A 6100 90 deg tube swap.
Needed to get a MH (tempest conversion) running. The 6100 tube was completely toast. Red/Green guns were 0 and Blue was faint. I honestly think the blue was just someone turned up the HV to see the lines because the Maze is not blue. Plan was to fully test this 90 deg swap theory. So pulled the monitor and started.
I pulled out the 100deg tube and removed the yoke and rings. And I took the neck board over to the table to change out the female connector. I pulled a CR-23 connector from a defunct 19K4600 chassis that was available and put that in it's place.
The connector was a match for the board with the exception of PIN 4 on the socket. PINs 3/13 are not used, and are a blank spot on the connector. There is no hole on the board for PIN 4. So I bent the pin under the socket and installed it.
Dropping the tube in and putting the yoke/rings on and reconnecting everything was standard issue. I didn't bother trying to set their position other than putting the rings in the correct place on the neck. Connected it up to the game and turned it on and was greeted with an image where the Z axis appeared to be shorted on. Since the game had been running with a blue image I thought maybe the board had an issue. So I dragged the monitor over to a nearby Black Widow. Same deal. Yanking out the connector on the bottom of the neck board (color inputs) had no effect and proved that something was going on with the monitor. Didn't have enough time to deal with this where I was so into the car and home it went.
At home I was able to reproduce the problem on my Star Wars and so I started debugging. I pulled another CR-23 connector from my stash and swapped it out on one of my known working neck boards. Tried this configuration with the same results.
At this point I went back to the original neck board and set the unit up in a configuration where I could start poking around. I looked at the following
- Heater voltage was correct,
- I could disconnect either the Brown or Black single wire from the deflection board and the image would go away (expected of course)
- Tried a different deflection board as a sanity check on heater voltage
- Looked through the color gun circuits on the board thinking maybe I've been shorting something
- Validated HV (was 1k low) but correcting this made no difference
Ok, I've exhausted the little stuff so time to back out from the problem. The tube I selected for the swap was sitting in the shop from a previous "repair" on a Cheeky Mouse game. (flyback died and no reproductions available). So I was assuming it worked. I've got a tube in my Star Wars that I know works so I proceeded to pull apart my SW while continuously swearing because this is the 4th time I've done this in the past month.
Out goes Cheeky Mouse burn, in goes Tapper burn. Power up and same Z axis maxed out image. Ah, so what' the hell, it's clearly something with this setup. Decided to start comparing tubes and schematics.
- According to Tubular both of the 90 deg tubes share the same pinout/heater/voltage specs but the Anode was 100v diff (negligible)
- Comparing to the Schematics I found issues....
- Looking up the OEM tube I found it has the same pinouts as the 90 deg tubes? Ok WTF.?
- Turns out it's errors in the Schematic for Printing 2 of the 6100 manual. Printing 3 is corrected: [edit: most of the pins were incorrect in printing 2, I just highlighted 2]
- Ok, so that means that the tubes are compatible and something else is going on. But what?
- Well the only thing sitting between the Tubes and the Chassis is the connector. Maybe it's not a direct match?? Placing the 2 types of connectors side by side you'll note that pins 4 (we saw that above) and 12 are NOT populated in the original CR-24 connector but they are populated in the CR-23!
- If we look at PIN 12 we note that it's connected to the GRY wire, which is GND. Obviously PIN 12 is NOT supposed to be used at all on a 6100 so I pulled the connector off the board, folded PIN 12 under (like I did for PIN 4) and reinstalled.
- After the above change I connected up the monitor and it works!!!!
So a successful 90 deg tube swap into a 6100.. You can read more about
the fitment and results after this debugging session in the linked thread.
