Repairing a fuse on solid state amplifier?

[suspencefull]

I have an Odyssey Stratos that the fuse is blown. I don't know whether their are any other problems. I have never tried to mess with amps only building speakers. I am wondering where to start on this. if it is possile to get a schematic for the unit.

[Bigred]

Obviously a schematic would be nice for the folks willing to walk you through. I love the diy spirit and love the learning process but personally I'm not big on telling folks to dive in amps not knowing their level of competence. There is the potential of serious injury and even death. I don't want to discourage just caution. I'm sure others will chime in here. At this point I would only advise you to NOT go popping in a new fuse expecting this to be it. They blow for a reason and you might get lucky but there is potential for causing more needless damage. Just my 2cents

[suspencefull]

I'm actually in school to be a EE. I won't say I am really experience, but could probably learn semi-quickly and understand semi how the amp operates.

[anatech]

Hi suspencefull,
Was the glass in the fuse greatly silvered or blackened? If so, do not try another fuse. If you can see where the element (wire) simply opened with possibly a small mark on the glass, it should be safe to try another fuse. I would not myself but we're looking at percentages here.

but could probably learn semi-quickly and understand semi how the amp operates.

From what I see in the field, very few service people understand how an amplifier works. Fewer engineers.

-Chris

[Original Burnedfingers]

From what I see in the field, very few service people understand how an amplifier works. Fewer engineers.

Everyone has a different idea and no one can agree.

I suggest you use the old light bulb in the power cord idea or borrow a variac to try to power up the unit.

[suzyj]

<facetious>

I've never tried repairing a fuse. Generally I just chuck them out and get a new one...

</facetious>

[Nordic]

I suppose the good old basics count... someone mentioned a lamp in series with the mains, disconnect loudspeakers before power on, if it doesn't drop another fuse, and doesn't smoke... take your multimeter in DC voltage mode 100V range should do it... and measure both outputs to ground... it should be virtualy 0V...

[unclejed613]

actually, measure on 1 or 2v range after measuring on 1v range. dc voltage should be less than 0.1v. then CAREFULLY (make sure you only touch the resistor leads and NOTHING else) measure across the 0.1 ohm (may be 0.22, 0,33, or 0.47 ohm) ceramic resistors in the output stage. if the output devices are BJT's, the voltage is usually between 0.005 and 0.03 volts. if they are Mosfets, it can be anywhere between 0.02 and 0.10 volts. current is calculated E/R, so .01v across a 0.1 would be 100ma. that would a bit high for BJT's, but normal for MOSFETS.
this test is best performed with a lamp in series with the power line. lamp wattage should be between half to equal the amp wattage. with most amps, the lamp will start bright and go dim. if it stays bright,you have a problem. if it doesn't light at all, you might have something (like another fuse) open. if it stays bright, you can do the emitter resistor test and find out where the problem is. the DC offset test might also be helpful, but an amp running off of less than 60V line voltage usually won't have a stabilized output voltage. what the lamp does is drop any voltage that the amp doesn't. if something in the amp is shorted, the amp will try to draw lots of current, reducing the amp's voltage drop, and so the lamp lights brightly.

another thing that's helpful with the lamp test is that after running a few minutes, components that are drawing lots of current will be warm to the touch, but usually not really hot (a temperature probe is still a good idea, saves the fingertips a lot of distress).

[anatech]

Hi unclejed613,
Oh my! I don't have that much patience at all. I just use my variac that is equipped with a voltmeter and an ammeter. I just start increasing the juice and watch the meters while I keep a nose and ear out of bad omens.

Hi suzyj,

I've never tried repairing a fuse.

You wouldn't believe how many repaired fuses I've seen. The foil from cigarettes was the number one patch used.

Hey Joe,

Everyone has a different idea and no one can agree.

Nope. You missed my meaning.

I didn't mean how to design one. The thing now exists and the design has to be accepted. So, there is only one answer to describe the way it works. What I meant is that by looking at how the job was (improperly) done, you can see the "technician" had no idea how these things work.

-Chris

[Pars]

Check the fuse and try a new one. If it blows, call Klaus at Odyssey... the amp has a 20 year warranty on it (I own one). I'd use it