Basic flyback transformer testing

BEdmonson85

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I'm fairly new to to working on these old monitors. I have an old Vs. Uni cabinet with a bad Sanyo 20ez monitor. It's blowing the 300mA fuse on power-up. I replaced the HOT, hoping that'd solve the problem. The flyback "looks" ok but now that's where my suspicions are turning. Does anyone have any tips/tricks for basic flyback testing with a simple multimeter. I'd rather not spend the cash on a new one if I can help it.

Regards,

Brian E.

P.S. If anyone has a link to the flyback datasheet I'd be much appreciative if you'd share. The monitor schematic I have here doesn't have the pin-outs clearly marked.
 
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Just a quick update, I pulled the flyback off the board to see if I could get it to fire up without the monitor connected. Sure enough the fuse held and I got audio from the audio board. Looks like I'm gonna be ordering a new flyback today. Regardless, I'd still love to hear any tips or methods for simple flyback testing procedures.

Thanks again,

Brian E.
 
You can do a quick check of the flyback with a multimeter. Set your meter to measure resistance and then, using the schematic, measure each coil. The coils are represented on the schematic by looping lines as shown in this drawing from pins 7 to 8 and 8 to 11. There should be a fairly high reading across these pins, though I am not sure what it will be because the schematic is not that specific.

In addition to that test you can look for shorts between circuits by checking each input point to the points it should not be connected to. For instance measure point 7 to all points except 8 and 11. There should be no connectivity (an infinite reading).

This is the manual for the 20EZV, I am not sure that the EZ is the same. Also, the flyback is the shaded area in the lower right corner of the first page.

http://arcarc.xmission.com/PDF_Monitors/Sanyo_20EZV_(R-C)_Rev2_Schematics.pdf
 
Yeah, the monitor I'm working on is the EZV, it was a miss-type on my part. I did do some resistance checks on a few of the coils before posting. I did get some pretty low readings across pins 7 & 8 and 8 & 11 (around 1.5ohms) which didn't seem too normal. But when i checked the reading across 7 & 11 I got around 3 ohms, but assuming 8 being the center tap for that coil I thought maybe it was normal. All and all I'm not to concerned with testing it at this point. As I mentioned, I decided to pull the flyback off and power up the board with the monitor disconnected to see if the fuse would hold without it. The fuse did hold and I got audio from the audio board. So, unless I'm totally missing something I feel Its pretty safe to assume the flyback is toast. Got a new one on its way. Thanks much for your help.

-Brian E.

EDIT: BTW, Oryk Zinyo, thank you for that schematic. The one I have is the original copy that came with the cabinet, so damn old you can hardly read it. The one you linked is much easier to read :) Defiantly going in my drawer.
 
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While it is very likely that the flyback is the source of your problem it may not be. By removing the fly you opened many circuits and another component in one of the now open circuits may be the problem.
 
yes, you can test transformers, coils, etc with this.

You just need to know which lugs are normally connected inside the transformer/coil, then put your leads on it to get a reading...
 
Thanks for the link, Mod. They offer the schematic for the kit on the site as well. Looks like I have most of the parts here. Think I'll put one together on some proto-board tonight.
 
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