Amp Problem - Maybe somebody can help?

[RockyStar]

PRS Archon 100. Amp works fine until I put some effects into the effects loop. As soon as I do I get a very high treble fuzzy sound and the volume drops drastically. When I hit a string the sound widens and expands (still in that high treble fizzy sound then narrows back out). Intermittent cutting in and out and sounds nothing like it is supposed to sound. Once I take everything out of the loop and run the amp by itself, no issues and the amp sounds great on both the clean and dirty channels. Nothing wrong with the pedals or cables or the power from the wall or the power supplying the pedals. All 4 power amp tubes seem to be glowing consistently. I bought this amp new and it has maybe a half hour of use on it so far. My other two Archons act fine in the same scenario.

What do you think the problem is?

Thanks in advance.

[harddriver]

I doubt it would be a dirty effects loop jack, send/return jacks but it could be.

More than likely if the jacks are PCB mounted/soldered then it might be a either a cold or broken solder joint to the PCB.

You could do some poking with a wooden chopstick on the send/return jack legs to the PCB board with a jumper cable and listen for crackles, pops and erratic volume effects.

They usually use ground shorting jacks on effects loop jacks so they short to ground when nothing is plugged into the effects loop. It is also possible that the shorting tab on either the send return jacks might be bent enough to short and the positive tab of the jack causing exactly what you are describing.

[RockyStar]

I doubt it would be a dirty effects loop jack, send/return jacks but it could be.

More than likely if the jacks are PCB mounted/soldered then it might be a either a cold or broken solder joint to the PCB.

You could do some poking with a wooden chopstick on the send/return jack legs to the PCB board with a jumper cable and listen for crackles, pops and erratic volume effects.

They usually use ground shorting jacks on effects loop jacks so they short to ground when nothing is plugged into the effects loop. It is also possible that the shorting tab on either the send return jacks might be bent enough to short and the positive tab of the jack causing exactly what you are describing.

So you don't think it is a bad pre tube for the effects loop?

[harddriver]

I doubt it would be a dirty effects loop jack, send/return jacks but it could be.

More than likely if the jacks are PCB mounted/soldered then it might be a either a cold or broken solder joint to the PCB.

You could do some poking with a wooden chopstick on the send/return jack legs to the PCB board with a jumper cable and listen for crackles, pops and erratic volume effects.

They usually use ground shorting jacks on effects loop jacks so they short to ground when nothing is plugged into the effects loop. It is also possible that the shorting tab on either the send return jacks might be bent enough to short and the positive tab of the jack causing exactly what you are describing.

So you don't think it is a bad pre tube for the effects loop?

Yes...It very well could be a failing preamp tube, If the Archon is a tube driven loop design. If it is a tube driven loop usually a single tube all by itself could be used to drive the loop signal, figure out which 12ax7 is the loop driver and or it might even be 1/2 of the triode on one tube and 1/2 the triode of another depending on how they designed the circuit. So yes I would start with replacing the 12ax7's involved with the loop before moving on to checking the loop jacks. Usually start with the most obvious good call there Rocky...

[RockyStar]

I doubt it would be a dirty effects loop jack, send/return jacks but it could be.

More than likely if the jacks are PCB mounted/soldered then it might be a either a cold or broken solder joint to the PCB.

You could do some poking with a wooden chopstick on the send/return jack legs to the PCB board with a jumper cable and listen for crackles, pops and erratic volume effects.

They usually use ground shorting jacks on effects loop jacks so they short to ground when nothing is plugged into the effects loop. It is also possible that the shorting tab on either the send return jacks might be bent enough to short and the positive tab of the jack causing exactly what you are describing.

So you don't think it is a bad pre tube for the effects loop?

Yes...It very well could be a failing preamp tube, If the Archon is a tube driven loop design. If it is a tube driven loop usually a single tube all by itself could be used to drive the loop signal, figure out which 12ax7 is the loop driver and or it might even be 1/2 of the triode on one tube and 1/2 the triode of another depending on how they designed the circuit. So yes I would start with replacing the 12ax7's involved with the loop before moving on to checking the loop jacks. Usually start with the most obvious good call there Rocky...

The pre tube is where I will start. It doesn't hurt to check there first anyway. There is a lot of talk about the Archon having loop issues when the amp first came out. PRS did say they fixed the loop issue a few years ago. The other Archon amps I have are older. This one with the issue was bought new recently. The odd thing is a few of the pedals I tried worked on the other Archons and not the new one. On the older ones I have I don't know if the loops were fixed by a tech, fixed via PRS or were the corrected ones made from the PRS factory. Anyway, It is a bit odd and based on all that, I was drawn to think it was a tube issue. Many tube amp issues are tube issues when it is all said and done.

Here is the layout.

[harddriver]

Swap out V6 with know good tube and go from there.

[RockyStar]

Swap out V6 with know good tube and go from there.

That's a good idea. I think I will try that.

[harddriver]

Since both sides of the 12ax7 is used in the Archon for the loop. If the loop was not being used no signal would be routed through V6. If the tube is starting to have issues when the loop in plugged in to could very well cause this issues you are describing. If you have had no issues with the amp in the past I would lean towards a failing 12ax7 loop tube.

It's going to be process of elimination troublshooting.

[RockyStar]

Since both sides of the 12ax7 is used in the Archon for the loop. If the loop was not being used no signal would be routed through V6. If the tube is starting to have issues when the loop in plugged in to could very well cause this issues you are describing. If you have had no issues with the amp in the past I would lean towards a failing 12ax7 loop tube.

It's going to be process of elimination troublshooting.

This particular Archon is new and I had only played it a few minutes at a time a few times and up until this loop issue I mentioned I hadn't tried anything in the loop. I had just used it dry or with an ISP up front if I was going to crack the volume up on it.

[harddriver]

Any luck with the Archon diagnosis Rocky?