LM317HV / TL783C

[u1176]

Given the attached schematic and reffering to the third leg (+48V Reg), what changes would I need to make to replace the original TL783C with a higher spec LM317HVK STEEL (TO3)?

 

[abbey road d enfer]

You don't need to change anything.
But what improvement are you expecting?
The 317HV has a higher current rating (1.5A vs. 0.7A) but it has a lower voltage rating (60V vs. 125)
Soundcraft PSU's have suffered a bad reputation but the 48V rails have never been a problem.

 

[u1176]

I simply wanted the headroom current wise.
This will not be used for a low draw phantom application but for powering a few Daking units.
I modified two CPS450's to supply DC rails for a preamp rack.
The aim was to rid the preamp rack of all the external power supplies bolted inside of it.
I added a transformer to one of the CPS450's to supply +/- 25 rails for Ward Beck and Chandler, trimmed the +/- 17.5's down to 15 for API and kept the 24 for Neve and Vintech.
The other supplie's unchanged 48 rail will be for phantom.
Out of 12 legs all works perfect except I have had trouble with this one. I changed R31 to 240. I may have cooked my 317 while pulling it out of the heatsink, the filter may have drained through it I believe i heard arcing from the heatsink to the pin. I ordered one more LM317HVK STEEL ($22) and hopefully all will be good.
The power supplies will reside in a seperate rack and I have constructed an umbelical to carry AC to them and DC back.

One last question, NS specs max Vin as 60 and the rectified unloaded shows 79 this is the only issue that I was worried about, beyond dissipation issues will the 317 accept this?

 

[abbey road d enfer]

I can't give a definite answer because it depends on timing and conditions of operation. Normally, the output voltage builds up quickly (though not as quickly as the input voltage), so the reg is submitted to an overvoltage for a very short duration, which will not probably kill it first time, but after a dozen of turn-ons may damage it. For certain, if the output is shorted, the reg will see the full 79V, which is a dangerous situation.
I don't think you'll ever need 1.5 amps of phantom power (that's more than 100 mics!).
Overall, I wouldn't do it.

 

[u1176]

This will not be used for a low draw phantom application but for powering a few Daking units.

The other supplie's unchanged 48 rail will be for phantom.

 

[abbey road d enfer]

These Daking things need 48v single-rail? Some guys will do anything to be noticed
Are you sure the xfmr will handle more current?

 

[u1176]

I did not realize that Geoff was British, he certainly does not appear to have an accent.
Yes I am quite certain that the transformer can supply the neccessary current.
I doubt that I will be drawing more than one amp but .7 seems too lean for me when you consider that the daking stuff is all Class A.

 

[mad.ax]

Humm... I wouldn't assume that because there's a 1A fuse, that the transformer is able to deliver 1A. That would mean 66 channels of phantom power, all shorted!
So, if you have less than 1000mA available, and you think that 700mA is not enough, your margin is very lean...
You didn't mention using the +/- 7.5V for anything. Since those rails seems beefier (3.15A fuses) you could use the two 10.8V windings and a voltage doubler. That would give you 51.84V after rectification...

Axel

 

[abbey road d enfer]

I did not realize that Geoff was British, he certainly does not appear to have an accent.

My mistake! I edited the post in the meantime. He certainly looks british, doesnt'he?

 

[u1176]

That he certainly does.

 

[Winston OBoogie]

He certainly looks british, doesnt'he?

Here he is with Pete Townsend and Keith Moon:

http://sunnypaul.net/page11/files/page11-1054-full.jpg

 

[u1176]

I wonder what's in the briefcase.

 

[Winston OBoogie]

I wonder what's in the briefcase.

Pete's "stash", dynamite for Keith to blow up a few toilets and, for himself, a few 80V regulators...chicks dig 'em!

 

[Andy Peters]

I did not realize that Geoff was British, he certainly does not appear to have an accent.

He doesn't have an accent because he is not British.

The Blues Magoos were from New York.

-a

 

[u1176]

Well gentlemen thanks for the input.
I asked Geoff what the current draw might be per 52270B. He stated 100mA per Pre/EQ.
Less than 5 Watts seems low but he would know best. Maybe the lack of any metering whatsoever is how he keeps current draw down.
So I will be returning the 48VDC rail to the original TL783C as I doubt I will be be adding a third Daking preamp to this particular rack.

P.S. Andy, I realize that Geoff is not British, I was merely responding (somewhat facetiously) to a since edited comment by a poster.

 

[u1176]

Response from NS

"In response to your request:

Yes, you should be fine - as long as the input to output voltage difference is less than 60V"