Quoted from ramegoom:Not an inherent problem, but rather a "potential" problem. If it were inherent, every single Twilight Zone clock would have failed early on. IMPO, the problem is created by the excess heat built up from the incandescent bulbs - four of them - that cause the internal temperature to rise above the maximum ratings of the opto switches - which were rated at 85degC (operating temperature) back then.
Not entirely sure that I buy the entire argument here. No debate that the heat from the incandescent lamps were an issue, just as there is little debate (generally) that these machines have survived well past the wildest imaginings of their designers and are still (for the most part) functioning as designed. So one must take into consideration the time in which the designs were done before getting on the 'this was a poor design' bandwagon. (not so much in this thread, but it pops up fairly often in general)
That said, some consideration needs to be given for the changes that electronics experience as they age. Electrolytic and tantalum capacitors being the worst (and most obvious) offenders, but the other circuitry can show it's age as well.
When I picked up a TZ fairly recently the clock board (the original) was baked! Not unexpectedly so knowing the history of the machine. So it was replaced with a shiny new Rottendog board that I had on hand. Single board, new optos, LEDs, what's not to like? Granted, it largely follows the original design as far at the circuitry surrounding the optos go.
And all looked good for the first week or so, but then the return of the random 'Clock is broken' error.
Have checked the connectors the related bits and discovered nothing obvious. Now, that said it causes me to wonder a bit. Photo-transistors being by their nature an analog device rather than digital are apt to be a bit more susceptible to issues impacting the signal levels from the sensor. Bad cable, bad connector, corrosion/oxidation on contacts and the like. Or potentially age related drift in the LM339 analog comparators that receive the signal. Any of these items, individually or in concert could cause the signals from the optos to fall into that grey zone between 0/1 and cause the kind of random issues referred to.
Now, to be honest I have never seen one of the 'Ingo' board (or their 'Lock When Lit' U.S. variant) in person. And it should be said up front that I do not have a stake in this either way (aside from just wanting the darn fool error to go away), but it does not seem like an unreasonable approach to a solution to integrate the additional circuitry on the clock board to provide a bit more 'drive' on the signal lines in order to avoid the thresholding issue that seems to be in play here. Plugging in a new clock board is a fair bit easier for the average game owner. Not to mention less risky if your PCB rework skills are not the best.
Granted, I may yet find that I am actually chasing a marginal connector or dodgy wire in the harness but just though it was worth the observation that there could be more involved here that might first meet the eye.
Finally a friend
If I repeat that often enough, perhaps I will start to believe it!
But, if that is what it takes in the end...
Did not much care for that flavor anyway.
Centerport, NY
