Building a symmetrical PSU B1 buffer

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Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
Atilla said:
Last small feedback:

CSS was at 80-84 mA. CSS heatsink was awrm-ish. Shunt heatsink didn't get any heat. No wonder, given the transistors were eating ~30mA in total.

So, another 51ohm resistor in the last spot, raising the current to 120mA. Now the CSS isn't much warmer, the shunt is pretty competing in heat - Bingo :)

My miniature heatsinks are gonna handle that, no more.

5 more drill holes for the RCA and the power-on LED and done. Weekend is coming, perfect.
Click to expand...

:) Don't forget the pics.
 
ClaveFremen

ClaveFremen

Member
Joined 2005
inserra.it
Paid Member
Troubleshooting

Hi,

I've just reconnected my DCB1 - Mezmerize and it doesn't work anymore as expected.

If power ground is connected to safety ground it's quite silent with slight hum but music appear a lot attenuated, say 1/50 of the original volume.

If power ground is disconnected a full volume hum with hiss is present (obviously I must shut off the amp suddenly...)

I've measured voltages on AC rails (ca 14,3 V, OK), on led VRef (ca -10,32V, +9,73V) on regulator output (-10,96V, +10,36V).

All relais seems to work as expected, as the input switching.

I suspect that the 2SK170s are broken...

I need help...

Thanks in advance
 
ClaveFremen

ClaveFremen

Member
Joined 2005
inserra.it
Paid Member
Hi Tea-Bag

first of all thanks, I've made the suggested measures and all seems fine.

I've measured ground continuity with the DMM in several point (all inputs and output ground vs power ground and all jumpers) and it seems OK.

Broken ground...mmh...Ouch!

I've inverted signal and ground on output cables! :eek:

Now it works!

Thanks again you drove me to the solution. :)
 
P

prooptiki

Member
Joined 2006
Comments

Some measurments after one hour working!!!
Comments about R1 ccs voltages?
 

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Malka07

Member
Joined 2009
Malka07 said:
A few days ago, i replaced the CCS resistors with Mills MRA-12 resistors.

2.09v/3.9ohm= 535ma
1.73v/3.5ohm= 494ma

I was previously running at about 350ma....

Well as expected once again i get an improvement in SQ :)

The soundstage seems huge on certain recordings, each musician is more easily decernable and can be followed with ease(good seperation) yet they gel and sound very musical. The bass also has gained weight and control and as a result also sounds musical...but the real supprise for me is the treble...Just easier to hear, and REAL sounding!! Adds alot to the experience.

I checked the heat of the mosfets after an hour of listening...fan running at 5v...the mosfets are now hot, but not burning...im easily able to hold my finger on them without having to move away.

HIGHLY RECOMMENDED...especially for those with the Blue Boards.

Alon
Click to expand...

Today i changed the 4700uf caps to 10,000uf mundorf caps i also changed the mur120 diodes in the dcb1 and the optivol to fairchild stealth diodes and also added the cl60 thermistor.

An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.


I measured up voltages again and found that the voltage drop accross the ccs resistors was different to what i previously thought i had.

When i first set up my dcb1 with 60ma ccs i measured the voltage drop accross the resistors which were at the time 2.09v and 1.73v, i just assumed that these voltage drops would stay the same when changing resistors.

However today i actually measured the voltage drop accross the resistors. on the -10.10v side i got 1.76v and on the +10.24v side i got 1.39v.

I also measured the resistors values i bought them as 3.9ohm and 3.5ohm what i actually measured was 4.1ohm and 3.7ohm.

So it seems im not actually running at 500ma but instead...

1.76/4.1=429ma
1.39/3.7=375ma

But it still sounds damn good :)

And after listening for 2 hours...mosfets are just slightly more then warm...

so how how do i calculate resistor values for running at 600ma, keeping in mind that the voltage accross resistors may again drop???

Thanks Alon.
 
Last edited:
A

Atilla

Member
Joined 2008
I promised pictures, here they are:

R0015709.JPG


R0015721.JPG


I finally have it boxed, tested, and properly grounded (with a ground loop disconnect - bridge rectifier, power resistor and cap, the works.) Those aren't on the photos, since I closed it up and got tired of unscrewing it :).

I also drilled a few holes in the case, for ventilation, since it could get up to 60 degrees in there. Now it's a fair bit lower, so everything should be at a comfortable temperature.

All photos are In this album.

Again, thanks Nelson, Salas, Tea-Bag and everyone else that worked on this build and helped in the forums.
 
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