A Marshall AFD Sqealing problem (video included)
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A Marshall AFD Sqealing problem (video included)
I built a ceriatone AFD 50 and it is a great amp, more scooped than i would have imagined but it is squealing a bit when I turn up the gain or volume...take a look at the video and i am open to any suggestions
http://www.youtube.com/watch?v=0HMmGK1O ... e=youtu.be
Thanks
http://www.youtube.com/watch?v=0HMmGK1O ... e=youtu.be
Thanks
Re: A Marshall AFD Sqealing problem (video included)
Something is creating positive feedback inside the amp.
It's your build or you receipt it already mounted?
It's your build or you receipt it already mounted?
Re: A Marshall AFD Sqealing problem (video included)
Brand new build? Does the squeal change significantly when you adjust the presence pot?
That sounds a lot like crossing up the OT primary leads on the output tube plates.
Try lifting the NFB lead from the impedance selector. If that fixes it, you will need to switch the OT primary leads on the output tubes.
Good luck!
Dave O.
That sounds a lot like crossing up the OT primary leads on the output tube plates.
Try lifting the NFB lead from the impedance selector. If that fixes it, you will need to switch the OT primary leads on the output tubes.
Good luck!
Dave O.
Re: A Marshall AFD Sqealing problem (video included)
If that's the problem, just switch the outputs from the PI to power tubes, it's easier.
Re: A Marshall AFD Sqealing problem (video included)
yes it is a brand new build and the presence pot really does not affect the squeal but rather acts like a second master volume, which is a bit annoying....as far the primary's on the ot being switch, i wish it was that easy but that's definitely not it.
here is the design if anyone is interested
http://www.ceriatone.com/images/layoutP ... 35_50W.jpg
here is the design if anyone is interested
http://www.ceriatone.com/images/layoutP ... 35_50W.jpg
Re: A Marshall AFD Sqealing problem (video included)
The problem is not the layout, but how you built it.
We need picture of what you have done.
We need picture of what you have done.
Re: A Marshall AFD Sqealing problem (video included)
Agree, sounds like major ground issues as wellroberto wrote:The problem is not the layout, but how you built it.
We need picture of what you have done.
Need a gut shot to help you.
Re: A Marshall AFD Sqealing problem (video included)
Here is are a few pics....and again thanks for the help!
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Re: A Marshall AFD Sqealing problem (video included)
Are the wipers of the each of those three trimmer pots wired to the 3rd leg?
In your amp the wipers looks like they are bare not connected to anything?
Mark
In your amp the wipers looks like they are bare not connected to anything?
Mark
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Last edited by M Fowler on Wed Sep 05, 2012 6:41 am, edited 1 time in total.
Re: A Marshall AFD Sqealing problem (video included)
First thing I would do is correct the lead dress to the master volumeyalesmith wrote:Here is are a few pics....and again thanks for the help!
Those wires for that type of master are extremely sensitive and IMO should be shielded. I would actually disconnect the master completely (add the bias dividers) and try it without it.
Re: A Marshall AFD Sqealing problem (video included)
Do you mean the PPIV master volume and when you mention "disconnect the master completely (add the bias dividers) and try it without it" - i am loss in what you mean.
thanks!
thanks!
Re: A Marshall AFD Sqealing problem (video included)
That end of coax going from the master to the return jack looks suspicious
at the jack. (M)
Be sure to trim the shield back from the center or it will short to ground.
Try swapping X and Y with each other.
Does it squeal inside a shielded head cab?
at the jack. (M)
Be sure to trim the shield back from the center or it will short to ground.
Try swapping X and Y with each other.
Does it squeal inside a shielded head cab?
Last edited by Structo on Wed Sep 05, 2012 2:03 pm, edited 2 times in total.
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: A Marshall AFD Sqealing problem (video included)
note that in the video the open side of the chassis is facing the spk. cab (i.e. right on top of it)
Re: A Marshall AFD Sqealing problem (video included)
Ditto, those three 10k trimmer are wired as fixed resistors. The wipers should be connected so that they become variable.M Fowler wrote:Are the wipers of the each of those three trimmer pots wired to the 3rd leg?
In your amp the wipers looks like they are bare not connected to anything?
Mark
TM
Re: A Marshall AFD Sqealing problem (video included)
I think he has the wipers connected to the resistors and caps sitting behind the trimmers.
Tom
Don't let that smoke out!
Don't let that smoke out!