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How to fix your Dremel 395 if it suddenly... Expand / Collapse
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Posted 9/26/2008 11:16:16 AM
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Some people asking for assistance on forums never get back with what happened after getting advice or "close the loop" to tell others what the outcome was. I know good people have taken  their valuable time to try and help, so I feel it only right and courteous to take some of my time to do the same. Here is my way of giving back to the Dremel forum and community.

Maybe this thread post will help others looking for answers to the problem of a Dremel 395 type 5 suddenly stoping, intermittent speed fluctuation, or speed stuck at some rpm.

Here are a few preliminary steps you should try first to get your Dremel working again:
1- Turn it off and plug it into a known good AND tested electrical outlet. (plug a lamp in or something to see if the outlet works, you might have blown a fuse to the outlet).

2- With compressed air, blow out the inlet and outlet openings on the sides of the Dremel. There may be a buildup of dust or debris inside on the rotor. If you have no air compressor you use a can of compressed air (wal-mart or target has them).

3- Change the motor brushes with new ones. (These can be purchased at hardware stores that seel the Dremel tools and attachments - such as Lowes or Home Depot). To change the motor brushes, use the end of the locking wrench that cam with your Dremel. On the outside of the Dremel you will find two caps with slots for replacing the brushes. Unscrew the caps (but be careful because the springs inside will fly out). When you get the cap off, remove the spring (if it hasn't flown away) and make sure the old brush is still attached to the spring. If not, turn the Dremel to get a little rectangular lead looking piece out. That is the electrical brush for the motor. Follow the directions on the package for the new brushes and insert them correctly. If you don't the motor will not run and may damage the rotor. Make sure the Dremel is not plugged in and give the end (where you put in an attachment) a manual spin to ensure it will turn smoothly. If not you have put the brushes in incorrectly).

Hopefully one or all of those steps will get your Dremel working again. If not, you may want to contact Dremel to have yours repaired or replaced. There is a 5 year warranty on Dremels, and if yours is beyond 5 years from purchase they will repair it for a fee that is much less than having to purchase a new Dremel.

This last option, (if you don't mind voiding your warranty and are handy at fixing things) is to open it up and try to repair it yourself. Keep in mind that Dremel may not work on it for you later if you work on it yourself.

Having said that, infrequently there is a problem with the Dremel 395 which seems to be with the switch contacts over time, getting dirty, buildup of carbon, and dependent on working conditions, dust accumulation inside the Dremel. For those of us that may be having a problem with intermittent operation, stuck on/off switch, sudden stoppage, or dead altogether. Here is how to take the Dremel 395 apart and work on it yourself. I have a 395 type 5 that has worked dependably for me for over 15 years. However, one day it just quit on me suddenly. I followed the 3 preliminary steps mentioned above but they didn't help this time. So it was necessary for me to open it up and investigate. After cleaning the contacts, my dependable little friend is working like a champ again.

Here is how to clean the contacts: First make sure the Dremel is not plugged in (you won't believe how many people forget to do that). Remove the brushes as directed in preliminary step 3 above. To take the case halves apart you will need a #15 torx head screwdriver or bit. If you don't have one and don't want to go get one, a very small head flat tip screwdriver or something else might work. There are 4 torx head screws on the outside of the Dremel 395 hard plastic casing. Lay the Dremel flat on a work surface and unscrew the round plastic collar at the attachment end. You can leave the metal screw lock and collets on. Now unscrew the 4 screws holding the case halves together. But before taking the halves apart, I suggest you make sure the variable speed on/off switch is facing down to the workbench. Otherwise you may not remember how the parts go back in correctly and they will fall off if upside down). Now gently pry the case half off revealing the inside of your Dremel and put that case half aside for cleaning later. You will see an electrical motor with a shaft and bearings on each end. Gently pry the motor out. At the attachment tool end is a small shiny flat but half round piece of metal that looks somewhat like a ring for your finger. Note how it is placed and that it has a hole in it for the outside "attachment lock button". This ring will need to go back in correctly or the motor may make a lot of weird sounds, lock not work, and possible damage to the shaft. The picture below (made by another forum member - if I can get it inserted into this thread) will show you the parts (minus the main shaft with bearings) and has a pointer to the switch mechanism. Once you have pulled the full motor out of it's resting place (note how you did it so you can put it back in correctly), pull the center shaft (with bearings on the ends) out and lay it aside for now. The heavy cylinder shaped outside part of the motor will have the electrical plug wire attached. Gently pry the box shaped switch mechanism off the heavy motor part (don't pull using the plug wires). The switch mechanism will come off and you will see four electrical leads (little copper looking fingers). Note how the orientation of how they came out so you can put them back into the heavy outside part correctly later. Put the heavy motor part aside also. Now the switch mechanism housing is in your hand and has the electrical plug connected to it. Before you go any further, move the slider switch as you would using the Dremel and see how it works paying particular attention to how the inside sliding parts and slots fit together. Move it back and forth so you can see and remember.

Now to take the switch housing apart. If you carefully pry the wide left and wide right sides of the switch housing apart (they are not glued) the inside of the switch and it's contacts will be visible and accessible to cleaning.You should now see the switch housing has 4 parts. One wide housing side plate which you already pryed away from the other and is attached to the plug wires. You can move that aside for cleaning later. Then there are the: moveable arm I'll call it (the part you move to turn it on and adjust speed), snapped to that is a small rectangular piece with 3 small bent and hooked shaped metal contacts, and last the right side of the housing switch which has a transistor on it along with some elongated looking metal pieces embedded on a shelf of the housing half. These elongated pieces are what the hooked contacts connect to. Take special note of where the housing has grooved slides for movement of the moveable arm. Hopefully you noticed those before pulling the housing sides apart like I told you earlier.  Side note: I took my camera to get pictures to post here with this thread but the battery was dead, sorry no photos. OK, now for cleaning. I "very very carefully" bent the 3 hooked shape contacts (on the little rectangular piece) out with a toothpick just a micro bit (being very careful not to break them) to ensure they would make contact. I don't have any electrical contact cleaner that would be best for cleaning electrical contacts (the cleaner can be found at a hobby store), so I used a very small piece of 400 sandpaper lightly and then some alcohol to clean the tips of those contacts where they would meet the lower contacts. Next, there are 3 flat contacts on the shelf of the housing that are elongated (I'll call them flat slide contacts). One of them doesn't appear to be metal but more like black silicone so I didn't sand that one. But did slightly sand (just to get rid of any carbon) the 2 metal ones (one copper and one shiny metal). Then I ran some alcohol over them with a q-tip being careful not to leave any q-tip filaments behind. The flat slide contacts looked much better. Then I used compressed air and the alcohol to clean all the other parts laying around on the table. I let it all dry and carefully put the switch housing back together. Then attached it to the heavy metal motor and assembled the motor back together (hope you payed attention when taking it apart). I thought about putting a little 3in1 oil on the 2 shaft bearings (which I also cleaned with a toothpick and a dry q-tip) but decided against it because I wasn't sure if the bearings were Teflon or greased. If they were teflon or greased, oiling them might have caused damage later. Also the oil may have attracted more dust and grime so I didn't oil them. Don't forget to put the little metal "ring" for the lock stop back in correctly before putting the case halves back on. And make sure all the electrical plug connections are still intact while positioning the end plug wire rubber square into the housing for reassembly.

After getting all the parts back together again, I plugged it into a known good and tested electrical outlet, crossed my fingers and turned it on. It ran great and the variable speed control worked great. I hung it on a bent hanger off a hook on my workbench at high speed for about 5 minutes and checked that it didn't seem to be overheating.  Turned it off and on again and let it run another 10 minutes to seat the new brushes I had put in while troubleshooting earlier. If you put new brushes in as suggested, let it run for about 10 minutes to set them into place (see preliminary step 3 above). Perhaps the work you do on your Dremel 395 contact switch will get yours running again and  correctly as it did for mine! Good Luck.

I hope this will be helpful to those needing to clean/maintain their Dremel and to those that find it necessary to clean up their Dremel switch contacts!

Mac

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Post #4517
Posted 9/26/2008 2:51:15 PM


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Thanks Mic

Doug


Post #4520
Posted 9/28/2008 4:31:00 PM
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Mac, what I nice job you've done! And I would say loud: "What a good guy!"

Thank's a lot

Enrique

Post #4533
Posted 9/29/2008 1:34:04 AM


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Hi Mac

Add my thanks to those of Doug and Enrique.

Enrique is right it was a good job. Concise, informative and knowledgeable all very valuable attributes!

Curt

Curt
Post #4538
Posted 10/24/2008 9:03:17 AM
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I tried waht you suggested.Actually last night i did open up the tool as you explained and read your info this am.the only thing I didn't do was replace the brushes,they look clean and new.Mine just stopped and hasn't worked since.This was about a week ago.Mine isn't used much.i was thinking more of the electronics in the switch.I cleaned the contacts with a small cloth and 'blew' out any dust but mine is/was clean. I'm stumped.
Post #4622
Posted 10/24/2008 11:10:06 PM


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Good post !!  I liked the part about unpluggung the tool.... aahhh! We won't go into that. But thanks again for the time and effort.

Bruce!
Post #4624
Posted 10/25/2008 7:30:02 AM
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SDBOB, You said that you used a cloth to clean the metal contacts inside the switch/speed adjuster. Cloth didn't work for me. So I used a very small piece of very fine sandpaper on the metal contacts everywhere they would meet. Then lightly wiped the contacts with alcohol and let them dry. In my case, I'm sure it was the removal of the carbon buildup on the contacts that made my Dremel work again. Since you said yours is still dead, you might try the sandpaper and alcohol. Hope it works for you and please come back and tell us if it did or not.
Post #4625
Posted 10/28/2008 1:42:36 PM
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Over the weekend I took it apart again. cleaned the contacts with worn out fine(100) sand paper and wipe down the contacts and blew them out. I didn't use any kind of liquid. Tried again no go.So I took it apart again-completely.Got my volt-ohm meter and checked for continuity in the cord and everywhere I could think-I'm not an electrician or tech.I cleaned all the brass contacts,still nothing.I'm thinking its the little board!?Any way to bypass it or check it? I'm not desparate just determined to fix it. Thanks Bob.I only get on maybe once or twice a week to view responses so be patient.
Post #4641
Posted 11/9/2008 7:35:11 PM
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MRMAC, THANKS FOR ALL THE INFO, ALL VERY CLEAR. ATTACHED PHOTO MADE IT EASY TO DISASSEMBLE AND WHAT PARTS I WOULD END UP WITH.
I FOLLOWED YOUR FIRST THREE STEPS, DID NOT WORK. THEN CLEANED CONTACT WITH CONTACT CLEANER,Q TIP, REASSEMBLED, NOW IT WORKS LIKE A CHAMP. YOU SAVED ME ABOUT $50 BUCKS.

THANKS,
NOTTOOCRAFTY
Post #4707
Posted 11/10/2008 10:46:25 AM
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Nottocrafty, I'm really glad to hear that you got your Dremel working again! There were many people here that led me in the right direction to get mine running also. Thanks for writing and telling us!

Hopefully it will help others and they will take a minute to comment also?

I was hoping to hear back from SDBOB. I wonder if he ever got his running and if so how he did it?

Post #4709
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