G07 - No Red

Thorvald

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Donor 2011
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Starting a thread on my troubleshooting of my G07 in my Defender to figure out my Red gun problem.

I've done the following:

- Swapped Red & Green wires on Defender PCB to see if that was the cause, no change, Red gun still dead.
- Swapped Red & Green wires on the neck PCB of the G07, no change, Red gun still dead. Proved my signals from my G07 main board are good however as the "green" was visible when red was told to come on in test patterns.

- Connected Apple IIGS monitor to Defender PCB, picture is good, proves Defender is ok.

- Connected Fluke ScopeMeter to Green and Red wires on neck PCB, signals looks the same when displaying colour bars.
- Connected Fluke ScopeMeter to Green Cathode (GK) and Red Cathode on neck PCB, signals looks the same when displaying colour bars. Leads me the believe the Red gun is actually dead.


Ordered up a B&K 490A Rejuvinator, arrived today. Connected to monitor, all guns tested in the "Good" range and no leakage or shorts.

- As a last resort, I swapped the Neck transistors X102 and X103 just "in case". Powered up unit, problem still persisted, no red.
- Connected Fluke ScopeMeter to Green and Red wires on neck PCB, signals looks the same when displaying colour bars.
- Connected Fluke ScopeMeter to Green Cathode (GK) and Red Cathode on neck PCB, signals looks the same when displaying colour bars.
- Still leads me the believe the Red gun is actually dead...

So now I'm stumped... the 490A thinks the Red gun is good but still no red on the monitor. Blue and Green are fine.

My next step once I've let the monitor sit for a while and again discharge it, will be to lift the two resistors leading the Gk & Rk and jumper the over each other so the Red is feeding the Green Gun and the Green is feeding the Red Gun. Just to totally eliminate the neck PCB.

Will update once this last test is done but if anyone has a suggestion, please feel free.

Cheers
Tim
 
You have a rejuvenator now, did you try rejuvenating it yet?

First try to clean the red gun, if your rejuvenator has that function. There could be just dirt or dust on the gun. If it doesn't look any better after cleaning, then try rejuvenating it then.
 
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Actually I didn't, since the red tested good, I left it alone.

Once it sits for a bit, I'll zap er and try the cleaning feature to see if that helps (B&K 490A so I should be good for that).

Thanks!
Tim
 
Thanks Fudd! I'm pretty sure the main board is good as I swapped the green and red wires from the main monitor PCB going to the neck PCB. The Main Board Red circuitry had no problem driving the green gun, and the known good Main Board green circuitry could not drive the Red gun, hence why I'm concentrating on the neck PCB or Tube.

---

I did a clean & balance cycle with the 490a. None of the guns would drop very much after spiking when pressing the button for each colour (Red would only drop down to .8 before it stabilized, pretty close for the others).

The manual indicates that it should spike and smoothly drop to some low value and that you should stop at 0.2, so since I never got that low, I assume it's ok.

(Too bad the Rejuvenator didn't also have a build in gun/pattern test... that way you could eliminate the monitor PCB's altogether).

---

I'm hesitant to do a rejuvenate cycle yet until I swap the signals on the neck PCB especially since the test/clean&balance all indicate the tube is quite good.

Cheers
Tim


P.S. Looks like I should also pickup some spare neck PCB's for future troubleshooting just in case :)
 
Thankfully I had a idea... what if the clean and balance had actually done something but the pots on the monitor were all out of whack for the red level...

Sure enough, starting playing around with the red cutoff and voila! Red again. Now the cutoff is nearly at it's max but at least it's back.

So no idea if the Rejuvenator did anything but it may have.

Now I need to fix the green (which looks totally yellow really) and then set up all the puts (white balance etc).

---

I notice there doesn't seem to be a document on how to setup the various gun cut-offs and drives, can't all be just trial and error?

Cheers
Tim
 
when ever i need to do it i center all the drives and gaines and go from there. it works good for me. as usually thers not much to do it. always looks good to me in the center positions.

Peace
Buffett
 
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