Metabo Drill Troubleshooting- Newbie needing Help

[KDoug]

Hi,

I have a corded Metabo hammer drill (Model KHE-32) that was given to me in non-working condition. I have tested the switch and it appears to be working, so I have removed the electronics assembly and have been trying to remove the epoxy potting. I have used a variety of ways to do that including: heating in boiling water and hot air with a Portasol and a blow dryer. The bottom half of the epoxy peeled off in chunks fairly easily, but the top side has been a bear.

I just need some advice for a beginner knowing what to start pulling and testing (what are some common components that go out?), because there doesn't appear to be any components that have been burned or have any physical deformations. Most of the marks that are on the components now were done by me trying to remove the epoxy.

A new electronics assembly is about $63, so if there is any chance of me repairing this, I'd appreciate any advice on where to start.

Thanks

Photos Below:

[Kleinstein]

I would see pretty little chance to repair. About the only chance is there if its an visibly bad part / solder joint or maybe a diac in front of a triac for control.

[KDoug]

I thought parts like capacitors go bad often? Or do they always have physical deformations when they go bad?

[Kleinstein]

Capacitors can go bad without a visible damage. However in the circuit the large cap is likely only for EMI purpose  so even if bad it would only increase EMI, but still run (or cause a short and than often blow by releasing magic smoke). It is not only caps that can go bad.

[wictor]

That big red cylinder seems like fuse, you could measure that with multimeter for continuity.  And that big black triac? in TO220 package you could also check that it is not shorted. The image is not very good, but it seems that one leg of TO220 has bad/cracked soldering. Check that all wires and big components are soldered properly.

Wictor

[KDoug]

Unless that red cylinder serves another purpose, I thought it was just an LED that turned on when the carbon brushes were worn. I had wondered about the cracked solder joints when I removed the epoxy potting, and first thought I had cracked them somehow. But that was the cause, I touched up 3 or 4 cracked solder joints and the drill turned on. Very happy!!

There are a couple parts that I have damaged a little bit trying to remove the epoxy though:

1. I chipped the ceramic coating of a resistor. It has lost some of the color coding, I'm assuming I can just measure it with a multimeter? Or do I need the color coding for more information about the part?


2. I melted part of what I believe is a JST style male connector that is soldered to the board.

 I could use some guidance in pointing me in the right direction of which parts I need.


Thanks

Photos Below:

[reboots]

1. That part may be an inductor, rather than a resistor. You can test it, but perhaps not in-circuit. You can clip one lead and measure for resistance. If the part isn't open-circuit but has measurable resistance or continuity, I wouldn't be inclined to replace it.

2. The connector looks identical to JST PH series. You can confirm that by measuring whether the pins are spaced 2.0mm between centers. Here's a replacement:

https://www.digikey.com/product-detail/en/jst-sales-america-inc/B2B-PH-K-S-LF-SN/455-1704-ND/926611

However, the header looks functionally intact. If you can remove the melted inside portion with a sharp knife, the plug may insert and stay engaged.

[KDoug]

Thanks Reboots for your link and information. The connector looks like a 2mm center. I measured .08 inch center with my caliper which is 2.032mm.

I removed the damaged resistor and measured it and got 6.71k ohms. There colored bands are blue, black, red, and gold, which is supposed to be a 6k ohm resistor with a 5% tolerance. Looks like this is the only option available in cut tape on Digikey:

 https://www.digikey.com/products/en/resistors/through-hole-resistors/53?k=&pkeyword=&sv=0&pv7=2&sf=0&FV=ffe00035%2Cc0002%2Cmu6+kOhms%7C2085&quantity=&ColumnSort=0&page=1&pageSize=100

Here are some more pictures:

[KDoug]

Will the resistor I linked above work, or do I need to find one with color bands like I have now?