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F5 Turbo Builders Thread
F5 Turbo Builders Thread
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Old 14th May 2013, 07:00 PM   #1851
Rixsta is offline Rixsta  United Kingdom
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F5 Turbo Builders Thread
Yes, I remember reading you saying this on another post somewhere.

Thanks Im thinking of going this way with good relays OR just putting appropriate fuses on the secondary AC or after Caps DC ?

Im Presuming with the right fuses, they would blow fairly fast and the speaker may see DC for a second or two.

Atleast fuses are some form of protection without having to worry about sound quality issues.
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Old 15th May 2013, 02:20 PM   #1852
WalterW is offline WalterW  Netherlands
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Two questions:
- When I power up my new F5Turbo v2 it consumes around 300 Watt total and after an hour or so they stabilize around 350 Watt ( that is the bias I set them to when they were hot). Is this a too big difference ?
The R11 and R12 resistors which are in series with the NTCs are already lowered to 1k21 instead of 2k2. Should I lower them further or even short them?

- One transformer starts sometimes humming for a few seconds, or a minute and then the hum dissapears slowly. With a cold and warm amp, very unpredictable... The amps bias and powerconsumption does not change when humming.
I noticed this behaviour already testing the transformers without load.
What is the reason of this? What can be done?

Walter
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Old 15th May 2013, 02:25 PM   #1853
6L6 is offline 6L6  United States
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Your power consumption seems normal.

The important question is what is your measured cold bias and what does it change into when it's warm?
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Old 15th May 2013, 02:40 PM   #1854
ijscobar is offline ijscobar  Netherlands
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Walter, what kind/brand/rating transformers are you using?
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Old 15th May 2013, 03:06 PM   #1855
oiphy is offline oiphy  Norway
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- One transformer starts sometimes humming for a few seconds, or a minute and then the hum dissapears slowly.

dc in mains?
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Old 15th May 2013, 03:47 PM   #1856
vdi_nenna is offline vdi_nenna  United States
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Default Transformer Rating

When building the v3, it's recommended to use a transformer with twice the rated VA. I have two Antek AS-4218 rated at 400v or approx. 11A each.
With secondaries in serial for 36v, will the secondaries deliver half the current?

Will the transfos be enough for mono block v3 F5? Would 5-6 amps be enough to drive 1 channel to 100w?

Thanks,

Vince
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Old 15th May 2013, 04:01 PM   #1857
WalterW is offline WalterW  Netherlands
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Quote:
Originally Posted by ijscobar View Post
Walter, what kind/brand/rating transformers are you using?
Two new Amplimo's 98016 : 625VA, 2 x 25V, 2 x 12.5 A, made in UK.
Total of 1.25 KVA for 320 Watt class A dissipation.
So 4 times the dissipation, which is good according to Papa
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Old 15th May 2013, 06:04 PM   #1858
WalterW is offline WalterW  Netherlands
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Quote:
Originally Posted by oiphy View Post
- One transformer starts sometimes humming for a few seconds, or a minute and then the hum dissapears slowly.

dc in mains?
DC in the 230 Volts? Is that possible?
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Old 15th May 2013, 06:17 PM   #1859
oiphy is offline oiphy  Norway
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Default afraid so.

Quote:
Originally Posted by WalterW View Post
DC in the 230 Volts? Is that possible?
yep..... and it saturates the trafo so it starts humming..
there's an easy fix with two diodes and two caps I believe... edit : AndrewT posted a link to it a while ago...


edit: http://www.federalpacific.com/litera...ormernoise.pdf maybe some help here
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Last edited by oiphy; 15th May 2013 at 06:46 PM.
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Old 15th May 2013, 06:20 PM   #1860
WalterW is offline WalterW  Netherlands
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Quote:
Originally Posted by 6L6 View Post
Your power consumption seems normal.

The important question is what is your measured cold bias and what does it change into when it's warm?
Hi 6L6,

I measured cold exact 0.2 volts over the 0,1 Ohm resistor in each PSU rail.
So cold 2.0 Ampere = 1.0 Ampere per MOSFET.
Over the P channel 0.22 Ohm sourceresistors I measured 0.217 V and 0.212 Volt, so that's indeed around 1 Ampere / MOSFET.

When the Amp is hot, I measure 0.252 Volts over the 0.1 Ohm PSU resistor, so my beloved 2.5 A per rail. The 0.268 V and 0.262 Volts over the sourceresistors confirm this. Around 1,25 Amp / MOSFET.

So that's what the bias changes from 20 degrees Celsius to 52 degrees Celsius.
Is that too much?
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