OK, for anyone interested, following Traumflugs suggestion I had a look at the schematic and selected the PWMPB4-pin (on the extension pin header) on the Sanguinololu and connected it (and ground) to the sevenswitch signal input. Then I adjusted the DEFINE_HEATER for the bed to PB4 in teacup firmware config.h and flashed the firmware. I hoped this was safe because PB4 doesn't use timer1, although it was not listed as a pwm-able pin.
After connecting the heat bed to the seven switch and powering the seven switch with a free molex power connector from the power supply and rechecking everything it was time for a smoke test, which was negative (ie no smoke).
Then I powered up the sanguinololu and tested selecting different heat bed temperatures, gradually increasing up to 100 °C - which worked right away.
And without any soldering on the sanguinololu...
PS. using the KTY 84-130 temperature sensor which was more readily available for me (from Reichelt) and it seems to be working ok for the heat bed (with adjusted firmware thermistor tables)
After connecting the heat bed to the seven switch and powering the seven switch with a free molex power connector from the power supply and rechecking everything it was time for a smoke test, which was negative (ie no smoke).
Then I powered up the sanguinololu and tested selecting different heat bed temperatures, gradually increasing up to 100 °C - which worked right away.
And without any soldering on the sanguinololu...
PS. using the KTY 84-130 temperature sensor which was more readily available for me (from Reichelt) and it seems to be working ok for the heat bed (with adjusted firmware thermistor tables)