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RealMFnG

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I think the worst case scenario just happened. Now I am in search of a TV that I can harvest a tube from, if at all possible. My buddy works at a recycle center/landfill. He says they have a ton of CRT's going through his facility, so I might have a leg up on finding a suitable donor and will report back here what I find.

This is a Blast City. The tube on it is A68KZN696X
  • Donor candidate #1 is 29" Panasonic TV w/tube number: M68LGL061X
Ignoring physical fitment for now, why will this tube work or not work as a donor candidate?

Status of Donor Search:
Non-suitable:
  • M68LGL061X
 
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nem

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I'm sorry to hear that. Honestly, I think it's inevitable if you're messing with this chassis on a more regular basis. I wonder how the repair shops are handling it?

Anyway,

http://tubular.atomized.org/#s/M68LGL061X

Correct neck and heater voltage, so you're good to go to testing it.

It will need to be yoke swapped (I don't know of any consumer TVs that come with 0.20mH yokes). Save the original convergence ring set from the Panasonic. It could work better than the ring set from the Tosh.
 

RealMFnG

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I'm sorry to hear that. Honestly, I think it's inevitable if you're messing with this chassis on a more regular basis. I wonder how the repair shops are handling it?
Yeah, it blows. The red decided to die suddenly on the monitor. So reflowed solder around the neck and neck wires down to the chassis. Red still did not come back. Ordered some new color transistors, but my buddy wanted to get it back going before the parts came. An MS9 chassis that was also awaiting parts for repair had the same color transistors so harvested it from there. Still red did not come back. At that point, we were using a CPS2 as a video source. Decided to shut down and hook up a MAME PC running CRTEmu@15khz (known to work well with the MS2930) and poof!!! Arching near the yoke, a scary zapping sound, and a puff of smoke coming from the chassis.
Anyway,

http://tubular.atomized.org/#s/M68LGL061X

Correct neck and heater voltage, so you're good to go to testing it.

It will need to be yoke swapped (I don't know of any consumer TVs that come with 0.20mH yokes). Save the original convergence ring set from the Panasonic. It could work better than the ring set from the Tosh.
Thanks! I've seen that site before in my travels. Never needed it till now.

So how does one test the heater voltage on the TV? What is "G1" and how does one test that? I know I have to test with the TV's original chassis, but what pins are they?
 

nem

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Why do you have to test it with the original chassis? Swap the yoke from the Toshiba, you can try either ring set, connect a compatible chassis (MS-293X) and turn it on. I'm positive you'll get a picture. No idea if it will be any good.

For measuring heater voltage, I've been led to believe there's no easy way to do it accurately. See here:

https://elektrotanya.com/files/forum/2014/03/kepcsofutes-mero_[ET].pdf

I don't know if it will give any meaningful readings if you try to do with a regular multimeter. I haven't tried.

As for G1:


The control grid (G1) control the brightness of the CRT. It is generally placed directly on top of the cathode. If there is no voltage on G1, the electrons can flow freely from the cathode. If there is some negative voltage
on G1, the electrons from the cathode are repelled somewhat, and the screen appears darker. The greater the voltage on G1, the darker the screen becomes, because more electrons reaching the screen equals a brighter image, and less electrons hitting the screen equals less brightness.

From here: http://lateblt.tripod.com/bit71.txt

The whole thing is a good read.
 

djcalle

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@acblunden2
In general, yoke swap is always better from my experience and what I have heard, especially here with a trisync chassis.

M68LGL061X seems to be a good potential donor (with yoke swap) as nem said. M tubes are usually higher grade, so it should be nice and sharp.

As long as the neck connector, heater voltage and curve matches, you can use any tube, so I would focus on higher end, branded tubes with as little use as possible, since you're in the US, JVC D-series?

I recently did something similar myself with good results, and guess what I also used a Panasonic M tube.
 

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RealMFnG

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@djcalle, are you confirming you successfully replaced an MS2930/31/33 tube with a JVC D-series tube?

I picked up 2 different Panasonic TV's. Both had the same M68LGL061X tube inside of them. The M68LGL061X won't work for a Blast City due to fitment. So I didn't bother going further with installing a chassis for it. Will check if it is a suitable donor for an MS8 (Astro City) or MS9 (Egret II & New Astro City). If so, will keep in storage for spare. If not, off to the recycle center they go. That pic looks fantastic.
 

Hedonism Bot 2.0

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@djcalle, are you confirming you successfully replaced an MS2930/31/33 tube with a JVC D-series tube?

I picked up 2 different Panasonic TV's. Both had the same M68LGL061X tube inside of them. The M68LGL061X won't work for a Blast City due to fitment. So I didn't bother going further with installing a chassis for it. Will check if it is a suitable donor for an MS8 (Astro City) or MS9 (Egret II & New Astro City). If so, will keep in storage for spare. If not, off to the recycle center they go. That pic looks fantastic.
That is the big problem with blast/windy 2/net city. They use a semi curved tube. I have rarely seen semi curved sets- either full curve (Astro/Egret2) or pure flat.
 

Niko

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Is there anyway to verify curvature without physically fitting the tube in the cab? Maybe part of the model number?
 

ebzero89

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Provided you could make it taut, you could use a string or something to measure a known curvature as a standard then check the variance from there. A more curved surface should result in the string being slightly longer.when pulled taut
 

RealMFnG

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Provided you could make it taut, you could use a string or something to measure a known curvature as a standard then check the variance from there. A more curved surface should result in the string being slightly longer.when pulled taut
Variance with string length is damn near impossible to gauge however. Masking and such will add to the string length. Need a jig made out of cardboard and that would have to be cut precisely. Other than that, the only way to really do it is to dry fit it, report out the TV model numbers and mfg year for others.

I am eyeballing a few Toshiba TV's on CL. They look very semi flat. Hope the listers holla back. Still trying to work with my buddy that works at a landfill to secure tossed out CRT's. Let you guys know what I find.
 

RealMFnG

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Yeap, thickness of the tube from the dog ear mounts to the screen is a bigger problem than the curvature. Almost-flat curved TV's are a rare find. They were only around for a short time before curved TV's gave way completely to flat tubes.

Really have to build a listing of model numbers and mfg dates, then report it out.
 

djcalle

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@djcalle, are you confirming you successfully replaced an MS2930/31/33 tube with a JVC D-series tube?

I picked up 2 different Panasonic TV's. Both had the same M68LGL061X tube inside of them. The M68LGL061X won't work for a Blast City due to fitment. So I didn't bother going further with installing a chassis for it. Will check if it is a suitable donor for an MS8 (Astro City) or MS9 (Egret II & New Astro City). If so, will keep in storage for spare. If not, off to the recycle center they go. That pic looks fantastic.
D series are exclusive to the US, I believe, so no. My tube is from a mid/high range panasonic TV: M68KTY167X this tube is made in USA so you should be able to find it over your side of the world. According to this page, it is a rebranded AMEC: http://forum.arcadecontrols.com/index.php?topic=28188.0

The swap is successful from an electrical perspective (I have tried both with a 2930 and 2931) but I have not put it in the blast frame just yet. The curve looks right to me but I'll have to wait until it is fitted to say for sure.

Although not an exact science, I think looking for tubes/TVs from the same years that the blast was in production helps with the curve. I have added a pic of the plastic cover's date, never knew how to read these things.
 

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djcalle

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Yeap, thickness of the tube from the dog ear mounts to the screen is a bigger problem than the curvature. Almost-flat curved TV's are a rare find. They were only around for a short time before curved TV's gave way completely to flat tubes.

Really have to build a listing of model numbers and mfg dates, then report it out.
you guys made me panic for a sec :) I went to check and the panasonic donor tube is just a tad shallower from front to neck connector than the original toshiba tube, phew
 

nem

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Wait, what thickness are we talking about? Length of the neck? Depth of the ear mounts in relation to the screen?

The latter is pretty easily fixed with different length spacers for anything other than the Blast City (Astro, Net City, Sega sitdown drivers, etc). And for the Blast City you can try mounting the tube on the other side of the frame and adding spacers there.
 

RealMFnG

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Thickness from the dog ear mounts to the front of the screen. Neck length isn't an issue yet.

Will try to give it a whack at mounting the dog ears to behind the frame and using spacers. Will report back.
 

djcalle

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My tube too has the bunny ears way further from the tube, printed some spacers...will report back
Zlyrtdx.png
 

djcalle

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Spacers work fine. Curve is not 100%, there’s a little gap but not too bad.

I got good purity, convergence is ok but I can’t get geometry right. Can’t even hide defects on the edges because my hsize is set to max and it doesn’t fill the screen. All in all great results for a curb find tube, if only I could get geometry right.
YbWUxuO.jpg
Tgj5o4e.jpg
 

RealMFnG

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S-S-S-S-S-S-U-C-E-S-S-!-!-!

Found a suitable donor (well at least curvature wise). Here is a snap of the tube resting on top of a heavy duty plastic bin with the Sega Net City bezel laying on top of it. As you can see, no gaps whatsoever. If it fits the Net City, it fits the Blast, it fits the Windy II.

ApexFitment.jpg

I swooped up 4 TV's and on the 2nd try, it worked! I need an MS9-29 tube, so hoping the other two work for it. Will check the yoke readings with the BSIDE Pro and fitment this weekend. Some surgery is going to be required either way as the yoke connectors are not the same. Worst case scenario, yoke swap and washers are needed for spacers. Here are the specs:
  • Brand: Apex
  • Mfg Year: 2002
  • Model: AT2702S - EDIT: A buddy of mine found the same tube in a later model Apex: AT2708S/mfg date 2003
  • Tube Number: A68AGA20X101
    • Interestingly enough, the tube number starts with an A. B-grade/arcade quality tube
  • Tube Mfg: Thompson
 
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