Identify cap, garage door opener.

[digge]

Hi

Have this garage door opener in front of me and seems like the caps is busted. I have a problem identifying the manufacturer and cant find any datasheets for them. With my limited knowledge that means its hard to know what to replace them with.

From what i can read on them the brand should be NKL and the series should be N, they are good for 85 degrees and there is a few different values on the board. The sleeve is grey with black stripe for negative side.

The broken one seems to be on the output (might be input didn't look that closely on the datasheet) of a 7818CSP voltage regulator so my guess is that's why its not working. Also the voltage regulator seems to have been very hot.

The one on the right in the picture is the one that's busted.

So does anyone have a clue what cap might fit the purpose? The cap in question is 100uF 40V, but im probably gonna replace all for good measure.

[Rob Northen]

Re: Identify cap, garage door opener.

Based on where the cap is used , I would go for something like Panasonic FC

[Krankshaft]

Re: Identify cap, garage door opener.

I take it this door opener was manufactured in the 80s? The caps have no stamped vents.

Why do you say the cap is bad?

You mention overheating of the voltage regulator. How is the input voltage to the regulator derived via a linear transformer or via a zener diode pre regulator stepping down line voltage to the 30-40 V input? Is the input voltage within spec and is the voltage below the input caps rating?

Zeners can become leaky and the input voltage can drift over time.

Board darkening from components like voltage regulators is normal especially with a device this old. The cheaper PCB materials tend to darken at the slightest exposure to heat.

[PCBONEZ]

Re: Identify cap, garage door opener.

Brand is Meritek
NKL is Series
N is tolerance +/-30%
.
Old series - no data sheet.
But with that high a tolerance they are obviously just a GP cap.
.

[digge]

Re: Identify cap, garage door opener.

The reason i think its broken is i measured ESR in circuit and that gave me 199 ESR, that sounded way to much even for a GP cap. Desoldered it now and it measures 1,6uF and 174 ESR, also i can see all the electrolyte have leaked out by one of the legs. Thats probably the gunk i saw on the board.

Also now when im home i can take better pics then my cellphone so here goes, a full pic of the board.

I was probing around a bit and on the input (of the regulator between middle and input pin) i measured about 38V AC, should be a DC voltage on the input of the regulator right? That would mean go hunting for some busted diodes as well?

The whole thing is getting its feed from a 24V transformer btw.

Still cant figure out why they put an 18V regulator in there, the relays are 24V, the actual motor is 12V so, maybe they are "overvolting" the motor since its running for such shorts periods?

[PCBONEZ]

Re: Identify cap, garage door opener.

When the motor is running the voltage will drop plus there is a high current when it first starts so, yeah, it might be overvolted on purpose.

Also might be some voltage drops between the regulator and the motor.

Yup, that's too much ESR.
.

[Krankshaft]

Re: Identify cap, garage door opener.

I was probing around a bit and on the input (of the regulator between middle and input pin) i measured about 38V AC, should be a DC voltage on the input of the regulator right? That would mean go hunting for some busted diodes as well?

As long as you're sure that it is a regulator and not a Triac yes.

The motor runs on DC that's weird. The openers in the US just use a zener diode regulator, a switchmode power supply, or a linear transformer for the control circuitry only.

The motor is a 120V AC Permanent Split Capacitor type (start cap and start winding are always connected) motor cycled by a relay on the control board.

That big fat diode is the half wave rectifier responsible for feeding the DC motor.

[PCBONEZ]

Re: Identify cap, garage door opener.

Seems to me an DC motor would be a more sensible choice.
More starting torque, easily reversible, and not much coast-down.

I dunno what they actually use 'cause I never broke one.
.

[Krankshaft]

Re: Identify cap, garage door opener.

Oh I know why they use them.

The newer garage door openers boast a battery backup system. An AC motor is impractical for this purpose an inverter would add way too much cost.

Because god forbid you'd have to haul your butt out of your car and manually open the door .

Just did some research DC motors have been available as an option in the US for awhile.

Funny when I bought one to install in 03 there was no mention of a DC motor being an option when I was looking at Sears. It seems that they have been available since the 90s. When the price of semiconductors dropped and cheap efficient power supplies could be built to drive the DC motor.

[digge]

Re: Identify cap, garage door opener.

The motor is actually something similar to a windshield wiper motor. Might even be one, who knows

I'm not 100% sure its a regulator, but at least thats what my google skills lead me to belive. Its an old Thomson(?) part and i cant find a descent datasheet for it. Thought it would be a sibling to the ol 7805 and cousins

To me it sounds like an AC motor for this kind of application doesnt make sense and over complicates it. The direction part is just 2 microswitches depending on what end the motor is at basically. (This one have the motor moving on the chain, they even use the chain for ground and the rail for positive, kinda crazy even if its low voltage :P )

Maybe i should go ahead and replace all the caps for good measure, as said earlier they don't even have vents like modern ones have.

[PCBONEZ]

Re: Identify cap, garage door opener.

Maybe i should go ahead and replace all the caps for good measure, as said earlier they don't even have vents like modern ones have.

Sounds like a good idea.

[Krankshaft]

Re: Identify cap, garage door opener.

Replace all the caps and see what happens. A high quality General Purpose series like Chemicon KMG for example will be fine.

An induction motor will easily rotate in either direction by just changing current flow (swapping the wires) to the start winding.

Disconnect the cap on any cap start motor and run it. It won't rotate but you can choose it's direction by spinning it either clockwise or counterclockwise and it will continue rotating in that direction.

AC motors don't require a high current power supply to run that's why they're popular. Nowadays with the proliferation of cheap power supplies that point is pretty moot. However AC induction motors are brushless which makes them more durable in the long run.

[digge]

Re: Identify cap, garage door opener.

Finally got my parts yesterday. I opted to swap more then needed just to save me one shipping cost. The shipping is more expensive then all the parts

So i swapped the caps for KMG ones, swapped all the 4007 diodes for good measure. Tried the board, still dead. Measured input on the voltage regulator, 38V DC, output nothing. So i swapped the voltage regulator as well and success, now it works!

Thanks for your input Krankshaft, PCBONEZ and Rob Northen, appreciate it.

[japlytic]

Re: Identify cap, garage door opener.

I am curious about whether modern garage door openers use switching power supplies - if the caps go bad, you can't open it!