Jarl,
Thank you for your help on this. It appears that either; the CPU has a bad
output pin, some unknown command has turned the heater off, or the firmware
is programmed that way. The 10 MHz frequency had always been very 'stable',
and I didn't know there was a problem until I bought a 2nd HP
John,
I have a similar unit (probably from the same seller), advertised as
an Z3805A upgraded to the features of 58503A, whatever that is
supposed to mean.
Mine also does not get warm on top, though it appears to be providing
a decent 10 MHz output and indicates GPS lock. This is the best
Jarl, OZ9MO
Thank you for those two links! They have the information I needed, and are
very well 'hidden' on the internet.
I have had partial success. Per the work-around on www.realhamradio.com, I
pulled P2-8 on the power board up to +5V, and the outer heater came on and
is now being
I have a HP Z3805A / 58503A with a cold outer oven. I have installed another
HP 10811-60165 DOXO, and then another power board. Still, the outer oven is
not heating.
Heater resistance is ok at 19 ohm, but voltage on red wires to heater are
both at 5.0 VDC. On another (good warm) HP Z3805A,
