Tuesday, August 19, 2008

The Sherwood 7310 Receiver

I have long regarded Sherwood gear as sleepers. In my young adulthood it was a brand that I could afford (via Illinois Audio: ahh, the days of discount mail order) and their receivers sounded good to my young ears. The 7310 is the middle of the line from about 1975 and boasts 38 real world, rms watts. Original list price was $380. I purchased a new 7210 in 1975, and remember it fondly.

Sherwood build quality is not as impressive as Marantz, but manages a significant sonic mojo. The receivers sound bigger than their advertised wattage and the tuners are solid all 'round performers. Cosmetically, Sherwood lags a bit behind Marantz, but a clean example represents '70s hifi style very well.
The 7310 offers the David Hafler's Dynaquad circuitry, an island of sanity in this era of quad madness:This 7310 worked well on arrival. Even the lamps worked. So, on with the restoration! The board layout is straight forward with only the treble/bass board presenting a significant challenge. Here is the bird's eye view from the top:
The power supply board is at the lower right, below the transformer. The output boards are in the upper middle and are accessible from below. The tuning capacitor is at the upper left, shielded. Immediately below it are the AM and FM boards that required removal of 4 screws and some tugging to restore. But whither phono?The phono board is located underneath the unit, at the upper left in this photo. Note the two power supply filter caps in the upper right corner. These slightly obscure the treble/bass board that hides just behind the face of the unit. Changing the caps on this board requires peeling the face and unclamping the filter caps. As luck would have it, my back order of Elna Silmic II caps had just arrived so the 8 4.7 mfd caps on this small board were replaced with silk. The tone control circuit is not defeatable, so it better sound sweet when driven by the cd player not yet imagined in 1975.

All other caps were replaced with Panasonic FCs with extra margin on the voltages. A total of 50 caps were replaced, the 6.8k main filters were left as is. Pots and switches were cleaned with Blue Foam and Deoxit Gold. The tuning capacitor was spritzed with Deoxit Gold.

The end result of my labors was a very sweet sounding unit that should last for another 20-30 years. The overall sound is lush for a string quartet with enough punch to do justice to Metallica. And it looks good. One more look with a bit of drama:


Crpetersen said...

Well , I was given two of these Sherwood amplifiers. The S7310 and an S7310A. Both seem to work, on the S7310A I noticed it does not have an power off. I turn the Loudness knob counter clockwise and it will not power off , no click .. Strange.
But since I use the one for my computer hookup, get all sound from the computer coming threw the stereo out to the speakers. Recently Received a Squire Fender, with out a guitar amp. I plugged in the guitar to the tape dubbing port, and works just fine as a temporary guitar amp. I am of course not turning the volume up past half way so , I think the possibility of burning up the amp is very small. Already have a plan for a guitar amp FENDER Bullet 15 DSP from the local pawn shop.

But all and all I am thoroughly impressed with the quality of this amp. As it is getting on in years when Powering on and off sometimes get some funny noises , crackles , pops. Also sometimes the right stereo channel will go out from time to time, but will usually come back if I cycle between the entire array of settings, AUX1, AUX2, AM, FM, Phono then back again it will come back. It has been suggested to me that If I wish to try and save this retro amp, I may want to take some contact cleaner to the inside. I am professional enough to work with the electronics inside, but until there is a catastrophic problem I think I will leave well enough alone.

Thanks for listening.

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Jon said...

I just encountered the same problem with the loudness knob on my Sherwood (no click off). Did you find a fix?

Crpetersen said...

No , I have not found a solution or cute to this problem. Basically leave the unit on 24 hours a day turned all the way down, sometimes I will shut everything down for a while.. But that is at the power strip. Im not sure I think it has something to do with a cam that is on the inside of the shaft, dealing with the power off switch.. When the cam is turned to the off position it moves the on off button.. Only thing I can think of. Get a power strip, and just power it off at the wall. Because your not going to have too much luck in finding replacement parts for the unit.

John.T said...

I used to work for Sherwood in the early seventies and at that time purchased an S-7310. The on off function was included as part of the loudness/volume control. This switch like others have experienced failed. Not a reliable design. Not able to find a suitable replacement, I was able to drill an hole next to the balance control where I was able to install an on/off toggle switch. It's a tight spot but workable. Well worth the effort for a receiver that's worth keeping operational.