Replaced the HV Diode on Battlezone- now monitor is black

TMIB

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I recently acquired a periscope-style Battlezone cab. It worked well with the exception of "bloom" where the image would grow and shrink while playing. To address this, I removed the HV cage and replaced the diode. I discharged the monitor with an HV probe (though it showed no charge when doing so). The diode boots were blackened and the springs were rusted up badly. I ended up soldering the HV Diode directly to the wires and covering it in marine grade heat shrink. This is the diode I used: https://www.arcadeshop.com/i/970/hv1809-hv-diode-atari-b-w-vector-monitors.htm

I also took the transistors off the side of the cage and cleaned the connectors with some DeoxIT contact cleaner.

Upon reassembly the game works (I can hear the audio and can tell the tank is moving around and such) but no visuals. Any idea what to check? What would I likely have broken/messed up to go from the working monitor to a non-working setup. I did not remove the monitor or do anything with the tube/neck. Sanity check: The diode has the band going toward the monitor/anode connector/red wire, this is correct right?

I replaced the diode a second time just in case I did something to mess up the first one, but the results are the same. What should I check next?


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Check the easy things first. You said you didn't remove the monitor from the cabinet. Speaking from experience, trying to remove and re-install the HV cage, with the monitor in the cabinet, requires nothing short of contortionist-style movements.

With limited visibility and lighting, is it possible that you are one pin off on the P900 connector that interfaces with the HV PCB?

When you removed the frame transistors, did you maintain the integrity and placement of the mica insulators? Did you unplug the deflection transistor headers from the deflection PCB? If so, are they in the correct locations and indexed properly (i.e. not one pin off)?

Doing all that you described, without having the entire monitor out of the cabinet to allow proper visibility and access, leads me to believe there is a connector not fully seated, a mica insulator that got displaced, a connector offset by one pin, or a short between one of the frame transistor pins and the chassis.

If you're lucky, it's one of these scenarios - which can be easily remedied - and no damage was done which will require additional troubleshooting and repair.
 
Heat shrink is not good enough. You must use silicone on the ends of the diode.
 
OP says he has a HV probe.
So, logically, the next step would be .... :unsure: :rolleyes: :cool:

And I agree, unless that heatshrink is rated 20kV or more, the HV is just going to eat through it.

If the old BOOTS are no longer useable, then "And use short pieces of silicone hose to replace the boots. '6mm (1/4") ID, 8mm OD flexible fuel/air vacuum hose' I believe was the search term." says, @andrewb
This can be found on Ebay and even on Amazon. The inner and outer diameter is important for a good fit and reasonable insulation properties.

 
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Soldering the wires to the diode doesn't work on these, because the anode wires are stiff, and the diode leads are soft. Any movement of the anode wire will weaken the leads at the diode, and they'll break.

You should dig the boots, springs, and cups out of the trash and put it all back together properly. (And as VC said, if the boots are burned, source some silicone tubing from ebay.) See this post with size and details:


The one thing you can do to improve the setup is solder the springs to the diode. I have a detailed post about this here:


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Beyond that, you may have other issues. Use your HV probe to measure what you're actually getting at the anode. If you do have HV but no picture, check the brightness and contrast pots on the deflection board. And make sure you have neck glow.

Also, to confirm that your game board and deflection system are working, use the spot killer LED on the deflection board as an indicator. With the game on and running, press and hold the RESET button on the game board, while watching the spot killer LED on the deflection board. The LED should turn on as long as you hold the reset button down, and then turn off again after you release it.

If so, you know the X and Y deflection are working. If not, you have other issues, either on the game board, and/or in the deflection system of the monitor (deflection board and frame transistors).
 
1. Use your HV probe and check the voltage at the anode. I think you'll find no voltage there.

Heat shrinking these - it's hard to solder to as it is, so the heat shrink probably pulled the connection away so you have an open.

Marine grade heat shrink not withstanding, its a problem unless it's rated for HV.
 
Is the new one installed in the right direction?


He said in the OP that the white band is toward the tube, which is correct.

@TMIB, you also said you removed the cage-mounted transistors and cleaned them. You're aware they both need isolating silpads (or micas) AND nylon washers, correct? The screws cannot be making contact with the metal cage.
 
He said in the OP that the white band is toward the tube, which is correct.

OP, you also said you removed the cage-mounted transistors and cleaned them. You're aware they both need isolating silpads (or micas) AND nylon washers, correct? The screws cannot be making contact with the metal cage.

Understood, I was just asking him to check. I have been sure of things in the past, only to find out there was a mistake after 3 hours of troubleshooting.
 
Ok, lots of great ideas here. I did some more testing/verifications and here are the results:

1) I did put the isolating pads and nylon washers in for the transistors when I cleaned them. I double checked and the nylon washers are correctly facing the right way (It'd be easy to get them reversed and thus not insulate the mounting screw.) most importantly, I just confirmed with an ohm meter that there is no continuity between the mounting screw and the cage.

2) I'm not a pin off on the connector that plugs into the board in the HV cage. Triple-checked, plus on this particular board it would be difficult to do so without bending a pin, as the spacing on the header pins and the filled-in holes on the connector would be a strong indicator something was wrong. (As a side note, there is quite a bit of room to maneuver here to get the cage in and out. This is the "periscope" model that has the monitor facing up, rather than directly at the user. It's pretty easy to slip the HV cage in/out as needed.)

3) I hooked everything up, plugged it all in, turned it on, and then used the HV probe to probe the anode while the alligator clip was grounded. No movement of the needle on the probe, no spark, no fireworks. I'd say it's pretty clear no HV is getting to the monitor anode.

4) As a diagnostic step, I used a scalpel and removed the heat shrink from the diode. I won't run it this way, but I wanted to determine if the soldered connections were still intact. They are. I don't have a setup to test continuity across the diode, but I can confirm that there is continuity between the end of the wires and the ends of the soldered leads that enter the diode.

Certainly soldering to the brittle leads is not ideal and if heat-shrink is inadequate for long-term use I will need another solution, but I don't thing I have a smoking gun yet. The monitor anode is not getting HV power, and the wired connections from the flyback transformer and the monitor anode to the HV diode are intact. What else is worth checking?

As far as a more permanent way of attaching the diode once I solve the unknown problem- unfortunately the springs and cups are long gone, so the option of soldering the springs to the diode and placing them in the cups is no longer an option without some replacement parts. The springs I took out were so badly rusted that they bent badly trying to remove them, and the cups were corroded as well. Is there a good source (short of scouring ebay for a whole HV cage) for the cups and springs do you think?

HV Cage installed.jpeg
Heatshrink removed.jpeg
 
With a voltmeter you can check if the flyback is switching and developing the lower voltages. (And confirm the input voltage to the HV cage).
With a scope you can confirm the 25kHz pulses at the #18,19,20 points of interest.


Personally, I would not power this up till I obtained the suggested boot insulator material noted above.
 
I've ordered some 6mm ID x 8mm OD high-temp silicone tubing to go over the diode when I reassemble.

Can you expand more on checking the flyback switching? I've not done that before.
 
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