Power feed blowup

A few weeks ago I was going to use my power feed on the mill to get a uniform travel speed for a MIG weld . Don't know if it was having the
welder ground on the mill or just chance , but when I turned on the PF it popped the breaker built into the PF. So I pushed the reset , and that's when the magic smoke was released ... I've replaced it already but got curious . So today I pulled it apart and discovered a trace on the circuit board is fried . This trace goes to the neon power light from the 110v supply input plug on the board . Other side of the neon bulb goes to a small resistor , then somewhere else . Something else I found is that a pair of 1N5404 diodes - each connects to one side of the 110v input plug on one end and both are connected to the same trace on the other end - both show 0 resistance both directions . No other discrete component on the board shows any sign of damage . I can get a replacement board for 65 bucks +s/h/t but I only paid 50 bucks for this thing originally so ... anybody familiar with these circuit boards ? All my electronic training was a long time ago and while I can trace circuits on a board it doesn't mean anything without a schematic . But I do think the blown diodes may be the problem ... OR they could be result of the real problem ... or ... I can get those diodes for .55 each , cheap enough I think I'll order some . Hey , they're bad and will need to be replaced anyway if this thing's gonna ever work again . If I can get it working , it'll be the basis for a variable speed rotater for welding - with the work suitably insulated from the unit !
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Snag
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Not familiar with those particular boards, but if you try the replacements (and I see no reason not to) you might as well get 1N5407 or 1N5408 diodes. They're bound to cost almost the same and have much higher voltage rating (probably what killed the originals)
https://www.vishay.com/docs/88516/1n5400.pdf
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On 31/07/2021 22:02, Snag wrote:




You didn't mention what power feed it is but if an Align a schematic is available in the manual if this model http://www.align.com.tw/ManuaLib/powerfeed/G00400-AL500D.pdf , there may be others. It does seem to show the diodes you mention.
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wrote:





Better than nothing, but not a very nice schematic. The SCRs would be suspect too. As well as the varistor.
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On 7/31/2021 6:51 PM, David Billington wrote:





It's branded Central Machinery , made by asong , and one of the Align boards looks identical . That's where I got the 65 dollar price tag . I'll look at that schematic !
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"Snag" wrote in message
A few weeks ago I was going to use my power feed on the mill to get a uniform travel speed for a MIG weld . Don't know if it was having the welder ground on the mill or just chance , but when I turned on the PF it popped the breaker built into the PF. So I pushed the reset , and that's when the magic smoke was released ... ---------------------------
Whatever stray current popped the electronics is also likely to damage any sliding or rotating surfaces it flows between.
https://evolution.skf.com/us/prevention-of-electric-erosion-in-bearings-2/
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"Snag" wrote in message
A few weeks ago I was going to use my power feed on the mill to get a uniform travel speed for a MIG weld . Don't know if it was having the welder ground on the mill or just chance , but when I turned on the PF it popped the breaker built into the PF. So I pushed the reset , and that's when the magic smoke was released ... -------------------------------------
Was the MIG turned on? If the only change was grounding the mill, the power feed may have had an undiscovered defect. Grounding faults can be difficult to trace with a voltmeter and a clamp-on ammeter may be helpful. I like the Uni-T UT210E which resolves to 1mA AC and DC:
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On 8/1/2021 6:24 AM, Jim Wilkins wrote:


I've ordered the diodes , after replacing them I'll check for voltage/current on the damaged trace . That is , between the 2 points that trace connects . This unit was purchased new old stock in the original box and I've already had to replace the speed control pot ... if it wasn't so damned handy I'd have gone back to manual feed on that axis . But now I'm spoiled by the ease of getting a nice finish without cranking until my arm falls off .
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I have a Millrite MVI that came with an Asong unit on the X-axis (side to side). It was always blowing speed pots. I have an electronics background, so I repaired it, upgrading the pot in the process. Multiple times, ultimately to no avail, so I replaced the unit.
It had a basic design problem, but I never did figure out the details, as the "schematic" was nothing of the kind. Not only did it not match the unit, it claimed an impossible circuit. Gibberish.
What I replaced it with is Servo's low-cost alternative to their standard unit. Works just fine. Took some lathe work to make the adapters to fit the MVI. They do have stock adapter kits for Bport et al.
Joe Gwinn
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"Joe Gwinn" wrote in message
...They do have stock adapter kits for Bport et al.
Joe Gwinn
-------------------------
Joe knows his Latin.
I use etc even when et al. might be more appropriate because etc is more common and perhaps better understood.
Survey: who / knows / doesn't know / doesn't care / what et al. means?
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On 8/1/2021 11:33 AM, Joe Gwinn wrote:



I had to fabricate mounts and modify parts to adapt the first one , I just had to modify the ring gear and resize a spacer for the second one .
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