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Help with Sherwood s-7800

S

Spudnik

New Member
Just picked up a Sherwood S-7800. Looks good, plays well except the audio level is very low for a 70 watt per channel receiver. Gotta turn it up at least half way for comfortable listening volume. Could this mean a problem with the output stage somewhere, as opposed to the preamp stage? Where would you suggest I look first. I haven't cleaned any pots yet, so I'll do that. The "hush" and the "preamp" controls on the front left of the panel have no effect when rotated as well.

Any suggestions are appreciated.
 
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First off, congrats on a fine receiver there!

I believe that the S-7800 was a 40w/ch receiver, and I'm not entirely sure if that was 'true RMS' watts or what the measuring method was. How efficient are the speakers you are using with it? Also, position of the volume control has nothing to do with the output of the reciever, just the taper (rate of attenuation) of the control. Does it ultimately seem to get to reasonable volume levels, appropriate of a 40w/ch receiver (regardless of the position of the volume control)?

Agree that the first step has to be cleaning pots and everything else you can. I was just working on what I thought was a nice, clean, fully functioning receiver when I noticed that the loudness button didn't seem to do anything at all to the sound - uh oh, all sorts of exotic ideas came to mind as to what might be the problem... Otherwise, the reciever worked fine. So, I opened it up, took off the front panel, sprayed with cleaner, worked the controls, sprayed with more cleaner, worked everything some more, and did it all a third time for good measure. Problem solved.

The 'hush' control adjusts the muting threshold - at what signal level the FM will unmute when the FM muting is on. The 'preamp' control, I believe, adjusts the level of the phono input (to match it to your other sources).

If after cleaning, the level still seems low, then I'd suggest starting down the troubleshooting path...
 
Thanks for the reply. The front and back panel proclaim this a 140 watt receiver, which I interpreted to mean 70 watts per channel. But even if it's only 40 watts per channel, it's not loud enough wide open. Sounds more like 10 watts if that. My dynaco sca-80q, which I think is 30-40 watts, sounds as loud at the 1/4 mark as this does fully open. I had read somewhere that taking the signal from the "tape out" connections into an amp and comparing the levels that are being supplied there could tell me whether the issue is at the preamp stage or not. Comments?

Going to give it a good cleaning though before I panic and start taking things apart.
 
Well cleaned it all up, and refreshed some of the dodgy looking solder joints, but no difference. Still lower volume than I expected, with distortion at low to moderate levels in one channel, and moving the volume control past the "0 DB" location makes both channels sound like it's being overdriven. (that's right, the volume knob graduation is not 1 to 10 or such, but is marked in db as a wattage meter would be).

So, suggestions on my next steps. Cap replacement?
 
Quaestion. Does it have a balance control that is a standard single ganged control as you see on just about every peice of gear in existence or is a 2x ganged control. On the tube units, the "balance" control is in reality an input level control with separate left and right gain. The theory was you would set the volume control to 0db and then adjust the "balance" control to the level that you normally listened at and also could balance the level individually for left and right channel. At first sounded very screwy until I realized that the loudness control on equipment is tied to the volume control and at some point on the control is removed from the circuit. But depending on input levels and speaker efficiency and room size, the relative spl is different when using the same unit with these variables factored in. By establishing the 0db point on the control as the average listening level, that sytem then is programmed for the loudness compensation. Really neat. But, rather screwy in relation to all outher makers. The theory seems to work with my 5000III since I go between my Klipsch and Advents and when I use the Advent settings on the Kipsch the loudness compensation is present at normal listening levels when it should not be.

If the 7800 has the same setup, then possibly the "balance" control needs to be adjusted. Just a thought.
 
Interesting suggestion Brian. I'll check that as soon as I get home. I'm pretty sure there aren't two concentric controls on the balance knob, but I suppose it could pull out to control one gang and push in to control the other. (I have another vintage receiver that you pull out the balance control to power it on).
 
Well, took a look and the balance pulls out but that selects mono, push in for stereo. Nice try though.

Anyone else have any ideas?
 
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