bitshox
Member
This is not so much a request for advice but rather documenting the innards of a not-so-common part for a Compaq Portable 286. It's the Sprague line filter unit (JN17-5259E) which houses the Class X and Y capacitors as well as the mains power connector, fuse and switch.
When I first powered up my Compaq it predictably released the magic smoke. Doing some research I thought that a RIFA line capacitor might be the culprit. However taking a look at the power supply board I couldn't find any line filter caps. It turns out the caps are located in this sealed box manufactured by Sprague Electric for Compaq. I thought at first the box was welded shut, so I took my Dremel to the perimeter and tried to open it up at the seal. However my Dremel kept slipping so I gave up on that idea pretty quick. I then thought the box might have been soldered shut, so I took my soldering iron to the seal and cranked up the iron to the hottest setting and used solder wick to get as much of the solder out as possible.
(The lid was rusty too, which made me think a electrolytic had leaked from the inside but this turned out not to be the case)
This ended up working well, and after half an hour I was able to prize the lid open. To my amazement the Class X capacitors were Mallory polyesters, both of which were intact, while the Class Ys were ceramic disc caps. Additionally the fowl odor I had smelt when magic smoke got released was not present anywhere inside the Sprague box.
Here is the diagram from the front of the box:
Unfortunately everything is epoxied together so even if there were a RIFA inside there's not much I could do to extract it. I think this Sprague unit is totally fine though; I got the rust off the lid with a wire brush and some vinegar and will be taping it shut. I've ordered a spare on eBay just in case however.
I went back to the Compaq and inspected the power supply board, and I think I found the culprit:
A blown tantalum at C22. Can't get a good register on it or else I'd write the specifications. Looks like I'm going to have to replace all these tants wherever I see them, not looking forward. Hopefully this post will help out a fellow faulty Portable 286 owner rule out the Sprague unit at least.
When I first powered up my Compaq it predictably released the magic smoke. Doing some research I thought that a RIFA line capacitor might be the culprit. However taking a look at the power supply board I couldn't find any line filter caps. It turns out the caps are located in this sealed box manufactured by Sprague Electric for Compaq. I thought at first the box was welded shut, so I took my Dremel to the perimeter and tried to open it up at the seal. However my Dremel kept slipping so I gave up on that idea pretty quick. I then thought the box might have been soldered shut, so I took my soldering iron to the seal and cranked up the iron to the hottest setting and used solder wick to get as much of the solder out as possible.
(The lid was rusty too, which made me think a electrolytic had leaked from the inside but this turned out not to be the case)
This ended up working well, and after half an hour I was able to prize the lid open. To my amazement the Class X capacitors were Mallory polyesters, both of which were intact, while the Class Ys were ceramic disc caps. Additionally the fowl odor I had smelt when magic smoke got released was not present anywhere inside the Sprague box.
Here is the diagram from the front of the box:
Unfortunately everything is epoxied together so even if there were a RIFA inside there's not much I could do to extract it. I think this Sprague unit is totally fine though; I got the rust off the lid with a wire brush and some vinegar and will be taping it shut. I've ordered a spare on eBay just in case however.
I went back to the Compaq and inspected the power supply board, and I think I found the culprit:
A blown tantalum at C22. Can't get a good register on it or else I'd write the specifications. Looks like I'm going to have to replace all these tants wherever I see them, not looking forward. Hopefully this post will help out a fellow faulty Portable 286 owner rule out the Sprague unit at least.
