This is going to sound really dumb

[Don]

but is there a power switch on this Fisher sa 100 I have? I have looed high and low but can't find one!

I'm trying to get it to power up but I can't figure it out.

I put a fuse in it and plugged it in. Then to see that it was at least getting power I plugged a tuner into the amps a/c out. The tuner had power so I assume the amp should also. I'm pretty sure this an unswitched a/c out.

I'd like to get it working and try it on my heresys so see if there's a discernable difference between tubes and SS amps.

 

[WildWest]

Don...I don't know that paticular amp exactly ( I know of Fisher and it's good stuff!) but it is very possible that there is no power switch. That this amp plugged into a pre amp and that was it's switch. My Marantz 240 has no switch, just plugs in. So plug it in, watch the tubes glow, look for smoke. That fisher is a fine amp and very upgradeable. Do you know what the driver tubes in it are?

Anyway, hook it all up and I feel confident that it will at least provide you with a bit of "eye opening" differance from your solid state gear. How efficient are those Heresys again? That amp can't be much more than 30 watts per channel. And knowing that typically one watt of tube power equates to 2.5 watts of SS power. You got some push there. There clearly is a differance between tube sound and SS sound. Will you like that differance? I fell in love with it myself.

 

[Don]

WW I think the heresys are quite efficient but am not sure of the actual numbers. According to another sa100 owner this is 25wpc.

I have l plugged this fisher in but got no glowing tubes Maybe it needs a signal from a tuner?

It looks like a nice amp and weighs a ton for its size.

 

[WildWest]

I sure hope you had a load on this amp when you plugged it in. Never plug in amps like this without a speaker load on them. Regardless, the tubes should still glow without a signal from a source. So no glowing at all makes me wonder about the fuse or power supply section. Anyway if it is toast, just send it on over to me okie dokie?

 

[Don]

ummm...load? Speaker load ....errrr, yeah, I had that. :


No, no load and no glowing tubes.

The original fuse cap was broken off and missing ...along with the fuse. I took a random cap and fuse out of one of the heathkit testing components I had kicking around and stuck it in the sa100. Maybe the fuse is too short?


If the unswitched a/c out on the amp has power wouldn't that mean that the fuse is doing it's job?

 

[WildWest]

"If the unswitched a/c out on the amp has power wouldn't that mean that the fuse is doing it's job?"

Hmmm good point. I reckon it would be yes. Bummer man, no glowing tubes what so ever. Well that clinches it. Just gonna have to give it to me then so I can save it from the clutches of the storage rack. uhhhhh errrrrrrr

 

[MikE]

No Killjoy

I certainly do not want to ruin anyone's fun but before you go "fire'in up" your amp or pokin' around inside I thought I would offer some friendly advice. When you receive a new piece of vintage equipment, before you hook it up I'd have someone check it out. In vintage tube gear caps, resistors and tubes can degrade or fail after years of use (or even non-use). If you're not qualified or comfortable (correct on both counts in my case) enough to service the gear than I'd entrust it to someone else. You could do more harm than good.

The other point to remember is that a tube amp can hold a letal charge EVEN when UNPLUGGED! The power caps need time to discipate that energy BEFORE you go pokin' your nose in there. My buddie discovered this when he was playin around with my old GTA se-40 amp and luckily only received a small reminder of what I'm talking about. I think it's great you guys are looking at some of that vintage gear, and as WW said, they sure made some beautiful sounding stuff back then. Have fun, just don't fry yourself or the equipment in the process.

MikE

 

[WildWest]

Well said Mike! A good word of warning.

 

[Don]

I got it to power up! It was the fuse and fuse holder. If you look at the picture you can see it under thw power cord. The fuse holder is broken.

All the tubes are warm/hot and glowing. PRETTY!

It won't produce any sound though. I'll play with it some more and see if it's something simple.

 

[Thatch_Ear]

Not sure but those blue pot stems are probably gain controls. I had a 30A which is basically half your amp being one channel but same tubes and it had a gain pot on the side close to the RCA input plugs. Hook up your speakers, a CD player and give her another go.