d8b Forum

I have two D8B's with proboxes, using them mainly as mixer, but recently one of them got broken and was thinking to turn it into a control surface with probox or maybe trying to repair it.
So, what happened - it was an electrical problem (my electrician forgot a loose cable in the general panel where all the AC wires are connected together in my house, and that wire was the one that got all the floor to powered up with AC (5x6mm section). One evening I was preparing to shoot a video, with some equipment plugged into AC (different plugs, different phases), and when I added a last light that I used for video, that light and 2 other lights that were identical blew up (with smoke and everything), and also an AC adapter for one of the cameras, and the normal LED bulbs from the ceiling were suddenly almost half dimmed...like there was an undervoltage situation - The D8B was plugged in also and it turned off - when tried to restart it, only the big red LED on the desk is lighting up, but none of the fans of the D8B processing unit (the box with the cpu) is moving anymore. Only a small hum from the big PSU can be heard, but nothing appears on the LCD of the desk nor on the VGA monitor that is connected. I guess everything that was sensible to undervoltage (due to the loose connection of one of the phases) blew up. I will put the multimeter to check if the big cable has voltage on the pins. I've checked the fuses, all are intact, also the condensators are not blown up or smth.
Will try to find a good pc service that might help me with measuring and finding the problem (I've called 3 of them in my area and they didn't seem to be interested in taking my request so far), but any hint will be greatly appreciated!

Regarding the fanless probox route, I've bought the 5, 12 and 15v sources from the Munkus' fanless guide:
1. Source Mean Well 12VDC, 8.5A, AC-DC, 102W, RS-100-12 - measured with the multimeter by default was 12.1v - should I set it to 12.0 v?
2. Source Mean Well 5V, 16A, 80W, RS-100-5 - measured with the multimeter by default was 5.1v - should I set it to 5.0 v?
3. Traco Power TXL 035-1515D on which I have a question: the gnd and V1 indicates 16.0 v (I've dialed in the rotary adjustment to get that) but on the gnd and V2 it indicates -15.3 v. When I set the rotary knob completely to the right the V2 is increasing to -15.4v max while the V1 reaches 17v or so. On the data sheet it is mentioned " Dual output version (TXL 035-xxxxD power supplies) do need a 10% minimum load on each output to ensure a proper and reliable regulation. " When asking the Traco Power technical department they asked what was the voltage under load - there was no load, only the multimeter pins on the GND + V1/V2 - also mentioned this: " Cross Regulation In a multiple output power supply or converter, the percent voltage change at one output caused by the load change on another output. Multiple output
power supplies often require balanced or minimum loads to achieve stated regulation specifications. " So, I will try to measure again with let's say a 5w ( since the max power is 36w, so it should be greater than 3.6w , according to the manual) tungsten 16v light bulb on V1 and also one on V2 circuit.

Wanted to ask if this is normal and can be used with -15.3v on V2 and 16.0v on V1 or is the unit is faulty and should be changed or If I should rather get 2x Mean Well 15v units, with 1A like this one: https://www.meanwell-web.com/en-gb/ac-d ... rs--15--15 Arjepsen (thank you!) just confirmed that he got the same problem with the +/_ source and that he ended up using two 15V supplies instead, where the negative one the first is tied to the positive on the other. - but I will check with him since putting to 15v sources in serial, as far as I understood, would give a 30 v source, just like when you put two 1.5v batteries in serial they sum up to 3v.
Can I just use two 15v Mean Well sources - one for +16v, one for -16v with V+ and V- inverted ?

Also, wanted to ask you if I would get a Mean Well one with 48v https://www.meanwell-web.com/en-gb/ac-d ... rs--15--48 could I have functional preamps with phantom power if connected to the right pins?
Thank you so much in advance for your answers!

I have no idea about the custom power supply thing and definitely less understanding of that sort of thing than is apparent that you do, so I won't be any help with that, sorry.

As far as possibly recovering the main computer, though... if the fans inside the rack unit don't turn on, then I'd think that there's a problem with the PC-type power supply that is in there.

There's actually a fuse (or two) INSIDE of the PC-power supply, within the larger power supply section of the D8B rack unit. So, I'd check that first.

...or, if you're willing to risk that, you could try connecting the console to your other D8B rack unit, to see if it powers up that way, or if the console also took some damage.

What I tend to do to figure out where a problem comes from, is to swap parts between units to see if I can get things to start again after that. If the fuse inside the PC power supply doesn't take care of it, I would probably swap a few parts (for testing purposes only) from the good unit to the bad unit to see if you can get the bad unit to boot again.

I'd start with the easy to swap stuff, like the memory... but my guess is more on the PC power supply, so I'd swap that next.

Once you figure out which component prevented booting, I'd put it all back to how it was, except for the defective component, and look for a replacement.

All this is of course associated with a certain level of risk... if something got fried inside the rack unit or console, in a way that creates a short or over-voltage, etc., you could of course blow up something else in the process - but I'm sure you know that, already.
I just happen to have a lot of spare parts, so I usually just take the risk...

But maybe someone else here has a more "scientific" approach, than me relatively dumb "swap and see if it blows up or starts working" kind of caveman approach, haha

Best of luck!

Update: I've used two 8w led light bulbs 12-42v compatible with DC https://www.dedeman.ro/ro/bec-led-lohui ... /p/1051779 with the Traco Power 15v +/- one. Gnd and V1 was fine with 1 bulb, GND and V2 made the bulb flicker (using only one bulb), when both light bulbs were connected, the flickering on the V2 one was gone, both bulbs were functioning properly, the voltages were not matched, though: when 16v was on V1, -15.3v was on V2.
Y-my-R, Regaring swapping parts, yes, I thought of that, too, but I keep that for later, since I need a functioning unit all the time.
The fuses are all intact, checked them all, inside the big PSU, too. The next step would be to measure everything with the schematics in front of me .

...I see.

Just to be sure... so, you did remove the PC-power supply, that is held in place by four screws on the back of the rack around its fan, break the seal and open the "sparkle" power supply to check if the well hidden fuse inside is OK?

(...and not just opened the big aluminum lid, that covers almost half of what's inside the D8B rack unit, and with it ALL of the D8B's power supply components. So, big aluminum lid off, and then the fuse I'm talking about, would be in that "smaller" metal box with the fan inside it, at the rear of the rack unit? Sounds like you did, but the way it was phrased, I wanted to make sure... I only opened that "PC" power supply unit once, to put a quieter fan inside it, and was surprised that there was yet another fuse, in addition to the obvious fuses on the directly accessible circuit boards, once that big lid is removed)

Y-my-R, didn't knew about that one, thanks for pointing that out, I've just checked it and it's fine, so all 7 on the big psu plus the hidden one on the ATX power supply, all good. Since it was rather an undervolting situation (I guess somewhere around 140v when measured the second day, instead of 220v), I think that the fuses weren't affected, but smth else in the CPU box. The resistors and capacitors checked visually, all seem to be fine.
Also, Jesper got back via email saying that his power supply had correlated values, so I guess mine is faulty.
"My 16v power supply supplied 15.98v on both plus and minus so it seems weird to me that you have 2 separate values. "

Too bad... I was hoping it would just be that fuse, but makes sense that it/they wouldn't blow b/c of a under-power situation.

I'd just also try to unplug the power cord, the BFC connector and all other cables connected to the rack unit, as well as the internal battery (and if your board has a clear CMOS jumper, set that to the "clear" position... I think one of the two boards used in different D8B model years had that - not sure anymore. But pulling the battery for a while should have the same effect), and maybe even the memory sims, and let the whole thing sit like that over night (and maybe try with only one memory bank filled after putting it back together, in case one of the memory sims went bad and prevents the computer from booting).

Then I'd put it all back, but not yet the BFC cable and DB25 cable for the the console, yet. Then power on the rack unit and see if the fans start spinning.

My thinking there is, that the BIOS or a mainboard component might have gotten hung up in a weird state b/c of the low power situation, and the mainboard/hardware doesn't initialize right (aka either the BIOS can't do its job, or some other component prevents it from doing it). Could be something holding a charge that shouldn't, and the desk thinks there's a short, or something. So, letting it sit over night should help to let such a potential charge dissipate, so you might have a chance that it comes back to life in the morning.

Not really with the D8B, but I had this sort of situation with a few different devices, before (for example, a Midiman 8x8 interface, that was dead, that must have gotten voltage from somewhere it shouldn't... it came back to life after disconnecting all cables and letting it sit over-night (just unplugging the power supply over night didn't help). I think one of the connected MIDI devices caused that, sending current back where it shouldn't have and putting that device in some sort of limbo state).

...it would at least be worth a try, IMO.

Also, for troubleshooting purposes, it can be helpful to add one of those little internal PC speakers that connect to the mainboard. There's a good chance that it would output a beep-code when attempting to power on the rack unit, that could give a clue about what's wrong with the mainboard or one of the attached components).

FWIW, I'm running a CF card as the harddrive (b/c its quiet), and I replaced the two fans in my D8B (CPU and PSU) with silent Noctua branded fans (...and the CPU has a somewhat higher heatsink and fresh thermal paste under it).
I also added an additional Noctua fan, that sits behind the opening for the floppy drive, and pushes hot air outward, and what comes out of there IS pretty warm.

I also added a speed controller that mounts in one of the card-slots in the back of the D8B rack unit. I drop the speed on all the fans down, until I can hardly hear them anymore (it already makes a lot of difference, if the pitch of the fan noise is lower... less obvious and less annoying). From where I sit, I can hardly tell if the D8B rack unit is on or not, and it's been working like that for a couple of years now. I think those old Pentium/Celeron CPUs could still run pretty hot without dying... I think I had even forgotten to plug the CPU fan in and had it running for a few minutes before I noticed, and the CPU still worked, hahaha... don't try that with a modern CPU, hah!)

Before I did this, I tried all kinds of things to avoid the noise from the rack unit... longer BFC cable (got a prototype... but the D8B would only work on internal clock with it) to put the rack unit in a different room, and also into a "gear closet" - it got too hot in the gear closet, and adding loud fans to get the hot air out, made the whole point kinda moot.

...anyway - sounds like you're almost there with the fanless power supply, if it turns out that the only problem was that likely defective power supply component.
...but just in case that doesn't pan out, or you want your other D8B to get quieter, I'm pretty happy with my silent Noctua fans & speed controller solution

Again, best of luck with getting this to work the way you'd like!

Hi Alex
basically the voltages are not that critical. so if you have 12V or 12,5 it doesn't matter.
Also 16V and -15,3V is fine. The console should work with that. Only point is that you loose a little headroom in the audio if you do not have +/-16V but if you run it only as controller this is no issue.
When you add a 48V supply for Phantom power, then you can use the preamps by accessing the audio signal via the Inserts on the send line.
BR Munk

Y-my-R, thank you once again for such a detailed info, will go on that route by ensuring first that at the end of the big cable the right voltages are on right pins, meanwhile I will proceed with turning the desk into a control surface.
Thanks for tuning in, Munkustrap!
The tech support of Traco cited from the tech specs of the product via mail: I think that this is normal. The voltage regulation factor for both outputs is in the 2-5% range.
Also, regarding a 48V power supply, I found one with 310mA, nothing with a lower amperage : https://www.distrelec.ro/ro/dc-power-su ... p/30121143
Traco has one with 2.3A: https://ro.farnell.com/traco-power/txln ... dp/3647840
Should I go for the one with 310 mA or do you think there's a chance to find one with 100mA?

I will repost smth that you mentioned on another topic, maybe is useful for other users:

By the way: maybe interesting for all that have problems with the d8b.
Power supply design:
5V supply for digital and Leds
12V for faders AND additional regulators down to 5V for reference voltages for ADCs.
+/-16V for OPAMPs mainly Audio, but also Fader moving circuits OPAMPs.
Yes I have NO CPU/PSU, only the console. Thats why I build in an own supply (5V/20A, 12V/10A, +/-16V, 2A) without fans .
the supply is build into the console. The microcontroller will also be build into the console but can also be used outside.
Attention: the Motors of the Faders have an own Grounding that is tied to digital GND via the case of the console.
yesterday I found the time to measure the +16V Domain that takes 0,9Ampere, so for everyone who is interested my proposal for the customized supply:

5V / 20A
12V / 6A
+16V / 1,2A
-16V / 1,2A
+48V / 100mA

Yup, got it up and running, thank you all for your support! Used 1.5 mm2 cables, just to be sure. The power supplies got a bit warm, but not so that they would need radiators. Will get back with photos. If you follow the instructions in the Ralph's guide, you can't go wrong.
The next question would be on which pin is the GND for phantom power and if I should look after a 48v power supply that has 310ma or rather 2-3A so I could benefit of the 12 preamps (sound wise, they're not great, not terrible).

SoundForSoul wrote:Yup, got it up and running, thank you all for your support! Used 1.5 mm2 cables, just to be sure. The power supplies got a bit warm, but not so that they would need radiators. Will get back with photos. If you follow the instructions in the Ralph's guide, you can't go wrong.
The next question would be on which pin is the GND for phantom power and if I should look after a 48v power supply that has 310ma or rather 2-3A so I could benefit of the 12 preamps (sound wise, they're not great, not terrible).

That's f'n slick... I've had this back burnered for while, and I've been exclusively using one of Ralph's ProBoxes for a year now as a control interface for Logic Pro X... couldn't be happier. I would absolutely be geeked to move that f'n CPU behemoth out of my rack (and into storage) and regain 4U of space and a reduction in ambient noise! Thanx for all this, y'all... now I have another project on the personal agenda...