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Intermittent connection, possible to repair?

post #1 of 15
Thread Starter 
Hey

I've got an old reciever which while not very nice to listen to would be a shame to throw out. I've been quoted $150 for the repair, but i'm a bit too cheap for that.
Basically the connection is very intermittent. There's nothing i can do to set it off, but there is something I can do to bring it back to normal.

In the 5 channel prologic 2 decoder it's only the front L/R channels which intermittently frissle out with a nice scratchy sound.
It only happens at lower / ish volumes.
It happens mainly in summer.
It fixes itself when i turn up the volume and turn it down again.

Now my guess is somewhere on the output of the amp (oh it's got 2 massive Class-B amplifier chips which do the work), there's a solder joint which isn't to happy to have low levels of current going through it, however is still happy when the volume is up a bit. I've excluded the volume control as the source of the problem since if I turn my source down and my volume up, the intermittent connection still occures. The fact that only the L/R channel do it leads me to believe that the prologic / input / other assorted decoder stages in the amp can be ignored.

Is this a likely situation? Is it possible that I could fix the problem by running my soldering iron over all the soldier joints I can see in the relevant areas?

Incase it matters it's a Sherwood RV-6010R prologic reciever.
post #2 of 15
Garbz,

I'd certainly give it a go... sounds like it could be a cracked or otherwise flaky solder joint.
post #3 of 15
Thread Starter 
thanks. I'll also go over it with a microscope, could be a faulty leg on one of the components.
post #4 of 15
Here in the U of Illinois we have a problem in our studios that can cause the same problem -- good old humidity. Your "it mostly happens in the summer" partially points to that. Build-up in mechanical switches and knobs causes extreme intermittence in many cases.

I get the funny feeling you'd have paid about $150 for the person to take one look at it, spray it with contact cleaner, and give it back to you.

Look around at hardware stores for contact cleaner, that might be all you need. Make sure that what you buy is safe on most materials. Spray the knob liberally with the power off & unplugged, then work it for a while. You could also give a spritz to other spots that may be causing similar problems.

Hopefully that's all there is to it. It obviously may be something larger than that, but it's worth a shot.
post #5 of 15
Thread Starter 
Initally the reply for the $150 price was there was a crack in the board. Now which board I don't know. Considering our humidity is about 80-100% usually (damn tropics), i'll have a look at it.

What contacts are you refering to anyway? Contacts between components and the pcb? THere's not a lot of switches that I could see affect the signal in this way. Certainly fiddling with the loudness, mute, bass, trebble, and blance controlls did very little, and it was volume dependent (not dependant on the actual volume control setting).
post #6 of 15
Does the receiver have output muting/protection relay(s)? Sometimes the relay contacts get dirty and cause intermittent output.
post #7 of 15
Thread Starter 
Yes it does. I'll have a good look at them when i crack it open.
post #8 of 15
If contact cleaner doesn't solve the problem, get a can of freeze spray (tetrafluoroethane) and systematically chill sections of the circuit to localize the problem.
post #9 of 15
Thread Starter 
how would the freezing spray help me? I mean what technically happens when i freeze some components?
post #10 of 15
If a part malfunctions when it gets warm, chilling it will make it work again. You said the problem happens mainly in summer, so perhaps it is heat related.
post #11 of 15
Thread Starter 
and that adds another bizzar element. It happens only in summer, but then it also happens more often when i just turn the amp on (although it does also happen occasionally if it's been on for a while).

Anyway i'll crunch though this amp when i get the time in 2 weeks and let everyone know how it went. Thanks for all the troubleshooting tips.
post #12 of 15
Did you ever find the problem? Mine does the same thing, but each channel in turn, after it heats up. I can restore the channel by either winding up the volume or using the A-B speaker switches.

It could be dry joints, relay contacts, intermittent caps or even some sort of fault in transistors.

It isnt in the input stages as signal is always there at the record out jacks.

Like you, I hate to chuck out the Sherwood, even though it's no good for 5.1 (I need an external HDMI-5.1 decoder)

cheers

ZB
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Quote:
Originally Posted by Garbz View Post
Hey

I've got an old reciever which while not very nice to listen to would be a shame to throw out. I've been quoted $150 for the repair, but i'm a bit too cheap for that.
Basically the connection is very intermittent. There's nothing i can do to set it off, but there is something I can do to bring it back to normal.

In the 5 channel prologic 2 decoder it's only the front L/R channels which intermittently frissle out with a nice scratchy sound.
It only happens at lower / ish volumes.
It happens mainly in summer.
It fixes itself when i turn up the volume and turn it down again.

Now my guess is somewhere on the output of the amp (oh it's got 2 massive Class-B amplifier chips which do the work), there's a solder joint which isn't to happy to have low levels of current going through it, however is still happy when the volume is up a bit. I've excluded the volume control as the source of the problem since if I turn my source down and my volume up, the intermittent connection still occures. The fact that only the L/R channel do it leads me to believe that the prologic / input / other assorted decoder stages in the amp can be ignored.

Is this a likely situation? Is it possible that I could fix the problem by running my soldering iron over all the soldier joints I can see in the relevant areas?

Incase it matters it's a Sherwood RV-6010R prologic reciever.
post #13 of 15

I have the same exact receiver. Same exact problem. Not too impressed with this unit. Came bundled with a pair of DX-9 speakers that I've wanted for a long time. I gave it a thorough cleaning front and back, and looked at the insides with a magnifying glass closely. Hit the volume pot with CRC 556. Still has the problem... Prolly is a cold joint on the pre-amp board. I am gonna service this to the best of my ability, make it work well, and sell it on eBay.

 

I think the original poster said he didn't have a manual for this ? It is 105 X 105W in stereo mode. I have the owners manual. Anyone need any info out of it, just let me know.

post #14 of 15

Sure it's not the pot's problem?

post #15 of 15

Sorry for bringing up an old thread. I was searching around the internet for some input on my own 6010r when I came across this.

 

I have the same problem, and have identified it to the speaker relays. I believe they're called something ending with 321 or 323. Finding a replacement should be fairly easy, just make sure it's 24V, draws the same amount of current and can tolerate the same amount of stress as the original. And don't expect to find a drop in replacement. Most likely you'll have to do some degree of modification.

 

Unscrew the radio board (the one with the FM radio and most of the RCA connectors on it. Underneath you'll find a few fairly large relays. connect your speakers and a sound souce and tap on one of the relays with a screw driver the next time the problem occurs to identify which one it is.

 

Mine has developed more problems recently. The center channel is blown and the main outs have completely died. I'm not giving up though, and I've just got hold of the service manual. I don't know much about electronics but I will figure it out smily_headphones1.gif This is a reasonably good sounding amp IMO. Too bad sherwood use such low quality components, or it would still be working fine.

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