# Delta 37-280 Jointer



## RobLW900 (May 8, 2018)

I picked up a Delta jointer for free that I was told the motor loses power when a load is applied.
I fixed it up and yes it lacks power so I unbolted the motor and tapped on the start capacitor and could hear a difference in how the motor sounded up until the capacitor blew up in my face.
My question is was the capacitor bad and lightly tapping on it did it in or is the issue beyond that?
Right before it exploded the motor sounded and ran great and if course Delta lists the most needed parts as obsolete like my craftsmsn that was awesome until the motor went out


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## Steve Neul (Sep 2, 2011)

RobLW900 said:


> I picked up a Delta jointer for free that I was told the motor loses power when a load is applied.
> I fixed it up and yes it lacks power so I unbolted the motor and tapped on the start capacitor and could hear a difference in how the motor sounded up until the capacitor blew up in my face.
> My question is was the capacitor bad and lightly tapping on it did it in or is the issue beyond that?
> Right before it exploded the motor sounded and ran great and if course Delta lists the most needed parts as obsolete like my craftsmsn that was awesome until the motor went out


If tapping on the capacitor affected the motor it was probably a loose connection. You might take the cover off and check for something wrong with the wiring.


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## TimPa (Jan 27, 2010)

hope you didn't get hurt! it is probably obvious that tapping on it would be a bad idea if it was on or near the connections with a metallic object. 
I would try to just replace the cap, not obsolete. it should have markings on it for voltage and microfarads.


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## RobLW900 (May 8, 2018)

When it blew I got most of the force on the right side of my face, thankfully to burns or damage except my pride

The terminals are or were under a rubber cover and it was still mounted.
I was tapping lightly with the handle of a screwdriver so there was no contact metal to metal.

I'm guessing the capacitor was the issue to begin with, a few light taps shouldn't have caused it to explode unless it was faulty in my thinking.

I ordered a new capacitor $10 plus shipping and have 2 different companies trying to help find a replacement relay which I'd like to replace right away.

I'm anxious to get this going, the motor is super clean and there's zero play in the bearings.

Other than the electrical issues it's also missing the fence and mounts but I can make a wooden fence which will be fine for my use.


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## Mycrossover (May 18, 2018)

I think a little more info might be needed here. Some motors use a relay whose coil is in series with the motor. The contacts connect the start capacitor. When the high start current drops, the contacts open, disconnecting the cap. This is an alternate method to a centrifugal switch. Start caps are rated for very brief use and if left in the circuit they BLOW UP!! It is good that you are replacing the relay, too because that was probably the culprit. The relay should be rated to open a little above the amps rating on the motor plate. Too high and the start cap disconnects to soon for a weak start. Too low and it never disconnects and the cap blows up. There are solid state replacements for those old relays. You only need the current off the motor plate to select the correct size. They can also be used to replace a bad centrifugal switch.

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## Catpower (Jan 11, 2016)

Mycrossover is right, when the motor is running the start cap should be out of the circuit. The relay you are replacing is a potential relay, as the motor gains speed the start windings produce back electromotive force or EMF, that will open the contacts in the relay when the motor is at about 75% RPM, sounds like yours didn't de-energize the cap and it blew


And yes there are solid state relays that will replace yours, but beware it is a thermistor and will need to be turned off for about 5+ minutes before it will cool the thermistor down enough to work properly. that is about the only down side of an SS relay


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## RobLW900 (May 8, 2018)

Sorry about the delay in responding, it's been one of those kind of weeks and I'm trying to get you guys as much info as I can.

The capacitor in the picture is from my jointer, the relay picture is a borrowed from the internet but an identical relay.

As of yet I haven't gotten any answers from the 2 companies and haven't found any suitable replacement.

I'm also confused with the relay being 240V10A which I take as being 240 volts on a 120 volt machine, I admit my electrical knowledge is lacking beyond knowing simple wiring.

The relay sticking makes sense but for the 20 or 30 seconds I had the power on prior to failure why was I the lucky one to have it fail and not the previous owners that ran wood through it trying to figure it out? I'm assuming I'm just the lucky one as I don't understand how the brief time I had it powered up and tapped the capacitor and the motor sounded like it went to full power that it didn't fail under a load or due to the vibration when it was used.

How do I test the relay? The new capacitor should be here by Tuesday but I don't want to blow it up as well.


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## Catpower (Jan 11, 2016)

I have never seen a potential relay that looks like that one, most are enclosed and have about 5 terminals on them but you only use 3, the numbers 1,2, and 5 is common, 2 goes to the start winding, and 1 goes to one of the terminals on the start the cap and the other wire off the start cap goes to the run winding. If you use a solid state relay one wire goes to start, the other goes to the cap and the other cap wire goes to the run winding 



Since it is an open relay, with the power off slide a small piece of sand paper doubled over between all of the contacts to clean them off, then when you get the new cap watch the relay as you power up the jointer, and if it is working right the contacts will open up within a second, if not shut off the power


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## Mycrossover (May 18, 2018)

Catpower said:


> Mycrossover is right, when the motor is running the start cap should be out of the circuit. The relay you are replacing is a potential relay, as the motor gains speed the start windings produce back electromotive force or EMF, that will open the contacts in the relay when the motor is at about 75% RPM, sounds like yours didn't de-energize the cap and it blew
> 
> 
> And yes there are solid state relays that will replace yours, but beware it is a thermistor and will need to be turned off for about 5+ minutes before it will cool the thermistor down enough to work properly. that is about the only down side of an SS relay


No, a solid state relay is a lot more than a thermistor. I have experience installing and testing them. It has four leads Two are in series with the motor and is undoubtedly a current transformer with a very low resistance primary. The othe two leads replace the centrifugal switch. The active element that does the switching is a triac. There are a bunch of additional components in there. It is a current type relay and not a potential relay which operates differently. Unlike a mechanical relay, it is not low resistance when there is no power. It "closes" when current is applied and then "opens" when the current drops to near the motor plate rating. There is no delay. We used them at work and they stopped and started constantly. If fact ours came as original equipment on a Leeson motor.

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## RobLW900 (May 8, 2018)

I found a relay for $92 with shipping, a little steep considering they used to be $47.
I pulled my relay apart and found the contacts were slightly burned so I cleaned them up and hooked up the new capacitor plugged it in and nothing, WTH, rechecked all the connections and tried again and again nothing, since I had the power switch to the back I forgot there's a breaker by the switch, I reset that and it runs good.

After complete assembly I tried it with a piece of wood and it works good.

For $15 for the part with shipping I got a nice $15 jointer, I still have to figure out a fence and get some new blades for it next spring when I go through and get all my tools fixed up, updated and ready for another summer of projects.


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## TimPa (Jan 27, 2010)

glad it is working for you. be careful without a fence, I think it adds a level of safe operation. maybe use some angle iron, with a 1x board attached to the front face?


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## RobLW900 (May 8, 2018)

Thanks, as far as the fence the jointer is oiled and mothballed until I build or find a suitable replacement and make a stand for it which I'll make out of a gas grill frame like I have for my miter and table saws.


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## Catpower (Jan 11, 2016)

Mycrossover said:


> No, a solid state relay is a lot more than a thermistor. I have experience installing and testing them. It has four leads Two are in series with the motor and is undoubtedly a current transformer with a very low resistance primary. The othe two leads replace the centrifugal switch. The active element that does the switching is a triac. There are a bunch of additional components in there. It is a current type relay and not a potential relay which operates differently. Unlike a mechanical relay, it is not low resistance when there is no power. It "closes" when current is applied and then "opens" when the current drops to near the motor plate rating. There is no delay. We used them at work and they stopped and started constantly. If fact ours came as original equipment on a Leeson motor.
> 
> Sent from my SM-G900V using Tapatalk



They have been in use for the 45 years I have been in the HVAC/R bidness, and yes there are different ways to do it, but if you go to a supply shop and ask for a generic solid state relay, it will 99% of the time be a thermistor


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## Maylar (Sep 3, 2013)

Catpower said:


> They have been in use for the 45 years I have been in the HVAC/R bidness, and yes there are different ways to do it, but if you go to a supply shop and ask for a generic solid state relay, it will 99% of the time be a thermistor


Not to nit-pick, but a thermistor is a resistance device that changes resistance with temperature. An SSR is an optically coupled triac (AC version of a thyristor).


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## Catpower (Jan 11, 2016)

Maylar said:


> Not to nit-pick, but a thermistor is a resistance device that changes resistance with temperature. An SSR is an optically coupled triac (AC version of a thyristor).





And that is how they work, as soon as current is applied, for a very short time the thermistor will allow current flow, as it warms up the resistance rises and the current flow stops. As long as there is power to it, it stays too hot to pass any current, so the start winding is left up powered


The start winding also supplies back EMF to the thermistor stays warm. That is the down side to them, if the machine is running and power shuts down for a few seconds, the motor will try to start but no flow because the thermistor is still too hot


For many years, HVAC/R manufacturers would install "Solid State Relays" instead of true start gear, they work great until there is a hiccup. For comfort cooling it is no big thing, but for refrigeration and freezing, that small hiccup can cost thousands of dollars by letting food spoil 



When ever I ran into them I would replace them with the right parts, to eliminate the problem


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## Maylar (Sep 3, 2013)

Catpower said:


> And that is how they work, as soon as current is applied, for a very short time the thermistor will allow current flow, as it warms up the resistance rises and the current flow stops. As long as there is power to it, it stays too hot to pass any current, so the start winding is left up powered
> 
> <snip>


OK, as a motor start device that sounds appropriate. But my nit-pick about terminology stands - a thermistor isn't a solid state relay. An SSR is simply an electrically controlled switch. The electronic equivalent of a mechanical relay, usually optically coupled for isolation.

BTW what you've described is a PTC (positive temperature coefficient) resistor. It's resistance increases with heat. There are also NTC (negative tempco) resistors that go down in resistance with heat. They're used as temp sensors though, not current limiters.


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## Catpower (Jan 11, 2016)

Maylar said:


> OK, as a motor start device that sounds appropriate. But my nit-pick about terminology stands - a thermistor isn't a solid state relay. An SSR is simply an electrically controlled switch. The electronic equivalent of a mechanical relay, usually optically coupled for isolation.
> 
> BTW what you've described is a PTC (positive temperature coefficient) resistor. It's resistance increases with heat. There are also NTC (negative tempco) resistors that go down in resistance with heat. They're used as temp sensors though, not current limiters.



The first ones were flat little plastic encased things the MFGer's called thermistors, possibly misnamed when Carrier started using them they were listed a PTCs and looked like this










They were the cause of many after hours calls, on new units because they got short cycled and didn't have enough starting torque so the compressor would lock out on over temp, and it took some of them 3-4 hours to cool down enough for a restart.


Anyway the OP was about how to get his motor running and he got it done without having to buy anything it looks like, and he wanted to go cheap as possible as generally we all do, and a start "themistor" would have done the job for a couple bucks, I was just telling him the down side of the low bid


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## RobLW900 (May 8, 2018)

Got a start on making a fence, going to get a piece of angle iron to make it taller but as is it worked great on some scrap wood.


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## JimmehMac (Apr 18, 2021)

RobLW900 said:


> I picked up a Delta jointer for free that I was told the motor loses power when a load is applied.
> I fixed it up and yes it lacks power so I unbolted the motor and tapped on the start capacitor and could hear a difference in how the motor sounded up until the capacitor blew up in my face.
> My question is was the capacitor bad and lightly tapping on it did it in or is the issue beyond that?
> Right before it exploded the motor sounded and ran great and if course Delta lists the most needed parts as obsolete like my craftsmsn that was awesome until the motor went out


I'm having a real hard time finding the start relay for the Jointer. I picked up the 37-280 at an auction for $40. Super clean with zero rust. However I get it home and notice some disconnected wires. Turns out the start relay is missing. Every where I've searched is sold out.


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## ETguy (Apr 18, 2021)

I have pretty much all the information but you are going to need someone with basic motor skills to get you going. I went to E Replacement parts and was able to take the number off the start relay. Delta bought this stuff; they did not make it. The relay is a Klixon 4CR-48-782. They are now part of Sensata Technologies. Something is really screwed up on your machine. With the relay removed only one side of the capacitor is connected (to the start winding). Tapping should have done nothing. However, start capacitors are only normally connected until the motor comes up to speed. They are not rated for continuous service and will blow up if not disconnected by the relay just before the motor comes up to full speed. For a test, this type of motor can be run without the relay and the internal start winding in the motor. The wire from the motor main winding goes directly to the line instead of the relay coil. Plug it in and give a yank on the belt If that t gets the motor going it should run normally but if it bogs down under load the motor is shot. This is diagram that is similar to what you have. That relay looks like $50 item if you can find it This current relay is an alternative design to an internal centrifugal switch. The relay coil is always in series with the motor main winding. When power is applied, the stationary motor pulls gobs of current, closing the contacts and connecting the capacitor in series with the start winding, which gives the motor a "push" to get it moving. As the motor gains speed the current through the man winding drops and when it drops low enough the relay opens and disconnects the capacitor. The relay should be rated to drop out before the current drops to the current shown on the motor plate. Otherwise, it will not disconnect and the capacitor will stay connected and blow up. There are solid state replacements for this type of relay and all you need to know is the Amps rating on the motor plate and you select one that has a slightly higher drop out rating than the motor run current on the plate. They are probably cheaper than the Klixon and far more reliable but again, I suspect you would need a little help with this.


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## JimmehMac (Apr 18, 2021)

ETguy said:


> I have pretty much all the information but you are going to need someone with basic motor skills to get you going. I went to E Replacement parts and was able to take the number off the start relay. Delta bought this stuff; they did not make it. The relay is a Klixon 4CR-48-782. They are now part of Sensata Technologies. Something is really screwed up on your machine. With the relay removed only one side of the capacitor is connected (to the start winding). Tapping should have done nothing. However, start capacitors are only normally connected until the motor comes up to speed. They are not rated for continuous service and will blow up if not disconnected by the relay just before the motor comes up to full speed. For a test, this type of motor can be run without the relay and the internal start winding in the motor. The wire from the motor main winding goes directly to the line instead of the relay coil. Plug it in and give a yank on the belt If that t gets the motor going it should run normally but if it bogs down under load the motor is shot. This is diagram that is similar to what you have. That relay looks like $50 item if you can find it This current relay is an alternative design to an internal centrifugal switch. The relay coil is always in series with the motor main winding. When power is applied, the stationary motor pulls gobs of current, closing the contacts and connecting the capacitor in series with the start winding, which gives the motor a "push" to get it moving. As the motor gains speed the current through the man winding drops and when it drops low enough the relay opens and disconnects the capacitor. The relay should be rated to drop out before the current drops to the current shown on the motor plate. Otherwise, it will not disconnect and the capacitor will stay connected and blow up. There are solid state replacements for this type of relay and all you need to know is the Amps rating on the motor plate and you select one that has a slightly higher drop out rating than the motor run current on the plate. They are probably cheaper than the Klixon and far more reliable but again, I suspect you would need a little help with this.
> View attachment 426712


Hey there, I'm not the author of this thread. But do you see a place to purchase the 4CR-48-782?


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