Attax 80 no sound

Bought used.

Today it just stopped making sound.

Amp comes on, power switch light etc but no sound from either channel.

A few days ago there was an issue whereby it would come on, but *way* low output volume until I turned the volume /gain knob. Now I get nothing at all.


Help! I love this amp.

Hi Octavist. That's an old girl you are playing with there isn't it?

When you say no sound do you mean the amp is absolutely silent, or do you mean that no music plays but there is still a slight background hiss or hum as though you had the volume turned fully down? This is the starting point because it tells us as whether the problem is in the output stage or the preceding circuitry. We can work our way forwards testing each part at a time until we get some sort of indication we have reached the fault.

In the meantime try this. The signal line feeds through the Fx Send and Return sockets using the switch wafers to route the signal either straight through or around the loop. These are notorious in many amps for getting dirty and dropping out of contact, particularly at the age of your venerable lady. The whole amp then goes silent (barring hum and hiss). Just put a patch lead or a guitar lead in the Send and Return sockets. See if that brings back sound. In which case the sockets need a damned good clean with proper fluid - NOT WD40 or any other such stuff, proper contact cleaning spray. Also try putting your guiitar straight into the Fx Return socket. It will be very low volume but you should get sound back which indicates the power amp is fine and problem is before the Return socket.

bordonbert wrote:Hi Octavist.  That's an old girl you are playing with there isn't it?  

When you say no sound do you mean the amp is absolutely silent, or do you mean that no music plays but there is still a slight background hiss or hum as though you had the volume turned fully down?  This is the starting point because it tells us as whether the problem is in the output stage or the preceding circuitry.  We can work our way forwards testing each part at a time until we get some sort of indication we have reached the fault.

In the meantime try this.  The signal line feeds through the Fx Send and Return sockets using the switch wafers to route the signal either straight through or around the loop.  These are notorious in many amps for getting dirty and dropping out of contact, particularly at the age of your venerable lady.  The whole amp then goes silent (barring hum and hiss).  Just put a patch lead or a guitar lead in the Send and Return sockets.  See if that brings back sound.  In which case the sockets need a damned good clean with proper fluid - NOT WD40 or any other such stuff, proper contact cleaning spray.  Also try putting your guiitar straight into the Fx Return socket.  It will be very low volume but you should get sound back which indicates the power amp is fine and problem is before the Return socket.

thank you so much! Will be trying this tomorrow and reporting back! youre the best! thank you! (and yes, it is quite old, my father's , when he was gigging!)

@bordonbert patching the send/return jacks worked! And plugging into the return worked too! So I just need to clean the send/return jacks, yeah?

Yes, just get a contact cleaner spray, give a good spray into the sockets, and push a plug in and out a few times to open and close the switches. That should gently wipe the corrosion off the switch contact points.  It absolutely MUST be "electrical" contact cleaner spray.  WD40 and similar products are often described as contact spray and said to do the job - they don't!  They leave a film of oil on the surface which creates the problem pretty quickly and is much worse to clean off second time around.

Good sockets have a wiping action built into the design of the switch wafers so they slide over each other slightly as they make and break and this helps to keep them clean in use.  If they aren't used for a while corrosion starts and works its way between the contacts and you get just what you found.  The sound diminishes, drops out occasionally, then stops all together.  If you are inside the amp it can be done by taking a thin folded strip of ordinary paper, inserting a plug, fitting the paper between the switch then remove the plug.  By gently pulling the pinched paper out a few times it again wipes the face clean.  You can often see a dark smear of corrosion on the paper the first time or two.  NEVER USE ANYTHING ABRASIVE LIKE EMERY OR SANDPAPER!  The switch wafers can be thinly coated to improve their performance and abrasives will remove that pretty quickly making the problem reoccur much quicker.  It's enough to just gently rub off the corrosion.

This is an incredibly common problem with a huge number of amps with old style Fx loops.  The later H&K amps do not use the switch wafers on the sockets to perform the Fx loop routing, they have separate encapsulated relays or solid state switches.  This prevents them from suffering from these dropouts.  It's only down to long term corrosion.  It is speeded up by the atmosphere the amp is kept in.  A Smoky or damp atmosphere will cause this more quickly.

Anyway, as a quick temp fix you have seen that a lead between the two sockets bypasses the switches until you can repair the issue.  A contact cleaner spray is a good thing to have in your maintenance bag.  Happy playing!

Thank you again sir! She's sorted now!
Can't thank you enough!

bordonbert wrote:Yes, just get a contact cleaner spray, give a good spray into the sockets, and push a plug in and out a few times to open and close the switches. That should gently wipe the corrosion off the switch contact points.  It absolutely MUST be "electrical" contact cleaner spray.  WD40 and similar products are often described as contact spray and said to do the job - they don't!  They leave a film of oil on the surface which creates the problem pretty quickly and is much worse to clean off second time around.

Good sockets have a wiping action built into the design of the switch wafers so they slide over each other slightly as they make and break and this helps to keep them clean in use.  If they aren't used for a while corrosion starts and works its way between the contacts and you get just what you found.  The sound diminishes, drops out occasionally, then stops all together.  If you are inside the amp it can be done by taking a thin folded strip of ordinary paper, inserting a plug, fitting the paper between the switch then remove the plug.  By gently pulling the pinched paper out a few times it again wipes the face clean.  You can often see a dark smear of corrosion on the paper the first time or two.  NEVER USE ANYTHING ABRASIVE LIKE EMERY OR SANDPAPER!  The switch wafers can be thinly coated to improve their performance and abrasives will remove that pretty quickly making the problem reoccur much quicker.  It's enough to just gently rub off the corrosion.

This is an incredibly common problem with a huge number of amps with old style Fx loops.  The later H&K amps do not use the switch wafers on the sockets to perform the Fx loop routing, they have separate encapsulated relays or solid state switches.  This prevents them from suffering from these dropouts.  It's only down to long term corrosion.  It is speeded up by the atmosphere the amp is kept in.  A Smoky or damp atmosphere will cause this more quickly.

Anyway, as a quick temp fix you have seen that a lead between the two sockets bypasses the switches until you can repair the issue.  A contact cleaner spray is a good thing to have in your maintenance bag.  Happy playing!

(Oh, by the way, I love the Signature.  You don't often find people quoting things like Petronius on the forum.    At least nowadays!    Maybe I should change mine to:  "Quidquid praecipies esto brevis."  [No, maybe not!    ] )