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Here are a few pics of my latest project. I knew going in that using a "Non Standard" layout could present some proplems or even result in a total teardown & rebuild. - well I had an idea of how I wanted it to look and I rolled the dice and here it is. . . there are a few minor problems, but I think they can be fixed with your help and advice.
The amp works and sounds fine with no humm or hiss at all untill the both volume controls reach 7 or 8 and with everything all the way up the humm is rather loud and there is a low in volume but high in pitch squeal that will go away if I touch V1. I have a couple things im going to try but if any one sees anything that may help please let me know. The voltages are on the high side, the powertrans is out of a hammond organ 275-0-275 but I think its meant to run on 115 volts and My house has 122 volts at the wall sockets. pin 7 on the power tubes is 368 volts and pin 3 is 10 volts. V1 pin 1 =130, V2 pin 1 =156, V3 pin 1 =248.
For starters Im just going to mess with the lead dress. I cut the wires from the board that go to V1 pins 1+3 too short and trying to move them seems to want to vary the humm so im gong to legenthen them so I have some room to play with them. Also Im going to try un-bundeling the wires that go to the volume,bass & treble controls so I can move them around to see if that helps. I will let you know what happens & any help or advice will be appriciated. . . . JOE

Joe,

It looks pretty compact. Nice job too.

Putting those wires back over the top of the board to the controls may have something to do with picking up some noise.

If you just crack the MV and trun the vol up, does it hum? And if you turn the vol a bit and max the MV does it hum? Just trying to isolate the section of the amp wher hum is getting in.

Do the Bass/Treble have any effect on hum? I noticed you have only 3 filter caps. Where are the other 2?

I'm assuming you have something plugged in and the inputs are open and not grounded?

When there is no input at all, what are the symptoms?

How did you do the grounding? Same as the Trinity layout? I can't see from the pictures.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Stephen - I will check out the the thinkgs yu asked about tommorow and let you know what I find. the other 3 filter caps are under the 3 that you see in the picture.
JOE

I did some experimenting today and here are the results. I legenthened the wires from the board to V1 and tucked them back out of the way and this seems to have cured the humm.
The high pitched noise is still there. The tone control seems to have the most effect on it. it dosnt start untill the volume controls are 75% or more.
If I crack the volume and turn the master up or vise versa there is no problem the amp functions normaly. It only starts when both volume controls are at 75% or above, then turning the tone control from half to full creates a high pitched squeal that varies while turning the control, with the tone control full on the noise is very low in volume but very high in pitch, so high that it seems like I hear it more in the side of my head than in my ears.
While the amp was on and squealing I used a set of jumper wires to put diffrent value capicetors from lug 3 on the volume control to ground and a .01uf cap completly cures all the noise but with this cap in place the amp is dull and has no gain at all.
since the wires to the controls run across the board does anyone think that sheilded wire may help? , : JOE

Is the wire frm the Vol contol to grid of V2 shileded? If not try that. Ground it at only one end.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I agree, I would definitly think about using sheilded cable on the signal wires especially in a compact build like this one. Also it's important to place the coupling caps first in the signal path before running a length of wire to eliminate the HV traveling any distance further than the socket. eg linking gain stages in the preamp.

Bryan

Stephen - yes that wire and the wire from the inputs to V1 is sheilded & grounded at only 1 end. You can see them in the pictures, because of the layout they are very short.
I was thinking of sheilding the wire from the .0015 cap to lug 1 on the volume pot. I havent seen it done before but moving this wire around seems to vary the squeall. . What do you think?, Worth a try?
JOE

Nice work. Is the front panel made from wood?

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PJM

http://www.diyguitarist.com

If you are still having trouble, try putting a resistor between 68K and 470K between the shielded wire coming off the volume pot and the tube socket. It will have very little impact on gain, but together with the Miller capacitance of the tube, can cure the squeal. Use the lowest value you can get away with (because it does limit treble a tiny little bit) and be sure to solder it directly to the tube socket.

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--s2
www.s2amps.com
www.category5amps.com

I reversed the output transformer wires to the power tubes and that cured the squeal. I remembered reading a post about a squealing bassman and that was what fixed it. I dont know exactly what it does to fix it but it did. I would like to know the technical explanation if anyone knows. . . There is still a little humm that I will try to eliminate by moving some ground wires and maybe sheilding the inside of the Wood chassis, other than that shes good to go!
Joe

Good news. You are only the second person I have heard with a squeasling Lightning. Maybe because of the mini size?? or the output trasnformer you used??

Anyway, one of the primary leads is in phase with one of the secondary taps. In a high gain amp, this phase relationship needs to be maintained. When you do get a squeal, reversing the leads accomplishes this phase correction - from s2.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps