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Quadra 605 No Power

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My buddy @sclements sent his Quadra 605's power supply to take a look at. It simply does not power on. I desoldered all of the capacitors (except the big chonker in the middle), and none of them look bad. 

 

Are there any common points of failure on these? Any chance that recapping it would fix it?

 

IMG_0442.thumb.jpg.3608d5926a5733a21178284b2c5ee005.jpg

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I'm not the brightest bulb on the tree, and I can't speak to this specific PSU, but on the SE/30 PSU I had one with dead fast switching transistors - I don't remember what exactly they were anymore with my memory these days, they might have been called simply "transistors", but it certainly seems like a point that could fail.

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With the capacitors desoldered and loose, have you tested them with with a capacitance meter?  Prior to desoldeirng, did you test for any voltage output when turned on?

Edited by Byrd

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14 hours ago, Jinnai said:

I'm not the brightest bulb on the tree, and I can't speak to this specific PSU, but on the SE/30 PSU I had one with dead fast switching transistors - I don't remember what exactly they were anymore with my memory these days, they might have been called simply "transistors", but it certainly seems like a point that could fail.

Okay, I'll be suspect of those as well, thanks for the tip!

14 hours ago, Byrd said:

With the capacitors desoldered and loose, have you tested them with with a capacitance meter?  Prior to desoldeirng, did you test for any voltage output when turned on?

I don't have a capacitance meter, and on top of that, I didn't consider how easy it would be to connect it to mains power and check output voltages. I'm so awful at troubleshooting! :lol:

 

I did find that one of the caps (THE BIG CHONKER) had leaked when I desoldered it, and a new set of caps was a whopping $7 from DigiKey (including the large one). So I'll clean the board, recap it, and troubleshoot further if that doesn't fix it. Shotgun troubleshooting, hooray!

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Follow-up on this one: I specced out and purchased new caps, soldered them in, and it fixed it! I verified that it was outputting the right voltages on each pin before send it back to my friend, who said it booted right up. :)

 

If you open up your Astec PSU and find that it is identical to mine, you can follow this link to add the same capacitors that I used to your cart on Digikey.

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