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previous: slideguy NOW I KNOW HOW NOT TO BLOW IT UP -- 8/13/2000 3:23 PM

Re: boss psa-120T power supply problems

8/14/2000 3:16 PM
Doc	Re: boss psa-120T power supply problems Usually wall wart cases are sealed with an exotic industrial adhesive or a high frequency weld. You have to half-destroy the thing to get inside. The older ones were easier to get a crack going around the seam by judicious coaxing between the jaws of a bench vise, but current ones are almost impossible to split at the seams. You can use a hacksaw to carefully cut a line around the case at the seam. Go only as deep as necessary. Go around a few times, deepening the cut line a little at a time until you see the break. Once the thing is open, check to see if the transformer is still healthy. Many consumer electronics devices, including transformers, have little in-line fuses or fuse wires that open up to prevent fires and product liability consequences to manufacturers. Sometimes you can jumper the broken fuse wire and be back in business. Sometimes the fuse wire is hidden under the first few layers of tape on the coil. It's possible that one of the small rectifier/filter components blew, on the low voltage secondary side of the transformer. Make sure you check all those, or substitute new components. They're inexpensive. A replaceable fuse is a nice addition to a power supply that seems prone to getting knocked out. You may be able to fit a sub-mini fuse, and even a holder, in the wall wart case if you find there's enough empty space between the case & the guts. Otherwise, splice in an in-line fuse holder (like commonly seen on car radios) in the DC output wire between the wart and the power jack. This doesn't look so wonderful, but it works well in practice.

8/14/2000 3:16 PM

Doc

Re: boss psa-120T power supply problems

Usually wall wart cases are sealed with an exotic industrial adhesive or a high frequency weld. You have to half-destroy the thing to get inside. The older ones were easier to get a crack going around the seam by judicious coaxing between the jaws of a bench vise, but current ones are almost impossible to split at the seams. You can use a hacksaw to carefully cut a line around the case at the seam. Go only as deep as necessary. Go around a few times, deepening the cut line a little at a time until you see the break.

Once the thing is open, check to see if the transformer is still healthy. Many consumer electronics devices, including transformers, have little in-line fuses or fuse wires that open up to prevent fires and product liability consequences to manufacturers. Sometimes you can jumper the broken fuse wire and be back in business. Sometimes the fuse wire is hidden under the first few layers of tape on the coil.

It's possible that one of the small rectifier/filter components blew, on the low voltage secondary side of the transformer. Make sure you check all those, or substitute new components. They're inexpensive.

A replaceable fuse is a nice addition to a power supply that seems prone to getting knocked out. You may be able to fit a sub-mini fuse, and even a holder, in the wall wart case if you find there's enough empty space between the case & the guts. Otherwise, splice in an in-line fuse holder (like commonly seen on car radios) in the DC output wire between the wart and the power jack. This doesn't look so wonderful, but it works well in practice.