Twilight Zone
Bally, 1993Quoted from rkahr:Don't cut the traces - use vinyl screws/nuts to isolate the heat sink from ground so the resistor hack can be un-done more easily. I get the man/machine logic...I'll be around if that calculus changes.
Great idea; thanks.
OK, after further testing/re-flowing/replacing solder, my conclusion is there's now no resort on this but the Last Resort.
Question: on the pics below of the Last Resort mod done to the same board/different version (A-12697-1 vs. my TZ's A-12697-3), what's the green jumper for? (PinWiki doesn't show this jumper as being necessary in 4.8.17.)
Thanks.
Jumpers fix bad connections. Any damaged area could require a jumper. Pin wiki just shows the common ones.
Quoted from donjagra:Jumpers fix bad connections. Any damaged area could require a jumper. Pin wiki just shows the common ones.
Well yes, I realize that but I just thought it was a possible related variant to the Last Resort mod--because the left side of the jumper runs to the negative leg of the capacitor at C9.
Also: on the right side of the jumper, there's no related component--it's just spliced into the trace ahead of the 22-Ohm 1/2 Watt Resistor.
Is this perhaps just an alternative to cutting the two traces on the back as shown in 4.8.17 below?
You WILL have to cut traces if you use this method. That's the only way to isolate the LM323K from ground.
I don't know what is going on in the first picture...it's too dark to tell.
The hack in the second picture is one that I did, for a board that had a regulator on the low end of spec.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info
Quoted from RobKnapp:OMG my ST:TNG is now rebooting when flippers are presses. And in attract mode. This is not going to be easy. My Technical skill is lousy .
There is a very well documented guide to help you find and fix the problem. The steps are ordered based on a balance of likelihood, ease of diagnostics, ease of fix, etc. Follow the steps in order!
http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Game_resets
Start at section 4.8 and read. You'll learn a ton! You'll find "Step 1: measure line voltage" in section 4.8.3.
Quoted from NM:Curious what's your recommended method of cutting the traces?
My favorite method is a dremel with a ball cutter bit.
It won't want to drive itself across the board.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info
Quoted from RobKnapp:OMG my ST:TNG is now rebooting when flippers are presses. And in attract mode. This is not going to be easy. My Technical skill is lousy .
You can do it--just methodically follow the steps of the guide.
Thanks to Chris and all contributors for PinWiki!
Don't cut the traces - if you are going to do the hack do it in a way that has a hope of being undone. Replace heat sink screws with vinyl screws/nuts from home depot/lowes. If I remember correctly I put a vinyl nut between the board and the heat sink AND on the rear of the board. This isolates the regulator from the copper traces. Tie resistor between ground test point on the top side of the board and the casing and to the heat sink. photo-944.JPG. Incidentally I did this and my PZ still reset... which drove me to design the circuit board I mentioned earlier in the thread.
Quoted from rkahr:Don't cut the traces - if you are going to do the hack do it in a way that has a hope of being undone. Replace heat sink screws with vinyl screws/nuts from home depot/lowes. If I remember correctly I put a vinyl nut between the board and the heat sink AND on the rear of the board. This isolates the regulator from the copper traces. Tie resistor between ground test point on the top side of the board and the casing and to the heat sink. . Incidentally I did this and my PZ still reset... which drove me to design the circuit board I mentioned earlier in the thread.
Sounds great in theory--let's see if I've recapped these steps correctly:
Component side: vinyl screws through the heat sink, then vinyl washers against the solder mask under the heat sink.
Solder side: threaded screws poke through the PCB, then simply tighten with vinyl nuts.
(In other words, just basically just float the heat sink off the solder mask with vinyl washers--so no metal is touching solder--and secure the vinyl screw threads with vinyl nuts.)
And in so doing, this precludes having to cut the two traces on the solder side and the single trace on the component side leading to C9.
Then, just solder a ring terminal end to one end of the 22 Ohm 1/2 Watt resistor and place it under the lower vinyl screw--and lastly, solder the other end of the resistor to the ground test point (TP5) directly below TP7.
NM, you got it - particularly like your improved wording of "float the heat sink" as it is more descriptive. Vinyl screws come in limited lengths so plan on cutting down the screw so your board fits back in the back box.
Rob.
Quoted from rkahr:NM, you got it - particularly like your improved wording of "float the heat sink" as it is more descriptive. Vinyl screws come in limited lengths so plan on cutting down the screw so your board fits back in the back box.
Rob.
Very good Rob.
Looking forward to rounding-up the vinyl parts at Lowes and giving your very clean, Non-Hack Version of the Last Resort Mod a whirl!
Quoted from joe2012:hi nm,keep us posted if you do rkahr's fix. thanks joe
You got it!
EPILOGUE 
:
Happy to report this game is now fixed via the Last Resort Mod (and with no hacks thanks to Rkahr: what a fantastic idea)!
The voltage on my PDB's TP2 has now soared from the initial pathetic reading of 4.8 V to now a stout 5.17 V!
Rather than cutting/hacking the three traces, I used Rkahr's excellent suggestion of floating the heat sink off the board with nylon hardware to eliminate the ground--and then installing the 22 Ohm 1/2 watt resistor on the component side of the board (with one end of the resistor connected to a ring terminal under the bottom nylon screw securing the LM323K, and the other end of the resistor soldered to the ground at TP5).
Got the nylon parts at Lowes and the inventory is simple: two 8-32 X 1/2 nylon machine screws (Lowes item #138981) , two #8 nylon flat washers (use the thin ones, Lowes item # 139061), and two 8-32 nylon hex nuts (Lowes item #138980).
Reason to use the thin nylon flat washers is if you're reusing your LM323K like I was (the legs going through the through-holes were already cut of course and were almost too short...made it work with the thin flat washers mentioned above).
Anyway, many thanks to all contributors and a big thank you to both Chris Hibler for his help here (and for PinWiki!)--and many thanks to Rkahr for his fantastic hack-free version of the Last Resort Mod shown directly below!
TP2 "Before":
TP2 "After" With The Last Resort Mod Installed (Rkah's Hackless Version shown!):
Awesome!
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info
Quoted from joe2012:thanks nm.if I do it I'm going to use heat shrink on both leads and hot glue that sucker in place. thanks again joe
That's a good idea Joe--I thought of that too after looking at the pics: the ground lead is dangerously close to that 20V TP @ TP7!
Although the solder connection is firm, might as well do it while you're there--as the investment is just a penny or two (LOL)!
Thanks again to all responders!
Clean work NM. Remember though, a meter can hide what an O-scope can show. This blurry picture is about 2 years old - it shows what a brief collapse in the 5 volt line looks like on a PDB - yes, with the resistor jumper in there to push up line voltage. It's tough to see for a lot of reasons (I took it with my old blackberry, my 30 year-old yard sale-purchased scope (that I revived from the dead) doesn't have screen captures, resets were pretty random so I kinda had to get lucky to catch it), but the steep drop and rapid recovery are clear enough. And it can be enough to take 5.1+ volts down to a reset. Even with the hack you may want to consider using my new daughterboard to move the MPU off the 5 volt line. It is certainly as well thought out as my "Float the heat sink" update to the resistor hack.
photo-979.JPG
Rob
Quoted from rkahr:Clean work NM. Remember though, a meter can hide what an O-scope can show. This blurry picture is about 2 years old - it shows what a brief collapse in the 5 volt line looks like on a PDB - yes, with the resistor jumper in there to push up line voltage. It's tough to see for a lot of reasons (I took it with my old blackberry, my 30 year-old yard sale-purchased scope (that I revived from the dead) doesn't have screen captures, resets were pretty random so I kinda had to get lucky to catch it), but the steep drop and rapid recovery are clear enough. And it can be enough to take 5.1+ volts down to a reset. Even with the hack you may want to consider using my new daughterboard to move the MPU off the 5 volt line. It is certainly as well thought out as my "Float the heat sink" update to the resistor hack.
Neat shot of the scope dip.
Indeed: it will take many games on the clock yet before an All-Clear can be issued.
If I run into further problems, I'd be happy to purchase and try one of your daughterboards--as you've clearly demonstrated a successful ability to think outside the box/present new solutions to old problems.
Many thanks again Rob!
Quoted from rkahr:my 30 year-old yard sale-purchased scope (that I revived from the dead)
LOL...a little OT on the scope. I have access to all kinds of state of the art equipment if I need it, but I inherited a really old B&K 1477 from my dad and use it in my shop. It's enough for pinball.
Gah, I wish people would stop calling the added resistors to the LM323 circuit a hack or a last resort, the manufacturer of the part recommends a resistor here and Bally used the resistor in the circuit on their power supplies from 1977-1985 (R50 a 2.2ohm resistor). I use it as a supplemental part of all power supply rebuilds. In addition to replacing the LM323 and the Bridge and Cap and usually the Molex input and output pins I add an 11 ohm resistor to increase the voltage from 4.9 ish to a solid 5.1
The cuts to the traces on the board can be simplified down to the single cut on the right side as pictured here
http://img-f.pinside.com/201403/1504456/200755.jpg
Instead of making the cut on the left side in the picture and on the front side of the board simply cut off the small cap at C9 just between the regulator and C5 on the front of the board. This cap is no longer in circuit when the other 2 cuts are made so it's simpler and cleaner to just remove the cap.
I would not recommend adding the resistor to the front as pictured later in the thread. Also to the OP please make sure that you soldered the resistor to the ground test point in your picture. If that is just wound around it can come loose and if it does come loose you will potentially be in a lot of trouble. If the resistor tie down to ground is lost you can end up with the full 12Volts coming out of the regulator to all of the 5V circuits in your game, which is a lot of busted IC's.
Quoted from kbliznick:Gah, I wish people would stop calling the added resistors to the LM323 circuit a hack or a last resort
I think the Last Resort nickname is here for good: Clay's Guide first called this mod the "Last Resort" many years ago--and when he removed his guides, PinWiki referred to it by the same name.
Quoted from kbliznick:The cuts to the traces on the board can be simplified down to the single cut on the right side as pictured here
http://img-f.pinside.com/201403/1504456/200755.jpg
Instead of making the cut on the left side in the picture and on the front side of the board simply cut off the small cap at C9 just between the regulator and C5 on the front of the board. This cap is no longer in circuit when the other 2 cuts are made so it's simpler and cleaner to just remove the cap.
If I'm hearing you right you're saying only one cut only on the solder side (the one in the right circle).
But your last sentence above refers to two cuts...guessing by second cut you mean cutting the ground leg on C9?
So in summary: your method involves only cutting the single trace, and then removing C9?
Quoted from kbliznick:Also to the OP please make sure that you soldered the resistor to the ground test point in your picture. If that is just wound around it can come loose and if it does come loose you will potentially be in a lot of trouble.
Thanks, yes mine is wound and soldered to TP5.
Quoted from NM:If I'm hearing you right you're saying only one cut only on the solder side (the one in the right circle).
But your last sentence above refers to two cuts...guessing by second cut you mean cutting the ground leg on C9?
So in summary: your method involves only cutting the single trace, and then removing C9?
the first time I was shown this mod it involved making 3 total cuts. 2 on the back of the board as pictured above plus one more cut on the front of the board just to the left of the lower leg of C9. This completely isolates the ground traces from the voltage regulator I originally followed these directions until I looked closer at what was being done and realized that 2 of the cuts were unnecessary if you removed C9 instead. If you make those 2 cuts and leave C9 in, then C9 does nothing as it is no longer in the circuit. So I found it cleaner to simply remove C9and eliminate 2 cuts.
So yes, simply make 1 cut and remove C9.
I'll have to look again and try it out first but I believe even cutting C9 is probably not necessary either, as it is just a cap between the 2 legs of the regulator
Quoted from kbliznick:I'll have to look again and try it out first but I believe even cutting C9 is probably not necessary either, as it is just a cap between the 2 legs of the regulator
C9 was meant to be a high frequency noise filter. But, it wasn't connected correctly on the board.
http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#WPC_Power.2FDriver_Board_Layout_Error
As such...it really does no good.
Keep in mind that there were several PCB revisions to the board. Without knowing all of them precisely...I'd be careful.
I do like the idea of lifting C9 instead of cutting. Although, repairing a cut trace is trivial.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info
Quoted from ChrisHibler:I do like the idea of lifting C9 instead of cutting. Although, repairing a cut trace is trivial.
Chris: what do you mean by "lifting C9 instead of cutting"?
(Perhaps through breaking the ground of the heat sink via Rkahr's nylon hardware idea?)
Thanks!
Quoted from NM:Chris: what do you mean by "lifting C9 instead of cutting"?
(Perhaps through breaking the ground of the heat sink via Rkahr's nylon hardware idea?)
Thanks!
I should have said, "lifting one end of C9 instead of cutting the left side of the trace".
I'd really have to make sure this severs the trace from ground.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info
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