All I think about is "look at all the pretty colors"

First, to clarify -
The optos in the TZ clock are not 'more sensitive'. The different part # is simply because the minute optos needed longer legs. The exact optos can be replaced with others - you would just need a standoff to raise the height. Because of the distance needed, they (Williams) needed a non-standard lead length on them.

The difference (as far as I can remember, I'd have to go downstairs and double-check. One of the downsides to having a game in pieces, tracing stuff out is difficult. :/) is that that clock optos are NOT connected to the 10-opto board, but connected straight to the switch rows.

So, unlike other optos in the game, that are latched via LM339's on the Opto Board, the optos here are driven directly by the column driver (on the 8-Driver PCB). The column driver, however, is controlled by a TIP102 (since the board could be re-used to send that driver to a solenoid or flasher), so it can handle the current.

For all optos, you can replace them with QVEs. All they are is a IR receiver connected to the LM339, and an IR emitter, connected to a resistored +12v. (Hence the heavy resistors on the 10-opto board.)

Edit: I forgot to clarify - The reason the LM339's are in use is to filter out the columns used. On the 10-opto board, when "Col 1" is active, the LM339 will then only report for optos 2-6. When the 'Col 2' is active, the other group of gates are active, so only optos 1, 3-5, and 7 are reported.

The reason that the 8-Driver board doesn't have an LM339 is simple - only one column is used, so no gate is needed.

Part 2 - Why optos are ACTIVE when they're blocked..

The IR reciever (Phototransistor) allows the row circuit to be closed (i.e. switch closed, current flowing from collector to emitter) when it detects IR light. When there is no IR light detected, the phototransistor is open, stopping current from flowing.

Since the ball blocking the IR beam is activating the switch, this is why in switch test that -

An ACTIVE switch is one that is not in its normal state. For regular switches, this is when the switch is closed, current flowing. For optos, this is when the switch is open (the IR beam is broken, switch is open).

This is also why, when running switch tests, and looking for help on here, you need to pay attention to whether the switch is Active - has an "(A)" after the name/status) or simply 'On'. 'On' is a misnomer, since optos are supposed to be on, other switches aren't.

I'm not 100% sure I have faith in that - however, since those QVE's are no longer available (not only the .0086's used in TZ, but that model in general) I couldn't verify.

My knowledge came from RGP back in the mid-90's, when optos on the clocks first started dying because of the heat. Someone had contacted the maker about ordering them, and was told they were special order, and that the .0086 part-number addendum was referencing lead length and ordering them was limited to WMS. (They wouldn't even let him order any..)

Now, if new information came to light recently, then my info could be outdated. However, I'm not sure about why the clock optos would need to be 'more' sensitive.. it's not like the clock hand is translucent..

about to change the opto's on my NGG at switch #46 (?), if I remember correctly. so I bought a new upper play field as well, since it needed to be changed. and of course it is now turning into a teardown , shop job etc. I blame you, altan, for making me think i can do this stuff! If i am not mistaken you had the pics/posts up of a TZ that you redid beautifully. (was that you?). It was such a good documentation that I got the crazy idea to completely tear down mine! I must say I learned an awful lot from your site and posts about it. did you ever document a NGG teardown? lol
now i am about to order the rubber kit from steve at pinball resource but I don't have my ID numbers. very nervous! lol

"more sensitive" might perhaps be better stated as "tighter tolerances"; Quality Technologies appears to have binned parts for Williams based on slightly better specs than allowed by Williams. Perhaps QT had a hand in the opto design for the TZ clock and wanted to operate the parts a little further away from the edge? Unfortunately, I don't have the outline drawing that would help prove/dispel the ".0086 means longer leads" folklore, just the production document.

(it is interesting to note, however, that QT opted for parts with a significantly higher minimum VR.)

QVE11233.0086-1.jpg

Interesting abouty the doc, thanks for sharing!

And yes, maybe tighter tolerances is a better description then. It would also explain why the hour optos were also .0086 part numbers (when the leg length didn't have to be any longer)..

altan raised a good point about IC(on); the Fairchild and QT data sheets for the QVE11233 both specify 0.5 mA as the minimum value, but neither specify a typical value, so you're dealing with the luck of the draw with non-QVE11233.0086 parts.

As for why the need for the ".0086" part in the clock, that's the only opto usage of which I'm aware that drives the switch matrix directly; in all other cases there's an LM339 voltage comparator ("buffer") that drives the switch matrix based on the opto transistor voltage drop. Modern designs of the clock board, such as Ingo's, use the buffer approach to drive the switch matrix and are thus immune to the flaky opto problems that plague the clock.

See my post above. The TZ clock optos are NOT tied into the Opto Board, but are instead driven from the 8-Driver PCB in the backbox.

This is because those optos are all on the same column (Col 9), and don't need a latch driver. (As opposed to the Opto boards, which have two columns running into it, and depending on which one is active (being scanned by the CPU) activates the associated row for low (non-active) optos.

Ah, I see your confusion. The manual is misleading. J5 is the opto board OUTPUTS - J5 is the switch matrix row/column lines.

The manual should have said that the clock board was connected to J208-1, -2, -3, -4, etc.

So what happens is this -
The MPU polls Col 1, Col 2, - etc, up to Col 8.
When Col 6 & 7 are active, it activated the associated LM339s. While those columns are active, the MPU then scans through each ROW, and looks at the status of the row input.
Then the MPU activates Col 9 through the 8-driver PCB, and does the same for the rows. No LM339s need to be latched, since ALL eight optos are on the same column.

--Mike

The whole thing regarding this has to do with CTR or Current Transfer Ratio.
The important factors that differentiate the QVE11233 from the QVE11233.0086 are the IC(ON) -- Collector current when output transistor is turned on and VCE(Sat) -- Collector to Emitter saturation voltage also when the output transistor is turned on.
QVE11233 has max VCE(SAT) of 0.4V when IC is at 0.5mA
Williams spec'd a part that has a max VCE(SAT) of 0.8V when IC is at 10mA.
That's 20x the current drive!

Given the same emitter forward input current (or "IF"), the QVE11233's CTR is too low, the special ordered QVE11233.0086 was barely above borderline high enough.
For the amount of energy put into the emitter, the detector can switch a maximum current load while retaining a minimal forward voltage drop. This ratio is called the Current Transfer Ratio or CTR. Some people call this 'sensitivity', some call it 'drive capability'. In a way, they're both right.

At one time, I did an analysis from beginning to end on current levels and voltage drops. This was an effort to determine if the OPB804 would be an acceptable sub (it isn't). I believe the analysis is on RGP somewhere.
As it turns out, there is a VERY significant current load on the opto output -- a current that exceeded the rated QVE11233 and OPB804 IC(ON) while maintaining that maximum 0.4V VBE or voltage drop. Due to the excessive current load, the VBE voltage drop was increasing so high that the comparator's input voltages were with the "no-man's land" zone - resulting in indeterminate values. Would sometimes work, sometimes not. Got progressively worse as time went on.

Rather than ***FIX*** the problem the right way, Williams had opto's custom made that would maintain a lower VBE while switching the high current load. In addition to this, they drove the opto's emitter VF/IF at a quite high level in order to get as high as possible CTR. This drove the emitter inputs and opto outputs with a fairly high current which resulted in a shorter life span.

If somebody were to redesign this board *properly*, they would NOT special order even more future failure optos and directly drive the comparators. Instead, they would put a transistor on the output of the opto and let the transistor do the high current switching (see many later Stern designs for the right way to do this).

This may help a little.
-note 2 comparators are renamed
A-16807 5768-13536-00 Twilight Zone schema + correctie+clock.jpg

Big thanks for this. Interesting read - I got most of it (though admittedly, current goes over my head. Logic and voltage I got.. current has ALWAYS messed me up. )

I still think that 'sensitivity' is the wrong word in this case, since the phototransistor detects IR light, by saying it's more sensitive, that means that LESS IR light would be needed to cause it to latch/unlatch. In this case, that's not true. (Is it? Did they measure light brightness needed to the photo?)

It's probably better to just say that Rows 1-8 on the minute board connect to the switch column row wires. The row wires hit all other switches (in their row) and the opto board.

Reference zaza's modified image - that's perfect. (Well, except for a few junction dots missing. )

hmm, found 3 missing dots. If there were >4, I would have corrected the picture.

Sure, if you look under the playfield, you will see that the wires coming from the clock are looped into the connector (J5 A-16807) and from there following the path (via other switches) to the CPU.

The wires are going from connector to connector, from switch to switch.
IMG_TZ wire row.jpg

Drive capability is closer to being right but sensitivity also works (I prefer "Current Transfer Ratio" -- more current on input to force more current on output).
Don't think of it as an 'on/off switch' but more of an amplifier which gets maxed out.
Low input current results in low output drive capability, high input current results in high output drive capability.
If there was a light load, it wouldn't take much forward current on the IR emitter to cause the base voltage (opto detector input) to rise and fully turn on or "saturate" the transistor on the output. Since it is a heavy load, the output transistor requires more umph on the transistor base in order to switch that higher load. This is done by increasing the IR emitter current.

This works much the same was as a standard transistor. Light load and transistor requires light base current to turn on. Heavy load and the transistor requires higher current to turn on. Biggest factor in this is 'how much current' does the base require to control the high current load. For a transistor - this is called "gain" or hfe, for an opto this is called current transfer ratio or CTR.

yep, that was you! Have gone on to become fairly adept at fixing and restoring(I use that word loosely around here! lol) machines and even do some soldering on circuit boards when necessary. interestingly I have an opto problem on my NGG that i am about to "fix", I hope. But seriously, your postings of the TZ really helped give me the confidence I needed to begin to try to do this stuff on my own. always thankful.