New ghost notes, plexi

[sonofmickel]

Plugged in the amp after being in storage since covid(3 years I'd guess).
It's a 4 hole plexi with split or shared first tube bypass caps.
Even at low volume(2-3 on lead channel)getting lots of ghost notes on the high strings.
Same thing on bass channel.
Both low and high inputs produce ghost notes as well.
Possibly the caps going bad?

[xtian]

You've eliminated the possibility of strings, guitar, speakers?

Easy to tack in a new reservoir cap in parallel with the existing one to see if it's filtering.

[sonofmickel]

Tested with strat and les paul.
Tested with 1x12 open back cab and 2x12 closed back.

[Roe]

check the mains and screens filter caps

[sonofmickel]

I'll paralell some caps tomorrow.
PI resistors measure in spec, 82k/100k

[Roe]

highly unmatched tubes and driver may contribute here. but check caps first

[pdf64]

Plugged in the amp after being in storage since covid(3 years I'd guess).
It's a 4 hole plexi with split or shared first tube bypass caps.
Even at low volume(2-3 on lead channel)getting lots of ghost notes on the high strings.
Same thing on bass channel.
Both low and high inputs produce ghost notes as well.
Possibly the caps going bad?

So this is a 1987 or 1959 model based build?

Yes a bad cap at the reservoir / screen grid HT supply nodes is a likely suspect, but equally it could just beca bad connection in those circuits, eg a loose lug to the chassis.

[sonofmickel]

Today is tomorrow.

The amp is "all" of the plexi amplifiers.
Ceriatone Plexi 51 All Access. The amp wiring is "immaculate" some of the best I have ever seen, doesn't mean something isn't wrong...

I was perusing the Larry reforming caps thread on the Metropolis site. https://forum.metropoulos.net/viewtopic.php?f=4&t=8396
I don't know if I have my head wrapped around it as far as the center tap is concerned.
Would the CT need to be lifted in a 50 watt plexi or would it just need the 100K/1W across the standby switch?
I believe the original thread was using a 100 watt plexi that has the CT injected between the Mains filter caps.
It is too late for me to try reforming the caps as I just plugged in the amp and let it rip, ooops!

[sonofmickel]

One at a time, tested a paralleled a 40uf 450V across all power capacitors.
No change, ghost notes in upper register, single coils and humbuckers.

Voltages:
1 3 4 5 6 8
1 180, 1.37 180 1.37
2 162 .92 282 169
3 217 36.3 215 36.3
4 426 422 -38 426 -.2
5 426 421 -38 426 -.2

[cdemike]

If the character of the ghosting didn’t change at all with the paralleled filtering, I’d wonder what happens if you reshuffle your 12AX7s per Roe’s comment. Also wondering if the ghosting changes depending on the PPIMV setting. My understanding is that ghosting should get worse as the power section works harder so that might help distinguish between true ghosting and an issue elsewhere.

[sonofmickel]

Starting with a "thanks for the help people"!

I'll swap tubes tomorrow. Starting with the phase inverter.

Ghosting is absent when the master volume is turned down 9pm-2pm.

The amp actually sounds great with the master at 2pm lead channel at 10pm , has a little grit on the clean tone though and compressed, understandable with the ppimv.

[sonofmickel]

Swapped tubes, PI and power tubes. Not much difference.
Swapped an ECC81 for the ECC83s and the amp was slightly quieter at volume but still ghost notes.
Found out that I prefer the tone of EL34s over E34Ls, more balanced tone on the EL34s. I suppose the E34L tone could be matched closer to EL34 with eq settings.

When "chugging" on an "E" note (10th fret A string) I measured the bias.
The rough average bias draw of 120ma on the left tube and 133ma on the right tube.
Idle bias left 38ma, right 41.2ma

[FourT6and2]

Starting with a "thanks for the help people"!

I'll swap tubes tomorrow. Starting with the phase inverter.

Ghosting is absent when the master volume is turned down 9pm-2pm.

The amp actually sounds great with the master at 2pm lead channel at 10pm , has a little grit on the clean tone though and compressed, understandable with the ppimv.

Have you tried AM instead of PM?

[FourT6and2]

Can you record a phone clip of this ghosting? Sometimes people call different noises/oddities different things. One person's ghosting might just be another person's "nothing's wrong". I also notice this amp is running the PT HT secondaries (center tapped) to a tube rectifier and then to a solid state rectifier. Is ghosting present with both rectifier settings?

[Roe]

to provoce ghost tones try using the neck pickup of a humbucker guitars, preferably a les paul or similar.

then try (unison) bends at b and g strings between 10th and 15th frets when you crank the amp.