Salas hotrodded blue DCB1 build

[Salas]

I want to install my DCB1 buffer into a metal case. It's ok to connect the case to the GND of pcb ? I'm using isolated RCA connectors.

Its OK.

 

[Salas]

My DCB1 is working fine, but I have a few questions.....

I'm running 10 ohm R's (200ma config) with two separate 60VA 12V single secondary transformers (so 120VA total). My DC output voltages are +10.04 and -10.11 and the unloaded transformer voltages are about 13.2VDC. I understand that for most of the various hot rod configs at least 15VDC/50VA is recommended. How do I test/verify that I have enough voltage headroom with my transformers? Should I measure the DC output voltage stability with a 5K or 10K load on the outputs at full input signal?

I'm also measuring 2V across the 10R on the IRFP240 side and 1.75V across the 10R on the 9240 side, so 200ma and 175ma. I understand this is the quiescent current for the shunt part of the PS.

Is it normal to have 25ma different between the + and - sides? I am assuming that it is, and is probably no big deal.

VAC on secondaries you probably mean. Measure DC across DCB1's filter capacitors. If it is >VDC rails by 5V even in your lowest mains expected, then you are OK. Signal demand is a minute portion, the PSU setting is the constant current hog.
Its normal to have differences in non Vgs matched MOSFETs especially when opposite sexes like those in opposite rails here that have more Vgs differences than in same sex batch spread. That leads to some (inconsequential) quiescent dif. You may trim that by the setting resistors but to no perceptible gain.

 

[boywonder]

Yes Salas VAC on the unloaded transformer secondaries.....sorry.

My rectified DC voltage at the second 4700uf PS cap is 17.85VDC.

Thanks!

 

[Salas]

More than adequate Vout to Vin margin. No problems at all.

 

[suburra]

See if they show Vgs.

Checked Vgs: 0,00 V on either Mosfets...

Marco

 

[Salas]

The output ones? Or all 4?

 

[suburra]

Just the output pair

 

[Salas]

Do you have spares to exchange?

 

[suburra]

Ordered some days ago...

i'm waiting RS delivery

 

[Salas]

Lets see if they got zapped during soldering rework then. Were the new caps charged by any chance?

 

[suburra]

No...was new caps

But it's possible i'm attached my solder station into a power strip without ground connection

Can a static fry the Mosfets?

 

[Salas]

Sure.

 

[suburra]

I did not think were so delicate...

Hope tomorrow or friday to have new mosfet

thank you very much for help me

Marco

 

[mjock3]

Almost done, but want to fuse the line before plugging in. What size should I use?

Thanks,
Mark

 

[Salas]

What your trafo's primary notes, or tell us more about your trafo.

 

[mjock3]

I am using an Antek AS-1215

 

[mjock3]

http://www.antekinc.com/pdf/AS-1215.pdf

 

[Salas]

500mA

 

[mjock3]

Thanks Salas.
Now how did you figure that out? I'd like try to remember for the future.

Mark

 

[Salas]

*Slow blow. I gave you a conservative rating, if it draws too much at start up when building magnetic field and blows it go up empirically. Should not need more than 1Amp fuse in any case.