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Old 19th March 2012, 05:55 PM   #701
Variac is offline Variac  United States
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Since we're so close, we should wait until beta is done I think before ordering. It should take under a month to have the boards in stock once we order.
The Build thread looks like it will be a huge factor in making these amps popular.. Great start fitzfish!
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Old 20th March 2012, 08:39 PM   #702
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Thanks Variac!

I'll be in contact and send files as soon as we have a few built. The artwork didn't change, just went to a production house here in the states.

Dave
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Old 23rd March 2012, 08:20 PM   #703
EUVL is offline EUVL  Europe
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For those interested in designing their own Class A Power Amplifier case properly,
I wrote a 15-page article on the subject, using the F5X case as an example,
in Volume 3 of Linear Audio, due to be publish on 1 April.


Happy reading,
Patrick
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Old 24th March 2012, 08:14 AM   #704
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This whole project is truly impressive. Well done indeed.
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Old 25th March 2012, 06:00 AM   #705
EUVL is offline EUVL  Europe
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I have been asked about Fuse ratings for the PSU circuit published in post #109.

Under normal operation, you have a total power consumption of 330W for 2 channels F5X plus protection.
So for those with 115Vac mains, 3A slow-blow is definitely too low. You might wish to try 6A slow-blow.
This should also cover the transient inrush current during power-up, which is limited by the Ametherm MS32 20010 NTC.

For people using 230Vac mains, a 3A slow-blow would have been OK.
But the inrush can be as high as 11A even for a very short period of time.
So you may reconsider replacing the MS32 20010 with a MS32 50006L, or MS22 75004.

Ametherm MS32 50006-L ---50 ohm / 6 Amp Inrush Current Limiter Data Sheet
Ametherm MS22 75004 ---75 ohm / 4 Amp Inrush Current Limiter Data Sheet

In that case, the max. inrush current is 4.5A and 3A respectively.
A 3A or 5A slow-blow would be the one I try first.

We'll put up a revised schematics for the power supply later.


Patrick
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Last edited by EUVL; 25th March 2012 at 06:23 AM.
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Old 25th March 2012, 12:58 PM   #706
EUVL is offline EUVL  Europe
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As promised.


Patrick
Attached Files
File Type: pdf F5X PSU 120325.pdf (42.6 KB, 352 views)
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Old 26th March 2012, 12:07 PM   #707
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Quote:
Originally Posted by EUVL View Post
As you are closer to actual building now that the parts are being shipped, here is an article to describe a simple 3-point matching method for both the JFETs and MOSFETs for the F5X.


Patrick
Patrick,
Would you care mind explainaing the importance of the variable current on the lab supply. Variable voltage is self explanantory, but i am not quite sure of the purpose of the current regulation. Is it to try to match the current level thta the fets would see from the input Jfets under normal operating conditions? Also, should the fets be tested with source resistors in place. I will not be doing the oven trick, instead going the slow route of letting them heat up on a heatsink.
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Old 26th March 2012, 03:13 PM   #708
EUVL is offline EUVL  Europe
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I said in that article that you should use a power supply with an adjustable current limit. By that I mean you get set the max. current, and not constant current. When you are testing a FET at say 4A, you probably want to set the current limit at say 4.5A, so that even if you have accidentally applied too much Vgs, or the FET has a high tempco, you are still safe. It is purely a precautionary measure.

It is not necessary to measure with the source resistor in place.

Hope this answers your question.


Patrick
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Last edited by EUVL; 26th March 2012 at 03:19 PM.
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Old 26th March 2012, 03:18 PM   #709
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OK, I misunderstood. Thanks.
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Old 29th March 2012, 03:18 PM   #710
Studley is offline Studley  United Kingdom
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Default GBs

This project is fantastic for a relative novice like me and I really appreciate the efforts put in by the team and everyone else who has helped out. That includes the organisers of the GBs, which are also a big help. However, I suspect I am not the only person who has struggled to keep up to speed with the multiple GBs. I therefore thought it might be useful to try and capture in one place brief details of the GBs and the current status. So here is an initial stab at this:

Toroidy trafos: shipped
Fuku resistors/fets/keratherm pads: shipped
Case & heatsinks: pending
CRC PCBs + MPC74 resistors: pending
2 amp boards + 8 cap boards + protection board: pending
Protection board parts kit + spares + small parts kit: pending
Matched output fets: trying to source?
IEC connector : pending

If I have got any of the above wrong or missed something then please amend it and re-post.
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