One bad fan and the other is wonky, so replacing both. Original fan did
come on at switch on and assumed to run faster on warming of amp as amp
never cut out.
Replacements do not come on at start other than a slight flick. One will
sometimes with the fans in a vertical plane , but amp used with them
horizontal. I tried heating the area of the PTC on the main heatsink,
with neither running at start and neither started up to the temp I was
prepared to take it.
The SM out there is for a different 1062 without SMPS and simple fan
circuit and fans in series. The PTC is 290R at 20deg C and it is PTC.
With the back now off again. The fan voltage, for 12V fans parallel in
this flavour of 1062 is 5.1V climbing to 5.5V at switch-on and first 10
seconds with no fan load.
The fan control circuit is off board, mixed in with complex SMPS not on
the PA panel and its heatsink. At the moment I intend putting 470R or so
in series with the PTC, if this fails to make fans start at powerup, ie
startup voltage of 8 or 9V say, where next? At the moment I don't know
if the control is proportional or stepped. When I've added the 470R I'll
jury rig and check the fan voltage response with hot air on the PTC
directly .
Are there specific types of fan ,and spec'd as such, that will start up
with progressively increased voltage and some that fail to start unless
given a good "kick" to start with?