JRR
Member
Caution - do not use 19" flyback for 13" Electrohome chassis
I have just run tests on a 13" chassis with the A29951-B flyback vs a second chassis with the original A19183-A flyback (called LOPT outside of North America).
My serious safety concerns are that the common 19" flyback (A29951-B) is NOT a suitable replacement for the 13" monitor. That size requires the A-19183-A flyback. The reason is the 19" flyback (A29951-x) runs with a higher HV circuitry for the 19" tube vs. the requirements of a 13" tube and this puts the monitor close to X-Ray emission with a HV of around 28KV on a 13" picture tube.
The design safety feature of the X-Ray protection circuit is bypassed when you put the wrong flyback in, so do NOT depend on the X-Ray protection circuit! That only cuts in when the B+ regulator shorts or the B+ is too high. The X-Ray protection circuit does not monitor the output of the Flyback/LOPT.
The Focus voltage go up to 11KV (19") instead of the 8KV (13") that the A19138-A produces. This is too high a voltage for these 13 inch picture tubes.
Also the Screen voltage minimum is 300VDC (19") instead of the 240VDC (13") that the 19183 generates, and this can cause people to think their picture tubes are shorted or bad when they are not.
I hope to have a cure for this - perhaps a dropping resistor in series with the HOT - but until someone comes up with a SAFE FIX do not use this flyback for 13" E-Home monitors.
I have just run tests on a 13" chassis with the A29951-B flyback vs a second chassis with the original A19183-A flyback (called LOPT outside of North America).
My serious safety concerns are that the common 19" flyback (A29951-B) is NOT a suitable replacement for the 13" monitor. That size requires the A-19183-A flyback. The reason is the 19" flyback (A29951-x) runs with a higher HV circuitry for the 19" tube vs. the requirements of a 13" tube and this puts the monitor close to X-Ray emission with a HV of around 28KV on a 13" picture tube.
The design safety feature of the X-Ray protection circuit is bypassed when you put the wrong flyback in, so do NOT depend on the X-Ray protection circuit! That only cuts in when the B+ regulator shorts or the B+ is too high. The X-Ray protection circuit does not monitor the output of the Flyback/LOPT.
The Focus voltage go up to 11KV (19") instead of the 8KV (13") that the A19138-A produces. This is too high a voltage for these 13 inch picture tubes.
Also the Screen voltage minimum is 300VDC (19") instead of the 240VDC (13") that the 19183 generates, and this can cause people to think their picture tubes are shorted or bad when they are not.
I hope to have a cure for this - perhaps a dropping resistor in series with the HOT - but until someone comes up with a SAFE FIX do not use this flyback for 13" E-Home monitors.
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