F5 power amplifier

I'm using the original ground scheme in 14167 post.
The hum starts as I connect an rca cable, even if it's not connected to a source device. I've tried only phone and notebook as source.
I think next step is manage psu board to short more holes in gnd and stin, to have a lower impedance path. Right?

Do not plug rca's in while the amp is turned on. Every amp on the planet will hum when the inner rca connection is made before the shield.

jn
 
Acumos, None of us are in any hurry and neither should you be. If it takes a while to get the pictures - that's fine. Sadly it seems we missed some steps in the reassembly. Let me try to relate what I understand.

1. You removed both F5 boards from the chassis.
2. A CL60 was installed between the AC inlet ground and the chassis. Whether you did or did not do it, the photo from the build guide shows the best method - including the capacitor.
3. At that point you had +24VDC/0VDC/-24VDC from your power supply.
4. This is where pictures of both sides of both populated boards should appear. It is simply impossible for us to confirm all the connections on those boards are correct from verbal descriptions. It makes no sense to proceed further without that confirmation. If your last assembly attempt still produces a hum, it is necessary to pull back to the point where proper operation can be confirmed - then proceed forward from there - with photos.

Again, we got all the time we need - be that a few hours or a few days.:)

EDIT: Somewhere around 2 -3 there should be assurance that nothing on the underside of the power supply is making contact with the chasis.
 

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There are several wires with dangling strands. If your wire is too thick (doesn't appear to be) trim off the excess with some fingernail clippers right at the insulation and bring that insulation down to the PCB.

It may be the angle of the shot, but the in/ingnd twist appears to have a similar problem. Try to bring the insulation on each wire down to the board.

R2 looks suspicious as though it was soldered from the top. Was there a problem with the via? The bottom of R2 looks like it could be a cold joint.

You need to remove the board from the heatsink to get all those items done correctly.:mad: Take a picture of the bottom side when that is being done.
 

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My question is: Do I run into prolbems with jfets if I use a transformator giving 2x34V DC to a genuine F5 (not cascoded)? I do have a lot of this transformers and I can not rewind to lower voltage. If it is ok with 2x34V DC, is there any changes that is recomended to do?

Eivind Stillingen

Maybe you want to consider building the F5 Turbo design instead, which requires 32Vdc.
 
I have already buit two F5 V2 cacode for members on Hi-Fi sentralen,Norway. They did not feel comfortable to do the entire job. I am also about to fullfill a prosject with F5T V3 with a +/-42 V DC power an a blower tunnel. I of course now of the benefit to use diyAudios PCB (divided), but I am looking for a possibility to build F5 on one PCB only, and after cvillers cacode PCB was withdrawn from diyAudio store, it is difficult to find alternative PCB.It is also a matter of price when you intend to buld more than one. PCB from diyAudio cost twice the price of what I paid for cvillers PCB.
Now cviller has been so kind to give me his gerber files to one of his F5 PCB(cascode). A friend of mine is possible to give me a helping hand, but I am also looking for members here on diyAudio that produce small amont of PCB. Years ago I was in concact with one members here that made some PCB for me to a very fair price, but I have lost his adress (a private person, not a firm) Any to recommend?

Eivind Stillingen
 
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I have already buit two F5 V2 cacode for members on Hi-Fi sentralen,Norway. They did not feel comfortable to do the entire job. I am also about to fullfill a prosject with F5T V3 with a +/-42 V DC power an a blower tunnel. I of course now of the benefit to use diyAudios PCB (divided), but I am looking for a possibility to build F5 on one PCB only, and after cvillers cacode PCB was withdrawn from diyAudio store, it is difficult to find alternative PCB.It is also a matter of price when you intend to buld more than one. PCB from diyAudio cost twice the price of what I paid for cvillers PCB.
Now cviller has been so kind to give me his gerber files to one of his F5 PCB(cascode). A friend of mine is possible to give me a helping hand, but I am also looking for members here on diyAudio that produce small amont of PCB. Years ago I was in concact with one members here that made some PCB for me to a very fair price, but I have lost his adress (a private person, not a firm) Any to recommend?

Eivind Stillingen

I use ezpcb - easy to deal with, prices are fair and quality is good. Usual options as well (eg gold plating, copper/pcb thickness etc etc). The pricing on the web calculator is what they actually charge. I am happy to take a stereo pair if you decide to go for it. PM me if youre going through with this. cheers
 
With the power off, check with a multimeter R11, it looks burnt, is it high resistance or open circuit? While your at it, check R12.

Does the resistance across P1 & P2 change when you adjust them, if not, replace them; re-check that the resistance changes with a multimeter, then set them to 0 ohms.

Power up, don't forget the light bulb tester.

First check that you psu rails are correct.

Do you have some voltage across R1 & R2 (5mV to 10mV) that will show the JFETS are conducting.

Begin the bias procedure; as soon as you get any voltage across R11/R12, power off and remove the light bulb tester, then power up and carry on with the bias procedure; if you fail, can you achieve 4.5V to 5V across P1 & P2, if not you may need to increase the value of R3 & R4, also check that you have nearly the same voltage across the gate source pins.
 
With the power off, check with a multimeter R11, it looks burnt, is it high resistance or open circuit? While your at it, check R12.

Does the resistance across P1 & P2 change when you adjust them, if not, replace them; re-check that the resistance changes with a multimeter, then set them to 0 ohms.

Power up, don't forget the light bulb tester.

First check that you psu rails are correct.

Do you have some voltage across R1 & R2 (5mV to 10mV) that will show the JFETS are conducting.

Begin the bias procedure; as soon as you get any voltage across R11/R12, power off and remove the light bulb tester, then power up and carry on with the bias procedure; if you fail, can you achieve 4.5V to 5V across P1 & P2, if not you may need to increase the value of R3 & R4, also check that you have nearly the same voltage across the gate source pins.

Thank you for reply. The resistance across R11/R12 is 2 ohm (the same as in the other working board). P1 and P2 change their resistance from 0 ohm and I have 0.1 v at R2 and 0.05 v at R1...