Fisher SA-100 Tube Amplifier Restoration

This is one of the first stereo amplifiers made by Fisher Radio back in the early 60s. This amplifier uses some of the largest transformers for any amplifier utilizing 7189 output tubes and it's capable of putting out about 20 watts per channel at 8-ohms. These 7189 tubes were essentially beefed up EL-84s to handle the increased plate voltage present in certain amplifiers. I believe vintage Fisher amplifiers can hold their own against similar McIntosh and Marantz units of their day as well as British products from Leak and others. I've replaced nearly every single resistor and all of the capacitors. I go over the things to look out for and what I'd do differently a second time. If you enjoy the video, please click the thumbs up and subscribe to my channel as I'll be posting more soon. Happy to answer questions, hear feedback.

[@M0D60]

Does this Amp has a slight hum? .. considering purchasing restored sa100

[@wesleymorris1]

I just got one of these, I'm going to restore it, check the tubes there all good, reading 80 percent but 1, my guess why someone stuck it in the closet and stopped using it. Im used to working on guitar amps, this will be my first stereo amp. I'm alittle Intimidated by 2 push pulls running perfectly in synced.

[@brianmccowan1949]

I am a fan of Fisher tube amps. I have an SA-100 and its a favorite. The massive iron for an EL-84 amp is one of the things that really helps its sound. I went through mine as you did, replacing caps and many resistors. EL-84s are sweet audio power tubes. I also have a pair of SA-30 monoblocs that are also EL-84 amps that have a bit simpler signal path - very easy to work on and also sound great. I also have an SA-300 which has 4-EL34s. Its a beast with two rectifier tubes and a hybrid combination of cathode and fixed output tube biasing. It pushes the power tubes really hard so I detuned mine a bit to save expensive old Telefunken EL-34s and because it smoked a resistor. I now use really efficient tube friendly speakers and the 300 is way more power than I can use, so will likely sell or trade it in the near future. I bought it 25 years ago at a junk shop that was going out. $25 for the SA-300, a 400Cx preamp and a tube caddy full of NOS audio tubes. Kind of a "good deal."

[@MrRourk]

So a Subwoofer could be hooked up on that Center?

[@robertyoung1777]

My guess is that it would be better to power your subwoofer with a class a/b class d amplifier. Subs were not a thing when these tube amplifiers were created

[@willayre1979]

I'm interested in a SA300 for sale locally. I'm considering recapping it myself. I'm good with a soldering iron, and have built a nelson pass designed diy class A amp, and a pre amp. I know the SA300 and the SA100 are different but how difficult do you think it would be to recap it myself?

[@chrisw.3077]

It’s not difficult if you take your time and work section by section, testing the unit after each small section of replacement. You’ll want to disassemble the gain pots and clean them as well as the stereo/mono switch (I probably mentioned this in the video) Overall, the SA-300 is easier to work on since there’s more space and the power supply is less complicated. I can answer some questions if you have them along the way. I’d use the authenticaps to replace the can capacitors. There are going to be a lot of resistors out of spec as well.

[@Sans_Solo_]

Would have use Mundorf instead of the Sprague caps

[@chrisw.3077]

Literally would’ve been a waste of money.

[@Sans_Solo_]

@@chrisw.3077 No not really, Mundorf's sound the best for filters I have tried many

[@chrisw.3077]

@@Sans_Solo_ you couldn’t fit a 50uf film cap under the cover so take your crap elsewhere.