Make sure the pop switches have a gap. I know that the circuitry on these early Williams SS games did not use one-shot circuitry, meaning if the switch is closed the pop will remain energized. There is also a score switch just below with a capacitor. If this capacitor shorts I believe it can cause the pop to lock on, not 100% sure, just thought I remember reading that a while back. Just a couple things to try that can be overlooked.

If those check out, follow the schematic for the drive transistors back to a predrive chip. The predrive transistors could be shorted causing the drive transistors to lock on. If all the pops share the same predrive chip, might be the issue.

Always replace the little pre-driver transistor whenever you replace the TIP102, as they are often stressed.

Did the game ever work correctly or did you buy it broken?

Which three pop bumpers? They might be all associated to a single logic chip (probably ic6 if i was to bet on it) which could be a major clue. Specially if the main transistor tests good and they still lock on.

The special solenoid circuits do not like to be locked on. The 7408 logic gates for the pf switch fry out pretty quick when they get stuck on.

Which 3 (by number):

twpops.jpg

viperrwk

20 and 21 are driven through IC6 and 23 is driven through IC7. What are the diode readings on Q3, Q5 and Q9 compared to the rest of the 4401s?

viperrwk

do you have a logic probe? You can watch the signals at the 7408/7402 when closing switches on the pf and during solenoid test.

power off test you can set your DMM to diode test. red lead on ground. black lead probe the special solenoid 7408/7402s. All the associated pins you should see a voltage drop type of reading like if you where testing a diode. A bad reading on a gate pin would be shorted or below maybe .300 or so. Compare reading to other circuits that work.

Whoa, Whoa, Whoa!
Lets go back a few posts and catch a mistake here! The diagram of the play field is a switch diagram. Look at the top of the page shown here:
Time Warp switches2.jpg

Switches 20, 21 and 23 are the scoring switches for three of the jet bumpers (20= Left Center Jet bumper, 21 = Left Bottom Jet Bumper and 23 = the right Jet Bumper.) There are only 21 solenoid (and two flipper coils) on Time Warp. The switches in the diagram are from the switch matrix. These switches are for scoring ONLY. There should be two switches on each of the bumpers. One that is activated by the bumper skirt, and one (the scoring switch) that is triggered when the bumper pulls down. Solenoid 16-22 on the driver boards are known as "Special Solenoid". Special Solenoid switches are not part of the switch matrix.
They are triggered by the skirt switch on each bumper, and fire the solenoid circuit directly from the driver board (theses solenoids can also be fired by logic control like in the solenoid test). The scoring switches have absolutely NOTHING to do with telling the driver board to fire a special solenoid, rather, when a special solenoid is fired, it closes the score switch when it fires. If you take the score switch out and leave the trigger switch in, the bumpers will still fire, but not score.
Solinoids.jpg

The bumpers solenoids are:
Solenoid name Special solenoid # Drive transistor Scoring switch
Left center jet bumper 18 Q-4 20
Left Bottom Jet6 Bumper 19 Q-8 21
Right Jet Bumper 21 Q-10 23

Here are some links for some of the documentation for the game:
http://mirror2.ipdb.org/files/2568/Williams_1979_Time_Warp_English_Manual_no_schematics.pdf
http://mirror2.ipdb.org/files/2568/TimeWarp_Essentials_Only.pdf

Now you know which transistors to check, and where to work back from.

The reason I used the switch diagram and cropped it is because it is the only image in the manual on IPDB which individually numbered the pop bumpers so the OP could identify the pops which were not working and not to further confuse. Notice I didn't mention switches at all in my post.

The bumpers in the switch diagram labeled 20 and 21 are driven through IC6 and the one labeled 23 is driven through IC7. The one "mistake" was the typo in identifying the predriver for Q8 which is Q7 and not Q5. Brain fart is all I can chalk that up to.

Thank you for your thorough explanation for the OP on how the special solenoids work. GL to the OP on getting this resolved.

viperrwk

Dup post.

viperrwk

Duplicate post.

To properly resolve this issue in a logical way (hah logic probe) you are going to need one and know how to use it. You watch the signals as they travel through the circuits finding out where things get locked up at. Solenoid signals you can think of them cascading through multiple devices as they ramp up in current. Solenoid triggers start as small logic level signal and has to ramp up to turn on a high powered solenoid. The path is basically PIA/switch trigger to TTL chip to(maybe a second ttl) to Predriver to main driver (which is two transistors built in one package).

If you are really handy with the desoldering iron just replace all four special solenoid ICs (2x 7408 2x 7402) and the driver and predriver for all locked up circuts and you will probably fix your problem (not recommended at all unless you are very good with re work).

Send the board to a repair person (like me) who can rebuild and bulletproof your driver board. I typically charge $50 shipped back for the driver or send me the MPU and Driver and i will bulletproof both for $100 shipped back.

Andrew