F-5 boards

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I noticed an F5 rev 3.0 pcb in the store.....can somebody tell me what the differences are to rev 2 (which I currently have?)

Thanks
Neville

V3.0
Change to F5 schematics from F5 Turbo article
  • Minor diagram change in NTC and limiter sections
  • P3 added to adjust N/P variations to reduce distortion
  • Relabelling of resistors to match schematics

Layout changes
  • JFETs moved further away from current traces
  • Hole for OUT moved to other edge of board to make it prettier and increase symmetry
  • Middel mounting roles removed
 
Hi Jason, I thought it in everybody’s intrest to put this message out. I received the F5 v3.0 boards a while ago and only today got around to start looking at them properly. However it turns out a lot of the component numbers have changes from V2.0 (BOM in post 1 of this thread), or any other F5 schematics I’ve come across so far. Where can I find the updated documentation for these boards? Is there anywhere where I can find a picture of a populated board as an example, that would be usefull. Is the orientation of the JFET’s, as depicted on the board for the 2sj108/2sk370 or 2sj74/2sk170?

Also what do I do with P3, it wasn’t part of the original design, what value does it need to be, how do I set it?

I hope you can help.
 
Looking at the board. At first sight the component names have changes as follows:
V2.0 -> V3.0
R10 has become R2
R9 has become R1
R2 has become R4
R 1 has become R2
R5 has become R9
Ect..

Is this intentional or has there been a mistake, since you didn’t mention these changes in your post earlier?
 
Switches things on and off again
Joined 2000
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Hi Jason, I thought it in everybody’s intrest to put this message out. I received the F5 v3.0 boards a while ago and only today got around to start looking at them properly. However it turns out a lot of the component numbers have changes from V2.0 (BOM in post 1 of this thread), or any other F5 schematics I’ve come across so far. Where can I find the updated documentation for these boards? Is there anywhere where I can find a picture of a populated board as an example, that would be usefull. Is the orientation of the JFET’s, as depicted on the board for the 2sj108/2sk370 or 2sj74/2sk170?

Also what do I do with P3, it wasn’t part of the original design, what value does it need to be, how do I set it?

I hope you can help.

The F5 V3 boards use the part numbering from the F-5 Turbo article, which is the latest official version of the F5. The P3 is only used for advanced builders with advanced equipment - you can leave it out if you don't know what it's used for. Any more questions don't hesitate to ask :)
 
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Thanks, I’ve found the diagram on page 2 o the F5 turbo article with which the boards corresponds. I can work with that.
It seems it's still possible to build the old lay-out without cutting traces, like omiting R19 &R20, which weren't in the origimal design. Does somebody know what these are for?
Might be worth mentioning the fact that this is an updated design from the orginal F5, to future customers, to avoid more confusion.
 
Thanks, I’ve found the diagram on page 2 o the F5 turbo article with which the boards corresponds. I can work with that.
It seems it's still possible to build the old lay-out without cutting traces, like omiting R19 &R20, which weren't in the origimal design. Does somebody know what these are for?
Might be worth mentioning the fact that this is an updated design from the orginal F5, to future customers, to avoid more confusion.

I'm pretty sure R19 & R20 were in the original F5 circuit as R21 &R22. Part of the protection circuitry. Nelson just rearranged the schematic. I'd think the latest circuit would be preferable since Nelson has been tweaking it for a few years.
 

6L6

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F5_Schematic_w:P3.jpg

This schematic is from the F5T article and should match the latest version of PCB.

P3 should be set to it's mid-point -- equal resistance from pin 1-2 and from pin 2-3. The track isn't 200 ohm long exactly, so measure. As for setting it to find the distortion spectra you like the most, you can just count turns in either direction as you adjust it... but keep notes!

R19, R20 in the latest schematic are part of the limiter circuit.

The orientation of the Toshiba K170/J74 or K370/J108 match the orientation drawn on the silkscreen. The silkscreen for Q5, Q6 is shown genderless, but the Collector, Base, Emitter are labeled so you can determine proper orientation - the reason for this is that the most common transistors used in the position, the ZTX and the BC, have different pinouts.
 
Thanks for all the input. Yes I see now R19&20 where in the original design but drawn in slightly differently.

Thanks for the suggestion on the adjustments of P3.

If this is not the place to ask these question then please let me know but I see the values for R13&14 ( BOM part nr. have stayed the same in both old and new schematics), have changed from 47R to 100R. What could have been the reason for doing this?

I noticed the rail voltage has been decreased from 24v to 23v on the drawing . I’ve not build up the PSU yet, but I don’t see a way to adjust output voltage other than adding "off" board components, or am I missing something? I think 1Volt + or – won’t be a big issue, but it still caught my attentions. Can someone comment on this?
 
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6L6

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- R13, R14 are 'gatestopper' resistors that damp very high frequencies (200K+) and keep the posibility of osciliattion low. It's a very non-critical value, anything from 47R to 680R will work. Use whatever you have, if you need to order, 100R is fine.

- Most people use a 18V+18V transformer, and under load will give 22-23V rails, although the nominal value will be 23-24V. Again, no real difference.