[R-390] R-390A Replacing HR202 Capacitors

[Jacques Fortin]

Hello Jordan,

I used the 0.1µF, 630V, polypropylenes I used everywhere else.
However, for C256 and C309, a 100V rating should suffice.
If there is 400V film units there, they are OK.
Crashing sound you hear:
_ Does the Calibrator is on ? (Function switch in CAL)
_ Does it happens on the 7MHz band and below, and not on 8MHz and up ?
_ If the HR202 is removed as a whole, does the crashing sound still present
on the 8MHz and + bands ??

There is a way to check the HR202 operation out of the RF deck, but it will
require a DC power supply that can be adjusted at 6.3V and something to
monitor the current drawn by the oven element when it is "on".
A "normal" HR202 will draw about 800mA with 6.3V applied.
You will be able to feel the heat quite rapidly.
There should not be current variations when the case is tapped, as this
indicates bad contacts in the thermostat within.
When the 75C internal temperature will be reached, the current will drop to
zero and the current drawn will began to cycle, at about 4 sec. on, 6 sec.
off.
The current drawn have to read the same each time, proving that the
thermostat contacts are not dirty.
If you see current variations just after the "on" or just before the "off",
you should search for another HR202 in better shape.

73, Jacques, VE2JFE