Max Arc / Hummel Welder

[AcornCivil]

Hi all posted in another thread about my restoration project....................................

(Well apologies for excavating such a prehistoric thread but I came across it while trying to get information on a restoration project I'm at.
I have a single cylinder lister engine driving a Hummel alternator welder which I now believe is a Max Arc welder unit. What I'm trying to do is to get it running and working. It was welding but had little or no power at the higher amps, so I removed the transformer and rectifier in an effort to check the diodes. What I found is that six of the eight don't read on the multimeter, and the model numbers are corroded making them illegible. RS do a similar looking item but as I don't have a value I'm caught again. Anyone know where I might get the value of the diodes and more importantly the polarity of them)

These are the diodes from my unit....................

@HughF @Seadog thanks for your help thus far............................

 

[Seadog]

It's probable that there are two flavours of the same diode in the welder. One with the stud as anode for the positive lead (70HFR30) and the other with the stud as cathode for the negative (70HF30).

 

[AcornCivil]

It's probable that there are two flavours of the same diode in the welder. One with the stud as anode for the positive lead (70HFR30) and the other with the stud as cathode for the negative (70HF30).

What would be the issue if one was to replace them with 70hfr 60 & 70hf 60 or 80hfr 40 & 80HF40??

I did make out 75 -04b on one diode today least I think it was so was thinking to go higher if possible.........................but what effect will it have...........

 

[Seadog]

As long as you replace with like for like or higher rated ones you'll still have full output available.

The 60HF will be rated at 60A whilst the 80HF are 80A. The end figure is voltage, so the 40 equates to 400v.

The 80HF40 will therefore replace the original with room to spare.

The 75-04B could be a DS75-04B which is rated at 400V 92A, so once again more than adequate.

 

[AcornCivil]

How are you on selenium rectifiers? can they be rebuilt?

 

[Seadog]

Obsolete technology. I remember the old Lucas selenium rectifiers found on 50s and 60s British bikes. No end of problems when they got a bit damp. You could build yourself a replacement rectifier with silicon diodes.

 

[HughF]

http://www.ebay.co.uk/itm/200A-1600...155385?hash=item1c593b7df9:g:598AAOSwax5YuBLk

I've used those ^^^ before and they hold up well.

 

[Seadog]

But it's got 4 positive terminals

 

[AcornCivil]

G'day gentlemen my thanks for your invaluable assistance thus far. When it comes to wrench bending I've no issue dismantling an engine or such to it constituent parts and rebuilding or modifying it, however unless it a simple electric circuit I am completely lost.
I have the selenium rectifier in pieces on the desk but some of the aluminum plates are damaged or corroded so my plan (all be I foolish) was to replace the plates clean the selenium washers replace the insulation and reassemble it, connect the wires and put it back where it came from.
It has two wires one it but that is the extent of my knowledge of it, and as for replacing it I would not know where to begin. The plates are50x100mm, the washers are all good except the selenium ones look a little corroded so I was going to clean them and put some contact paste on them when assembling them.

Am I mad ?
Any advice in relation to this issue is gratefully appreciated.................

Acorn Civil

 

[AcornCivil]

Got the diodes yesterday so the rebuild has commenced....................

 

[seadog52]

Got the diodes yesterday so the rebuild has commenced....................

i too am rebuilding the exact same one welding sice works well but the 240 doesnt have you got a diagram by any chance please