zd-987 zd987 desoldering station - Strange behaviour

[Mamejay]

Hi guys,
I have a zd-987 desoldering station which I have had for a few years.
What I found today which I never really noticed was that when the auto temp shutdown kicks in, the pump has heaps more power.  You can hear it in the motor speed.
What I want to do is have that amount of power all the time while the gun is heating and at temp.

Any ideas where I should be looking?

[Chris56000]

Hi!

This is due to deficiencies in the internal power supply circuit, what's happening is that when the heater shuts down in the "sleep mode", the voltage to the pump motor rises quite a bit!

There's not a lot you to can do to improve the internal power supply without a major PCB re–design, but if you fit a panel–mounting external 2.5 mm DC power connector to the back panel, you can wire an external power supply (e.g., an old laptop charger) to the pump motor via the microswitch in the handle/gun assembly!

It might be worth opening the unit and looking for any bulging/dried–up electrolytic capacitors on the main board as well!

Chris Williams