted to ground Pin 40 on U1 but that did nothing.

6. Performed slam switch mod.

7. Added 5V LED. Board is getting good 5v power. Checked at board.

8. Installed PI-80X4 and unit works flawless

Any ideas?

Please ignore ugly solder work. Not a solder pro... yet. Backside of clock area looks ugly but everything is connected.

Could the 100uF 10v cap cause this if it was bad? I tested it and when connected to the board is has a resistance of .760 and does not continue to climb. I removed it and rested it and it went to OL, so I am not sure its bad but if this might cause issues I would replace it anyway being cheap.

Would a Logic Probe show anything that the diode test did not on the ICs?

Would going to a TTL oscillator be a better option? https://www.pinwiki.com/wiki/index.php?title=Gottlieb_System_80#Replacing_the_quartz_crystal_with_a_TTL_Oscillator

Since this problem started before doing all the rework I am thinking that it is not the rework or anything that I replaced is the root cause but who knows.

Thanks!

HH_T_Credit_Window (resized).jpeg

MPU_Clock_Post_Mod (resized).jpeg

MPU_Rear_Post_Mods2 (resized).jpeg

MPU_Reset_Post_Mod (resized).jpeg

MPU_Slam_Mod (resized).jpeg

#2 7 months ago

GPE

G-P-E

GPE

Omaha, NE

12y 75,800 2,750 4

Sounds like the memory cap was probably not the problem but the act of working on board (connectors, etc) may have been the problem.

Make sure the case of the oscillator isn't touching one of the traces on the top of the board. It should be raised up a hair.
Get some alcohol and a soft bristle brush - clean up some of the flux on the top and bottom of board and then recheck solder joints.
The 100uF cap is old but not the source of your problems.

Before you do any more mods to that board - easiest to get a logic probe and go from there.
With logic probe & voltage meter, you want to divide and conquer - figure out where the problem is: power, clock or reset.

Very first thing to do is verify you have good power at the CPU board. Measure for 5V directly across that 100uF cap, C1. How close to 5V does it measure?

With logic probe, see if the clock divider is running or not. Can be checked at Z2, pin 9.
If pin 9 has no activity then the oscillator isn't running, check Z3, Pin 6.
If the clock is running then I would double check the board for the reset modifications you made.

Next with logic probe, see what your reset is at the CPU, U1 pin 40. Catching the actual reset pulse is unlikely with just a probe.

The quick tests above will tell you if it is a power problem, reset problem or clock problem.

#3 7 months ago

JWK

sparky672

Pinside member

Manhattan, IL

10y 49,550 977 1

Just a note/observation about your new IC sockets; how do you know if you flowed enough solder to connect the socket pins to the top traces which are completely covered/hidden by the socket?

I see copper on top traces near pins in a couple places... are these top traces making an electrical connection with your socket pins?

Screen Shot 2022-08-24 at 8.42.09 PM (resized).png

On mine I'm seeing at least seven pins on this chip that need a connection to top traces. All are completely obscured by your socket.

IMG_2725 (resized).JPG

I like using strip sockets so I can easily see/verify that the traces on the top of the board, and under the socket, are also flowed properly. The metal pins have a collar which stands the socket up off the board so you can really see if the top traces are flowed. Also, if you need to repair a copper trace on the top of the board, this style of socket gives you proper access.

These are something you buy as long strips and cut to length. No more need to stock various size sockets. You can use an old chip, or extra strips, to hold the proper spacing during soldering.

a4aaf3faa253044e36eabc736120c4cd33018209 (resized).jpg

#4 7 months ago

MRS

stvns78

Pinside member

Keller, TX

<1y 22,800 56 1 1

Quoted from sparky672:
Just a note/observation about your new IC sockets; how do you know if you flowed enough solder to connect the socket pins to the top traces which are completely covered/hidden by the socket?
I see copper on top traces near pins in a couple places... are these top traces making an electrical connection with your socket pins?
[quoted image]
On mine I'm seeing at least seven pins on this chip that need a connection to top traces. All are completely obscured by your socket.
[quoted image]
I like using strip sockets so I can easily see/verify that the traces on the top of the board, and under the socket, are also flowed properly. The metal pins have a collar which stands the socket up off the board so you can really see if the top traces are flowed. Also, if you need to repair a copper trace on the top of the board, this style of socket gives you proper access.
These are something you buy as long strips and cut to length. No more need to stock various size sockets. You can use an old chip, or extra strips, to hold the proper spacing during soldering.
[quoted image]

I used a jumper on the back side to make that connection as the trace on the front side was broken and not easily fixed.

Is there a reference web site I could use to see what each IC logic should be when probed?

#5 7 months ago

MRS

stvns78

Pinside member

Keller, TX

<1y 22,800 56 1 1

Quoted from G-P-E:
Sounds like the memory cap was probably not the problem but the act of working on board (connectors, etc) may have been the problem.
Make sure the case of the oscillator isn't touching one of the traces on the top of the board. It should be raised up a hair.
Get some alcohol and a soft bristle brush - clean up some of the flux on the top and bottom of board and then recheck solder joints.
The 100uF cap is old but not the source of your problems.
Before you do any more mods to that board - easiest to get a logic probe and go from there.
With logic probe & voltage meter, you want to divide and conquer - figure out where the problem is: power, clock or reset.
Very first thing to do is verify you have good power at the CPU board. Measure for 5V directly across that 100uF cap, C1. How close to 5V does it measure?
With logic probe, see if the clock divider is running or not. Can be checked at Z2, pin 9.
If pin 9 has no activity then the oscillator isn't running, check Z3, Pin 6.
If the clock is running then I would double check the board for the reset modifications you made.
Next with logic probe, see what your reset is at the CPU, U1 pin 40. Catching the actual reset pulse is unlikely with just a probe.
The quick tests above will tell you if it is a power problem, reset problem or clock problem.

Thanks for the advice. I am going to rework the clock section as I am not happy with what I did and will redo using the strip connectors as mentioned by sparky. I already measure the voltage across the cap and it's 5.0x volts.

Will report back when I probe those pins.

Thanks!

#6 7 months ago

JWK

sparky672

Pinside member

Manhattan, IL

10y 49,550 977 1

OP
Quoted from stvns78:
I used a jumper on the back side to make that connection as the trace on the front side was broken and not easily fixed.

There are at least seven top traces that connect to socket pins on this one chip alone. Switching over to strip sockets is a wise move.

OP
Quoted from stvns78:
Is there a reference web site I could use to see what each IC logic should be when probed?

Have you tried PinWiki? There is quite a bit of solid technical reference material there. "Clay's Guide", which is difficult to find now, has a huge amount of information about using a logic probe. However, this guide needs to be used with caution as I found it contains quite a few technical errors and ambiguous explanations.

I think once you rework the socket connections, you'll be good to go.

#7 7 months ago

RPT

bontango

Pinside member

5y 51,650 454

OP
Quoted from stvns78:
I am going to rework the clock section as I am not happy with what I did and will redo using the strip connectors as mentioned by sparky.

You may also try to replace the quartz with an oszillator. Years ago I had a board similar damaged as yours,
where I couldn't get the clock running, after days of soldering this helped ...

https://www.pinwiki.com/wiki/index.php/Gottlieb_System_80#Replacing_the_quartz_crystal_with_a_TTL_Oscillator

#8 7 months ago

MRS

stvns78

Pinside member

Keller, TX

<1y 22,800 56 1 1

Quoted from bontango:
You may also try to replace the quartz with an oszillator. Years ago I had a board similar damaged as yours,
where I couldn't get the clock running, after days of soldering this helped ...
https://www.pinwiki.com/wiki/index.php/Gottlieb_System_80#Replacing_the_quartz_crystal_with_a_TTL_Oscillator

I saw that on pin wiki. That will be my next attempt if the rework does not help.

Thanks for the reply

#9 7 months ago

MRS

stvns78

Pinside member

Keller, TX

<1y 22,800 56 1 1

Quoted from G-P-E:
Sounds like the memory cap was probably not the problem but the act of working on board (connectors, etc) may have been the problem.
Make sure the case of the oscillator isn't touching one of the traces on the top of the board. It should be raised up a hair.
Get some alcohol and a soft bristle brush - clean up some of the flux on the top and bottom of board and then recheck solder joints.
The 100uF cap is old but not the source of your problems.
Before you do any more mods to that board - easiest to get a logic probe and go from there.
With logic probe & voltage meter, you want to divide and conquer - figure out where the problem is: power, clock or reset.
Very first thing to do is verify you have good power at the CPU board. Measure for 5V directly across that 100uF cap, C1. How close to 5V does it measure?
With logic probe, see if the clock divider is running or not. Can be checked at Z2, pin 9.
If pin 9 has no activity then the oscillator isn't running, check Z3, Pin 6.
If the clock is running then I would double check the board for the reset modifications you made.
Next with logic probe, see what your reset is at the CPU, U1 pin 40. Catching the actual reset pulse is unlikely with just a probe.
The quick tests above will tell you if it is a power problem, reset problem or clock problem.

Ok.... after doing some rework, on the bench power supply I have the following...

Z2 pin 9 is pulsing.
Z3 pin 6 is also pulsing.
U1 pin 40 is low. However sometimes when probed it's high then goes low.

Is this expected behavior? If so I will throw it back in the machine and see if it boots.

Are U4-U6 supposed to be warm? Specifically U4 I'd almost too hot to touch? I was reading that could mean a bad RIOT.

Thanks!

#10 7 months ago

MRS

stvns78

Pinside member

Keller, TX

<1y 22,800 56 1 1

OP
Quoted from stvns78:
Ok.... after doing some rework, on the bench power supply I have the following...
Z2 pin 9 is pulsing.
Z3 pin 6 is also pulsing.
U1 pin 40 is low. However sometimes when probed it's high then goes low.
Is this expected behavior? If so I will throw it back in the machine and see if it boots.

Also is U4-U6 supposed to get hot. Specifically U4 is also most too hot to touch. I read that could mean a bad RIOT

Thanks!

#11 7 months ago

GPE

G-P-E

GPE

Omaha, NE

12y 75,800 2,750 4

Clock circuit appears to be working. Pin 40 being low says your reset section is not working (part is being held reset).
Do you have the reset module plugged into TC1? If so, unplug him and try measuring pin 40 again.

U4 may be bad but you can't even get to checking him until resets are working.

#12 7 months ago

MRS

stvns78

Pinside member

Keller, TX

<1y 22,800 56 1 1

Quoted from G-P-E:
Clock circuit appears to be working. Pin 40 being low says your reset section is not working (part is being held reset).
Do you have the reset module plugged into TC1? If so, unplug him and try measuring pin 40 again.
U4 may be bad but you can't even get to checking him until resets are working.

Nothing is plugged into TC1. I did the reset mod per PinWiki at the same time I did the abatement on the clock section. I had checked all the connections and everything was fine. I used the D1811-10

20220831_204121 (resized).jpg

#13 7 months ago

MRS

stvns78

Pinside member

Keller, TX

<1y 22,800 56 1 1

OP
Quoted from stvns78:
Nothing is plugged into TC1. I did the reset mod per PinWiki at the same time I did the abatement on the clock section. I had checked all the connections and everything was fine. I used the D1811-10
[quoted image]

I probed the DS1811and noticed the pin closet to the input power was low. If I wiggled it, it would go high and so would pin 40. Continuity was fine at the pin so I guess I had a bad DS1811. This is why I always buy atleast two of a thing. I installed the spare and now Pin 40 on U1 stays high. Now that's out of the way how do I check U4 or should I just see if it boots?

#14 7 months ago

MRS

stvns78

Pinside member

Keller, TX

<1y 22,800 56 1 1

I am pleased to report that the MPU is booting and doing so reliably after replacing the DS1811. Even the thunk mod I did on the driver board is working fine. However I noticed a new issue.

The three lamps on transistor Q8 on the aux lamp board do not fully go out when the lightning flashes in the head. I first probed the transistor and base remains low. The other transistors pulse from off to low. I then kept moving back to U6. Pin 6 remains low where as Pin4 on Q7 pulses from high to low like all the others. I probed U4 Pin9 and it behaves like all the others on U4 so this tells me the U6 or the 7405 is bad. Is that a logical conclusion?

This problem may have been present since I got the machine and just never noticed.

20220831_230627 (resized).jpg

20220831_230705 (resized).jpg

#15 7 months ago

TOX

ChrisHibler

Chris' Pinball Repair

Chesterfield, MO

11y 117K 9,317 46

I’m sure that problem was there prior to any other repairs.
Common problem.
You need a CEN-U45 or equivalent.
—
Chris Hibler - CARGPB #31
Http://chrishiblerpinball.com/contact
http://www.PinWiki.com/ - The new place for pinball repair info

#16 6 months ago

MRS

stvns78

Pinside member

Keller, TX

<1y 22,800 56 1 1

Quoted from ChrisHibler:
I’m sure that problem was there prior to any other repairs.
Common problem.
You need a CEN-U45 or equivalent.
—
Chris Hibler - CARGPB #31
Http://chrishiblerpinball.com/contact
http://www.PinWiki.com/ - The new place for pinball repair info

Replaced the transistor with one of the two spares on the board and the problem has resolved.

Thanks

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