View Full Version : Tandy CRT swap


lnx64
10-11-2017, 09:22 PM
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.

zeno
10-12-2017, 09:55 AM
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:smoke:
LFOD !

tom.j.fla
10-12-2017, 10:54 AM
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

Jon A.
10-12-2017, 11:46 AM
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.

Electronic M
10-12-2017, 12:35 PM
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.

tom.j.fla
10-12-2017, 01:09 PM
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

lnx64
10-12-2017, 02:26 PM
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:smoke:
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.

CoogarXR
10-12-2017, 05:42 PM
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?:

MIPS
10-12-2017, 08:37 PM
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.

Jon A.
10-13-2017, 02:36 AM
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.

lnx64
10-17-2017, 05:44 PM
I still haven't heard from him in a while to either relay him information here, or get information, sorry about the delay.