Crackling amp - what to check ?

[fleabag]

I've checked the suspect bits -  speakon cables, guitar cables, and swapped amps, and its definately the amp.

 

It has dual speakon outs and the crackle/static is apparent on both outputs.  It's also a dual channel,  ( Tube + Fet )  and swapping channels makes no difference.

 

What is the next procedure for a home detective  before it goes to a pro ?

[fleabag]

Just to say, the amp plays fine otherwise. No loss of volume or EQ , and the crackle/static doesnt get louder with amp volume

[Bigguy2017]

If it has FX send/return plug a patch cable and clean the jack sockets.

As it's not affected by volume control its in the power amp section (probably).

 

Try the usual - open it up, visual inspection, unplug/replug any connectors, look for anything iffy, swollen caps, and especially dull/dry joints.

Have a good sniff - anything smell burnt.

Then with the power on tap all areas of the boards and pots with a wooden chop stick and try and localise the fault.

 

Most likely it's a dry solder joint but it could be a cap, transistor or chip...

 

What amp is it?

[fleabag]

Thanks !

I'll have a go at all that - the amp is Genz Shuttlemax 9.2

[fleabag]

Looking at the hundreds of solder joints, and their location, i may have trouble in that respect

 

 

 

 

 

 

 

 

 

[fleabag]

No swollen caps, no burnt smell, connectors that i could reach without dismantling PCB boards reseated

[fleabag]

After poking and pushing,  static/crackle seems to have disappeared, and that's before i put a short cable in the master FX send / receive channel, so i guess i dont need that FX send sockets cable anymore ?

 

I guess time will tell

 

Edited August 9, 2022 by fleabag

[Bigguy2017]

Also press the ICs into their sockets - they work loose over  time.

Reseat the valve/s.

Tapping with a chopstick is the way to find a hidden dry joint.

[fleabag]

Yup, did the single valve re-seat,  but many of the solder joints are hidden, so unless i dismantle the amp, there's no way i can get to them. I did press the IC's

 

I'll leave it alone now, as i seem to have sorted it, but  i dont know how 

 

[tauzero]

You've also got a few connectors to the PCBs, so it might be worth unplugging the connectors and cleaning with contact cleaner if the crackle comes back.

[Downunderwonder]

I am no tech but I know a guy who is: @agedhorse , who designed your amp.!!!

 

My 10c is if it's unaffected by the volume knob it has to be after the knob where it starts or in the knob itself.

[agedhorse]

I thought I would let this play itself out, see what kind of armchair (or chesterfield) suggestions bubbled out of the primordial ooze. 
 

In the hundreds of these amps I have serviced and supported world wide (out of tens of thousands built), I have seen exactly 2 cold (dry) solder joints. Why is this? Because the flus chemistry and solder alloy used, combined with the double sided PCBs with plated holes, this is the most reliable way to build an amp, backed up by a matching history of less than 1 ppm wave solder joint failure. That’s probably the last place to look.

 

Unless you are familiar with proper safety procedures, don’t go poking around with anything inside an amp. 
 

Now, when you say the noise in unaffected by the volume knob, WHICH volume knob… there are 2 channel volume controls and a master volume control.

 

Does the noise change when you tap on the chassis? You can leave the cover on for this.

 

dies the noise go away when you plug a 1/4” (6.35mm) plug into any of the 3 effects returns? 
 

by doing this, you can eliminate 1/4 of the amp at each step without even opening the amp up.

 

Do not spray anything, anywhere in the amp, that just makes things more expensive down the road.

[fleabag]

Well, as the amp is behaving itself,  there's no need to fiddle with it anymore, but just for the record, none of the 3 Vols  ( 2 x channel , 1 master ) had any affect on the loudness of the crackle.

 

It's been fine and dandy these last couple of weeks. Thanks aged h and Thanks all !

[agedhorse]

If this is the case, it’s likely that the noise was external to the amp, possibly entering through the power source. Another possibility is that the noise is from a cell phone, wireless router, Wi-Fi device entering the signal path post master volume control (unlikely but possible).