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Here are two links that might be helpful: https://www.dragons-lair-project.com/tech/pages/alg.asp https://www.dragons-lair-project.com/tech/images/alg_gun.jpg I know that the Who Shot Johnny Rock gun does not have the mercury switch for the reload feature, so that might prevent you from being...

That placement is correct, and there should be another one actuated by the flip-down side panel.

Check / replace all the electrolytic capacitors in the sound generation section. I tried to merge the two sections of the schematic and note the suspect caps. If you were to pick one, I would replace C25 (Base of Q13, 10 uF, 25V) first - as it is part of the White Noise generator and can wreak...

Very helpful - thank you. The Rev B Manual (which seems to be the most commonly available) shows it as a fixed value resistor:

You can use a good ol' MPSA06 for Q13 (White Noise Generator). Here's a diagram showing the Rotary Switch Functions and the Free Game Switch Settings:

Thank you for posting the video showing the diagnosis and repair! Kudos to the individual for providing a superb explanation of the theory of operation, compromises made due to the technology available at the time, and identification of the counterfeit parts. That was very informative and...

Seems that might be a monitor issue or something in the video connector / cabling - as red appears to be missing altogether (and swapping game boards did not restore / change the appearance).

You can also go with a divorced 50VAC Center-Tapped transformer, such as this one from Hammond, to supply the 6100: https://www.hammfg.com/part/167P50 More details in this thread.

Testing before permanently mounting the fan - whatever your choice - would be a good idea.

Yes - the AC in the stator windings produces an associated magnetic field of varying magnitude and direction - which acts like a degaussing coil operating continuously in the vicinity of the 6100. This causes very undesirable variation in both the display color and image stability. Bad idea...

Just one additional thought related to the post above: cold solder joints on the power supply PCB itself (diodes, filter cap, etc.) They are notorious for passing voltage at no-load or light load, but the voltage drops significantly under load.

I have found this one to be affordable and accurate: https://www.amazon.com/DER-EE-ELECTRICAL-INSTRUMENT-CECOMINOD066433/dp/B00S298KJO

Reminiscent of our 1943 board set that had (we think) AC applied to it. Virtually every ROM was bad.

Glad to hear you are making progress. I can't tell if that's rust on the diode spring, or well-aged dielectric grease. Removing the dried grease residue and soaking the springs in vinegar to remove the rust would be preferable. The goal is to minimize the resistive losses between the cups...

If the pins are heavily oxidized, it will be necessary to add fresh solder to get any kind of wetting action. But, don't stop there - remove all the solder you just applied (old &new), and clean the pins carefully with a soft brass brush. The solder will only wet properly when the oxide layer...

If you have not already done so, reflow ALL the header connections on the Deflection Board - and look for them elsewhere as well. After all the years of use, thermal cycling, and plugging / unplugging connectors, it's guaranteed there will be cold solder joints.

Check to see if Pin 11 of the LS157 (@D6) goes low when you press the SuperZap button. If that checks out, check Pin 9 of the same LS157 (@D6) to see if it goes low when you press the button. Lastly, confirm that Pin 13 of the Pokey (@C/D2) goes low when you press the button. If all this...

Working on a Stunt Cycle PCB which exhibited erratic and abnormal throttle control. Motorcycle would not wheelie and Attract Mode cycle speed was way too fast. Could never build enough speed to jump more than 13 buses. Read through the manual and focused on the Horizontal Motion Control...

Not sure if you checked here and also saw high shipping cost, but the switch is $19.95: https://shoprelayspec.com/Honeywell-Microswitch-Switch-1TB12?srsltid=AfmBOooy6NR59f-yikIcWyq6oUU5Vb6Pfwr7XtvomQHKGKRhkLYhKyp9

1995-98 for TDS 744A isn't exactly new. :ROFLMAO: It's also a PITA lugging around a suitcase-sized scope.