Rosac Bassmaster Head

[jet460]

I picked up this old Rosac head yesterday. Someone has replaced the switch and left the carcass of the old one in the circuit, among other messy bits.
I am no amp tech, but this is something I should be able to sort out.
I work on guitars, normally. So I can handle a solder iron and all that.
A google search for the schematic gets me nothing.
Curious if anyone is familiar with these, and might actually have a schematic.

In case you are not familiar, Rosac was a mid-late 70's spin off of Moserite.
They were in socal.
There is a doc about randy Rhodes, and he can be seen playing through a rosac guitar amp.
I have a folded horn 115 bass cab of theirs that is truly remarkable.
They made a little of everything, including pedals.

[jet460]

The switch.

[jet460]

the switch

[jet460]

The rest of it.

[The Dude]

I can't tell for sure from the pictures, but it doesn't look like there is a grounded AC cord. There is the power switch, and then (most likely) that switch laying inside the unit was used for flipping phase from the input mains to the PT. Obviously, you don't want a switch with mains wiring connected flopping around inside an amp. If it were mine, I'd install a grounded AC cord (grounded to chassis), wire to the fuse holder, power switch, and power indicator neon. Just unhook/forget about the ground/phase switch. Make it safe.

[glebert]

That's funny that you got that amp, I was half considering ordering it from GC myself. I have a Rosac Nu Amp and thought it would be cool if someone would document them, draw up schematics, etc.

[loudthud]

How about a pic of the preamp ? What's the Voltage on those big caps ?

[g1]

Looks like there is also a 'death cap' under one of the switches, can't tell what it is connected to.

[jet460]

That's funny that you got that amp, I was half considering ordering it from GC myself. I have a Rosac Nu Amp and thought it would be cool if someone would document them, draw up schematics, etc.

It was in Huntsville, AL.

[jet460]

I can't tell for sure from the pictures, but it doesn't look like there is a grounded AC cord. There is the power switch, and then (most likely) that switch laying inside the unit was used for flipping phase from the input mains to the PT. Obviously, you don't want a switch with mains wiring connected flopping around inside an amp. If it were mine, I'd install a grounded AC cord (grounded to chassis), wire to the fuse holder, power switch, and power indicator neon. Just unhook/forget about the ground/phase switch. Make it safe.

The cap was wired from one side of the gnd sw to the chassis. Yes, 2 prong cord. The gnd switch had no continuity between the terminals in either position. It is either dead or I don't get what it does.

[g1]

Doesn't the ground switch have 3 terminals?

[jet460]

Nope. 2.

[g1]

Nope. 2.

That would mean the cap is directly connected to one of the green wires? Are you sure there is not a 3rd terminal on the bottom side of that ground switch?

[jet460]

Each green wire goes to either side of that switch, and to one of the two transformer wires. I do not think there is another terminal on that sw. I will look again. The amp is so gutless, it makes me thing it's using half the trans. All the way up it has the volume of like a 5 watt amp. Stay pretty clean too. It's wired wrong to some degree. Gonna have some coffee and have another look, since you mention a 3rd terminal.

[jet460]

Won't let me upload any more [pics for some reason.
But yes, there is a 3rd terminal. That cap goes to it. I don't have my meter right now, but I assume either side of that sw goes cap to gnd, not across the 2 main terminals?
Also, there is no continuity across the 2 wires for the lamp, but it did light up.
haha this is why I am not an amp tech.
Invisible forces baffle me.