Connecting FX send & return to fix amp problems......

[Beedster]

Just tried this with a rather perplexing problem and it did the tirck. So, why does this work?

 

On 05/01/2024 at 21:21, wateroftyne said:

Temporarily connect the FX send and return with a jack lead and report back…

[SimonK]

That's a pretty common fault when the switching jack sockets go (edit the switch is normally on the return). A small patch lead makes sure your send always goes to your return and the signal keeps running without the middleman so to speak!

Edited October 22 by SimonK

[Beedster]

Thanks @SimonK but why does simply inserting a cable and then removing it do the trick?

[Norris]

The sockets get a bit mucky over time, and the contacts that normally touch when there is no jack in the socket can stop letting the signal. A short patch lead between the two sockets means you're not relying on those contacts and instead the signal travels through the cable.

 

A squirt of electrical contact cleaner in the sockets may be enough to clean up the contacts. The lead will still probably make a better contact though, because plugging and unplugging the lead will tend to keep the contacts clean.

[Beedster]

Thank you guys 🙏

[SimonK]

If I'm not using the effects send of an amp I almost always put a patch cable between send & return to avoid this problem which seems to happen to most amps over time.

 

Certainly one of the most joyous discoveries of an ebay/reverb bargain for a "broken amp" is when this little trick fixes the problem - but the aim is not to do it in the sellers presence!

[Beedster]

10 minutes ago, SimonK said:

If I'm not using the effects send of an amp I almost always put a patch cable between send & return to avoid this problem which seems to happen to most amps over time.

 

Certainly one of the most joyous discoveries of an ebay/reverb bargain for a "broken amp" is when this little trick fixes the problem - but the aim is not to do it in the sellers presence!

Indeed!

 

So is it simply a function of unused sockets, I’m still a little unclear on the actual cause? For example if it were simply an unused socket problem you’d not need to link send and return with a cable, just insert a plug? Am I being daft?

[pete.young]

32 minutes ago, SimonK said:

If I'm not using the effects send of an amp I almost always put a patch cable between send & return to avoid this problem which seems to happen to most amps over time.

 

 

 

Presumably this is not an issue for parallel effects loops since you still have a signal path which bypasses the loop?

 

I've also had success with spraying some switch cleaner on a jack plug and putting it into the socket a few times to lubricate the contact. This is a temporary bodge, leaving a cable there is a permanent bodge!

[SimonK]

2 hours ago, Beedster said:

Indeed!

 

So is it simply a function of unused sockets, I’m still a little unclear on the actual cause? For example if it were simply an unused socket problem you’d not need to link send and return with a cable, just insert a plug? Am I being daft?

 

Assuming it isn't a parallel effects loop as @pete.young says, there is an internal switch on the return socket detecting whether a cable is plugged in. So if nothing is plugged in the signal bypasses the effects loop altogether essentially internally routing send to return. This is where the fault you describe probably lies - the amp "thought" something was plugged into the return so cut the internal signal routing expecting a signal from the return which wasn't there, hence no sound. The "bodge" is to route the send to the return manually using a patch cable, or as you say, wiggle something in the return socket hoping that it's just some dirt that can be cleared!

[Beedster]

1 minute ago, SimonK said:

 

Assuming it isn't a parallel effects loop as @pete.young says, there is an internal switch on the return socket detecting whether a cable is plugged in. So if nothing is plugged in the signal bypasses the effects loop altogether essentially internally routing send to return. This is where the fault you describe probably lies - the amp "thought" something was plugged into the return so cut the internal signal routing expecting a signal from the return which wasn't there, hence no sound. The "bodge" is to route the send to the return manually using a patch cable, or as you say, wiggle something in the return socket hoping that it's just some dirt that can be cleared!

Thanks @SimonK so that’s why we don’t have similar issues with other old and unused sockets on the same amp?

[SimonK]

49 minutes ago, Beedster said:

Thanks @SimonK so that’s why we don’t have similar issues with other old and unused sockets on the same amp?

 

Depends on what the socket is supposed to do and what it is connected to internally! But as we have been discussing the failure of an FX return in particular is quite a famous cause for an amp to suddenly have no, or reduced, signal.

[tauzero]

Just to add - the switch on the return is actually one bent bit of metal in the jack socket resting on another bent bit of metal in the jack socket. When a plug is inserted, the top BBOM is lifted off the bottom one and the circuit broken. The surfaces that touch each other will gradually oxidise and eventually break the circuit. Inserting a plug will disturb the contact patch enough to start things going again but if you can easily get into the amp then contact cleaner on the return jack is the best way to go.

[agedhorse]

Reminder, when using any kind of contact spray (on switching contacts), it hast to actually get in the contact as well a not get elsewhere which can cause new and more expensive issues.

 

never use contact cleaner on pots, it’s a good way to ruin them. DeOxit D5, and only the tiniest amount in the slot that the terminals exit from is generally safe and effective. 

[bremen]

12 hours ago, agedhorse said:

Reminder, when using any kind of contact spray (on switching contacts), it hast to actually get in the contact as well a not get elsewhere which can cause new and more expensive issues.

 

never use contact cleaner on pots, it’s a good way to ruin them. DeOxit D5, and only the tiniest amount in the slot that the terminals exit from is generally safe and effective. 

This (the text, not the solvent) should be a Sticky.

 

"...the pots were a bit crackly so I squirted them with wd40..."

[Phil Starr]

Here you go, this is a 'typical' switching jack socket. You can see two silver connectors on the left hand side dangling below the socket and two more on the far side. If you look carefully the ones on the far sidereach across and lightly touch the ones on the near/left side. You shoulkd just be able to make out the little dimple where they touch. The left side is the input side and the right side is the output side to the power amp, that light touch is enough to complete the circuit and connect the ttwo. When you push a jack plug in these contacts are lifted and the input side is disconnected. Pull the plug out and the contacts spring back down and re-connect the pre amp to the power amp.

 

The problem is that this isn't a great design. The contacts aren't spring steel and constant re-use weakens the spring. When the contacts are lifted dirt can get into the gap and block the contacts and as everything is open to the air the contacts themselves can corrode and the oxidised metal blocks the connection.

 

The 'correct' fix is to replace the socket. A new socket is going to last 10-20years probably. However if you can get to the innards of the amp you can clean the connectors. Some rubbing alcohol will clean out any dirt and corrosion can be removed by a very fine abrasive or even scraping with a sharp blade but this will be temporary as the abrasive/blade will scratch the connector and it will corrode again but more quickly. Switch cleaner like DEoxit or Servisol in the UK will help but obviously you need to get it between  the contacts ideally, just spraying it through the jack from the outside is going to cover the circuit board it is probably soldered to. Not all components respond well to this   you can try spraying the contact cleaner onto a cotton bud and try rubbing it against the contacts which you can usually see from the outside. If you get enough in and wiggle the contacts with a jack plug you can get temporary relief. A new socket gives you a nice strong spring and clean contacts. The socket costs £2 and takes 5 mins to fit but you'll need to pay a set fee for anyone to open up and disassemble your amp to get to it. 

 

If the socket has failed then using a jumper lead completes the connection so the switch doesn't need to work. If it is just dirt on the connector then wiggling a jack in and out will clear it for a while.

[agedhorse]

13 hours ago, Phil Starr said:

Here you go, this is a 'typical' switching jack socket. You can see two silver connectors on the left hand side dangling below the socket and two more on the far side. If you look carefully the ones on the far sidereach across and lightly touch the ones on the near/left side. You shoulkd just be able to make out the little dimple where they touch. The left side is the input side and the right side is the output side to the power amp, that light touch is enough to complete the circuit and connect the ttwo. When you push a jack plug in these contacts are lifted and the input side is disconnected. Pull the plug out and the contacts spring back down and re-connect the pre amp to the power amp.

 

The problem is that this isn't a great design. The contacts aren't spring steel and constant re-use weakens the spring. When the contacts are lifted dirt can get into the gap and block the contacts and as everything is open to the air the contacts themselves can corrode and the oxidised metal blocks the connection.

 

The 'correct' fix is to replace the socket. A new socket is going to last 10-20years probably. However if you can get to the innards of the amp you can clean the connectors. Some rubbing alcohol will clean out any dirt and corrosion can be removed by a very fine abrasive or even scraping with a sharp blade but this will be temporary as the abrasive/blade will scratch the connector and it will corrode again but more quickly. Switch cleaner like DEoxit or Servisol in the UK will help but obviously you need to get it between  the contacts ideally, just spraying it through the jack from the outside is going to cover the circuit board it is probably soldered to. Not all components respond well to this   you can try spraying the contact cleaner onto a cotton bud and try rubbing it against the contacts which you can usually see from the outside. If you get enough in and wiggle the contacts with a jack plug you can get temporary relief. A new socket gives you a nice strong spring and clean contacts. The socket costs £2 and takes 5 mins to fit but you'll need to pay a set fee for anyone to open up and disassemble your amp to get to it. 

 

If the socket has failed then using a jumper lead completes the connection so the switch doesn't need to work. If it is just dirt on the connector then wiggling a jack in and out will clear it for a while.

A properly built jack (like Neutrik brand) uses phosphor-bronze or Cu-SN6 alloy bronze components that are very spring-like and extremely reliable (rated for 10k mating cycles minimum). Of course there are lesser quality parts with issues, but that's not a design problem. Lesser quality parts may be good for 1k mating cycles or less.

 

 

[Phil Starr]

7 hours ago, agedhorse said:

A properly built jack (like Neutrik brand) uses phosphor-bronze or Cu-SN6 alloy bronze components that are very spring-like and extremely reliable (rated for 10k mating cycles minimum). Of course there are lesser quality parts with issues, but that's not a design problem. Lesser quality parts may be good for 1k mating cycles or less.

 

 

Yeah this is true and I did think of including that, I even wondered if you would comment. I've a tendency to long-windedness in some of my posts which I'm trying to curb, usually unsuccessfully

 

Sadly a lot of amps aren't built with the best of components and the fact that so many musicians know about bridging the fx loop and/or cleaning up the socket suggests that a lot of cheap components are sitting in this critical position.

[Chienmortbb]

10 hours ago, agedhorse said:

Lesser quality parts may be good for 1k mating cycles or less.

Something i noticed some years ago. I noticed that an Amphenol plug was rated at 1000 cycles when Nuetrik and Cliff were  quoting many more (5000 or 10000), I contacted Amphenol and was told by the CEO that actually they do the same as Neutrik/Cliff. I kept with the other brands.