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Main => Monitor/Video Forum => Topic started by: kyle__ on June 24, 2020, 12:13:04 am

Title: Help with a (generic?) H-12 Universal Chassis
Post by: kyle__ on June 24, 2020, 12:13:04 am
I'm trying to use a somewhat generic universal chassis labeled, "H-12" on the board, and "EPSP648" in some places in the listing I bought it on. I can't find much information about it.  The tube I'm using is labeled WG 1220872.  It came to me in an otherwise empty cabinet.  No boards/chassis etc, but was told it worked.

Anyway, I can't find docs on this exact board, but from reading various sources, I thought I had things hooked up right.  However, whenever I power it on, it pops the circuit.  I am not using an isolating transformer but thought I read newer chassis didn't need that.

When I measure the windings, I get 2.3 and 5.6 ohms.

If there are other pictures or measurements needed, I'd be happy to provide.
Title: Re: Help with a (generic?) H-12 Universal Chassis
Post by: kyle__ on June 24, 2020, 12:14:26 am
It didn't like so many pictures in one post.
Neck board.  The other two pictures I took probably aren't that useful (model label on the tube & screen printing of the board name on the chassis).
Title: Re: Help with a (generic?) H-12 Universal Chassis
Post by: grantspain on June 24, 2020, 03:33:26 am
are you running the chassis from a iso transformer?
Title: Re: Help with a (generic?) H-12 Universal Chassis
Post by: PL1 on June 24, 2020, 03:55:03 am
are you running the chassis from a iso transformer?
I am not using an isolating transformer but thought I read newer chassis didn't need that.


Scott
Title: Re: Help with a (generic?) H-12 Universal Chassis
Post by: Ken Layton on June 24, 2020, 11:03:14 am
That chassis REQUIRES operation from an isolation transformer.
Title: Re: Help with a (generic?) H-12 Universal Chassis
Post by: kyle__ on June 24, 2020, 11:35:11 am
Oh.  OK.  So, is that something you can tell from looking at it, or the model?   How does one figure that out?

Edit, also ordered this from Jameco: https://www.jameco.com/z/ITR300-Power-Transformer-Isolation-120VAC-120VAC-300VA_181315.html
Title: Re: Help with a (generic?) H-12 Universal Chassis
Post by: Ken Layton on June 25, 2020, 12:03:40 am
I can tell by looking at the chassis. There would have been a large yellow transformer in the power supply section. That would have been part of a switching regulator power supply. Since it didn't have that transformer, this is a chassis that needs an isolation transformer.

By the way the transformer you ordered is a bit overkill for the common monitors. Here is what most games requiring isolation use:

http://www.arcadeshop.com/i/1346/monitor-isolation-transformer.htm
Title: Re: Help with a (generic?) H-12 Universal Chassis
Post by: kyle__ on July 01, 2020, 09:50:57 pm
So .... if I plug in the chassis to the isolation transformer, and plug it in, it blows the fuse on the transformer.  Did my plugging this in without an iso transofrmer kill it; is it a lemon of a board; or do I just have it hooked up backassward?
Title: Re: Help with a (generic?) H-12 Universal Chassis
Post by: grantspain on July 02, 2020, 01:24:32 am
check the diodes in the bridge circuit and the regulator
Title: Re: Help with a (generic?) H-12 Universal Chassis
Post by: kyle__ on July 02, 2020, 06:39:21 pm
I tested all the diodes I could identify.  They seem fine.

I don't know if it's related to what's happening, but what are these circled in white here?
The short wires jumpered to one of two pins.
Title: Re: Help with a (generic?) H-12 Universal Chassis
Post by: kyle__ on July 09, 2020, 08:30:59 pm
Well, I decided to try yet another new chassis, and it lives!

So either my naive rough handling killed that first chassis, or it was a lemon.    As a bonus, this one had a degaussing coil and one page (duplexed) of documentation.    It's not perfect, but it works enough for my proposes. 

Before I bundle this into the cabinet again, what is this E pin for?
Title: Re: Help with a (generic?) H-12 Universal Chassis
Post by: grantspain on July 10, 2020, 02:28:53 am
crt earth, its the single wire that comes from the dag earth that surrounds the back of the crt( the metal braid)
absolutely critical