Installing FUSEs on the Power Supply **SOLVED**

[Matt Sartori]

I am going to post here what keith Skerrett wrote on the SSLMIXED Facebook page.

quote:

"I saw when I was lurking on the forum that the group was looking for a PSU lineup procedure, so I thought I'd offer my thoughts on the matter for the +/- 18V as a starter as at this time of night and after a beer or two I can't remember all the values for the other rails.
Before starting, read all of what I have written below and if any of it doesn't make sense then do not attempt to do it. These supplies have exposed high voltages and you could quite easily do more harm than good to it or yourself.

So, Turn the V trip preset fully clockwise and adjust the V out on the + 18V rail to 22.5V. Then back off the V trip until the rail just shuts down. Turn the Vout down to minimum and restart the supply. Then repeat this for the -18V.
The I trip is set in a similar way by drawing 25A from the +18V rail using load resistors and backing off the I Trip preset until the output voltage just begins to drop. Repeat this for the -18V.
The I sc preset is set so that when you short out the + or -18V rails the current delivered is 5A. Yes you really do need to short circuit the output to do this that's why it's called I sc.
You may want to short circuit the 25A fuses in the +/- 18 V rails before doing this for obvious reasons.
Set the output voltages to + and - 18V and then connect to console and calibrate in the usual way for the correct voltages measured at the desk centre section.
All measurements are made at the connector on the rear of the supply, with no console connected.

Any question feel free to ask on our Recycled Audio Ltd facebook page.

By the way I was the one who told Graham how to do it."

and then he added :
"OK, here are the values that were missing from my post last night.

For the 7V rail ISC should be set to 2A, Imax should set at 7.3A. For the 250V rail ISC is set for 0.15A, Imax should be 0.55A. There is no Vtrip preset for 7V or 250V rails. For the 48V rail ISC should be 0.15A, Imax should be 0.5A and Vtrip set at 52.5V"


Mattia.

[marcmozart]

Awesome! Thanks Mattia and Keith, the lurker ;-)

[Artur D'Assumpção]

Hey this is awesome!!

Keith rocks! if he is seeing this post... THANKS KEIIIIIIIIIIIIIIIIIIITHHH!!!! \o/ \o/ \o/


Maybe if someone is adventurous enough to be the first one to try this out and live to tell the story could turn this into a document with a step by step + photographs procedure? This would be really really awesome!

Cheers,

Artur

[kilmister]

Great info!

-Paavo

p.s copied info to tech area

[Showcase]

Awesome info!

Something I wondered about, Where in the centre section do I check these voltages? Anyone knows?

[marcmozart]

You slide the centre section up, and on the right side (green backside of motherboard PCB) you will find the rails if you look closely. More towards the bottom, clearly marked -18, +18, +7, etc. - let me know how you go, don't have a photo at hand right now.

Something I wondered about, Where in the centre section do I check these voltages? Anyone knows?

[Showcase]

You slide the centre section up, and on the right side (green backside of motherboard PCB) you will find the rails if you look closely. More towards the bottom, clearly marked -18, +18, +7, etc. - let me know how you go, don't have a photo at hand right now.

Something I wondered about, Where in the centre section do I check these voltages? Anyone knows?

Thanks alot, today I will have a tech look at my PSU´s since I have had my fuse blown a couple of weeks ago. Did the measurements and found this at centre section:

estimated :   +48     -18      +18       +11       +13

measured:   +39     -17,5    +16,2    +9,8      +9,4

not good right? He´s a very good tech, just not an SSL one, is there anything me or the forum can help him with? I got the manuals and printed the lineup procedure (Big thanks to Keith for that)

Thanks in advance

[sintech]

Surprised to see 48v as low as 39,.. just to throw this in the mix, I had a similar situation, and it transpired.. the battery in my multimeter needed changing.

[Showcase]

Ye it looks very low

I´ll see what happens when first of all the PSU´s are fine, and then I guess other factors could be involved, like the changeover unit, or is this only related to PSU?

[marcmozart]

Don't think the 39 on the +48 rail are a problem, but the rest looks WAY OFF!!

[waltzingbear]

You should check the voltages at the power supply as well if it is this far off. If there is too much difference between them, then you should investigate the condition of your cabling between the board and the psu.

Anyone have a quantification of what "too much difference" is for the standard cabling? In my experience its either been good or painfully obvious.

While 39V will allow many mics to work with phantom, quite a number will not. Also, that gives cause for concern in the power supply as to why it is so far off.

Alan

[Showcase]

I havent had any issues with phantom power,  but realise its not very good.

Cant say i know much about Electronic and dont wanna misquote the tech but it seemed the difference between +18 and -18 was his biggest concern

[waltzingbear]

the question for me is WHY is it that far off?

the difference on the 18V rails is not great, but to me the real question is WHY.

Obviously those voltages will allow the board to work, it will be better with designed values, but this should be taken care of as it moves everything toward not working correctly.

Alan

[Matt Sartori]

is your PSU (or your PSUs) set for the right mains voltage where you are?

M.

[Showcase]

I have full confidence in the tech so im sure he will fix it, I report back when he has found the problem, If the problem lies in the psu's, Ive taken vacation mean while