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Old 16th October 2013, 07:08 PM   #2491
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so the left (on the thermo pic) P ch source resistor has a drop of 300mV. then the rigth one must have alot more voltage drop. and the N ch resistors too.

Last edited by AudioSan; 16th October 2013 at 07:11 PM.
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Old 17th October 2013, 12:22 PM   #2492
emyeuoi is offline emyeuoi  Italy
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Hi to everybody,
I think that I need some advice about the F5T V2 that I just complete and biased.
2 days ago I installed the trasformer and start the bias following the suggestions found on the forum and in particular the advices from Walter and Buzzforb... slowly! And slowly I reach the 331 mv on both sides in the right channel with the best offset of -0.1.
The same I can't reach for the left channel. I have always a difference of 4.5 mV between P and N and the offset is unstabile. When I reach the 0.0 and I cover the enclosure the offset start to move to - 0.1, -0.2 up to -3.9 (now). The same for the 2 source resistors... the reading increase following the offset. This happen only in the left side while the right is stable.
I suppose that is relevant to the increasing of the temperature but why only for 1 channel? The ampli play music fantastic but I am scare for this channel... may be is normal but some advice should be greatly appreciate.
Many thanks
Enrico
Ps: Just read the meter and the offset is now -5.1. I will reopen and return back to 0.0 as I do already 3 times But I am sure that after half hour it will be the same
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Old 17th October 2013, 12:28 PM   #2493
Zen Mod is offline Zen Mod  Serbia
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-5.1 of what ?

MA , MV , MJ or ........ maybe mV

everything up to +/-50mV is completely OK for home gear , in temp equilibrium

btw. do not compare volatge across Rs of upper and lower part ; choose one side and measure on it ;

so - offset and current on one side is what's needed for proper setting of F5 ( and many other amps)
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Old 17th October 2013, 12:43 PM   #2494
emyeuoi is offline emyeuoi  Italy
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Thanks Zen... so, nothing to worry about.
I am still curious to understand why is not stable... I will check the offset time to time
Cheers
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Old 17th October 2013, 12:45 PM   #2495
Zen Mod is offline Zen Mod  Serbia
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well - just for test - cover all air inlets on case , and you'll see it will be more stable

but , do not leave covers for good

it is stable enough and as intended , so do not worry
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Old 17th October 2013, 12:50 PM   #2496
emyeuoi is offline emyeuoi  Italy
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ahahaha... Ok thanks!
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Old 21st October 2013, 11:25 AM   #2497
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Default Thermistors ?

How closely do the thermistors have to be coupled to the Power FETs?

Is this good enough ? I can add a dob of araldite to keep them in place.
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Old 21st October 2013, 12:25 PM   #2498
emyeuoi is offline emyeuoi  Italy
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I install the thermistors touching the washers with a little glue.
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Old 21st October 2013, 01:31 PM   #2499
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I'm a fraidy-cat, so I measured 3 different MUR3020 diodes.
I wanted to know the forward voltage drop at 53C, which is the operating temp of my own F5V2 at summer.
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Old 21st October 2013, 02:09 PM   #2500
6L6 is offline 6L6  United States
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Katie and Dad - That looks fine. Close is good enough. They will still do their job of changing resistance as they warm up.
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