need advise for current measurement

[zamproject]

Hey

Restoring console and want to measure and set up current max and shortcut for the 3 regulators card.
I want to put more modules in the frame, i need to check this before, to be sure I have enough margin!

My first problem is i only have 2A multimeter when each reg can produce 3A (but i think only the "audio" one are set close to 3A)
The second, more problematic is that at the multipin connector lot of supply cable are soldered in // going to the desk, each one for one or more card. Desoldering one by one to put a A meter in series and sum all this are not a good solution for me.

I'm wondering if there is some place in the board/schematic to have a Volt reading through a knowing resistor where I can deduce output current, and also shortcut current.

According to manual
P3 voltage adjust (22v in my case)
P2 Imax (3A)
P1 short cut (50...100 mA)

For info, in the desk the +22 output is the 0v and the "-" is -22V

Zam

 

[PRR]

Measure the voltage across R2.

 

[zamproject]

tks PRR

this is a shunt?
I was suspicious about it as it is low ohm and 4W on the pcb. But not so confident... confused with the 0v ref inverted.

What is the common practice? Set the regulator close to it's max Amperage? Or to the load requirement, with some extra % ?

Zam

 

[zamproject]

Measure the voltage across R2.

Done, have about 150mV, this is 1,5A right ?. This is low regarding what is loaded in the frame right now, but have to test more.
No audio performing through and line out are not calibrated, all gain trim at min, and this line out card are rated from 24mA (quiet) to 220mA (at +24dBu)

 

[zamproject]

hey

have another question.
C5, alu 220u/35v have been recapes
What about C1 and C3, 47u/20v, those are tantal, and I'm wondering if some modern alu lytic could be better choice,
I'm thinking about avoiding destructive short failure, especially in the PSU ???
I keep all tantal in audio pass on this desk as i love the sound

Zam

 

[PRR]

The part I would worry about is the '723 chip. It hasn't been made in decades. It isn't fully protected. You ought to get many known-good spares while you still can.

22V 3A is well within the reach of modern fully-protected (boosted) regulators.

 

[zamproject]

The part I would worry about is the '723 chip. It hasn't been made in decades. It isn't fully protected. You ought to get many known-good spares while you still can.

???

I buy some for a previous restoration 2 or 3 years ago, and still available.
http://radiospares-fr.rs-online.com/web/p/regulateurs-de-tension-lineaires/5343778/