Electrohome G07-CBO sync modification...

KevinSin

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Hello there-

I recently purchased a cap kit for an Electrohome G07-CBO 19" Monitor from Happs and it had some additional instructions on a sync modification which prevents horizontal curl. The instructions are pretty vague and have me replace two ceramic capacitors (no polarity) with two electrolytic capacitors which we all know are polarity sensitive and could burst if installed incorrectly.

The instructions are:

On the mother board, replace C303 with the 10 uF @ 50V radial lead capacitor with the positive lead connected to the collector of X305. Then replace C501 with the capacitor taken from space C303.

I am pretty sure I have the C303 one figured out but some verification would be appreciated. As for the C501 (non polarity) capacitor, I'm really unsure which way to install it since its replacement is an electrolytic capacitor which has polarity.

I hope I explained this clear enough....please help...

Thanks a million as always.

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It's pretty easy actually. Remove cap C501 and throw it very far away. Remove cap C303 and solder in the holes recently vacated by C501. This cap is not polarity sensitive. Put a 10uf 25v cap where C303 used to be. Make sure the positive lead goes closest to the edge of the board.

Hope this helps for you.
 
<cut-n-paste> From Bob Roberts

- A Couple G07 Notes -
The first thing is the mod to the G07 chassis that upgrades the sync circuit to handle the newer PCBs eliminating top curl in the pic. The way the instructions were written seem to be hard for some to follow, so I'm going to put my own notes on it as posted in RGVAC in 1998 here & hopefully they will be easier to follow. To make the upgrade do this:


-First.. remove C501 & chuck it out.
-Second.. remove C303 & place it in the holes for C501 & solder.
-Third.. clean the solder from the hole between the 2 holes where C303 was removed & fill in the one furthest from the chassis edge with solder.
-Fourth.. put a 10 to 22uf @ 25 volt minimum in the now closer together holes at C303 with the longer positive lead going thru the hole closest to the edge of the chassis PCB & solder.
-Fifth.. after reinstallation of the chassis adjust the H hold for a center point without the curl.
Next is the original G07 chassis G07-CAO and the installation of a cap kit. This uses the same cap kit as the G07-CBO with the following changes:


1. C517, which is a 470uf 16v cap will be replaced with the caps from the kit marked for C517 (100uf 25v) & C518 (220uf 25v) at the now unpopulated site of C518. This is a parallel network which adds to total 330uf 25v across the side pin xformer T503 and since it is parallel, it makes no difference if you mix up the two positions so long as you install them with the correct polarity. Hint: Both ground sides will be closest to the flyback xformer. Note: Electrohome warned about replacing these 2 caps with a single larger value cap in any of their chassis'. This 2 cap bridge should always be used on any G07 version.
2. C302 (220uf 25v)is not used.
3. C407 (4.7uf 63v)is not used.
4. The extra cap used for upgrading the CBO version's sync will not be used.... C303 (10uf 50v).
So you should have 3 spare capacitors from the kit to have on hand for the next project that is almost certain to need one of them... well, positively if you did not have them on hand... isn't that always the way it happens :-(

Thanks to Bryan Kruzynski for supplying a lot of info to work with here.
 
Hello All-

Thank you so much for the information!

I was a little confused because I was doing a cap kit on two GO7-CBO monitors and one of them already had the sync modification half way done and the other did not have it done at all. LOL. Thanks for clearing it up.

I have developed a new problem however...I hooked the monitor back up and now it displays a 2 inch verticle section of the picture and I cannot make it any larger verticle. Horizontal is fine....
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Can you think of any other verticle adjustments or anything else I should check?

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V Height/size and V Lin should be checked. Bob Roberts mentions the two vertical output transistors mounted on the aluminum heat sink and the white "fuseresistor" next to cap C412 going bad.
 
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