I did too, just to use the solder cups on the 14 awg wire.
Careful on the FE board, with the two holes closes to IN/GND/LINK. Those are vias, that take the ground to the top of the board. That section is used in the voltage divider than drives the cascode. I don't think you need to drill those out.
If you do, you must re-establish those vias or the voltage divider has no ground reference.
Yes, I left those alone. They are the only two wire holes with vias on all the boards. Are those the ones you drilled out and had the resultant problem with the voltage feed to the Jfets?
Nash
I have a couple suggestions for V4 output boards, if that's ok :
1) O/P, V+, V- to fit 14 AWG
2) Added pads for 2k2 to enable flipping the boards upsided down and locating all transistors at center of heatsink. Useful when building F5T with multiple boards per sink.
And a question, why only two transistors per output board? Why not more, say 4 Q and 4 D?
Thanks for making the boards!
FYI: Amp is nearing completion.
1) O/P, V+, V- to fit 14 AWG
2) Added pads for 2k2 to enable flipping the boards upsided down and locating all transistors at center of heatsink. Useful when building F5T with multiple boards per sink.
And a question, why only two transistors per output board? Why not more, say 4 Q and 4 D?
Thanks for making the boards!
FYI: Amp is nearing completion.
Help please!
Hi at all!
For the second time my f5 v2 turbo burned!
I have noticed you that this happened because I connected at the input a tube preamp of my friend that unfortunately at turned off and on pulled out 144Vdc.
My F5 burned after a few seconds!
I must tell you that I thought that inserting in parallel to R2 47,5K two zener diodes connected in anti-series would have kept away of risk my amp but this did not happen unfortunately.
Now I must also tell you that by controlling which components are burned, I found that only the Power MOSFETs are burned.
It 'strange to find that both the protection diodes in the input ad also the FET 2SK170 / 2sj74 are safe, I expected to find them burned.
I would think that as an additional protection I would insert a capacitor input immediately after R1 1K as done by Nelson Pass Aleph series.
What do you think about that?
I know that in some way could deteriorate signal ...
But since I am now also sostiuendo the IRFP9240 / IRFP240 with the most beautiful and expensive ECW20N20Z / ECW20P20Z, I would not want to risk burning them in again.
Do you have any advice on the input capacitor to be taken?
Thank you in advance.
Antonio
Hi at all!
For the second time my f5 v2 turbo burned!
I have noticed you that this happened because I connected at the input a tube preamp of my friend that unfortunately at turned off and on pulled out 144Vdc.
My F5 burned after a few seconds!
I must tell you that I thought that inserting in parallel to R2 47,5K two zener diodes connected in anti-series would have kept away of risk my amp but this did not happen unfortunately.
Now I must also tell you that by controlling which components are burned, I found that only the Power MOSFETs are burned.
It 'strange to find that both the protection diodes in the input ad also the FET 2SK170 / 2sj74 are safe, I expected to find them burned.
I would think that as an additional protection I would insert a capacitor input immediately after R1 1K as done by Nelson Pass Aleph series.
What do you think about that?
I know that in some way could deteriorate signal ...
But since I am now also sostiuendo the IRFP9240 / IRFP240 with the most beautiful and expensive ECW20N20Z / ECW20P20Z, I would not want to risk burning them in again.
Do you have any advice on the input capacitor to be taken?
Thank you in advance.
Antonio
well , trouble ...... 
as there is no substitute for cubic inches (especially if you're Yank , paying gas 55% of EU price , just to drive 40mph , 200m without curve in sight
) , there is no substitute for mileage in any hobby ........ and there is no substitute for minimal amount of luck needed
best cap is no cap , but what you need is good and high voltage cap , with friends as you have
so - fave combo of Elna Silmic 10uF elco bypassed with 1uF polycarbonat (MKC by Philips) is sorta outa question
find whatever you can find , labeled as 4u7/250V and put it on input
or - even better - stop messing with bad equipment , upstream of both your speakers and amp , then you'll not need patches
remember that there is no 100% foolproof-ed amplifier . It can be safe (fire and explosion vise ) , but no way that you can plug chain saw on input of your amp and save your wallet in same time
as there is no substitute for cubic inches (especially if you're Yank , paying gas 55% of EU price , just to drive 40mph , 200m without curve in sight
) , there is no substitute for mileage in any hobby ........ and there is no substitute for minimal amount of luck needed best cap is no cap , but what you need is good and high voltage cap , with friends as you have
so - fave combo of Elna Silmic 10uF elco bypassed with 1uF polycarbonat (MKC by Philips) is sorta outa question
find whatever you can find , labeled as 4u7/250V and put it on input
or - even better - stop messing with bad equipment , upstream of both your speakers and amp , then you'll not need patches
remember that there is no 100% foolproof-ed amplifier . It can be safe (fire and explosion vise ) , but no way that you can plug chain saw on input of your amp and save your wallet in same time
help
Hi Alex thanks for your reply!
I have to update you,today i have just replaced old mosfet with ECW20N20Z / ECW20P20Z,and the amp nont work correctly
It distorts and often intervenes speaker protection, what bad luck!
Yet somepeople had guaranteed that with exception of different physical dimensions and the inversion of pin Drain and Source, it would have played!
Is possible can do something?
Also if you should use a 10uF why not use a polyester 400V type?
Could you tell me where insert it exactly in circuit?
Before or after R1 1k input resistor?
Also I read that too about the version V3, however:
Depending on layout and other little issues, we might ultimately have to
consider using capacitors to perform frequency compensation which have
been absent (along with coupling capacitors) in previous F5 versions. In
actual testing I found that ringing and oscillation issues can be dealt with by
optional C3 and C4 in values ranging around 1 nF.
You think so that is a solution to be adopted in the version V2 or you can avoid if the test of the square wave is ok?
Thanks in advance
Antonio
Hi Alex thanks for your reply!
I have to update you,today i have just replaced old mosfet with ECW20N20Z / ECW20P20Z,and the amp nont work correctly
It distorts and often intervenes speaker protection, what bad luck!
Yet somepeople had guaranteed that with exception of different physical dimensions and the inversion of pin Drain and Source, it would have played!
Is possible can do something?
Also if you should use a 10uF why not use a polyester 400V type?
Could you tell me where insert it exactly in circuit?
Before or after R1 1k input resistor?
Also I read that too about the version V3, however:
Depending on layout and other little issues, we might ultimately have to
consider using capacitors to perform frequency compensation which have
been absent (along with coupling capacitors) in previous F5 versions. In
actual testing I found that ringing and oscillation issues can be dealt with by
optional C3 and C4 in values ranging around 1 nF.
You think so that is a solution to be adopted in the version V2 or you can avoid if the test of the square wave is ok?
Thanks in advance
Antonio
check every mosfet Iq , measuring voltage across (each!) source resistor
safety cap - I said - use whatever you think is good for your ears , value not critical (but no less than I said)
if square test is OK and you can't see any oscillation in MHz range , no need for lag caps
however - check all needed (current through input JFets also ) then write back
after 170V-ish adventure , I would replace input JFets ; as all semis , JFets can easily became fatally depressive , remembering stress from the past .....
safety cap - I said - use whatever you think is good for your ears , value not critical (but no less than I said)
if square test is OK and you can't see any oscillation in MHz range , no need for lag caps
however - check all needed (current through input JFets also ) then write back
after 170V-ish adventure , I would replace input JFets ; as all semis , JFets can easily became fatally depressive , remembering stress from the past .....
Hi there 
I am thinking of finally building the F5T Based on the convertible boards by tea bag.
No cascoding, just the basic version.
I can see there are several versions of BOM available on the diyaudio store web site. And there is no dedeicated BOM for the convertible boards.
So a question (don't beat me) is what BOM can be used, the one from the diyadio store, or there is some modified version out here for these set of boards why not.
I am thinking of finally building the F5T Based on the convertible boards by tea bag.
No cascoding, just the basic version.
I can see there are several versions of BOM available on the diyaudio store web site. And there is no dedeicated BOM for the convertible boards.
So a question (don't beat me) is what BOM can be used, the one from the diyadio store, or there is some modified version out here for these set of boards
why not.
BOM are hard to keep up-to-date, which is why they are not often used in this community.
The schematic has all the information needed to populate the circuit, and some other questions are answered in Nelson's article.
That said, PLEASE DO ask whatever questions you have as they come up, there are plenty of people here who are happy to help you find all the right parts.
The schematic has all the information needed to populate the circuit, and some other questions are answered in Nelson's article.
That said, PLEASE DO
ask whatever questions you have as they come up, there are plenty of people here who are happy to help you find all the right parts. Compile your own Bill of Materials to suit the sch you intend to implement.Hi there
I am thinking of finally building the F5T Based on the convertible boards by tea bag.
No cascoding, just the basic version.
I can see there are several versions of BOM available on the diyaudio store web site. And there is no dedeicated BOM for the convertible boards.
So a question (don't beat me) is what BOM can be used, the one from the diyadio store, or there is some modified version out here for these set of boards
calculate the quiescent dissipation and estimate the peak instantaneous dissipation. From there apply a suitable Factor of Safety and then select a suitable power rating.
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