Intermittent right channel - back again

[62vauxhall]

Some time ago I posted about this and at the time, was fairly sure there was a poor connection at the amp's speaker jack. I thought this because when this problem previously exhibited itself, manipulating the speaker connection seemed to bring the channel back. I cleaned the jacks and spread apart the segments of the banana plugs for better contact and afterwards, when the channel did not drop out, I thought the problem solved.

But, it is back.

The right channel meter still operates when the speaker cuts out so signal is getting at least that far.

What brings the audio back is turning up the volume control a bit but at some time after it is returned to it's previous position, the right channel drops out again.

Any suggestions as to where to start checking for faults?

 

[Gepetto]

Some time ago I posted about this and at the time, was fairly sure there was a poor connection at the amp's speaker jack. I thought this because when this problem previously exhibited itself, manipulating the speaker connection seemed to bring the channel back. I cleaned the jacks and spread apart the segments of the banana plugs for better contact and afterwards, when the channel did not drop out, I thought the problem solved.

But, it is back.

The right channel meter still operates when the speaker cuts out so signal is getting at least that far.

What brings the audio back is turning up the volume control a bit but at some time after it is returned to it's previous position, the right channel drops out again.

Any suggestions as to where to start checking for faults?

Dirty relay...

 

[laatsch55]

Dirty pot??

 

[Gepetto]

Dirty pot??

meter is still moving Lee

 

[laatsch55]

Protect relay??

 

[fitz43]

Some time ago I posted about this and at the time, was fairly sure there was a poor connection at the amp's speaker jack. I thought this because when this problem previously exhibited itself, manipulating the speaker connection seemed to bring the channel back. I cleaned the jacks and spread apart the segments of the banana plugs for better contact and afterwards, when the channel did not drop out, I thought the problem solved.

But, it is back.

The right channel meter still operates when the speaker cuts out so signal is getting at least that far.

What brings the audio back is turning up the volume control a bit but at some time after it is returned to it's previous position, the right channel drops out again.

Any suggestions as to where to start checking for faults?

What amp are you discussing?

 

[62vauxhall]

It's a converted 700B and Jerry bypassed the pots.

Back when, I thought relay too but wasn't that also negated by the fact the meters move?

 

[orange]

Replace the speaker wire or input cable. Drink the lime and the coconut and call me in the morning (? )

 

[laatsch55]

It's a converted 700B and Jerry bypassed the pots.

Back when, I thought relay too but wasn't that also negated by the fact the meters move?

Bypass the DC protect board and see if that does it...

 

[NavLinear]

If your DC protect board has relay sockets you may consider swapping the relays and see if the problem moves to the other channel.

 

[Gepetto]

It's a converted 700B and Jerry bypassed the pots.

Back when, I thought relay too but wasn't that also negated by the fact the meters move?

no, the meters are directly on the amp output BEFORE the DC protect relay

the relay contacts become oxidized

 

[62vauxhall]

Thanks, I'll pull the amp out later today when I get back home, have a look and try the suggestions.

 

[laatsch55]

If your DC protect board has relay sockets you may consider swapping the relays and see if the problem moves to the other channel.

Navo, the 700 DC protect boards have soldered relays...

 

[62vauxhall]

Murphy's Law

I've had the amp pulled so it's accessible for a while, left it connected and the face plate and top cover have been removed. Of course, in the intervening week or so, it has not exhibited that problem and the right channel has not cut out.

What may (or not) be a clue to the cause was that at the time I pulled the amp from the stand, the right channel had just quit. When I went to turn it off, I did not have a firm grip on the switch so it did not "click" into the Off position. Rather, the power was interrupted just for the fraction of a second that it took to return to On and the right channel was restored.

Could that brief interruption of power, deactivating then immediately re-activating the relay be the telltale that it is malfunctioning? If so, what do I need to know to get a replacement?

 

[laatsch55]

Ill post the Mouser part number when I get home.

 

[62vauxhall]

Standing by. Thanks Lee, much appreciated.

 

[MarkWComer]

Could that brief interruption of power, deactivating then immediately re-activating the relay be the telltale that it is malfunctioning? If so, what do I need to know to get a replacement?

FWIW: I have a 400/II plugged into a power strip with a foot switch. My obese cat hit that footswitch momentarily while climbing into the window. The meters were still pulsing, but the sound was out. A power cycle restored the output, apparently the interruption latched the DC circuit.

 

[laatsch55]

Mouser Part # 677-PCLH-204D1S

 

[62vauxhall]

Thanks again Lee, I'll place the order when I get home tonight.

It is so typical for things to transpire like this, at least for me anyway. To have the amp on the floor, open and accessable, waiting for it to hiccup and nothing. Of course were I to close up and put it back, it would do it's thing in five minutes.

 

[laatsch55]

Of course!!