Focusrite Saffire Pro 40 re-cap

[canonball]

Hello, Like many of you, I now have a dead Saffire Pro 40 power supply. I am hoping someone may be able to provide a little information for me. On the back of the board, R17, R18, R19 and R20 are 100% bad. I think U1 (LD7537), R9, R11 and Q1 (cs8n60f) are also bad. I am planning to replace all of these items along with all of the capacitors. Are there any other items that should be replaced? I don't have the tools or know how to test components at this level.

Thanks for any advice you may have.

[SolderFumes]

I just recapped the power supply for one of my Pro40's.

I thought it would be a good idea to test the power supply before connecting it to the mainboard. I have read that these switch mode power supplies need to have a proper load on each of the rails for them to work correctly and/or to prevent damage. The problem I am having is determining the correct load resistors to use. There are 4 rails: 5V, 15V, -15V and 51V. I know that the whole Pro40 draws 12.3 Watts or .17 Amps.

If I understand correctly (there's a good chance I don't!) Ohm's law would say the load of the whole interface is (R=V/I) 119.9V/.17A = 705Ω, but that doesn't really help me figure out the load for the 4 power supply rails.

The 51V rail is likely for the phantom power. Assuming a max current draw of 14mA, could I use Ohm's law to here? If so, it seems a 3.5KΩ/.5W resistor should work. But what about the 5V and +/-15V rails? Does anyone know how I could figure this out?

Thanks

[b0bster]

Another board, my second one with the exact same issue as a few of the posts above. Can't seem to get a replacement this time. :/

[saffire]

Re: Focusrite Saffire Pro 40 re-cap

Hi newbie here! First time poster:

Can this PSU board of my beloved Liquid 56 be resurrected
It's toast, unfortunately, or do I have to order a new PSU?

Did you managed to get a replacement psu and if so did that work?

I have exactly the same problem with my saffire pro 40, exectly the same pattern of frying ;D

[JoaoSalles]

Re: Focusrite Saffire Pro 40 re-cap

U1 is a LeadTrend part on the one i have here for repair, markings are JP 35 but i can't find it exactly.... LD7535 is the exact part.

LD7535ABL is P1 35,
LD7535BL is YP 35,
and more QP 35, WP 35, S1 35, XP 35A, G1 35, and so on.

but i can't find JP 35 anywhere, it is for sure LeadTrend LD7535 part. i might change it for a P1 35 and see what happens.

I'm also looking for this U1, could I find a component that can replace it? I can't find this JP35

[JoaoSalles]

Hi newbie here! First time poster:

Can this PSU board of my beloved Liquid 56 be resurrected
It's toast, unfortunately, or do I have to order a new PSU?

Hi, did you manage to solve it? I have the same problem!

Finally got around to taking the top off one of my Saffire 40's, so here's a hopefully-clear-enough photo of the bottom.

Since all those resistors are toasted on yours, there's a pretty good chance the MOSFET is also gone, as is the PWM controller.

No idea what the stock PWM controller was, but as i mentioned, i managed to find a nearly-pin-compatible one, in the Diodes Incorporated AP3105NAKTR-G1.

The photo seems to be from the other Saffire 40's power supply which was ok. If memory serves, in the first one, with the new PWM controller, i removed the 100K R12.

I can't find another one to replace this U1, I searched on google and there is no datasheet talking about this U1 (VP35)

Here it is cleaned

what is written on that U1? Mine was damaged and I can't read what it says

[panthera86]

Re: Focusrite Saffire Pro 40 re-cap

Hi newbie here! First time poster:

Can this PSU board of my beloved Liquid 56 be resurrected
It's toast, unfortunately, or do I have to order a new PSU?

[прямо]

Re: Focusrite Saffire Pro 40 re-cap

I got this lovely and versatile audio interface a couple years back, for some multitrack recording with my (former) band, and as a "foundation" for my (future?) home-studio.

A while back, i decided to "pop the hood" and check out the insides. The PSU made me cringe - C(r)apXon It puts out 5v for the digital/logic stuff, +/-15v for the analog stages, and 51v for the phantom-power. I haven't yet replaced the mains filter cap (since i figured it's not under THAT much strain, plus i don't have a suitably-sized one in stock... for now ).

Well, you can't blame Focusrite. Everything that is made in China these days has to use parts that are also made in China, unless requested specifically by who ordered the production. It's one of them govt's rules.

With that being said, I wasn't surprised at all when I peeked inside Liquid Saffire 56 to find ChangXin caps in the audio path and in the PSU section.

What surprised me is when I had to service a $4000 SSL channel strip rack unit 5 years ago. For power, they use a cheap low quality switching PSU that cost $1 a piece if you buy in bulk (which they did of course), and they put a price tag of 150 pounds before tax and shipping for it on their online store. What a rip off!

I revived the mic pre by replacing the blown out fuse and PWM IC (it's a TOP PWM IC, I forgot the series but it has a TO-2XX transistor package if I'm not mistaken), also recapped it with Chemicon KY. Took 3 days to disassemble and assemble including a 24 hour test period in which I abused the thing just to see if the PSU would hold up in performance and stability. I charged $75 for service labor and parts, which the client happily paid me. The preamp is still running to this day.

[redwire]

Re: Focusrite Saffire Pro 40 re-cap

The small cap C5? is most important. It's 10-22uF 50V I am guessing.
Be careful to discharge ALL the capacitors before plugging in the connector.

Focusrite PSUI001007 Power Supply PCB for Scarlett 18i20, Saffire, OctoPre MkII, RedNet 1. Gee it's got cheap electrolytic capacitors used in it.

[pcperez72]

Re: Focusrite Saffire Pro 40 re-cap

Hi.
I decided to post here because it's about Focusrite PSU.

I own 4 octopres MKII. They remained unused for a year. This week I had a recording gig and took them to do it. Out of 4, two units presented the same problem when turned on. The clock front panel remained dead with all LEDs unlit. No word clock out or in.

What I found is that the PSU might be the origin of the problem. I disconected the 5v supply cable from the main board and checked with a multimeter. I found that the 51v pin measured around 58v steady, but the other voltages were varying all over the place. The 15v and -15v went from 12.1 to 13.4, back to 12 and started all over again. The 5v pin went from 0 to 2.5 to 3.2 to 4v back to 0 and so on.

I think this is not normal and should get all the voltages steady as the 51v pin, tough it's a little higher, 58.2v.

I thought some capacitor was the cause and changed all the electrolytics after the transformer secondary. I replaced the caps with the same value but not with the same voltages for all of them. Regarding the 470uf caps, 3 are 63v, one is 50v and the other is 16v. The 2200uf is 16v and the other 100uf are 100v as the originals.
All replaced, nothing changed.
So I checked all resistors in the back and all are ok.

Regarding the ICs and transistor, I have only checked the Mosfet which seems to be ok.

So my question is... what might be the origin of the problem? I believe this varying voltages are not normal and this is the reason why the clock panel does not light.

Thanks in advance.

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

The part i used isn't "the only hope", it just happened to be the cheapest pin-compatible device that one of my preferred suppliers had in stock at the time. And since i couldn't know what the stock part was, it was a bit of a crapshoot, but it worked.

[Shteff]

Re: Focusrite Saffire Pro 40 re-cap

yea, main issue now is the part is only available in china so maybe the AP3105NAKTR-G1 is our only hope, or the new PSU fullcompas sells. idk

if i find a decent supplier and i don't forget, i'll post it here

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

Markings are on page 2 of the datasheet. First letter is the week code, while the "P 35" indicates the part number, looks like.

The -A version seems to be spec'd for only 21V for the overvoltage protection trip point, while the non-A is rated for up to 28V. Installing an -A could be pushing your luck for no good reason.

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

Thanks for the update. Assuming one can find a datasheet for that chip, i would expect the differences (if any) to be somewhat visible.

[Shteff]

Re: Focusrite Saffire Pro 40 re-cap

U1 is a LeadTrend part on the one i have here for repair, markings are JP 35 but i can't find it exactly.... LD7535 is the exact part.

LD7535ABL is P1 35,
LD7535BL is YP 35,
and more QP 35, WP 35, S1 35, XP 35A, G1 35, and so on.

but i can't find JP 35 anywhere, it is for sure LeadTrend LD7535 part. i might change it for a P1 35 and see what happens.

[bfpgio]

Re: Focusrite Saffire Pro 40 re-cap

Thank you

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

Finally got around to taking the top off one of my Saffire 40's, so here's a hopefully-clear-enough photo of the bottom.

Since all those resistors are toasted on yours, there's a pretty good chance the MOSFET is also gone, as is the PWM controller.

No idea what the stock PWM controller was, but as i mentioned, i managed to find a nearly-pin-compatible one, in the Diodes Incorporated AP3105NAKTR-G1.

The photo seems to be from the other Saffire 40's power supply which was ok. If memory serves, in the first one, with the new PWM controller, i removed the 100K R12.

[bfpgio]

Re: Focusrite Saffire Pro 40 re-cap

allright let me know the list of component, I could also simply change a maximum number of them all arround

[Khron]

Re: Focusrite Saffire Pro 40 re-cap

Well, you're somewhat in luck. I do actually have two Saffire Pro 40's that i need to put up for sale, so i suppose i could take a look under one of the power supplies in the mean time.

But until then, determining what was the root-cause of the damage would be very useful, and so would figuring out which components are blown. You can bet your life those resistors are NOT the only things that let the smoke out.

One of these two Saffires i have, turned out to have a faulty PWM controller in the power supply - the feedback side of it was wonky, so the output voltages were about twice what they should have been. I have no idea what the stock chip was, but replacing it with a pin-compatible one (and removing a now-unused resistor) cured that.

Considering that group of four parallel current-sense resistors is that well toasted, is a safe bet that the MOSFET is now just a wire, ie. shorted drain-to-source, at the very least. Probably blew the gate as well, going by the seemingly cooked 10 ohm resistor (marking "100" in the last photo), which likely killed the PWM controller as well.

There's gonna be quite a bit of measuring to do, before drawing up a list of parts that need replacing...

[bfpgio]

Re: Focusrite Saffire Pro 40 re-cap

first of all, clean off the soot (black stuff) from the bottom of the board.

Here it is cleaned