F5 power amplifier

[mfrimu]

Position of Thermistor on FET?

Hello,

I have large washers and they pretty much cover the entire FET.

On the 6moon audio site picture, the production model F5 thermistors are not touching the FTEs.

On this thread and build guides, it is being recomended they do touch the FET

In my case, would it be ok that the thermistor touch the Washer on top of the FET ?

Thanks,

I'm building original F5 R1

 

[Zen Mod]

much better to touch case of mosfet , not washer

in case of scratched insulation of NTC itself , amp will go Dodo

 

[mfrimu]

Thanks !!

I find it weird that the production model thermistor is 'in the air'
See pic attached.

Also sorry, but how would the insulation of NTC itself get scratched? My mishandling?

I was planning to put a dot of thermal conductive expoxy to hold the thermistor in place as my thermistors are soft-leaded with a tiny head, all black.

Thanks !

much better to touch case of mosfet , not washer

in case of scratched insulation of NTC itself , amp will go Dodo

 

[Zen Mod]

I'm usually not having too much doubts in Papa's solutions , same case here

it's us - Greedy Boyz , chasing our tales .........

so - whenever you are puzzled how to do something , just take a look how he made it

insulation scratched - dunno - don't ask me , but few guys on board had exactly that problem

 

[mfrimu]

Yes, best solution always more gratifying...

 

[dieringe]

You could also do it like this

 

[WalterW]

Thanks !!

I find it weird that the production model thermistor is 'in the air'
See pic attached.

Also sorry, but how would the insulation of NTC itself get scratched? My mishandling?

I was planning to put a dot of thermal conductive expoxy to hold the thermistor in place as my thermistors are soft-leaded with a tiny head, all black.

Thanks !

You describe the same NTC I used. Scratching is almost not possible.
I did it like this:

 

[WalterW]

I see Papa changed his 0.47 Ohm to 0.39 Ohm also😀

 

[Zen Mod]

smartypants

 

[mfrimu]

Yes, I have the same ones as WalteW.

I guess the temp reading is not super important in terms of accuracy...

You describe the same NTC I used. Scratching is almost not possible.
I did it like this:

 

[AndrewT]

one requires fairly fast response to temperature change.
The Thermistor glued to the Drain Pin is probably the fastest.

If that gives a "too good" compensation for temperature changes, then change the feedback ratios via the resistors.

 

[mfrimu]

AndrewT

In the production model looks like the thermistor may be touching the drain pin, so I'll do just that.

Thanks !

 

[bcmbob]

Agreed - if you go to the Six Moons article and look at the first two inside photos you can see the bend angle more clearly. Note the offset from the silkscreen visible from the top view.

 

[stijn001]

I'm sure the answer to my question is burried somewhere in this thread but. Will the F5 be suitable to drive a low impedance speaker/driver say 4ohm's or there about?

 

[jackinnj]

I'm sure the answer to my question is burried somewhere in this thread but. Will the F5 be suitable to drive a low impedance speaker/driver say 4ohm's or there about?

FIRST WATT F5

 

[stijn001]

FIRST WATT F5

Thanks,

 

[mfrimu]

Is there any issue mounting the PCBs on the heatsinks but with FETS on the down side?
I don't think there would be much more heat going up to PCB that if the FETs were on top.

Just in case, I could go throught trouble of mounting it at 90 deg, but I want to get this done soon 🙂

Thanks

 

[Zen Mod]

plenty of examples where pcb is on 5-10mm spacers on heatsink

 

[mfrimu]

Upside-down?

plenty of examples where pcb is on 5-10mm spacers on heatsink

 

[Zen Mod]

clarify