Yes, just the three main connections. The top connection (bridge common) going to the capacitors and I assume the output connection. The middle and bottom connections (+ and -) go to the split core transformer leads. To me this looks like a dual diode connected in parallel, which is not what I expected. I'll need to do a little more research on the split core transformer.
Excellent information, thank you. That is what I was suspecting. I wonder if I could just install two single diodes in parallel and "bus" the cathodes together. I'm assuming 130 amp and 40 volt rating based on the 130-4.Hello and welcome to the Forum !
You have done a good job of cleaning the dust out of the machine. If it is metallic grinding dust, that can cause shorts.
There have been a few earlier threads about the Dan-Mig. It seems to be a US re-brand of the original Danish Migatronic machines ( hence "Dan" ? ). Some of them look very like a Migatronic, with identical front-panel control boxes and Siemens rectifiers, using press-fit diodes in green aluminium cooling plates.
I have not seen any of this type of "dual diode module" in a mid-range MIG before. The original part ( EWM MDDM 130-04 ) contains two diodes back-to-back, with common cathodes. This means the secondary of the main transformer is centre-tapped, producing something like "20-0-20" V AC, and needing only two diodes for full wave rectification ( as opposed to the four diodes in a bridge rectifier ). Sometimes this is called a "half-bridge" rectifier, but it is not a half-wave rectifier.
The anodes of each of the two diodes are connected to the outer ends of the transformer secondary. In your second photo, these are the lower two bolts on the diode module, with sleeved tags on thick solid wires. The top bolt on the module is the positive output from the common cathode, joining a flexible cable that goes to the positive bus of the capacitor bank and the MIG torch.
The centre-tap of the transformer secondary will go to the capacitor bank negative rail, and then via the inductor to the front-panel Dinse socket for the work return cable.
As voipio said, the markings on your original EWM diode module are not consistent with the way the diodes are actually embedded in that block. In your last photo, from the left, the three terminals are marked: AC, +, - . In fact the way the module is used in your machine, they should be marked: +, AC, AC.
I have found an EWM diode module in Ireland:
However, the part number "110" rather than 130 implies that maybe the current rating would not be high enough.MESSER EWM MDDMF 110-04 F02 DIODE (R4S9.5) | eBay
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Looking on eBay USA, I found this Fuji one, which is rated at 200 Amps:
It is a common-cathode module and would be suitable, but the two diodes are installed "nose-to-nose", so you would have to gently bend and re-arrange the transformer secondary wires. Using the eBay Seller's photo, from the left, you would have to connect: AC in, +ve output cable to MIG torch, AC in.* Fuji Dual Diode Module, 2FI200A-060C, 200A, 600V, Used | eBay
Find many great new & used options and get the best deals for * Fuji Dual Diode Module, 2FI200A-060C, 200A, 600V, Used at the best online prices at eBay! Free shipping for many products!www.ebay.com
The base uses 4 mounting screws - and don't forget to use some silicone thermal paste too.
