F6 Illustrated Build Guide

[Zen Mod]

pics

 

[Zen Mod]

Can someone please guide me how to check the conditioning of the mosfets? I will desolder them tonight, but how can I measure to see if they are burned inside? Which legs should I measure with the multimeter to check for proper functioning? I checked the datasheet and diagram of the IRFP240 but I am not sure where to measure.

Thanks in advance,

Koos

if you can measure short (buzzer test on your DMM) anywhere , it's Dodo

if there is no short , read Mosfet testing/matching article at FW site

don't forget that usually you need to heatsink mosfet while testing

 

[Acoustic Emotion]

if you can measure short (buzzer test on your DMM) anywhere , it's Dodo

if there is no short , read Mosfet testing/matching article at FW site

don't forget that usually you need to heatsink mosfet while testing

Thank you Sir Zen Mod!

The First Watt website is a paradise for me, so much new information in the articles about the functions of the components. After reading all of this I will probably have less questions and I can continue without asking too many questions to you guys

Thanks again,

Koos

 

[fabrice63]

Hello lads,

I almost finished my F6 build and I'm now trying to set the bias.
I'm having my meter across the 0.47ohm source resistor but there is no voltage at all (on both side) =(
I did test my PSU and it works fine.

Am I missing something? Thanks for your help!

Well , yes I am afraid

.

 

[JulesOz]

pics

Which part specifically?

 

[6L6]

The PCBs, the PSU, and the wiring.

 

[Zen Mod]

Which part specifically?

I presume front porch pic could be easiest to get ?

 

[RobLK]

Hello lads,

I almost finished my F6 build and I'm now trying to set the bias.
I'm having my meter across the 0.47ohm source resistor but there is no voltage at all (on both side) =(
I did test my PSU and it works fine.

Am I missing something? Thanks for your help!

You might have the zeners in backwards or they could be to low of a voltage rating.

 

[JulesOz]

The PCBs, the PSU, and the wiring.

F6 - Google Drive

The voltages in and out the PCB are fine, I have a small tension at the RCA's but nothing at the 0.47ohm resistor =(

 

[6L6]

Measuring across the resistor means exactly that... meter on DC volts, one probe on one side of the resistor, the other probe on the other side. If you don’t have an auto-ranging meter set your scale to 2v.

 

[BruceInOz]

Hello lads,

I almost finished my F6 build and I'm now trying to set the bias.
I'm having my meter across the 0.47ohm source resistor but there is no voltage at all (on both side) =(
I did test my PSU and it works fine.

Am I missing something? Thanks for your help!

I'm just finishing up my build too and made the same observation.

Just need to crank up the bias until the mosfet fires... Look at the gate voltage to see which way to turn the bias pot (it might be around -23V and you want it less negative) and then go for it - slowly - may take quite a few turns but you'll eventually see volts climbing across the source resistor if everything is fine

 

[JulesOz]

I'm just finishing up my build too and made the same observation.

Just need to crank up the bias until the mosfet fires... Look at the gate voltage to see which way to turn the bias pot (it might be around -23V and you want it less negative) and then go for it - slowly - may take quite a few turns but you'll eventually see volts climbing across the source resistor if everything is fine

Thank you very much

 

[Prologue]

R4 problem too

Like others i'm (trying to) building a F6 and i have smoke from the R4 resistor after 10-15sec the first time i tried to power it up. The voltage arriving to the board is 24.7v and the board led does not emit light (i guess it is mounted the wrong way)


I have no voltage when mesuring across the 0.47 ohm resistor.


Do you have an idea where could the problem? Should i power it up with a bulb tester or a load?


Thanks!


ps: screws on mosfet have been changed since picture

 

[eddyvb]

Check/measure that both output fets are isolated from the heatsink. There is something wrong with these fets. (And is R4 still ok?)

 

[algg]

Can F6 be bridged into monblocs?

I searched forum and could not find an answer. Can two identical F6’s be bridged to create monoblocs that deliver more power? If yes, how would this be accomplished on circuit/chassis? Thank you

 

[Prologue]

Check/measure that both output fets are isolated from the heatsink. There is something wrong with these fets. (And is R4 still ok?)

There is a mica insulator between the fets and the heatsink, i am going to replace them just to be sure.

The burned resistor was measured @18ohms before soldering and after the R4 smoke, still read an impressive 18 ohm, i will replace it too



The transformers deliver 18v AC and after the power supply boards 24.7 DC, i will post pictures of my "amplifier" i surely made a mistake somewhere. Thanks!

 

[Robin De Wolf]

I searched forum and could not find an answer. Can two identical F6’s be bridged to create monoblocs that deliver more power? If yes, how would this be accomplished on circuit/chassis? Thank you

Please see post #889 and #890 and look up funny^6.

 

[Acoustic Emotion]

Check/measure that both output fets are isolated from the heatsink. There is something wrong with these fets. (And is R4 still ok?)

Hello eddyvb,

Can you recommend a material that I can place in between the mosfets and het heatsink?

I have no isolation material in between the mosfets and the heatsinks until now, can this be the reason for the burned R4 resistor?

Thanks in advance!

Koos

 

[2 picoDumbs]

Use the keratherm pads sold in the diyaudio store

 

[ColinA123]

Use the keratherm pads sold in the diyaudio store

Or Mica pads from E-bay with white (non conductive) thermal compound.
The silver compound "may" cause shorts.