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F5 Turbo Builders Thread
F5 Turbo Builders Thread
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Old 2nd January 2018, 08:17 PM   #4991
esprit is offline esprit  Europe
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Quote:
Originally Posted by 6L6 View Post
It's probably better to arrange as CRCC, to keep losses to a minimum. This is a power amp after all...

(6) 0.47 3W resistors in parallel (as in the original PSU) is roughly an 18W 0.1ohm resistor.

You could search for something like that, or just parallel a bunch of the 3W resistors, which is a lot easier.
Hello
I have now a working power supply giving 33.6 L&R.
Using 800va22v center tap, 4 BYW 99 w 200, 2 Nippon chemicon 47,000uf, 6x .47 3w in parallel and 4 Nippon chemicon 47,000uf.
Many Thanks
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Old 4th January 2018, 10:07 AM   #4992
esprit is offline esprit  Europe
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Sorry My bad.
transformer 24-0-24v
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Old 4th January 2018, 10:20 AM   #4993
Rixsta is offline Rixsta  United Kingdom
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F5 Turbo Builders Thread
Quote:
Originally Posted by johnhenryharris View Post
The cascode does not make the amp more stable it only reduces the voltage to the front end FETs protecting them from overvoltage condition. You could have an amp with the higher voltage for the multiple outputs and reduce the voltage before feeding the front end, though I don't know what that would do to the drive to the output. The only thing for stability on the F5T, that I see, is at what point the diodes across the output emitter resistor starts to conduct, that can burn out outputs. You could just have the emitter resistors on the outputs and would be stable but would not support the high currents of the diodes.
If the Fets were overpowered and blew could other parts then blow as a result.
I once built an F5 turbo and it kept going wrong. I rebuilt the PSU 3 times with no result.
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Old 4th January 2018, 10:29 AM   #4994
Rixsta is offline Rixsta  United Kingdom
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F5 Turbo Builders Thread
So I'm thinking of trying again with an F5t build. With the new diyaudio boards. Last time I tried it was revision 1 of the boards which were not as good.

Just a couple of questions about F5t
If u had say 32v rails and 35v caps in my PSU. Is that too close to the caps Max rating?

If I create dual PSU then it's two transformers with 1 rectifier each?
I'm guessing this will create a better separation.
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Old 4th January 2018, 10:37 AM   #4995
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Rixsta View Post
....................If u had say 32v rails and 35v caps in my PSU. Is that too close to the caps Max rating?
.................
Rixta,
you are in the UK where we use the harmonised mains supply.
The normal range of mains supply voltage is from 216Vac to 253Vac.

Find out what secondary voltage your transformer will give when the nominal 230Vac primary has 253Vac applied.

Then you can determine what capacitors you should use.
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Old 4th January 2018, 10:48 AM   #4996
Rixsta is offline Rixsta  United Kingdom
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F5 Turbo Builders Thread
Thanks. Don't have a transformer yet but have 8 x 35v 10.000uf caps so far.

I'm Looking for 2x 400va 24v transformer

Yes I'm in UK
OK o get what you mean. In case the mains fluctuates too high at some time it may go over the assumed 32v from 24v transformer.
I'll keep that in mind then.. Thanks Andrew
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Old 4th January 2018, 11:03 AM   #4997
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Rixsta View Post
Thanks. Don't have a transformer yet but have 8 x 35v 10.000uf caps so far.

I'm Looking for 2x 400va 24v transformer

Yes I'm in UK
OK o get what you mean. In case the mains fluctuates too high at some time it may go over the assumed 32v from 24v transformer.
I'll keep that in mind then.. Thanks Andrew
I think your maximum voltage after the rectifier could be ~39Vdc from a 230:dual 24Vac 6% regulation transformer.
I would NOT use 35V capacitors.
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Old 4th January 2018, 11:07 AM   #4998
Rixsta is offline Rixsta  United Kingdom
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F5 Turbo Builders Thread
OK thanks for that. Those caps are perfect for the original F5.

Will try find some good quality 50v caps or something similar or use lower voltage transformer. Thanks for the help as I now know how to work it out

Sometimes there's a good deal here on the forums for parts.
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Old 4th January 2018, 08:43 PM   #4999
esprit is offline esprit  Europe
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Quote:
Originally Posted by Zen Mod View Post
it's essential to squeeze as many Kendeils you can - in amp box

rectifier and first C cells can be in separate box
Many thanks.
I now have transformer/rectifier/4x 68,000 U32d in seperate box and 8x 22,000 Kendeils in amp box.
There are a few issues relating to this build of which I am uncertain.
a, which box should house the R.
b, how much R is recommended (I have some 0.47 1%,3w dales).
c, at which position on the power supply ground, should the,
bridge/thermistor be returned to earth.
d, with respect to the above power supply, what amp rating of plug/socket should be used to connected box 1 and 2 together.

At the risk of sounding like a complete lunatic, the above build is running as well as the one described at #4991
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Old 5th January 2018, 05:32 PM   #5000
esprit is offline esprit  Europe
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Sorry my bad, again,!

In my last line, I should have written, "in build". and not, "running".
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