Is this a ghost note ?

[hebaton]

Just picked up a 1970 Dual Showman reverb with matching 2x15 cab.
When playing especiay high notes, I hear a second note just following what I play, perhaps a bit out of pitch. Is this what is refred to as "ghost notes" and, what can be done about it ?

Tanks !

[pdf64]

Maybe, but it could also be other stuff like cone cry.
A soundclip of it may be helpful.

[Stevem]

If it’s not due to the amp needing power supply filters then it’s due to it being a CBS era amp.

In these silver face amps the CBS engineers changed the age old correct wiring layout to speed up production line numbers.

The end results where these amps needing 2000 pf caps on the output tubes to try and stop the oscillation issue from the wiring change.

If not as I posted your amp having a need for a filter job then you have a oscillation problem making for that added note hanging on after your main note has faded off.

It’s not a quick easy job, but you can rework the wiring back to how it was done in the blackface amps.

[Stevem]

I have also heard a few times what you have taking place turn out to be a bad preamp tube or a bad speaker.

[Scumback Speakers]

That's called cone cry. It shows up as a weird one octave off, but slightly out of tune following note (ghost note if you will) from the one you played. It could be a bad tube, but usually it's the speaker.

[hebaton]

Thanks guys, I've ruled out the speakers as I have the same issue with another cab.
I will order a set of caps, the age of the amp makes that a good idea anyway. I'll also try swapping out tubes.
As for the CBS wiring issue, When did CBS take over ? And, where can I find correct wiring diagrams ?
As far as I know, their was a black face Showman but never a Dual Showman Reverb Am I correct on that ?

[Stevem]

The CBS guys got a hold of Fender in 67, but the silverface Amps started in 68.

There was a silver face non reverb duel Showman until 69 when the duel Showman reverb came about.

Try the cap job out first, but if this issue is taking place on both channels then it’s an oscillation issue and it’s likely taking place from the 12AT7 PI tube on down stream thru the output section.
If it’s only taking place on the vibrato channel then it could be starting in the 4th preamp tube which is the reverb recovery tube/mixer.

[hebaton]

The CBS guys got a hold of Fender in 67, but the silverface Amps started in 68.

There was a silver face non reverb duel Showman until 69 when the duel Showman reverb came about.

Try the cap job out first, but if this issue is taking place on both channels then it’s an oscillation issue and it’s likely taking place from the 12AT7 PI tube on down stream thru the output section.
If it’s only taking place on the vibrato channel then it could be starting in the 4th preamp tube which is the reverb recovery tube/mixer.

Thanks ! that is very useful info and wil help locating the problem for sure !

[hebaton]

Well, I ordred a set of caps before I looked inside, silly me. Here are a couple pics of what I found.
Was this amp recaped already at some point ? THose elctrolitics look , not recent but not 5o years old. And how about those white Mallorys....

What do you guys think ? I ordered Spague atom reacements for all the electrolitics already.

[pdf64]

The white Mallory cathode bypass ecaps are most likely original.

[hebaton]

So them, most likely all of them are. Should those all be replaced whil in there ?

[hebaton]

The white Mallory cathode bypass ecaps are most likely original.

I was expecting to see a cover with a buch of power filter caps inside like you would on a twinn, but no such thing !
I am surprised and somewht confused...

Does anybody have pics of the inside of one of those amps ?
WOuld love to see what a stock one looks like !

Thanks

[xtian]

The main filter caps are in the "doghouse" on the flip side!

[dorrisant]

I'd change out those bypass caps while you're at it. And that single cap that is filtering the bias supply, the 89uF... And notice that the positive lead is connected to the chassis. Those, along with the caps in the doghouse or ashtray on the bottom of the amp.

[hebaton]

I'd change out those bypass caps while you're at it. And that single cap that is filtering the bias supply, the 89uF... And notice that the positive lead is connected to the chassis. Those, along with the caps in the doghouse or ashtray on the bottom of the amp.

actually that 80uf is disconnected and, I didn't notice if it was reversed or not ( positive to chassis ) are you saying it needs to be ?