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wh20 weird reset issues

4.9 volts is marginal. Drop from power board to CPU should be less than 0.03v. Have you replaced the connector on the loom yet at j114 on power board. This is always my first step.
 
pinballmania said:
4.9 volts is marginal. Drop from power board to CPU should be less than 0.03v. Have you replaced the connector on the loom yet at j114 on power board. This is always my first step.
Click to expand...
Not yet Andy but just by re-seating J114 on the power board and J120 on the CPU it is now up to 4.94v on pin 32 on the ROM and stopped resetting so far...... Guessing this is my cause rather than an ASIC issue? If so do you replace both J114 and J120 usually or is it always J114 at fault ?

Cheers again

Kev
 
Usually J114. It takes the power out to all the boards, whereas 120 just takes it in to the CPU. So roughly three times the current through 114
 
Check your pcbs are all screwed down nicely as well as this can effect the pull on the 5v line.
 
pinballmania said:
Usually J114. It takes the power out to all the boards, whereas 120 just takes it in to the CPU. So roughly three times the current through 114
Click to expand...
Andy, what is the shut off boltage for the watchdog - I read it was 4.7v but the cpu board is getting no where near that and it still resets - does this mean it's something else ???

Cheers Kev
 
Hi
i see you measured 4.98V at TP2 on the driver board, that just seems way too low. It would be worth measuring that again but with the meter set for ac volts, you're ideally going to measure something like 0.5V ac or less being better. Any higher and it would point to C5 being poorly and needs replacing
bob
 
Thanks bob will try that. What would you expect on tp2 normally ? Over 5v dc ??
 
no it should be 5.0V spot on, but can be between 4.75V to 5.25V and everything should be happy!
measure TP2 (5V) WRT to TP1 (0V) on the board itself, rather than to a cabinet braid or other metal point
cheers
bob
 
pinballtoys said:
no it should be 5.0V spot on, but can be between 4.75V to 5.25V and everything should be happy!
measure TP2 (5V) WRT to TP1 (0V) on the board itself, rather than to a cabinet braid or other metal point
cheers
bob
Click to expand...
err!!! so why is 4.98v no good then ???
 
4.98v is fine. If you have resistance in the contacts then when current demand changes you'll get a voltage drop over that resistance. The transients are too fast to see on meter, which gives an average reading, but long enough for the wAtchdog to see a voltage drop and reset. It can be other things, but until you replace that connector, and clean up the header pins, you can't progress.
 
OK
pinballmania said:
4.98v is fine. If you have resistance in the contacts then when current demand changes you'll get a voltage drop over that resistance. The transients are too fast to see on meter, which gives an average reading, but long enough for the wAtchdog to see a voltage drop and reset. It can be other things, but until you replace that connector, and clean up the header pins, you can't progress.
Click to expand...
OK Andy thanks for that.
 
well it is! but maybe not all the time!!
The bridge rectifier converts ac to DC but there's still a lot of so called voltage ripple that the filter cap C5 is designed to smooth out. If this capacitor has lost this ability over time then occasionally the voltage may dip below the magic 4.75V causing a reset.
Your meter probably only updates its display three times a second so you wouldn't necessarily witness a voltage drop. By measuring the ac voltage across the capacitor this shows how effective it is at smoothing, ideally it should have no mV, eg no ripple voltage
hope that makes sense?
bob
 
SO today I switch it on and after a minute it resets and then re-boots with 'Factory settings restored' so are we now looking at another issue here ??? I metered the voltage against ground and TP2 and I get 5v DC and 0.002 v AC is that anything to be concerned about @pinballtoys @pinballmania ?

Cheers Kev
 
Well before I did anything else I got an ASIC remover tool and pulled the asic - cleaned it up and re-installed it and since then (touch wood) not a single reset !!! looks like that may of been the culprit

CHeers Kev
 
newdos said:
Well before I did anything else I got an ASIC remover tool and pulled the asic - cleaned it up and re-installed it and since then (touch wood) not a single reset !!! looks like that may of been the culprit. CHeers Kev
Click to expand...

so basically the first thing that Andy Legend suggested! - a lesson there for all of us, if @pinballmania ever suggests a fix, that's gonna be the answer 99% of the time

sorry to resurrect this dead thread, i came across it while looking for something else, but it makes good reading from first to last post
(obviously not now, as this is the last post)
 
Well the reason I was searching was because of something I heard on a podcast- so I was collecting reasons for resets. Have you -
Replaced J114 and its header pins
Checked wall voltage
Checked all boards secured
Replaced thermistor in power box
Reseated all ribbon and power cables
Reflowed solder to BR2, C5, LM323 voltage regulator
Checked (replace or reflow) flipper coil diodes
Tried seeing if it happens with disconnected DMD
Tried seeing if it happens with disconnected sound board
Tried replacing those things in the list above
Finally, considered that tweak to increase the output of the LM323 from 4.95 to 5.1V or so by adding a resistor between it and earth

?
 
cooldan said:
Well the reason I was searching was because of something I heard on a podcast- so I was collecting reasons for resets. Have you -
Replaced J114 and its header pins
Checked wall voltage
Checked all boards secured
Replaced thermistor in power box
Reseated all ribbon and power cables
Reflowed solder to BR2, C5, LM323 voltage regulator
Checked (replace or reflow) flipper coil diodes
Tried seeing if it happens with disconnected DMD
Tried seeing if it happens with disconnected sound board
Tried replacing those things in the list above
Finally, considered that tweak to increase the output of the LM323 from 4.95 to 5.1V or so by adding a resistor between it and earth

?
Click to expand...
thanks Matey - will take a look at these issues. It will be a reseat of the ASIC againa first then J114 and see what happens

CHeers Kev
 
Machines that have a small extra driver board to the R.H.S. of the DMD driver board , e.g. TZ, STNG, Corvette e.t.c. have their 5v. supply from a very nasty, troublesome cable junction between the very short 5v. connection between the power supply board and the control board, it is split at this point using an arrangement of plugs and sockets. This cannot be seen! It is buried underneath the cable runs to all the upper boards. When it becomes bad, it causes resets at ANY time. Just tapping the cables at this point will sometimes cause resetting. Cut it out, stamp on it! Solder the new joints and use shrink tubing. Every TZ (4) I've serviced or operated had this fault sooner or later.
 
Thanks Matey but unless I'm wrong a WH20 doesn't have this extra board ??? My TZ does so I think I know what I'm looking for

Cheers Kev
 
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