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F5 Turbo Builders Thread
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Old 15th April 2019, 01:27 PM   #5491
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I've read about a third or so. It's not so bad, but then again, I don't know this stuff..... There are some questions coming up, but maybe finishing it will answer them.

For sure, you need to know how the circuit was implemented so that the HBR resistor can be inserted in the right place.

Last edited by BigE; 15th April 2019 at 01:45 PM.
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Old 15th April 2019, 02:32 PM   #5492
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Are the humbreaking resistors supposed to be inserted between the junction of R3/R4 and the audio signal ground?
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Old 15th April 2019, 05:26 PM   #5493
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Page 56 of http://hifisonix.com/wordpress/wp-co...ound-Loops.pdf should answer your question, the lowest bridge & cap in the bottom right corner are replaced with a CL60 in the FW designs.
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Old 15th April 2019, 07:16 PM   #5494
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Thanks Itsmee. Pages 36 and 37 are more detailed. I think 56 assumes that the amps are on a single PC board, while the F5T is spread over a couple.

My question is where on the FE board to attach the HBR.

Is it just at the GND point or is the GND point on the FE board on the wrong side of the feedback resistors ? ( I am at the office, so cannot check )

Last edited by BigE; 15th April 2019 at 07:21 PM.
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Old 15th April 2019, 07:41 PM   #5495
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Quote:
Originally Posted by BigE View Post
...My question is where on the FE board to attach the HBR...
You don't, it's in the PSU between 0V and chassis earth, unless your talking about low value resistors (10R ish) in the ground connection between the input socket and ground on the PCB; only do that if you have hum problems you can't cure any other way.
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Old 15th April 2019, 07:55 PM   #5496
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Hi Itsmee,

I have the diode bridge and CL60 in place already.

There is hum I'd like to get rid of, but before installing the HBR though, there are quite a few other things to implement -- proper wiring being one of them -- like a proper star ground or 'T'.

My main issue is space in the amp. I built the case to fit a stand, and that meant I had to either mount the transformer on the face plate, or mount the cap banks on the face plate. I chose the cap banks, since then the diode bridges had easy heat sinking. But that put the transformer in the middle of the amp.

I'm going to measure the noise with a QA400 as I go, to test for any changes.
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Old 15th April 2019, 09:10 PM   #5497
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Adding the 10R's may not help, thats for breaking hum loops, if it does, rewire.
Your problem may be induced hum from local proximity, first move the wiring, then try rotating the transformer, next try standing it vertically - it moves the flux lines by 90°, try both N-S & E-W 'doughnut hole' orientation to see which gives the least hum; decide from there what needs to be done.
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Old 15th April 2019, 11:26 PM   #5498
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It looks to me like the FE board needs to be modified for the HBR to be installed as per the Hiphonics article. Specfically, the article shows that the RCA shield is connected to the HBR on it's way to the zero volt line, as does the ground between R3 and R4 ( I think ).

A picture says a thousand words.... attached is how I think the HBR should be added. The diagonal line is the HBR, the thick ground is cut, and the link and group of G's are connected. It is labelled with black text.

BEWARE: I'm not an expert. Just trying to learn something. It's easy enough to operate as designed.... just replace the HBR with a jumper.

Does that look right?
Attached Images
File Type: jpg FE mods for HBR.jpg (107.9 KB, 52 views)

Last edited by BigE; 15th April 2019 at 11:49 PM.
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Old 16th April 2019, 12:30 AM   #5499
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Can't help with the PCB, I dont know it - haven't built one with those boards.
There are lots of sucessful builds without the HBR.
Pictures of your build would help.
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Old 16th April 2019, 01:21 AM   #5500
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Right now, I am working at cleaning up the power supply... again. I used a bunch of crimped push on connectors, and a nice tool, but it was just as powerful as a set of pliers.. So, I am soldering them all on, and heatshrinking after.

Four literally fell off the wires. I am amazed it was working.

I will be posting some shots once it's working again. And I do want to measure it again... I did 6 years ago, but I am a bit more cautious/scared these days.... I am slowly learning how little I know.
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