Sherwood S-5500 III Tube Amplifier Troubleshooting and Repair 

I saw a S5500 II on local Craig’s List and found your video trying to get some info on this amp. Based on the video I think I can make this my first Tube amp project and bought it ! Great Videos !

Thanks for sharing your expertises. Much appreciated. A gentleman was kind enough to sell and safely ship an S-5500 to me so will evaluate what repairs and mods to perform on the unit. Your video will be helpful in making this determination. Regards.

I really appreciate your professionalism and your expertise. I have two older receivers, a Luxman from 1988 and a Yamaha from 1977. There's no one in this area that repairs electronic equipment anymore. I found one gentleman who simply listened to the Yamaha for a few days to hear a loud popping sound that I told him about. When it didn't repeat for him he pronounced it fine. He didn't check anything with test instruments and when I mentioned that the amp needed biasing he seemed confused. I wish you lived closer, I live in eastern Kentucky. Could really use someone who knows what they're doing.

Great video, I have one in the way and will use this as a reference. Once the Bias is set would you recommend changing the pots out to resistors?

Thanks for sharing the bias fix, I would have definitely gone with that!

I've done several of these amps. I found it best to convert them to a traditional bias supply off one of the high voltage leads and bacon adjustable pot for each side of the amp. Also if you regulate the screen voltage you'll get a much cleaner output

The bias pots are dodgy as wired on the schematic; if the wiper lifts you lose bias as has happened here. Best to tie the wiper to the negative end or put a high value resistor like a 220k between wiper and neg bias supply. What's the music Mark please?

a perfect candidate for an auto bias system.....

Great job on the video. Very informative!

Instead of adding two more bias voltage sources, wouldn't it be easier to exchange the two 150k resistors at the grids for a balance pot?

If you were to bias the tubes by measuring the (idle) cathode current, how many milliamps would you be looking for on each tube? I'm guessing 32ma. I have a Sherwood S-5000 ii that uses 7868s. Plate voltage is 415. With the bias set at maximum (-19.71 volts), I measure 32ma across the 10 ohm cathode resistors you suggested. Comments?

Hello, I’m a newbie in terms of Hifi gears. I have this sherwood s5000. What is the use of “hum bal” at the back of the amp, on top of those source inputs. Thank you for any info about my question.

My S5500 has a OT that gets hot quickly. I have looked at all the schematics out there. Just not sure enough to order a replacement. Could you advise?

Personally I would use 1 ohm resistors there. Anything a 10 ohm would do, a one ohm would do well enough, considering digital multimeters and all, and the math is easier. 1 volt equals 1 amp; .025V equals 25 milliamps, etc. Nice video!

Great video, I've always wanted one of those.

Great work, Mark.

I had watched the original video, but not yet watched all of this re-upload. Can you point out what the correction was.

7868 tubes are 9 pin but why do the 4 red tube sockets at the rear (under chassis view) look like octal sockets?

Kewl this thing. Those high pitched sounds you play in these videos are murder on my tinnitus ears. Have to turn the sound off while its going.

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I would have elected to just re-stuff the original multi-section capacitors, then no functional/aesthetic issues.

Nice!

Why are you reshowing this video you showed it a days go I see the original ones not there anymore why is this?

Actually you are incorrect about the amp's power rating. In a push-pull configuration, the 7868's can do about 20watts each of plate power so ~~ 40W of RMS power is about right per channel. The line input power is probably more like 150 watts of power, IMO.

By the way, you refer in your vid's 'this thing", "these things" way too much, IMO. You should mix it up a little more with different verbiage, like maybe: this device, this unit, these components, etc. You get the idea. Dave Jones has the same tendency with being too repetitive with his vid's as well.

Please be teadious