Receiver issues

[S7910]

I have a Sherwood S7910 stereo receiver that is starting to show its age:mad:. When I power it up I usually need to turn the volume up a ways for the right channel to kick in. There are also some (occasionally very) loud pops of static when I adjust settings (source, turning off the tone controls, etc) with a switch instead of a dial or pot. Will a thorough cleaning take care of this, or will I need to invest in some test equipment in preparation for a rebuild?

Any advice is welcome.

Matt

[Æ]

I have a Sherwood S7910 stereo receiver that is starting to show its age:mad:. When I power it up I usually need to turn the volume up a ways for the right channel to kick in. There are also some (occasionally very) loud pops of static when I adjust settings (source, turning off the tone controls, etc) with a switch instead of a dial or pot. Will a thorough cleaning take care of this, or will I need to invest in some test equipment in preparation for a rebuild?

Any advice is welcome.

Matt

My first guess would be that the volume control (a potentiometer) is dirty, oxidized or plain simply worn. Cleaning and contact lube never hurts. If volume/balance controls and function switches are heavily worn, they need to be replaced.
Rotating all the knobs back and forth rapidly several times will knock off some of the oxidation buildup and reduce much of the static, pops, but will do nothing for excessively worn, pitted contacts.
Get some tuner lube or appropriate electronics spray. Do a GOOGLE search for "DeoxIT" (formerly "Cramolin" spray) the best cleaners and sprays for electronics.
http://www.caig.com/ also http://store.caig.com/

[johna_partsexpress]

http://www.parts-express.com/wizards/searchResults.cfm?srchExt=Mfg&srchMfg=30

[Æ]

http://www.parts-express.com/wizards/searchResults.cfm?srchExt=Mfg&srchMfg=30

Ok, great you guys sell DeoxIT.
Now how about some ferrofluid? Small quantities, enough for a couple of tweeters or a bit more.

[romanbednarek]

I have a Sherwood S7910 stereo receiver that is starting to show its age:mad:. When I power it up I usually need to turn the volume up a ways for the right channel to kick in. There are also some (occasionally very) loud pops of static when I adjust settings (source, turning off the tone controls, etc) with a switch instead of a dial or pot. Will a thorough cleaning take care of this, or will I need to invest in some test equipment in preparation for a rebuild?

Any advice is welcome.

Matt

DeOxit will fix the dirty switches and potentiometers, but.... I'm very familiar with the symptom you mentioned regarding having to turn up the volume in order to get one of both channels to kick in. This is almost certainly a dirty speaker output relay contact. I had the same problem with two different amps in the past (NAD 2100X and Yamaha A700) and a buddy gave me some tips on how to fix the relay. In my case the relay had a cover which was removeable and once removed he said to use a piece of brown paper bag in between the signal contacts of the relay in order to clean them (he said not to use anything too abrasive or it would remove the very thin layer of corrosion resistant material). He also said that contact cleaner wouldn't be enough to fix the problem because it really needs to be mechanically swept across the contact as is the case with potentiometers and switches which you should turn after spraying. If the relay contacts aren't accessible then you may need to buy new relays. Maybe somebody else can chime in with additional comments about the relays.

[Wolf]

http://www.parts-express.com/wizards/searchResults.cfm?srchExt=Mfg&srchMfg=30

For Contacts, use contact cleaner.
For potentiometers, use the 'Faderlube'...
Wolf

[blue934]

This is almost certainly a dirty speaker output relay contact.

where would one find this relay?
D
________
Lovely Wendie99 (http://www.lovelywendie99.com/)

[Paul Carmody]

DeOxit will fix the dirty switches and potentiometers, but.... I'm very familiar with the symptom you mentioned regarding having to turn up the volume in order to get one of both channels to kick in. This is almost certainly a dirty speaker output relay contact. I had the same problem with two different amps in the past (NAD 2100X and Yamaha A700) and a buddy gave me some tips on how to fix the relay. In my case the relay had a cover which was removeable and once removed he said to use a piece of brown paper bag in between the signal contacts of the relay in order to clean them (he said not to use anything too abrasive or it would remove the very thin layer of corrosion resistant material). He also said that contact cleaner wouldn't be enough to fix the problem because it really needs to be mechanically swept across the contact as is the case with potentiometers and switches which you should turn after spraying. If the relay contacts aren't accessible then you may need to buy new relays. Maybe somebody else can chime in with additional comments about the relays.
Yeah, I've had this happen with various amps over the years. It does seem to be a separate problem than dirty pots (been through that enough times to know the sound) So did you try his suggestion for cleaning the relays, Roman? Did it work?

[Æ]

where would one find this relay?
D

From the manufacturer of the relay or the manufacturer of the receiver.

But if the receiver is exceptionally old, you just might be out of luck.

However you may be able to substitute an equivalent replacement or substitute part. Some relays have standard pin outs. It's a matter of knowing what you are dealing with.

Call the company that made the receiver and ask for their parts department

Or do a GOOGLE search for the name and number printed on the relay.

[tom_s]

It looks like this is one of the easiest units to repair or replace the relay since it's hiding there in plain sight. A few gentle strokes of 800 grit paper might do the trick without inflicting too much damage. If it's been doing this for a while, the pitting might be too deep. Then it's time for a replacement. But all you really need to know is the contact closure voltage & current requirements and this is probably one of the safer DIY repairs to make. Worst case may be shorting the transistor driving the relay, but even that takes some seriously sloppy soldering!

[romanbednarek]

Yeah, I've had this happen with various amps over the years. It does seem to be a separate problem than dirty pots (been through that enough times to know the sound) So did you try his suggestion for cleaning the relays, Roman? Did it work?

I did work on the relays in my Yamaha A700, however this was prior to my friend's suggestion of using a piece of brown paper bag to clean the contacts. Instead I used 1500 grit sandpaper and while it did fix the problem temporarily, the relays had issues again about a year later exactly as my friend suspected (even 1500 grit sandpaper is too coarse to clean relay contacts without removing the corrosion resistant contacts). I have only been using my A700 as a phono preamp lately (I use my Hypex UcD180AD modules as my primary power amp) but I really need to replace those relays now since any "cleaning" will only last for a limited time.

Now with my Yamaha, the relays had thin black plastic covers that could be removed fairly easily. Most relays, however, have clear covers and are sealed. I suspect that the only way to work on that type of relay would be to cut the top off and then reglue it after cleaning the contacts. The picture in the previous post seems to show a clear relay case which may fit the category of having a non-removable cover.

In any case, I would strongly suggest the brown paper bag method of cleaning relay contacts over any type of sandpaper based on my experience and that of others who have had the same issue of quick corrosion after the fix. I guess that I don't have a controlled experiment because I didn't get the chance to use the brown bag method of cleaning to see if the fix would last longer but I trust my friend's advice since he collects, repairs and designs/builds amplifiers.

[romanbednarek]

It looks like this is one of the easiest units to repair or replace the relay since it's hiding there in plain sight. A few gentle strokes of 800 grit paper might do the trick without inflicting too much damage. If it's been doing this for a while, the pitting might be too deep. Then it's time for a replacement. But all you really need to know is the contact closure voltage & current requirements and this is probably one of the safer DIY repairs to make. Worst case may be shorting the transistor driving the relay, but even that takes some seriously sloppy soldering!

See my post above about using sandpaper to clean relay contacts...

[S7910]

Thanks for the responses. I'll definitely be getting the DeoxIt contact cleaner and Faderlube.

[S7910]

It looks like this is one of the easiest units to repair or replace the relay since it's hiding there in plain sight. A few gentle strokes of 800 grit paper might do the trick without inflicting too much damage. If it's been doing this for a while, the pitting might be too deep. Then it's time for a replacement. But all you really need to know is the contact closure voltage & current requirements and this is probably one of the safer DIY repairs to make. Worst case may be shorting the transistor driving the relay, but even that takes some seriously sloppy soldering!

I assume the picture is centered on the relay? I'd just like to make sure I know which part I'm looking for when I pop the hood on my unit to tackle this repair since this is the first time I've done electronics work on something other than a computer.

Matt

[philiparcario]

--------------------------relay is here-------------------------------------------
I
I
I
I
I
I
I
I
I_________________________________________________ ____________

it has clear plastic top some wires above small in size some wires below bigger in size

looks like this a bit


http://cgi.ebay.com/G2R-2-12V-Omron-12V-DPDT-PCB-Relay-100-pieces_W0QQitemZ270402612240QQcmdZViewItemQQptZLH_ DefaultDomain_0?hash=item3ef5406c10#ht_912wt_941

[S7910]

--------------------------relay is here-------------------------------------------
I
I
I
I
I
I
I
I
I_________________________________________________ ____________

it has clear plastic top some wires above small in size some wires below bigger in size

looks like this a bit


http://cgi.ebay.com/G2R-2-12V-Omron-12V-DPDT-PCB-Relay-100-pieces_W0QQitemZ270402612240QQcmdZViewItemQQptZLH_ DefaultDomain_0?hash=item3ef5406c10#ht_912wt_941

I see it now.

[arlis_1957@yahoo.com]

cool that johna was hangin' round:)

[cliffburge]

And for receivers that you do not know where the relay is (or what one it is!) just pop the cover off the receiver and put your fingers on each of the relays one by one as you turn the receiver on and off, you will feel when you have the correct relay because you will feel it click as you hear it click. Just be careful not to touch anything else for shocking reasons.