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Drum Sander speed control repair #1: I need help to identify a component on speed control circuit board

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Blog entry by lightweightladylefty posted 02-28-2016 03:20 AM 1133 reads 0 times favorited 15 comments Add to Favorites Watch
no previous part Part 1 of Drum Sander speed control repair series Part 2: PTL! It works! »

My drum sander's conveyor recently quit. We were able (with help) to narrow down the problem to a component on the speed control. My husband said he is willing to attempt to solder on a new component (a new circuit board is over $240) but after considerable web searching, I have been unable to find one. It might help if I knew what it was called so I could more easily narrow the search.

Here’s a photo. Can anyone tell me what the square, gray component on the lower left of the circuit board (indicated with an arrow) is called?

Thanks for any help you can render.

L/W

-- Jesus is the ONLY reason for ANY season.



15 comments so far

View DocSavage45's profile

DocSavage45

7706 posts in 2308 days


#1 posted 02-28-2016 04:02 AM

It’s been awhile, but I’m guessing it is a rectifier. Changing alternating current to direct current. Your husband is willing to solder a new one on the board, but is that the problem? I have worked in electronics many years ago. I’d see if I could locate the wiring diagram and schematic for the board?

A multimeter would be a minimum electronic tool to help determine if the rectifier was burned out. Also helps to know voltages.

Is there anyone in the area that does electronic repair?

Best of luck!

This is different from a mechanical problem.

-- Cau Haus Designs, Thomas J. Tieffenbacher

View KayBee's profile

KayBee

1083 posts in 2712 days


#2 posted 02-28-2016 04:18 AM

Yep, bridge rectifier. Doc, your memory is still good. If your husband is nervous about soldering, any neighborhood geeks around? Or there’s youtube.

-- Karen - a little bit of stupid goes a long way

View CO_Goose's profile

CO_Goose

120 posts in 1257 days


#3 posted 02-28-2016 04:39 AM

I’ll second the Bridge Rectifier (Trust me, I’m an Electrical Engineer).
If you are not wanting to so the soldering, try looking for your local TV repair shop (if they are still in business) or possibly the local vacuum repair should have the proper equipment for that soldering job as well, they also might have the rectifier that needs to be replaced as well as it is a pretty common part.

-- Just making sawdust

View TopamaxSurvivor's profile

TopamaxSurvivor

17671 posts in 3141 days


#4 posted 02-28-2016 04:51 AM

Soldering is pretty easy. Remember to not get your part too hot or use a small clamp as a heat sink to protect it. You can wick away the old solder from the board with a wire braid or fine stranded wire. Use rosin core solder or flux, not acid core. Acid east electricity ;-(

PS. Let the heat draw the solder through the joint. Hot solder on a cold joint doesn’t work very well.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View BobAnderton's profile

BobAnderton

219 posts in 2256 days


#5 posted 02-28-2016 12:57 PM

That is the bridge rectifier all right, but that may not be the faulty component. It should have AC voltage going in (the two corners with squiggly lines) and DC voltage going out (the two corners the the + and -). I’m thinking you’d have to know that that is the rectifier to know to be looking for DC voltage on the output. If the DC voltage isn’t on the output one of the diodes in the rectifier may be out or something downstream may be shorted, like one of the capacitors, pulling the output voltage down. It should be easy to test if you pull it out of the board. It’s just 4 diodes arranged as shown. You can verify that each leg passes a voltage in the correct direction.

Did your help already test each leg of the rectifier this way and that’s how they determined that it was faulty?

-- Bob Anderton - Austin, TX - Nova 3000 lathe, Alaskan Mark III mill, Husqavarna Saw

View SirFatty's profile

SirFatty

524 posts in 1678 days


#6 posted 02-28-2016 02:14 PM

Bob is spot on… and I don’t think I’ve ever seen one go bad.. usually they’re bullet proof. Second the idea about a cap going bad.

-- Visit my blog at dave.spalla.com

View TopamaxSurvivor's profile

TopamaxSurvivor

17671 posts in 3141 days


#7 posted 02-28-2016 10:23 PM

I have replaced them but it was back in the stone age in industrial controls. ;-)

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View lightweightladylefty's profile

lightweightladylefty

3139 posts in 3178 days


#8 posted 02-29-2016 12:47 AM

My dearest LJs,

I always know that I can count on you to get me through these things!

There seems to be some question why we should think it’s the rectifier when we didn’t know what it is! That is an obvious contradiction, but we did take the motor and controller to an electric motor shop and had it tested. He works on very large motors, but tested ours as a “courtesy” since there is no other place within driving distance to have it tested and we had no way of knowing if the motor or circuitry was bad. He didn’t even want to charge for testing it, so we didn’t want to continue to take up his time with more questions. He was the one who narrowed it down to the rectifier, after testing numerous other parts. Because he doesn’t work on little motors, he didn’t want to replace the rectifier but suggested it would be cheaper to replace the whole control box than replace the circuit board for $240. After discussing various possibilities when we got home, we couldn’t remember what he called the part. After spending hours looking on-line, I realized that there are geniuses here on LJs that could answer my question in minutes . . . and you certainly did not disappoint!

My husband is going to give him a call tomorrow to be certain that is the bad part, and then we’ll try to figure out where to get the right one.

Thanks for your help.

L/W

-- Jesus is the ONLY reason for ANY season.

View TopamaxSurvivor's profile

TopamaxSurvivor

17671 posts in 3141 days


#9 posted 02-29-2016 07:13 AM

They are a generic part. Finding one will be easy. Just be sure your inputs and outputs are correctly oriented.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View lew's profile

lew

11343 posts in 3221 days


#10 posted 02-29-2016 03:25 PM

Just a thought… the two long black cylindrical parts are power resistors- they get hot. The heat can weaken and crack the solder joints on the underside of the circuit board. Check those connections prior to replacing the bridge rectifier.

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View splintergroup's profile

splintergroup

829 posts in 688 days


#11 posted 02-29-2016 07:33 PM

I’ve had to repair the speed control on my Performax (several times 8^0).

The others are correct, bridge rectifier.

Your controller is different (non-Jet/Performax), but typically the conveyor motor is DC with speed controlled by a device very similar to a light dimmer.

The rectifier probably has a high voltage rating (most likely 1000V). This was the same part that failed on me the first time.

The other ‘vulnerable’ part is the SCR (probably the heat sinked device in the lower right of your image). These should be replaced with the associated DIAC. Since your controller is different, it may work on a different principle, but for these kind of things, it’s the parts that handle the power that usually fail first.

Good luck!

View splintergroup's profile

splintergroup

829 posts in 688 days


#12 posted 02-29-2016 07:36 PM

Oh yeah, and if you can post a close-up picture of the top of the rectifier with any printed markings it will be easy to tell you where to buy a replacement. The unfortunate problem is that the part will probably cost less than the shipping charge.

View lightweightladylefty's profile

lightweightladylefty

3139 posts in 3178 days


#13 posted 03-01-2016 03:36 AM

Today we confirmed with the motor repair shop that the rectifier is the problem. Now, to get the correct rectifier…

The only marking on the rectifier is on the side: MS14 PB36. If my research is correct, the rectifier is 3 amp 600 volt. In my searches, I came across a rectifier that says: “This part is the equivalent replacement for . . . PB36 . . . ”, but what confuses me is that it is an 8 amp; 600 volt rectifier.

Can a different size be used without causing problems? For example, could I use a 6 amp 600 volt or a 6 amp 800 volt? (I can find single/small quantity of those sizes for a reasonable price, but I’m only finding large quantities of 3 amp 600 volt.)

L/W

-- Jesus is the ONLY reason for ANY season.

View CO_Goose's profile

CO_Goose

120 posts in 1257 days


#14 posted 03-01-2016 05:17 AM

Yes you can use a rectifier that is rated at a higher voltage or current than the one that is in the circuit. Be careful that the physical dimensions also do not increase, especially the lead spacing or diameter.

-- Just making sawdust

View lightweightladylefty's profile

lightweightladylefty

3139 posts in 3178 days


#15 posted 03-01-2016 05:26 AM

CO_Goose, Thanks so much for your response. I did carefully check out the physical size of the rectifier and the pin locations to see that it would fit. Now I can order it and wait patiently. It’s nice to have an expert who is willing to share his knowledge! Thank you! Thank you!

L/W

-- Jesus is the ONLY reason for ANY season.

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