help needed!
Hi everybody,
I built my F5 about 6 months ago. It was working flawessly until tomorrow.
For some reason, I started to hear some some distortion on one channel. Then, I noted that the power mosfets on that channel were not getting hot.
The measure on the output reads 0.2V. Around R12 and R13, I read 0V. And after moving the pots to the minimum, I cannot adjust the bias anymore. Moving one pot changes the DC output, but not the other one. And nothing seems burned.
Any suggestion about what may by wrong? Should I replace all fets?
Thanks for any help.
Hi everybody,
I built my F5 about 6 months ago. It was working flawessly until tomorrow.
For some reason, I started to hear some some distortion on one channel. Then, I noted that the power mosfets on that channel were not getting hot.
The measure on the output reads 0.2V. Around R12 and R13, I read 0V. And after moving the pots to the minimum, I cannot adjust the bias anymore. Moving one pot changes the DC output, but not the other one. And nothing seems burned.
Any suggestion about what may by wrong? Should I replace all fets?
Thanks for any help.
Bourns 200R trimpot 3296W-1-201LF. That's a top adjust, multiturn trimpot with the leads on a single line. Change the "W" to "X" for inline, side adjust; "W" for top adjustment, inline; "Y" for top adjust, leads not inline; and, "Z" for side adjust, leads not inline.
You can look up the part at either mouser or digikey using the manufacturer's part number.
Dan
Transformer options for F5
Need some advice on choosing best option for my F5 build. I am located in Toronto and there is another source of quality transformers other than Plitron, and there is no $250 minimum order restriction. Company is called Richard Sumnor Technology SumR - Richard Sumner Technology
My options are,
400VA from Antek with steel case for shielding $105
350VA from SumR for $125 Encapsulated with shielding
500VA from SumR for $160 Encapsulated with shielding
I know most people are using the 400VA Antek, is the 350VA cutting it too close or should I just get the 500VA
Another option is using two Antek 300VA and doing monos but then I will need another power supply. Is the cost of monos justified by much better performance ?
thanks
Need some advice on choosing best option for my F5 build. I am located in Toronto and there is another source of quality transformers other than Plitron, and there is no $250 minimum order restriction. Company is called Richard Sumnor Technology SumR - Richard Sumner Technology
My options are,
400VA from Antek with steel case for shielding $105
350VA from SumR for $125 Encapsulated with shielding
500VA from SumR for $160 Encapsulated with shielding
I know most people are using the 400VA Antek, is the 350VA cutting it too close or should I just get the 500VA
Another option is using two Antek 300VA and doing monos but then I will need another power supply. Is the cost of monos justified by much better performance ?
thanks
The Antek transformers work fine. You can actually get by with a single 300VA so that is an option. However, a 400VA would be better. The metal can for the Antek isn't necessary, but do consider a shielded transformer (e.g., AS-4218 as opposed to AN-4218). Wire the shield lead to your chasis ground so that the shield can drain. The advantage of getting an oversized transformer is that you have more flexibility in re-using it for other, more power hungry designs and as such you might even want to consider a 500VA transformer.
Personally, I like monos. The second chassis tends to cost more than the second PSU. You might look at Michael Rothacher's Circolotron chassis for an idea on doing a monoblock F5 design. While not an F5, his chassis design and heatsink choices will work for an F5 if you use Peter Daniel's F5 PCBs. (I have attached those PCBs to the heatsinks used in the Circolotron design and they work just fine. As does the Circolotron itself -- a nice design also.) Documentation for the Circolotron may be found at the passdiy site under "Projects". Oh, and I used Antek 300VA transformers with Antek cans with the Circolotron chassis. I made a little tweak to accomodate the different spacing is all.
Dan
To Quote SumR,
"We use UL approved toroid cans produced by a German manufacturer. They are made from UL approved plastics.
The shielding is applied in several steps when the transformer is potted into the casing.
The casing has a bolt shaft through the centre for mounting."
"(There is sufficient room in this 500VA case to totally shield the sides, and both top and bottom of the transformer.)"
From my conversations with SumR, he states that thier transformers are built completely in house. Even Plitron aparently now out sources their smaller sized transformers to China.
"We use UL approved toroid cans produced by a German manufacturer. They are made from UL approved plastics.
The shielding is applied in several steps when the transformer is potted into the casing.
The casing has a bolt shaft through the centre for mounting."
"(There is sufficient room in this 500VA case to totally shield the sides, and both top and bottom of the transformer.)"
From my conversations with SumR, he states that thier transformers are built completely in house. Even Plitron aparently now out sources their smaller sized transformers to China.
Also, note that that 500VA torrids from SumR don't come with lower than 22 VAC (on the secondaries). Unless you plan for this in your PSU, you're going to end up with rail voltages outside of the recommended 23 - 25 VDC.
Dan
This is an illustrated guide to building an F5. This utilized Peter Daniel PCB.
http://www.diyaudio.com/forums/pass-labs/188691-illustrated-guide-building-f5.html
Here is the original manual and article.
http://www.firstwatt.com/pdf/prod_f5_man.pdf
The cviller circuit boards are available here -
Boards
The Peter Daniel circuit boards are here, they are not on his website, but send him a message and he will reply promptly -
www.Audiosector.com
Are your F5s set up to the standard output bias of 1.3A?
Two channels running at 1.3A output bias, uses up ~83% of the maximum continuous rating of your single transformer.
This is unusually high for a ClassA amplifier/PSU.
If the outside is just warm, have you any idea what the internal temperature might be?
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