Hi, I built a Rocket into a large chassis about twelve months ago and all has been good but I have found that with volume on 60% and treble 60% and Cut at 0% it produces a squeal through the speaker. Input jack shorted. Moving the bass doesn't change problem. I had a Master Volume with Cut attached but I removed that so PI goes to EL84's at the moment.
It seems low volume to me but my hearing is probably only picking up the lower range. Guessing it's oscillation of high frequency and I've tried relocating wires, chopsticking and putting the grid stoppers right on the EL84 tubes but it persists. Have absorbed info about layout and shielding and I had shielded from treble output to PI with grid stoppers on CF and PI grids
I have added some things to the original layout design (don't hit me yet : / )
It has an extra channel feeding the PI on the other side and channel switching at the first preamp tube. This is a one knob (volume) Marshall and it doesn't squeal when cranked.
About to try snubbing caps etc. I do have a scope and signal generator but I'm not very good using it besides output sine waves.
Thanks in advance Joe
Rocket Squeal at max setting
Moderators: pompeiisneaks, Colossal
Re: Rocket Squeal at max setting
Reading up on other posts I came across the comments of OT primaries too close to secondaries and when I started chopsticking the plate leads it seems to have been the culprit. The secondaries were about an inch next to the primaries at the run out of the OT and if I stretched them as far away as possible I could get the volume maxed and the treble at 90% before it squealed. Extreme settings I guess that would never be used but I hate having bugs in my amp. When it's cleaned up I'll post a pic. Cheers Joe.
Re: Rocket Squeal at max setting
Bummer , I jack my Rockets up full bore and use the volume on my guitar depending on what type of music i want to play
"It Happens"
Forrest Gump
Forrest Gump
Re: Rocket Squeal at max setting
Here are some pics of the amp, I have been on a point to point phase last year or so. Since these pics were taken
i added a zener diode on the centre tap of the HT to get about 60 volts off the vox iron. Also added a fan as before the zener I had a vvr which got really hot along with some really hot tubes.
http://s188.photobucket.com/user/kersan ... ary/Rocket
i added a zener diode on the centre tap of the HT to get about 60 volts off the vox iron. Also added a fan as before the zener I had a vvr which got really hot along with some really hot tubes.
http://s188.photobucket.com/user/kersan ... ary/Rocket
Re: Rocket Squeal at max setting
do you still have the squealing at 90%?
It is not easy to help out from here when you veer this far off the trodden path. There appear to be a lot of places in your photos where that might be coming from. And please don't take this as a criticism, but I don't understand the quantity of wire here. To my mind ptp is partly about keeping runs short and less connections.
One suggestion in the EL84 department: the stoppers should be right tight to the socket pins and your g2 screen resistors are also in way acting as stoppers. Any 4 tube or more output section will be more susceptible to HF oscillation than a two tube one. I would keep on paying attention to the output zone first.
Hope this is of some help,
tony
It is not easy to help out from here when you veer this far off the trodden path. There appear to be a lot of places in your photos where that might be coming from. And please don't take this as a criticism, but I don't understand the quantity of wire here. To my mind ptp is partly about keeping runs short and less connections.
One suggestion in the EL84 department: the stoppers should be right tight to the socket pins and your g2 screen resistors are also in way acting as stoppers. Any 4 tube or more output section will be more susceptible to HF oscillation than a two tube one. I would keep on paying attention to the output zone first.
Hope this is of some help,
tony
Re: Rocket Squeal at max setting
[IMG
682]http://i188.photobucket.com/albums/z265/kersanov/Rocket/100_8097.jpg[/img]
Too much wire !!!
Yes its a rats nest and I veered well away from the documented layout. I was trying the Matchless layout with individual heater feeds and ht and earth runs from and to each nodes filter cap and THEN I thought I'd try the home made ldr switching between channels which worked well but added more. The amp is actually very quiet except for that squeal. I put the signal grid stoppers right on the power tube pins and I'll try putting the suppressor grid stoppers right on the pins as well to see if that changes anything. The amp can switch two tubes cathodes out of the power supply and the squeal is there with two or four tubes being used. As I said moving the red and white primary of the OT had the only impact.
682]http://i188.photobucket.com/albums/z265/kersanov/Rocket/100_8097.jpg[/img]Too much wire !!!
Yes its a rats nest and I veered well away from the documented layout. I was trying the Matchless layout with individual heater feeds and ht and earth runs from and to each nodes filter cap and THEN I thought I'd try the home made ldr switching between channels which worked well but added more. The amp is actually very quiet except for that squeal. I put the signal grid stoppers right on the power tube pins and I'll try putting the suppressor grid stoppers right on the pins as well to see if that changes anything. The amp can switch two tubes cathodes out of the power supply and the squeal is there with two or four tubes being used. As I said moving the red and white primary of the OT had the only impact.Re: Rocket Squeal at max setting
I've found a fix by relocating lead dress. I put the suppressor grid stoppers right on the socket pins (no change) I re-routed the plate leads to get an extra inch or two to move them at the OT and while de soldering I shortened the parallel wire across the plates. I think that shortening the plate wire cross connection did it as the squeal has gone at max settings and I didn't really have to move the plate leads at the OT exit at all then.
Re: Rocket Squeal at max setting
cool, enjoy your Rocket!