JSR03 at 11 V using a LM329

[peranders]

You should try smaller loads to see when you will get a voltage drop.

[Branko]

I dont know how to measure loads. but it seems the voltage drops if the load greater than 800 mA (i have 4 loads in the dac 100+100+600+600; if i disconnect the one 600 it is 10,8 V again). how could i test loads. any way to increase this?

thx

Branko

[peranders]

Do you have at least 16 V in and this is the ripple voltage excluded?

[Branko]

i have 22 V at the leads of the 4700 uF smoothing cap. there is 18 V in to the rfb02.

Branko

[peranders]

Check the voltage drop over T3 or T4. It should be stable 2.5 V.

[Branko]

"Check the voltage drop over T3 or T4. It should be stable 2.5 V."

Sorry for this lot of questions. but how to do this?

Branko

[peranders]

Measure the voltage across collector and emitter.

[Branko]

The Voltages are 5,63 V (Adj. 10,88; Out. 17,19; In 11,56)

Branko

[peranders]

This isn't over the T3(T4).

[Branko]

Hi,

i measured this over T3 (BD139 STM) every leg aginst gnd.

Branko

[peranders]

So you have 11.56-10.88 = 0.68 V across the collector-emiiter. It's too little. It should be 2.5 V if the LM317 is working properly. If you really have 1.4 A it's very near the limit for the LM317. May I ask what your load is? 1.4 A for a DAC seems to be a very high current.

To solve your problem you could try to exclude the LM317. Remove C3 and R2, short pin 2 and 3 on the LM317.

[Branko]

Hi,

at the moment of the measurment (I checked right now again) the load was ca. 700 mA. (the dac use is a DDDAC  MKII (www.dddac.de) which uses 24 1543 chips in parallel. each module with 12 chips needs ca. 600 mA and the input board needs ca. 100 mA. If iuse booth dac-modules the voltage drops to 4,2V. with 1 module and the input board it needs ca. 700 mA and the voltage does not drop. it stays at 10,8 V)

i am already finished a second jsr03 with the same values and will measure it in a few minutes.

Branko

[peranders]

You should try to divide the power distribution into several regulators, or as I mentioned exclude the LM317.

I wonder also what good does it do to connect so many DAC's in parallel?

[Branko]

As i have 4 pcb and parts. what would be better in terms of stability and sound: several regulators or exclude the lm 317?

thx

[peranders]

This is a rather "massive" design with many audiofilical elements so I recommend that you take this with the designer. When I see the power supply you already have you can with a good conscious exclude the LM317 at least.