Progress on the SB-220 meter front.
This is the guinea-pig amplifier that gets the first pair of these substitutes. This should be a "beauty shot", but the bright white meter faces get overexposed.
The red wire on the plate meter no longer goes to point "A" on the meter board, but has to get moved here, to point "F".
This bypasses the original 3600 ohm resistor in series with the winding of the stock meter. The resistors on the Plate meter's pc board add up to 1000 ohms. They take the place of the resistor that gets bypassed.
The wires to the grid meter are a bit short.
I'll have to come up with a fix for that, if I'm going to market them as a "DIY" solution for a blown meter.
I still have no setup to illuminate these meters. The two brown wires that fed 5 Volts AC to the lights on the old meters should get taped up, at least for now.
For now, the right-hand meter reads grid current only. I'm going to try making it read the high voltage by changing the three 1.5-meg 2-Watt resistors on the amplifier's meter board to a series string of six 510k 2 Watt.
Should work.
More to come.
Later.
73
This is the guinea-pig amplifier that gets the first pair of these substitutes. This should be a "beauty shot", but the bright white meter faces get overexposed.
The red wire on the plate meter no longer goes to point "A" on the meter board, but has to get moved here, to point "F".
This bypasses the original 3600 ohm resistor in series with the winding of the stock meter. The resistors on the Plate meter's pc board add up to 1000 ohms. They take the place of the resistor that gets bypassed.
The wires to the grid meter are a bit short.
I'll have to come up with a fix for that, if I'm going to market them as a "DIY" solution for a blown meter.
I still have no setup to illuminate these meters. The two brown wires that fed 5 Volts AC to the lights on the old meters should get taped up, at least for now.
For now, the right-hand meter reads grid current only. I'm going to try making it read the high voltage by changing the three 1.5-meg 2-Watt resistors on the amplifier's meter board to a series string of six 510k 2 Watt.
Should work.
More to come.
Later.
73