F5 power amplifier

[lhquam]

Just be careful that the thermistor insulation is not compromised so that an electrical is possible from one of the thermistor leads to to any of the MOSFET leads (such as the drain). My first F5 build taught me this lesson.

As mentioned in the thread earlier, Would quick set epoxy work for thermal bonding glue to connect thermistor to FETS, or ok to just have them touching?

 

[Blink_PT]

I have also learned that lesson.

Burned a trail of pcb, one pot and R.

 

[AudioSan]

I have also learned that lesson.

Burned a trail of pcb, one pot and R.

one of the leads from the NTC got in contact with the bolt?

 

[Blink_PT]

one of the leads from the NTC got in contact with the bolt?

yes, the NTC was beside, on top of the washer, but diverted 1mm, to measure the Bias touched her hand and seemed a phosphor.

 

[AudioSan]

easy come easy go😀

 

[Renron]

Little cocktail straws (very skinny type) make great leg insulators.
McDonalds coffee straws work well too

 

[labjr]

Little cocktail straws (very skinny type) make great leg insulators.
McDonalds coffee straws work well too

Which color sounds best?

 

[Blink_PT]

Little cocktail straws (very skinny type) make great leg insulators.
McDonalds coffee straws work well too

I do not advise that type of ntc, even isolating the legs he has in mind the wire that easily and the heat may touch the dough, and it's like a rocket birthday...

 

[Zen Mod]

degrease top of mosfet case , right bellow washer
lean NTC right on it
put blob of RTV Silicone on it

voila!

or - just look at origigi FW F5 pics on 6moon , and stop over-engineering things

 

[Blink_PT]

It is a good idea, but also gives the silicone std? One put of the glass?

 

[Zen Mod]

probably you can use plain one , too

RTV Silicone is type used by all sort of mechanics , because is both temperature and oil resistive

 

[labjr]

Arctic Silver Thermal Adhesive

 

[Blink_PT]

probably you can use plain one , too

RTV Silicone is type used by all sort of mechanics , because is both temperature and oil resistive

I know, I have a brother in law who has a workshop and I've seen him put a black silicone to seal the bearings. I'll stare at a tube 🙂

 

[Renron]

Arctic Silver Thermal Adhesive

Uh-oH, now you've done it. You're gonna hear about why you shouldn't use it....blah.....blah......blah. Conductive.........short out.........My F5 has it on the Mosfets for 4 year, I use it every day. NO problems.😎 Not the adhesive btw
preferred straw color is red 😉

 

[6L6]

Guys with finished F5 -

Would someone with a scope (or really, really nice AC voltmeter) measure how much ripple you have on your rails?

I have 134mv peak to peak and curious if that's a lot or not bad.

I have a speaker hum and can't figure it out...

 

[Zen Mod]

usual procedure : words and pics , so we can figure out is it magnetic coupling or wiring deficiency

 

[oneplustwo]

Guys with finished F5 -

Would someone with a scope (or really, really nice AC voltmeter) measure how much ripple you have on your rails?

I have 134mv peak to peak and curious if that's a lot or not bad.

I have a speaker hum and can't figure it out...

With my fluke 45, I just measured 13mV on both positive and negative rails. So yours is 10 times worse....

For reference, I can hear a tiny bit of hum with my ear up against the speaker but not at all when farther than a foot or two away.

 

[6L6]

usual procedure : words and pics , so we can figure out is it magnetic coupling or wiring deficiency

Ok.

RCA jacks isolated from chassis. MAG here -

PSU --> AMP --> speaker connections shown here

Other than those photos, everything else as in this thread - all photos in top 2 posts.

http://www.diyaudio.com/forums/pass-labs/188691-illustrated-guide-building-f5.html

 

[Zen Mod]

grounded inputs - same reading ?

what's happening when you feed just one channel with present PSU ?

 

[biju55]

Remove the -ve wire ( black ) to speaker from amplifier board , and connect it to power supply board ground .