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jammaster
November 27th, 2016, 12:48 AM
Hello!
I have fixed my 5154 power supply.
I have changed the power resistors with bigger ones. capacitors ...
I have powered up the monitor and all work fine apart from a tight screen image. (I haven't try to tune the horizontal freq pot...)
The limiting current resistor mounted with the front power led have blewed up completly. (I believe it's R1...I haven't got it's value??? Do i need to put a bigger one? I know she drop the tension a LOT between the two big filter capacitors)
And the most severe problem.
My THT started to whistle in emiting a "red" light (amorce). The glue on the secondary cable output started to melt with a white smoke.
This transformer is very strange: an horizontal THT (8KV) with the secondary focus block (25KV).
This FBT seem to be a "thordarson" or "RCA" type?
If anybody know the ref?
thank a lot...

mikey99
November 27th, 2016, 07:32 AM
Did you replace all the electrolytic capacitors in the power supply ?
5154 power supplies run very hot, and the original capacitors are rated at only 85 degrees C
so most likely they are all bad to some degree

Which power resistors did you replace and what values did you use ?

What was the original problem with your 5154 ? Not powering on at all ?

You shouldn't turn the monitor on again until you determine whats wrong.
If the HV is running too high it could be the cause of the smaller display area.
Since most flyback transformers use a voltage divider to derive the focus and G2 voltages
those voltages would be higher too, meaning the screen could be excessively bright and the
focus would be way off. Do you also notice either of these symptoms ?

There's a good thread on 5154 troubleshooting here:
http://www.vcfed.org/forum/showthread.php?9462-IBM-5154-Troubleshooting

jammaster
November 27th, 2016, 08:28 AM
http://theangel540.free.fr/WP_20160825_003.jpg
http://theangel540.free.fr/WP_20160825_004.jpg
http://theangel540.free.fr/WP_20160825_005.jpg

1W 1.2Ohms resistors. (x2)
"all" the caps but c11/c13/c14 not changed but tested at ESR meter.

The wima line filter caps are stock, but I'll chane them.

Value of R1?

mikey99
November 27th, 2016, 08:56 AM
What wattage were those resistors originally ? I see in the schematic R41 and R32 are 1.2 ohm but it doesn't
provide the wattage. Do you have the 5154 schematic ? If not PM me your email and I can send you scans of
the schematic and some other troubleshooting pages from the manual.

Its usually not a good idea to increase wattage on a resistor, because instead of the resistor burning up, it allows
other components to be damaged if there's a problem.

In the schematic .......R1 shows to be a 4.7 ohm 10 watt

jammaster
November 27th, 2016, 09:25 AM
the stocks R32 and R41 are 1/2 watts.
PM sent