[jshorva65]

The product line of CE Manufacturing appears to be expanding, so there are some current production replacements available for certain FP twist-lock cans. Although pricey, they are made using the old Mallory production machinery. NOS units, properly pre-conditioned, may also be usable. In some cases, even the original electrolytics may be salvageable provided that their pressure seals do not show signs of stress or blowout. If this condition is met, it indicates that the unit has not been stressed by prolonged operation under conditions of high DC leakage. Whether a NOS unit or an original capacitor, the procedure for pre-conditioning / re-forming is essentially identical. With original capacitors, all connections must first be removed from the "+" terminal of the capacitor to be re-formed. With a NOS unit, the pre-conditioning is to be completed prior to installation of the capacitor in the chassis. With the capacitor to be re-formed or pre-conditioned confirmed to be out-of-circuit, the process is as follows ...

1 - Connect the "-" terminal of the capacitor to the B- terminal of an adjustable regulated DC supply such as Lambda Model 50, Heathkit PS-2 or equivalent whose output voltmeter calibration is known to be correct.

2 - Set and confirm the output voltage of the supply equal to the DCWV spec of the capacitor under test. Set the voltage with a DMM if desired. Place the supply in "Standby" mode.

3 - Connect one lead of a 20K/5W resistor to the power supply's B+ terminal. Shunt a DC voltmeter (preferrably an auto-ranging/auto-polarity DMM) across the resistor.

4 - Connect the other lead of the 20K/5W resistor to the capacitor's "+" terminal and set the supply to "On" mode.

5 - Within approximately 5 minutes, the voltage drop across the resistor should drop to less than 50% of the applied voltage. Within 30 minutes, there should be less than 10% of the source voltage across the 20K resistor.

6 - It may take 2 to 4 hours or longer to meet this next condition. The voltage drop across the 20K resistor will be less than 1% of the source voltage (0.2% to 0.5% is the preferred range) when the capacitor has been fully re-formed / pre-conditioned.

NOTE - Factory quality-control specs I have read for new capacitors call for leakage currents in microamperes of less than or equal to 1/5 the square root of the product of capacity in uF and voltage spec in volts. Imax=1/5*sqrt(CV). Voltage drop across the 20K resistor will NEVER actually reach zero as some tiny amount of DC leakage will always exist.

7 - Switch the power supply back to "Standby" and unplug the connection from the B+ terminal of the supply. Connect the lead just removed from B+ to the B- terminal such that the 20K resistor and DMM are now shunted across the capacitor and discharge the capacitor until the DMM reads less than 1V across it.

8 - Multiply the capacity spec (in farads) of the capacitor under test by 20,000 (value of the resistor in ohms) to calculate the RC time constant in seconds of the circuit fiormed by R and C.

9 - Reconnect the re-forming circuit so that R and C are again in series across the power supply with the DMM monitoring the voltage drop across R. Place the power supply in "On" mode and note the time in seconds required for the voltage across R to again equal 0.2% to 0.5% of the source voltage. This should be 5 times the RC time constant calculated in Step 8 (+/- the stated tolerance spec of the capacitor).

EXAMPLE: Suppose we have a 40uF/450V capacitor. Further suppose that we observe 1.35V (0.3% of 450V) across R at Step 6. The circuit time constant is 0.000040 farads * 20,000 ohms = 0.8 seconds. Suppose charging in Step 9 takes 3.8 seconds and the capacitor is rated +/-20% tolerance, we therefore have successfully re-formed our 40uF capacitor.

10 - Discharge the capacitor and reconnect it into the tv circuitry.

PRECAUTION 1 - Insert a 1/2A fuse in series with the B+ feed from the 5U4 filament in sets using a single 5U4. Use a 1A fuse for applications where a pair of 5U4 tubes are operating in parallel. This will help protect the set's power transformer and other costly parts in the event of an overload at some time after the set has been restored.

PRECAUTION 2 - If the manufacturer did not fuse the set's B+ Boost as part of the original design, insert a 1/4A fuse between the damper cathode and the junction of the Horiz Lin coil and first B+ Boost filter capacitor. GE models 800C, 810 and other similar models did not include a B+ Boost fuse. RCA, Fada, Dumont and many others included a B+ Boost fuse in nearly all models. Fusing the B+ Boost will help prevent a blown flyback in the event that the Horiz Output, Vert Output, or Damper tube becomes "gassy" or in the event that severe HV arcing or some other such condition should occur.

PRECAUTION 3 - A slow-blow fuse rated the next standard rating above the normal line current specified in the set's Sams folder should be added in series with the set's AC line circuit. For example, GE model 810 draws 2.2A and therefore should have its AC line circuit protected by a 2.5A slow-blow fuse.

WARNING - NEVER under ANY circumstances attempt to re-use any electrolytic capacitor whose seal is "blown" or bulging or for which the voltage drop across R in Step 6 remains greater than 1% of the capacitor's DCWV spec. Such a capacitor is excessively leaky and will overheat during operation, causing its leakage current to increase even further and is very likely to eventually overload the set's circuitry severely.