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SL40_Replace Capacitor (C874)

don’t think it’s the same capacitor, jt we recently had this one blow... planning on sending it to Garmin unless there’s a better way.
 

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Failure of a surface mount cap is extremely rare, looks like it's located in the power supply area, my suspicion would be a failed power supply likely caused the failure.
 
don’t think it’s the same capacitor, jt we recently had this one blow... planning on sending it to Garmin unless there’s a better way.

Jim, it's difficult to read the component designator on the board with the crud obscuring it. A little time with a toothpick or something similarly non-destructive would show whether that's C874 or C871 or something else. I'll be happy to have a look at it if you like. I'd be very, very surprised if there are any useful markings in the board underneath, but I'd be somewhat less surprised to find useful markings on the underside of the part itself.
 
SL40

Just sent an SL40 to Garmin for power supply issues

Flat rate is ( gulp) 850!
 
Just sent an SL40 to Garmin for power supply issues

Flat rate is ( gulp) 850!

I wish you had searched this forum before you sent it to Garmin. I hate it that Garmin charges so much. I've told many people here that mine was repaired for a flat rate of less than $500 here in Texas and if you send it and it can't be repaired he returns it without charging you for the troubleshooting. Mine's been working great since.
 
I wish you had searched this forum before you sent it to Garmin. I hate it that Garmin charges so much. I've told many people here that mine was repaired for a flat rate of less than $500 here in Texas and if you send it and it can't be repaired he returns it without charging you for the troubleshooting. Mine's been working great since.

Does your guy repair other brands (TKM) too? I have a radio in my C-172 that went T.U. with no volume. TKM says it's too old and won't touch it, but they are happy to sell me a new one for $2800. The radio part works but the sound is very faint (audio amplifier?).

-Marc
 
Does your guy repair other brands (TKM) too? I have a radio in my C-172 that went T.U. with no volume. TKM says it's too old and won't touch it, but they are happy to sell me a new one for $2800. The radio part works but the sound is very faint (audio amplifier?).

-Marc

Get some spray contact cleaner. Open up the radio as needed to gain access to the volume control, spray (you need to get it inside the control, look for an opening), ‘exercise’ the control. See if that fixes it. No guarantees but cheap and easy to try.
 
Get some spray contact cleaner. Open up the radio as needed to gain access to the volume control, spray (you need to get it inside the control, look for an opening), ‘exercise’ the control. See if that fixes it. No guarantees but cheap and easy to try.

Having been around the block with radios and rf circuits, I would have expected the volume control pot to at least give some indication of a problem that would indicate a dirty wiper was at fault. This radio just quit cold one day, and it was only after trying it with the engine off that I could faintly hear the audio. TX works fine, but exercising the volume pot changed nothing.

But thanks for the suggestion. Right now the radio is at TKM, but they flat told me that they just wouldn't touch it.

The frustrating thing is that they built the radio, now they want to sell me a new one that they presumably won't repair either in a few years....

It's an MX170 nav-comm for the record, and was installed in my 1960 C172 that I use (used?) for Young Eagle flights.

-Marc
 
Here is the info again:

Keith Peshak
235 Colovista Parkway
Bastrop Texas 78602

512-636-0851

$499 flat rate IF they can fix it if not they’ll send it back no charge. He's a "colorful guy" but as long as you follow his instructions EXACTLY as he tells you (don't offer advice or try to change his process or how he ships or does anything else), he fixes them cheaper than Garmin.
 
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I agree with your analysis. My suggestion was made in the spirit of ‘Try easy stuff first, even if unlikely’ (I recently wasted hours of my time when I forgot this rule!).
Edit: reply to Marc
 
I just spoke with Keith (Thank you!) but unfortunately TKM is one of the radios that he won't touch. If the plane was worth more I'd swap the radio out for a KX155 or even a 430w, but it's just not worth the upgrade.

-Marc

Here is the info again:

Keith Peshak
235 Colovista Parkway
Bastrop Texas 78602

512-636-0851

$499 flat rate IF they can fix it if not they’ll send it back no charge. He's a "colorful guy" but as long as you follow his instructions EXACTLY as he tells you (don't offer advice or try to change his process or how he ships or does anything else), he fixes them cheaper than Garmin.
 
I can't suggest what to do about your cap but I can provide some additional info which you can use as you will.

First off it appears that this cap is in parallel to the one that is right next to it. You could check this with a multimeter and look for 0 ohms. You might also be able see the connecting copper traces on the PCB. For switching power supplies this is often done to provide more capacitive filtering (caps in parallel add). I'm guessing it is the same exact value as the one next to it. Again this is a common design practice. If you were to remove the shorted cap does the circuit operate such that you could measure the voltage across the cap. That might give you an idea of the minimum voltage rating. Typically though a safety margin of 1.5x to 2x is used for design parameters. If the circuit operates it will have more AC ripple that desired by the designer so don't leave it like that.

Also if the cap shorted then the power supply circuit may or may not have current limited. If it did then the remainder of the circuit may still be OK. If it did not or did not soon enough the power supply regulator chip or the out board FETs may also be fried.

If it was me I would remove the cap. Then check with an multimeter the resistance across the cap PCB pads. If it is still shorted or very low resistance then you have additional damage. Then I would send the unit back to Garmin. If it is say over 1K ohms I would power it up and check the voltage. Then you could go down the path of figuring out the replacement cap. You might even be able to remove the parallel cap and measure the value if you have a multimeter which measures capacitance.

I hope this helps. Its up to you how you proceed. I've assumed this is a power supply cap, but that may not be the case. I cant tell from here so its just a guess.

Another option is that is an AC coupling cap for one of the audio paths. If that is the case everything I just said doesn't apply.

I'm willing to help if you want additional guidance.
 
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