F6 Illustrated Build Guide

[Dneu2011]

I just checked with 9V battery and get 8.9V on both devices. I also checked with a 100 ohm resistor and measured across it and both are closely matched.

 

[Dneu2011]

Actually, I just checked again and it appears the 2 Fets are about 3ma different where the K170 measures 7.3ma and the j74 measures 7.7ma.

 

[Dennis Hui]

Idss looks fine.

 

[Zen Mod]

yup

 

[Dneu2011]

I resoldered everything, checked my resistor values, and put the board back in. Still have issues with one channel louder than the other...

Any other ideas?

 

[6L6]

What value is your R3?

 

[Dneu2011]

110 ohm.

 

[Zen Mod]

there are so many parts inside ....... best to check them all , at least visually

after JFets, R3 and R4 being first candidates, ref. to schm Jim posted in #1

with power off, after visual inspection of all parts, waste some time fiddling with ohmmeter - checking all resistors m comparing good and bad channel

most of measurements will be inconclusive (absolutely) with parts still in circuit, but maybe somewhere you'll spot a difference between channels

 

[Dneu2011]

R1 and R2 are good. I’ll check resistances like you said and see if I can find the differences.

 

[Zen Mod]

if you were able to properly set Iq and Offset, no doubts in xformer secondaries

just in case, check continuity of primary

 

[Dneu2011]

What do you mean by that? Are you referring to the Jensen transformer or the Antek Power transfomer?

Yes. I am easily able to set BIAS and Dc Offset.

 

[Zen Mod]

signal one

 

[Dneu2011]

I’m reviewing the Jensen PIN-out. The bottom of the transformer which faces up in the amp
matches continuity tests on on both sides. I can’t easily get to the opposite side of the transformer so I’ll try tomorrow.

 

[Dneu2011]

Is it recommended I test the transformer removed from the board?

 

[fabrice63]

it is recommended to test every component out of the board , it may takes some time , but what is properly made has not to be made again

and at the end you will have all your solder joint new


.

 

[Stanney2017]

Im trying to bias channel B.
Channel A is fine.

Each time i power up, R4 starts to smoke.
Bias voltage is low at 0.98mv

Any ideas.

Thanks.

 

[6L6]

R4 smoking means you have a bad (shorted) Jfet, a solder bridge near the jfets, or a short in the transformer.

 

[Dneu2011]

I figured out my problem.... one of my 1000uf caps had a broken leg from me trimming/bending it to fit the board.. after replacing it the right channel now matches the left.

This cap I had to move around quite a bit to install the trimmer pot so I know that’s how I snapped it.

Amp sounds great and biased fine to .6V. I may try .65V after letting it play for a week.

 

[Stanney2017]

Thank you, is there a way to test the transformer?

 

[tamra]

I would like to say thank you to
Nelson Pass,2picoDumbs,meanie,6L6 and people who support for build and
diyaudio forum.
I could not build without support but learned a lot from trouble,also apologize for my mess.

Now my fullranges sounding fantastic. Biased 1.5A
Vocal is soft and smooth and slapping percussions tight.
I have changed some parts for my taste,still waiting for Panasonic erx.
I also addicted to build so I ordered aleph J and Ba-3 PCB...