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IBM 5154 EGA monitor on Tandy 1000 SX

aitotat

Experienced Member
Joined
Aug 13, 2009
Messages
351
Location
Finland
Some time ago i mentioned a problem with IBM 5154. Now i've finally decided to take the monitor to a professional for repair. So now i've been testing the monitor again for detailed problem report.

The 5154 does not work properly with Tandy 1000 SX. The colors or brightness doesn't seem to be quite right. I looked at schematics and pin 7 of the RGB connector is connected to green (like pin 4). IBM CGA connector specifications says that pin 7 is reserved and EGA mode 2 uses it for secondary blue. Could this be why the 5154 does not work quite right with Tandy 1000 SX?

The 5154 does show the symptoms i mentioned in the other thread with clone XT and 100% compatible CGA adapter. But at least the colors are correct.
 

Great Hierophant

Veteran Member
Joined
Mar 22, 2006
Messages
1,920
Location
Massachusetts, USA
The signal on pin 7 may be for composite video, just as on the RCA connector. That may be what is causing your colors to be wrong.

Try this:

Get a short DE-9 extension cord and cut pin 7, then connect one end to the SX and the other end to the EGA. If the colors are "right", then your problem is solved.
 

aitotat

Experienced Member
Joined
Aug 13, 2009
Messages
351
Location
Finland
I connected the IBM 5154 EGA monitor to the RGBI (CGA) connector on Tandy 1000 SX. IBM 5154 EGA monitor is compatible with CGA adapters.
 

aitotat

Experienced Member
Joined
Aug 13, 2009
Messages
351
Location
Finland
IBM 5154 is now fixed (TDA2653A Vertical deflection circuit needed to be replaced) so I finally build the adapter for Tandy 1000 SX. It helped and the picture now looks correct. IBM 5154 produces much better picture than the Commodore 1084S-P1 that I used until now.

So pin 7 must not be connected when using EGA monitor with Tandy 1000. Tandy supports composite through pin 7 that is normally reserved on CGA. The adapter I build connects pin 7 to ground just in case since I wasn't sure if CGA adapters ground it or leave it unconnected.
 
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