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  #1  
Old 10-11-2017, 09:22 PM
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lnx64 lnx64 is offline
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Tandy CRT swap

Not a television, but couldn't decide which section to put this in. Asking for a friend.

He's trying to swap out the CRT to a Tandy 80 model 4, but he can't get an image on it. He has the heaters lighting up, but there's nothing on the screen.

The CRT in the Tandy 80 model 4 is usually a 12VCMP31

The CRT's he's tried are:
1. MN1215H8AU - CPJ310N1U (Two numbers on the same CRT)
2. MP1433H8AU - CPJB340AHE (Two numbers on the same CRT)
3. 310KLMA

He has found that if he puts the Tandy's monitor in where the replacement CRT's are pulled, it produces an image that's far too bright. I was thinking maybe a G2 control on the Tandy's flyback could help? But he says there's no G2 control.

Hopefully anyone can help! Thanks in advance.

Last edited by lnx64; 10-11-2017 at 09:26 PM.
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  #2  
Old 10-12-2017, 09:55 AM
zeno zeno is offline
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Is it a monochrome set ? If so no G-2 control. Most CRT's
probably use the same basing & apx voltage. Start with the
original tube & write down the voltages. Then do the same
with a new one. IIRC the Tandys used a modified RCA B&W
Get some nudies & maybe we can figure out the chassis or see
if its got a KCS### stamped on the chassis.

73 Zeno
LFOD !
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Old 10-12-2017, 10:54 AM
tom.j.fla tom.j.fla is offline
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Zeno, that was true for TRS-80 model 1. That monitor was a moded KCS201. The model 3 & 4 had a custom monitor made by RCA still based on the KCS201, 12 volt only setup and hor. and vert. sweep. Had ttl video. By the by still have 6 model 4s' in use for our farm operations. Who says we yanks didn't know how to make good stuff. All the best,Tom.J
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Old 10-12-2017, 11:46 AM
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Quote:
Originally Posted by tom.j.fla View Post
Who says we yanks didn't know how to make good stuff. All the best,Tom.J
I've never heard anyone say such a thing. I'm knocking myself out all the time trying to get stuff made in the US or Canada, and sometimes Japan.

By the way, what are the model 4's used for?

I used to have the TV the model 1 monitor was based on, it was made in 1977. It would be nice to get hold of another.
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Old 10-12-2017, 12:35 PM
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Electronic M Electronic M is offline
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The brightness and sub-brightness (a service adjustment) may have been cranked to get the most from the old weak CRT, and may need to be backed down with a healthy one installed.
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Old 10-12-2017, 01:09 PM
tom.j.fla tom.j.fla is offline
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Jon A., Our 4's are used for bookkeeping, crop and live stock records and inventory control for material for the up keep of equipment and buildings. Yes we have the latest wiz-bang 'puters for the web and streaming but the 4's do records keeping a heck of a lot better then the new stuff. All the best, Tom.J
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  #7  
Old 10-12-2017, 02:26 PM
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lnx64 lnx64 is offline
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Quote:
Originally Posted by zeno View Post
Is it a monochrome set ? If so no G-2 control. Most CRT's
probably use the same basing & apx voltage. Start with the
original tube & write down the voltages. Then do the same
with a new one. IIRC the Tandys used a modified RCA B&W
Get some nudies & maybe we can figure out the chassis or see
if its got a KCS### stamped on the chassis.

73 Zeno
LFOD !
I'll see if I can get some pics of the board from him. I tried to Google it but oddly can't find anything, but yea, it's a Monochrome set.

He wanted to change it from a green phosphor CRT to amber.
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  #8  
Old 10-12-2017, 05:42 PM
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CoogarXR CoogarXR is offline
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I had a TRS-80 Model 4 shipped to me a while back. It arrived smashed. I took pictures, maybe these will help identify the CRT specs?:
Attached Images
File Type: jpg RIMG0099.jpg (87.1 KB, 39 views)
File Type: jpg RIMG0302.jpg (55.9 KB, 28 views)
File Type: jpg RIMG0303.jpg (56.3 KB, 37 views)
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  #9  
Old 10-12-2017, 08:37 PM
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Quote:
Originally Posted by CoogarXR View Post
I had a TRS-80 Model 4 shipped to me a while back. It arrived smashed. I took pictures, maybe these will help identify the CRT specs?:
Ugh, I can tell you first hand that the model III and model 4 are the biggest pains in the asses to economically shit. You pretty much have to remove the CRT and box it separately because as you found out as well their mounts don't hold up to modern logistics.
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  #10  
Old 10-13-2017, 02:36 AM
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Jon A. Jon A. is offline
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Quote:
Originally Posted by tom.j.fla View Post
Jon A., Our 4's are used for bookkeeping, crop and live stock records and inventory control for material for the up keep of equipment and buildings. Yes we have the latest wiz-bang 'puters for the web and streaming but the 4's do records keeping a heck of a lot better then the new stuff. All the best, Tom.J
That's awesome, keeps things interesting as well as keeping costs down. The only reason I use relatively recent computer technology is to keep up with the demands of the internet.
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  #11  
Old 10-17-2017, 05:44 PM
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I still haven't heard from him in a while to either relay him information here, or get information, sorry about the delay.
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