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Need replacement for KBP04-01

Part of the switch assembly for a Dremel model 260 - an old Dude.

Tool threw a brush, shorted out and blew the lead off one of the brush holders. I reattached the lead, replaced the brushes, serviced the rotor, plugged it in, turned it on and the resulting short fried the slide switch.

Took this 3/4"x1/2"x1/4" black component out of the circuit (wired in- between the slide switch and the brush holders. Tested across the input lead that came from the slide switch and the output lead that connected to white, got a solid connection, so I concluded the internals got fused in the first short and that caused the second short which fried the slide switch.

So, what is this devise? Has KBP04-01 printed on one side and 7237 printed on the other. Has (+) printed over one of the brush leads and (-) printed over the other, with AC printed in between.

What does it do?

Could I get by without this devise and wire directly from the brush leads to a 120V lamp dimmer switch to control on/off and speed control?

If not, I can fix this tool if I just knew what it is and where to find this, or a modern day equivelent, of this component.

Any help or suggestions will be greatly appreciated.

Reply to
Teflon
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I believe the suffix "-01" can safely be ignored and that it is an ordinary bridge rectifier rated at 400V VRRM and 1.5 or 2A, depending on manufacturer, made 25 years ago and still being made. Any half-decent supplier should be able to offer something suitable for around 1 USD. A lamp-dimmer alone would probably not be suitable, but should be once the bridge is replaced.

Reply to
Martin Crossley

Thank you Martin.

Am I correct in my assumption that the device is bad if the two AC leads show a solid internal connection via an Ohm meter test?

Should either of the brush leads show an internal connection to either of the AC leads? Or each other?

Sorry for the basic questions, but my EE classes were over 48 years ago. Ended up selling versus designing computers.

Reply to
Teflon

Yes.

A DMM with diode test range should show one diode drop (0.6-0.7V) from either AC lead to + and open to - with its red lead to AC, and the opposite when reversed. Also 2 diode drops - to +. Analogue meters often have opposite polarity on the resistance ranges.

Around the same time as silicon rectifiers started to supersede selenium stacks?

Ended up selling versus designing computers.

Reply to
Martin Crossley

Thanks again Martin, one last novice question. (I know, that's what they all say.)

I was rummaging through a neighbor's box of electronic parts and came across a new KBL04. Doing a little research (thanks to your lead, I'm learning), I found it is a 4 amp 400V single-phase silicon bridge. It's roughly the same size as the fried one, which is 1.5 amp 400V.

What problems / risks would there be if I used the 4 amp bridge in place of the 1.5 amp bridge? Would it provide too much power, make the motor run faster, burn it up?

Reply to
Teflon

You're welcome. It should be perfectly suitable.

(Theoretically, there might be a fraction of a volt more to the motor due to the slightly lower internal resistance of higher-current diodes, but it's offset by less heating of the rectifier. Silicon diode junction drops decrease with temperature. And compared to 120V, it's negligible anyway.)

Reply to
Martin Crossley

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