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An illustrated guide to building an F5
An illustrated guide to building an F5
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Old 16th September 2020, 12:52 AM   #1471
Ben Mah is online now Ben Mah  Canada
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An illustrated guide to building an F5
Chiptech,

A recap:

You had previously tested the power supply alone with the dim bulb tester and it passed.

You then connected one channel to the power supply and the bulb stayed bright - a problem.

Dennis asked you to check resistance at R5 and R6 which should be close to zero, and you measured 0.761R and 0.659R, which is good.

Looking at your pictures, you have red wires for both V+ and V-. Ideally you should have one colour for V+ and another for V- so that identification is easy and mixups are less likely.

To test the power supply without any boards connected, use your voltmeter and measure DC Volts between Ground and V+ and between Ground and V-. You should get somewhere around 25V or so.

If that is good, connect one board to the power supply and take pictures of the wiring and also take pictures of the amplifier board so that it can be examined for possible errors. Make sure you identify V+ and V- wires from the power supply. If both are red, wrap some coloured tape around the end of V- to differentiate it from V+.
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Old 16th September 2020, 12:55 AM   #1472
6L6 is offline 6L6  United States
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An illustrated guide to building an F5
^^ do everything Ben said.

( Using the same color wire for both V+ and V- is a pretty dismal idea as he hinted at, I’d make a run to the hardware store and get something different for V-. )
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Old 16th September 2020, 01:36 AM   #1473
KevinHeem is offline KevinHeem  United States
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An illustrated guide to building an F5
@Chiptech
I gotta say...I admire the methodical way you're going about this project. Saves on burnt parts!
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Old 16th September 2020, 05:47 AM   #1474
Chiptech is offline Chiptech
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Thanks to all.

I have my work plan sorted for tomorrow.
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Old 17th September 2020, 12:19 AM   #1475
Chiptech is offline Chiptech
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Ok. I get a reading of 24.33 from each PSU channel.

I have attached new photos. Blue cable is the V- connection.

I appreciate help in debugging this.
Attached Images
File Type: jpg PSU In 9-16.jpg (932.4 KB, 77 views)
File Type: jpg PSU Volt Reading.jpg (978.1 KB, 77 views)
File Type: jpg PSU Out 2 9-16.jpg (857.6 KB, 75 views)
File Type: jpg PSU Out to Right 9-16.jpg (953.0 KB, 76 views)
File Type: jpg Right Channel CU 9-16.jpg (711.6 KB, 80 views)
File Type: jpg Switch 9-16.jpg (766.4 KB, 54 views)
File Type: jpg Top View 9-16.jpg (814.0 KB, 30 views)
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Old 17th September 2020, 12:59 AM   #1476
Ben Mah is online now Ben Mah  Canada
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An illustrated guide to building an F5
Your power supply voltage is good. Your wiring to the amplifier board looks good.

Looking at the P channel Mosfet (right side of board), the thermistor wire may possibly be contacting the washer/screw. Make sure that only the body of the thermistor is in contact.

Once that is done you are ready for power up with the dim bulb tester. Having two meters for the biasing is best, with one meter set to DC Volts on the speaker out and the other meter across R7, also set to DV Volts.

If all is good, the dim bulb tester should dim after intially glowing bright.

The voltage across R7 should be very low (much less than 1V).

If good, then biasing is next.

Edit 2:

I can't tell from your picture but are the thermistors in the board thermistor holes? Looking at the picture it looked like they are on the Mosfet pins, but that is probably a illusion.

Last edited by Ben Mah; 17th September 2020 at 01:24 AM.
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Old 17th September 2020, 01:22 AM   #1477
KevinHeem is offline KevinHeem  United States
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An illustrated guide to building an F5
I don't think it's an illusion Ben.
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Old 17th September 2020, 01:23 AM   #1478
ItsAllInMyHead is offline ItsAllInMyHead  United States
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An illustrated guide to building an F5
Hi Ben - The thermistors have their own pads below the MOSFETs. FWIW, they look correct to me. P channel side goes to R21 / Source. N channel goes to R22 / Source.

Edit - Unless the photo is showing the legs directly shorted to the MOSFET pins...
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Old 17th September 2020, 01:30 AM   #1479
KevinHeem is offline KevinHeem  United States
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I'm changing my answer...I think it is an illusion.
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Old 17th September 2020, 01:36 AM   #1480
Ben Mah is online now Ben Mah  Canada
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An illustrated guide to building an F5
After looking at the schematic and a picture of the board I realized that there are holes on the board for the thermistors. I have never built a F5.
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