Anyone Familiar with the Bridgeport Power Feed circuit board F-6120?

Hi Tom,

Since you have decent drawings, have you done a simple wire-by-wire verification of the connections?

To me it looks like the wiring to those two switches do not match the diagram.
It may be just that I cannot see the colours, or that I'm not 100% sure I can read the "NC" vs. the "NO" contacts, but it's not what I expect.

It should be "low hanging fruit" before you dig too deep into the circuit board.

-brino
 
Brino thanks for the suggestion. I did verify the colors and connections. One of the components must be fried. Although, I do agree, that it is probably relatively simple. My plan was to start at the 110v AC connections, and just work my way back with the voltmeter through the AC and DC points. That should tell me pretty much where the pixies stop. Where that point is, is probably the toasted component. Again, I am comfortable with basic electrical blocking and tackling, but I am by no ways an expert.
 
Ok, I finally got a few hours to myself today, and broke out the Simpson. What I found so far is that there is 110 AC to the diode bridge. However, one of the diodes appears to be toast. I polarity tested all of them with the OHM meter, and found all at 10 ohms +/-3, except for the last one, which measured 2 ohms in both polarities. Failing diode is circled in blue:

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110v AC input is fine. 0v DC output. So, unless I am missing something, I have a cooked diode. Basic continuity and voltage testing of the 110v secondary circuit to the transformer was good. So, I guess I order one of those puppies, and swap the circled one out. Then continue the testing. OH, I found the micro-switch wiring was totally reversed as shown on the wiring diagram, so I re-arranged that to match the diagram. Lastly, I verified the rest of the wiring as per the diagram.
 
Tom: you may get goofy readings with the part still in the circuit- unsolder it and test again before you start buying parts- diode should give very high ohm reading in one direction and low (a few hundred ohms or so) in the other. The two scrs require a battery and light bulb test- maybe later on...
Mark
ps by the way do you know for certain that the motor itself is ok?
 
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Mark, I'll disconnect the suspect one, however I will add that each one did check out with the polarity check except for the last one. The failing diode had 2 ohm continuity in both polarities, hence my diagnosis. To be safe though, I'll follow your advice.......
 
Sorry, but you cannot check that diode in the circuit with certainty. It must be out of the circuit to check with a simple multimeter. There are ways to check in the circuit with more sophisticated equipment however. And I have never seen that diode fail. I would replace those 4 blue colored caps on the center right, whether good or not. And carefully check the board for bad solider joints, smoked component(s) and bad/melted circuit paths. Good Luck…Dave.
 
One other thing I should point out. 110 vac input to the diode bridge is working. Output from the bridge is 0 vdc. That is the other measurement that leads me to believe that diode is toast. While there still may be more fried components downstream, the bridge is definitely not functioning........I would expect to get some DC voltage reading on the output legs when energized, but alas, no DC Voltage and no joy.......
 
Tom: If the scrs are not being triggered you won't have any output from the power bridge. Also you need field power to the motor. One step at a time...
Lets zero in on the real problem before you go ordering any replacements
Mark S.
 
well guys, I made an executive decision, and I bought a new circuit board with some updates to components. Now, I plan to continue to diag the current board on the thread so I will have a spare. Time has become very tight for me lately, and while $300 is a moderate chuck of change, I also don't mind investing it. I have gone through the motor, and it is fine. The rest of the unit is fine......it all boils down to the board. I had a couple of discussions with H&W machine repair. Those guys are top notch. If you ever need Bridgeport parts, they are a bit pricey, but they are great people.
 
Great news. New controller arrived today (2 days after ordering from H W Machinery). Installed as per instructions, including updated components. Power feed chooches like a new one (well, almost new, the paint leaves a lot to be desired). Thanks to everyone. I am still going to work on the old board to see if I can figure out what is wrong, but for now, the power feed is ready for work!

Thanks again to everyone who responded.
 
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