Help Repair - Metcal/Oki MFR 1110

[Woznick]

Hi All,

I picked up a Metcal/Oki MFR 1110 Soldering Station and Iron which is faulty, and would appreciate any help to get this up and running.

The fault is that the unit when turned on will pulse both LEDs for a brief moment before then turning off until the mains is reset. Having pulled it apart all looks in tact with no damaged/blown parts inside. I've deduced that the protection circuit in the first switch mode  stage (FS7MO680) is kicking in which is why it initially powers up, but then the protection kicks in and locks up until the mains is reset.

The 5v & 12v regulators are working fine and I believe the issue lies with the protection circuit around the main PWM (MC34023) which links back to the 1st switchmode IC (FS7MO680) causing that to shut down. I've replaced the main Mosfet to no avail, interestingly removing the mosfet enables the unit to stay powered up with both LEDs lit, so it suggests that there is an issue with the protection / current monitoring after the main mosfet IC. Removing the front facing PCB (which looks to have the protection/ shutdown circuit)  enables the unit to stay powered on which is no surprise as the protection circuit is removed.

Does anyone have any ideas on how to fix the unit ? ideally I'm seeking schematic/repair manuals for the unit ?

Thanks in advance

[zapta]

This is a very long shot but maybe it's similar enough to the MX500 such that the MX500 schematic will help?

The MX500 has a disable signals that is connected to a few over collector protection signals such that each one of them can disable the power. The trick is to find which protection signal caused the shutoff.