G07 doing the "Hula" wave

Thorvald

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Another issue on my old G07 is it's doing the "hula", slow wave up the screen.

I've checked the large resistor as per Randy's chart and get 106vdc (instead of 120vdc) at the white wire end and 160vdc (instead of 145vdc) on the other side of the resistor.

Anyone have any experience with this symptom before I go tearing apart everything in the 900's?

Thanks
Tim
 
have you tried adusting the B+ or is it maxed out at 106 vdc? i had those waves before cause B+ was too low. or like the other guys said filter cap.
 
Thanks guys, I did a Zanen filter cap kit many years ago and the machine has only had extremely light use over the years (it was my first... :).

I recall it had a small hula wave when I first got it but it would tend to go away after heating up for a while. Now after a few years, it's quite strong and doesn't seem to go away.

I can't recall if the Zanen kit had the filter cap so I'll dig it out.

B+ adjustment only just read about that last night while reading some of Randy's docs, didn't even know it was adjustable! Will try that first.

Thanks for all the ideas!

Tim

P.s. Unfortunately after this issue, I have to figure out my dead red gun problem (hence why looking for a rejuvenator in Ontario). With the color bars on the screen, my scope shows the same signal on R119-R121 going straight to the tube pins, so it looks like all the signals are good.
 
Ok, just adjusted R909 to get 120v (actually 123vdc, that pot is too old a flakey, need to give it a cleaning) but still get the hula wave just as bad as ever, so I guess that's out.

I checked my old paperwork and yes it had a Zanen #101 (G07) kit installed years ago, so I'll have to see if that included the filter cap.

Next I guess is to chase down all the 900's as per Randy's chart.

Cheers
Tim
 
I picked up a 200v 680uf cap tonight just in case (thanks Bob) but since my scope showed a clean 123vdc on the B1, I don't think it's the issue.

I'll start scoping out like mad tonight and see if I can find something, my B&K490a arrives this weekend so I'd like to have this issue licked so I can fix the red gun (hopefully!) and have a nice happy Defender again.

Cheers
Tim
 
I personally wouldn't spend the time to scope it unless the main filter cap AND a new cap kit didn't fix it.
 
Well tonight I made up a quick cable for my IIgs monitor. Can't get the horizontal sync to stay but thats likely because the Defender isn't composite and the IIgs is (need something to combine the sync). However I was able to view the image and sure enough, the hula wave was still there!

So that ruled out the monitor... so I started to unplug various boards and what do you know, it was the sound board! It is somehow inducing the "wave/hula" on the monitor.

So my monitor is actually fine (besides the dead red gun), so now I can concentrate on the sound board issue after I beat on the tube.

Will post here what I find out just in case someone else gets this.

Cheers
Tim
 
I'm just posting here so I can be notified of any replies. I'm curious what caused this to happen, esp with a Williams sound board.
 
Well now that my monitor is mysteriously behaving (red gun that is), I'm back to the hula issue.

I checked all the inputs to the sound board (voltages) and they are all clean, no AC, so that one is out.

On a whim, I swapped out the main supply with a PC Switching supply (that I keep wired up for Defender repairs) and sure enough, the hula/wave was gone... even with sound!

The only item I can find that catches my eye when running on the original power supply is the +12v, it sits around +11.8 without the sound board and down to +11.45 with the sound board. Perhaps the +12 section of the power supply is weak causing all sorts of issues.

I'll grab a replacement LM723 and swap that out, then remeasure the test points around the +12v section (currently almost all of them read slightly low but the input +26vac, actually +30vac, is good).

The fun never ends :)

Cheers
Tim
 
Well I replaced the 723 on the +12v side, the rail is stronger now but still gets a little hulu.

I think (as per other thread) that I've narrowed it down to a grounding issue, not 100% sure but it cleared up almost totally once I ran a temporary ground to connect the power supply to the sound card (potential difference issue I assume).

Will keep at it and update as I dig.

Cheers
Tim
 
Grounding

I had a cabinet that did the same thing. I had to run new ground wires from all of the boards, coin door, monitor chassis, and the power supply transformers. After that, all waves, hula, and movement ceased. Good luck.

Randel
 
Have you tried running it without the degaussing coil plugged in? I wonder if the thermistor could be behaving badly and causing a high resistance, partial activation of the degaussing coil.

Worth a try :)
 
I had a cabinet that did the same thing. I had to run new ground wires from all of the boards, coin door, monitor chassis, and the power supply transformers. After that, all waves, hula, and movement ceased. Good luck.

Randel

Really delayed update to this but I finally got around to beating this with a stick again. I had just performed the 4164 mod and figured I'd work on the hula issue.

Sure enough, now the "hula" was crazy and all over the map so I knew something had changed. She has been sitting for a few years so after all the usual check connectors, chips, etc.

After reading all the posts on grounds and seeing that was something I was last chasing back in 2011, I ran a new ground wire from every board to each other, BAM the bad hula was gone and I was back to a gentle "wave".

Then I swapped out the supply for the PC supply and the wave is pretty much gone (every slight one there).

---

So just wanted to close out this thread the grounding (and supply) has temporarily solved this for me. I'll dig deeper but very strange as all the factory grounding straps are in place and good continuity.

Time to play more.

Cheers
Tim


P.S. Tip for anyone swapping out the power supply while testing, don't forget that the coin door controls Ground wire goes to the old power supply and not to the Rom board. Had me going for a few minutes (okay I admit it, a good hour with the logic probe, beer and bored Wife) before I traced that back and found the floating ground wire. Doh.
 
Well what do you know... it only took 6 years to get around to it but the fix is in!

(Time for all the old-timers to *sigh* along with me)... it was an IDC connector!

Never got around to replacing them on my own machine (always do it on other peoples lol) and sure enough with the wife watching the monitor poked and proded everything until the hula started to "twitch".

The was the main power connector to the CPU board. Replaced the pins with the good square molex (black) and the connected with the good crimp pins and voila! Works PERFECT now even with all those temp. grounds removed.

---

So as per the normal faq of repairing games... step 1. Replace all those horrible IDC's lol.

Time for a beer!

Cheers
Tim


P.S. I also performed the 4164 ram mod, added a jumper to select between + and - Sync for future testing and installed an AnyPin SRAM replacement (no more batteries, thanks Rob!).

Now I just need to find a local Joust or Robotron to work on next.
 
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