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Old 6th June 2014, 12:52 PM   #14221
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Quote:
Originally Posted by acumos View Post
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
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Old 6th June 2014, 01:30 PM   #14222
bcmbob is offline bcmbob  United States
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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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Last edited by bcmbob; 6th June 2014 at 01:43 PM.
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Old 6th June 2014, 05:29 PM   #14223
acumos is offline acumos  Italy
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Put a kleenex on the keyboard ZM!
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Old 6th June 2014, 06:03 PM   #14224
bcmbob is offline bcmbob  United States
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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. Take a picture of the bottom side when that is being done.
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Last edited by bcmbob; 6th June 2014 at 06:23 PM.
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Old 6th June 2014, 06:38 PM   #14225
bcmbob is offline bcmbob  United States
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Not perfect but an example. Do you have solder wick braid to use to clean the pads/holes?
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Last edited by bcmbob; 6th June 2014 at 06:58 PM.
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Old 6th June 2014, 07:11 PM   #14226
acumos is offline acumos  Italy
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Quote:
Originally Posted by bcmbob View Post
Not perfect but an example. Do you have solder wick braid to use to clean the pads/holes?
yes 1.5 mm and pump.
I'm desoldering all wires to free up psu and diodes. Tomorrow I'll put euroblocks.
The R2 I think it's ok cause I have continuity between the R2 and R1 pins.
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Old 6th June 2014, 09:38 PM   #14227
bcmbob is offline bcmbob  United States
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Old 11th June 2014, 10:47 PM   #14228
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Hooked up the F5 / Aikido Pre to the Maggies for the first time. Awesome!!!!
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Old 15th June 2014, 08:08 AM   #14229
acumos is offline acumos  Italy
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Now I have a f5 board working. But on the other board as I powered it up TH1 has blown. And now I don't have voltage through R15. ?????
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Old 15th June 2014, 12:54 PM   #14230
Liliya is offline Liliya  Norway
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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
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