PRS ARCHON 50 WATT HEAD PROBLEM.

[Read774]

Hi everyone, i bought a new PRS Archon head in March 2024 which is now out of its 12 month warranty so seeing as i cant go back to the supplier here in the UK i'd ask you fine people on here for some advice.
Basically it feels like I've lost a gain stage on the lead channel, sustain and the full on drive has gone and there seems to be more residual channel noise now. I've reduced the signal chain down to just guitar, lead and head and prior to this have checked my guitar, guitar and cab leads via my Kemper and there are no issues.
It gets used at home volume for a few hours per day pretty much every day and gets cranked a few times a month for rehearsals but not for the last month or so, it's been sat in my music room and used at home volume so it's not been knocked etc and it worked fine yesterday morning. Now today it doesnt.

Both power tubes are lit as usual. Any ideas anyone?

Thanks, Ben.

 

[Nick_S]

Pre amp valve being a little iffy could manifest in this manner.

 

[Read774]

Pre amp valve being a little iffy could manifest in this manner.

i might have to look at a replacement if thats the case, many thanks for your answer, much apprceiated.

 

[Nick_S]

i might have to look at a replacement if thats the case, many thanks for your answer, much apprceiated.

No worries bud. I've just had my Marshall TSL repaired for extremely similar sounding symptoms, failed pre amp valves were the cause.

 

[Read774]

No worries bud. I've just had my Marshall TSL repaired for extremely similar sounding symptoms, failed pre amp valves were the cause.

ah ok, thanks for the advice, just looking at the preamp valves which are JJ ECC83S x 6. Not sure whether id need a whole set or not or whether its a straight replacement job. Not had valve heads for years and in the past i kept chopping and changing heads every few years so never had to change a valve before. its all new to me!

 

[FatFingerBlues]

Only the power tubes need to be matched and biased set
pre- amp tubes are simple plug and play
in fact I put a 5751 in V3 of my Archon 50w head
it made the gain channel come on slower and the knob much more responsive to small changes
I highly recommend it

@DreamTheaterRules was a big help with my Archon and is a great source of knowledge on these amps

 

[Read774]

ah thats great to know, ive seen so many different options for them, factory tested, premium tested, matched etc, so i'll have to do some research. i might have buy a couple then and try replacing one valve at a time and see which one is playing up, if thats the way forwward.

 

[Prina]

If the clean channel works fine then it's highly likely it's a problem in (lead) V2 and V3 stages, either in the passive components or more likely the tubes. And you only need one new JJ ECC83S tube to check each one of those out.

Like @FatFingerBlues, I also switched in a 5751 in V3 to tame the lead channel.

Also, make sure you know about the dangers of high voltage & tube amps though rolling tubes isn't as dangerous as working on the board

 

[Read774]

thanks for the information, its much appreciated, i only have the lead channel at 2pm tbh, what was it that made you need to tame it? im guessing theres a schematic to show me which numbers the tubes are?

 

[FatFingerBlues]

thanks for the information, its much appreciated, i only have the lead channel at 2pm tbh, what was it that made you need to tame it? im guessing theres a schematic to show me which numbers the tubes are?

For me it was too much too soon
The 5751 allowed me to use the hole dial

The 5751 in V3 took me from about 8 O'clock to almost 11 O'clock in Gain on the lead channel
The gain also seems less harsh although that is probably due to the ability to dial it in easier

 

[Read774]

sounds like the replacement valve gave the amp much more useable range then, i'll definitley have a look at that option then. thanks for the information, much appreciated.

 

[RickP]

I think this will match yours. You can just get one good 12AX7 and test each by swapping it in at each location until you identify the one where the good tube fixed the problem. If that doesn’t do it, you’ll likely need a tech to check it out because your description doesn’t sound like a power tube issue.

 

[Read774]

hi, thats fantastic, thats bang on to my head, i'll order a replacement today and test the valves out. really appreciate your help with this, thanks.