Old Peavey 900 Mixer fuse in power circuit ?

[Jerry Overstreet]

https://assets.peavey.com/literature/ma ... 0mixer.pdf

Question for techs and/or knowedgeable electronics dudes.

Have an old 80s prolly worthless Peavey 900 passive mixer. If some of you would look at this diagram and see if a fuse is somewhere in the circuit, I'd appreciate it.

I looked at the diagram with my limited understanding but do not see a fuse anywhere nor is one visible anywhere on the mixer panel.
I'm not above opening it up and inspecting it but I really wouldn't know what to look for unless there is a fuse in there.

It's just an old mixer that I use in my music room to run audio through for practice so I don't expect too much.

Anyway, I unpugged the thing from power and cables with the switch on while working on some stuff and subsquently plugged it back in the same way without realizing it and now it won't power up.

Thanks for reading.

Could be the power supply or something in the circuit was blown.

[Dennis Detweiler]

There should be a fuse holder on the back of the mixer near the power cable (wire)? Looks like a black button that pushes and turns (spring loaded). There could be a fuse on the circuit board inside also. Those are easy to spot, metal clips about an inch apart with a fuse bridging the two clips. Replace with the same type and amperage.

[Jerry Overstreet]

Maybe internally, but there is no fuse anywhere on the outside of any of the panels. Guess I'll pull in apart and have a look see when time allows. Probably toast.

[Jerry Overstreet]

K, so there is a 3AG fuse soldered in the power line that passes a continuity test. The power cord also tests good on ea. leg to the switch along with the switch best I can tell.

And that's about the extent of my knowledge. Don't see anything obvious on the board traces. I suspect the transformer, but do they just go bad? I'm not sure if I need to be testing anything else under power though.

Probably not worth a repair bill but I can strip it for lots of good knobs, jacks etc. later on and there is a nice Accutronics reverb tank in there.

[Dave Grafe]

Not likely the transformer going bad as that would pop the fuse. If the fuse is good and the lights don't come on it's definitely a power supply issue, if they DO come on but no sounds it's something in the signal chain. If you plugged it back in before the power supply was fully discharged it would have seen a PSU spike that could easily pop caps or transistors.

At that age my first hunch would be power supply caps, which are overdue for replacement. It's a useful device so I would look it over thoroughly and maybe even get a repair quote before tossing it.

[Jerry Overstreet]

Thanks for your input Dave. No lights, no. No meter movement. There are 2 caps wired into the switch but I've no idea how to test all that. I can post a photo if anyone is interested. I don't know how to read the diagram but I figured it would show that.

I figured a voltage spike of some kind, yeah. I just got in a hurry to move a piece of equipment out of my way and unplugged the strip not realizing the unit was under power.

It's pretty old and out of date but it served my purpose so we'll see if I can find someone who might be willing to test it for a reasonable fee. Components are generally cheap but a diagnosis and repair costs are generally not.

[Richard Sinkler]

That diagram you posted is meant to show signal flow. It's not really a schematic that shows the components on the board. The schematic is what would be needed.

[Dave Grafe]

That diagram you posted is meant to show signal flow. It's not really a schematic that shows the components on the board. The schematic is what would be needed.

I did some digging but so far no schematics to be found. Still the power supply is likely very basic as this mixer predates the use of switching technology in music gear psu's so shouldn't be hard to troubleshoot.

[Richard Sinkler]

You have a better chance of finding a 5 pound gold nugget in your bathtub than find Peavey schematics