WG27K7500 B+ voltage?

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Hi;
I searched the forums, searched the manual as well as the schems and I cannot get a definite B+ setting. Strange as it is not listed matter-of-factly anywhere that I can see.

In the troubleshooting section, it stated that a condition of shutdown could be caused by the B+ being over 120v?? I don't have a shutdown condition, just mentioning what was written........I figure the best way to start is with the voltages.

I have what is best described as a B&W display........on a color monitor.?!

If anyone could help me, I would greatly appreciate it.

Thank you in advance

Jeff
 
There is a resistor near the remote cable plug, either R811 or R812 or something. It's probably bad.

As for the B+, it's checked at TP202 and should be about 117vdc...
 
Thank you for the guidance.
As for TP202, I was checking the voltage at TP203 which was returning 157v!
Silk screened at that test point are the words "TP203" and also "B+ Vid" which lead me to believe that it was the test point for the B+ but alas I was wrong in my assumption which also correlates to the 7500 manual TP voltage chart.
Thank you for the clarification.
I pulled the chassis and checked all the resistors and diodes in the area of the remote board header and all looks to be within specs as per the parts list for the 7500, I did not find any failed components, (does not mean that there aren't any). During the inspection, I noticed a couple of cracks in the outer casing of the HVT, which I failed to notice during the cap-out, which proves you shouldn't solder tired!
So I will be placing the order for the replacement HVT tonight and swap as soon as I receive it.
Once installed, I will take the B+ reading from the proper test point, (thanks again) and see if the new HVT made a difference in the display.
I will update as soon as I know and thank you again for your help.
Jeff
 
UPDATE:

I received and installed the replacement HVT and have 121vdc for B+ but the display is still grey and now it appears that there is something wrong with the sync and the left and right sides of the display are very weird, I will have to post a pic when I can as I cannot explain what it looks like.

I am now leaning towards a possible board issue. The game comes up, as you can here it play and before the sync went, you could see it come up but you could not get out of attract because it did not register the "shot" on the display.

I have a board-set that I purchased as "working" so I will be installing that later on tonight to see if that makes a diffference.

Thanks again
Jeff
 
Probably not. "shot" probably doesn't register because the screen is gray. Probably that resistor I mentioned. I have to remember which it was...
 
Hi;
I checked and did not find any bad components anywhere near the header but if you are that confident that it is the problem, I will pull the chassis and go over it again.......

Here is a screen shot:

(see attachment)

Before I could "tune" the display and get it to display properly, albeit grey, now this is all I get but I do hear the game in the background..

Thanks again
Jeff
 

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The resistor in question is R811. Pull it and test it. Even if it's close but off by more than 10%, replace it.

And I assume you have the chassis matched with a tube with the proper yoke?
 
Thank you very very much for taking the time to get me that specific resistor to check. I will pull and check it tonight.
Jeff
 
AWWWWWWWWRight!

You sir, were spot-on with the call!

I pulled R811 and it is OPEN!

Of course I do not have that in stock so I placed an order w/ Mouser and should have it by middle of next week.

Again, thank you very much for the guidance. I will update the post once repairs are completed.

Have a Happy Easter.

Jeff
 
Yeeeeeehaaaaaw! It's a great day to do some huntin' with my Big Buck Hunter II with the most excellent display!

Yes, R811was the culprit. Once I replaced that and carefully removed the glass epoxy from the B+ adjustment pot, I attached my probes to the B+ test point and quickly pulled a trace! I just bumped into the Electrolytic cap near the TP and it ripped the trace right from the board. I have never worked on a chassis with such delicate traces before. Even the 30+ year old Cine chassis have more robust traces than this 7500...... I had to repair something like 7 traces......

Anyway, fired it up, adjusted B+ to 117v, adjusted the horiz hold, screen, brightness, contrast, size and position and I must say, the display is beautiful!

Thank you very much for that tip regarding R811, I never would have found that on my own.

Have a great weekend.....
Jeff
 
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