Tube Swap Question - MTG-2901/WG 7302

mann0mann

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Question for you tube swap experts...

I've got a couple spare Tovis/Happ ProVision MTG-2901 chassis and WG 7302's, these are nearly the same...

A couple of them are the fat 10 pin neck (CR23 I believe)

I found what I thought was a suitable tube. Samsung A48KRD89. It measures at the yoke - 1.8 ohms and 11.5 ohms

However both chassis produced an image that was just too big width/horizontally and in fact when trying to adjust the image, if you went too far the opposite way it would cause the chassis to go into like HV shutdown and the image would lose sync and you'd have to power cycle. So is this an issue of the yoke being just a little bit out of spec in terms of compatibility? I was assuming it was just a yoke that was either too high or low impedence for the chassis.


I found another TV, ended up being the same tube, looks like a newer version. Same model #, Samsung A48KRD89 and it measures - 2.2 ohms and 13.5 ohms

Wondering if this will get me more in line? I've been trying to read and figure out which direction that measurement reads on the Horizontal side that would affect width.

If anyone can chime in. I would appreciate it.

Thanks for looking/reading
 
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I just want to bump this thread because I am in the same boat here. I don't have a yoke to match this chassis. The picture is good and stable just about 4" too wide. I was able to swap out the H-Size VR from a 5K to a 500R and bring it in but not enough. Does anyone know what the width cap is on this chassis or any other suggestions?
 
So just to add some more data, I do have a brand new Happ Provision/Tovis monitor, with the same 10 pin neck. It's complete, with stock original tube.

It measures as: 3.6ΩH x 12.8ΩV

I've read a post from ieure that being more than 50% out of spec. on Horizontal impedance will cause issues. I'm hoping this second tube which meters at 2.2H x 13.5ΩV will get me in working range. That just barely puts me (39%) there. :-/ I'm just waiting on a frame to show up I purchased from a member here to be able to test and confirm.

behmr: would appreciate a pointer to where to pick up that pot for the remote board if that did help adjust a little. I'm just thinking ahead if I get lucky.

What's the yoke readings on your end?

It would be awesome if we could just change a cap value like you can on a K4900. Hoping someone will be able to chime in.
 
I'll send you one. PM me your address. I think yoke readings were 1.1 and 11.0 so that makes sense that horizontal is out of whack.
 
Thanks! If don't find a solution via a cap value, let me return the favor and send you this yoke from the other tube I have. It was only about a 1/2 inch each side out of spec, maybe with the new pot value, its enough to get you in business?
 
I happen to have 2 of these chassis here. One works perfectly and the other has the issue with being too wide. I swapped in the 2DS2058 at Q405 from the working chassis and now the width adjusts properly.
 
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