Roland KC 550 fuses?

[lowell]

Hey all,

This amp has no output, but powers on. There IS signal at Pin1 of W5 which is the connector to the power amp. There is signal at Q9 and Q16 emitters. I am not getting a beep across the series emitter fuses. These are odd looking. I've never seen fuses like this. They are cylindrical looking radial lead fuses that actually look like those bridge rectifiers that are radial lead and cylindrical. Make sense? Here's a link: MRT 100-BULK Bel Fuse Inc. | Circuit Protection | DigiKey. My question is - Do these measure as SHORT when there is no power as your standard passive fuse would? If they do then these are both blown. I see that the resistor R41 looks compromised in the zobel network. It still however does measure 27ohms.

[olddawg]

I always just replace those with small standard glass pigtail fuses of the same value. If there isn't enough room l stand them verically. A fuse is a fuse.

[Enzo]

AMen, a fuse is a fuse, doesn't matter what they look like.

If those blew, Q9 and Q16 are certainly suspect.

[lowell]

I replaced the fuses with in-line holders and fuses. Amp works fine. Maybe I shoulda replaced Q9/16. Already gave back to the owner. If he comes back I'll take care of him and replace those transistors. I figured a blown or suspect transistor would be showing signs if they were bad and don't fix if it ain't broke. We shall see.

[Enzo]

I hope it is OK, but what does a damaged transistor look like? The silicon inside one of those drivers might be half evaporated, and that thin spot is just waiting to erupt one day.
To me the transistor WAS showing signs - the signs were the burnt resistors.

[lowell]

Good point