Built a custom D8B external power supply

[RJH_MUSIC]

It is in process. I have gotten the OS up and running. Now just fabricating the mounting of cards in the back of the case. I successfully mounted the motherboard and the power distribution board, (Fuse board) from the original d8b. None of the low profile video cards would work, so I had to purchase a ribbon cable extension for the existing PCI video card so I can mount it sideways. Tonight I hope to finish fabricating the rear mount for the video card and the data cable. Once that is finished, I will turn my attention to the console power supplies. I won't be able to test the +/- 22 Power supply with the velleman kit to generate the +/- 16 V until the molex connectors come that I ordered and I am still not sure the +5 Power supply is going to work yet because the one I originally ordered does not have +5 sense capability. About a month ago, I was able to power up the console using the separate power supply I built, and the OS using the unit I pictured here above. The problem was that some of the faders were jumping around and the V-pots did not want to work. I think this was related to the incorrect voltage being output by the MEANWELL 3535 +/- power supply I was using. I followed all the instructions posted by Weritz and bought all of the recommended parts, but quickly found out that those instructions were for using the console as a pro-box, not as a mixer, so I had to start over.

There is another alternative that will also work. The 2 RU case is big enough that I can get all of the original d8b parts in it with added cooling. As a last resort, if nothing else works, I can mount the original linear power supply board and the big frigin transformer and just find a new +5 switching power supply to replace the LPS 152 power supply which keep failing. I just did not want to have to use the big friggin transformer.

[RJH_MUSIC]

Also, I am taking pictures of everything and documenting the cable pin outs. I will post cost sheet and parts list as soon as I successfully have it all running, along with instructions on how to make it all work. it just has taken me longer because I had to scrap the original remote power supply I built because the power was not stable. Not sure if it had to do with the +/- 15V or the +5V power supplies I used.

[RJH_MUSIC]

Here are some recent pictures of work over the weekend.

[arjepsen]

Yeah, I've also wondered about that 5V sense thingie...
I think someone mentioned it might be a circuit part, that will automatically adjust the 5V supply, which could make sense, since there can be a varying amount of circuitry that it would have to supply (plugin cards, tape cards, etc.).
However, I _think_ shortening the supply wires to the desk might solve some of the problem.

I made a test on noise the other day:
On a "clean" startup profile, having all faders go to unity, I was kinda surprised about the amount of noise generated...
Interestingly, I measure quite a bit less noise, using the +/- 15V powersupply from tracopower.

I actually don't think that the lesser voltage of that supply is what makes the desk unstable. I originally thought so, but it rebooting a couple of times actually got it working, so I suspect the issue could be more related to old electrolytic caps throughout the desk, and also the "stability" of the 5V supply, maybe in relation to the 5V sense thingie...

Anyways, I should recieve the components I ordered this week, so I should be able to make a very quiet +/- 16V supply out of it - I'll post the results when I get around to it.

[RJH_MUSIC]

I think you are right. I may have been hasty assuming the problem was with the +/- 15 V supply. I did some more research on this last night. The original post by Weritz included a parts list for the various power supplies. The recommendation for the 5VDC power supply appears to be inadequate. The output Amp rating is only 8 amps. The LPS-152 power supply in the d8b has an output rating of 22 amps. This may explain why I had instability in the faders and lights on v-pots when I plugged in the new power supply I built. I think the TRC REL 150 Series would be better suited for the task, and they offer + and - sense. The REL-150-3005 has three outputs, +5V 15 amps / +15V 3 amps / -15V 3 amps. The sense is only available on output 1 which is 5V so that is good. If not worrying about getting the +/- 15 VDC to +/- 16 VDC, this power supply would make perfect sense. The other alternative is to use the REL-150-1003 which is single output of 5V 30 amps with sense. I am starting to think that the best route is to use the existing transformer and Linear power supply board from the d8b and replace the 5V power supply with the REL-150-1003. I am going to test that theory after the molex connectors to come for the +/-22 VDC I bought because I do not think the amperes will be sufficient when connected to the velleman kit. Who knows, maybe i will be wrong.

One thing is for sure, i should have bought stock in TRC Electronics! Maybe they will give me a trade up value for all the power supplies i bought.

[arjepsen]

Well.... as far as I can tell from the datasheet, that sense line on the TRC REL 150 can only compensate up to about 250mV - so 0.25V. I did a bit of testing on the original power supplies, and if (big if) I measured correctly, it seemed they have quite a bit of noise - sort of close to those 0.2V....
Anyways, I think that if you measure the voltage under load - like when you're using the desk the way you usually are - and adjust it for 5V under that load, you would probably be fine.

I actually don't think I would recommend getting that tripple output supply you mentioned - I imagine it will be quite a bit cheaper to simply get the two seperate 15V supplies i mentioned. This has the benefit that you can adjust each side seperately - not as much to hit +/- 16V as to be able to compensate for the loss of the filtering circuit I'm going to try out, and to be able to balance the rails.
Also - even though the +/- 15V supply from tracopower actually seems to be less noisy than the original linear circuit, as far as I've read - smps supplies can have some noise in specific frequencies, so it is a good idea to still filter the output.
I hope to recieve these supplies and components in a couple of days, so I can start testing all this.

[RJH_MUSIC]

So I think my problem might be a little different as I haven't even gotten to audio yet I'm just trying to get the console to just power up correctly. With the power supply I built up over a month ago using all the parts that weritz described I couldn't get stable V pots on the console, and the faders on the software screen were jumping all over the place, and would not respond to any movement on the console. So I immediately thought my problem was with the 15 volt power supply not being able to output +/- 16. I should have looked closer at the 5vdc power supply, because I think that was the problem. I ordered the REL 150 5VDC 30 Amp single output ps with sense.. yesterday and it will be about 2-3 weeks for delivery. If it works, I will seriously consider using the original transformer and linear power supply board from the d8b because it will generate +/-16 and 48v by itself, and I would just connect tge new 5v supply to the linear power supply board.

So a question. Are you saying the only difference between +/- 15 and+/- 16 v is noise? The +/- 15vdc would still work correctly? And related to the caps, are you referring to the ones on the console I r the ones on the linear power supply board?

[arjepsen]

The +/- supply is used to power the op-amps. Larger voltage means larger headroom. So +/-15V still works - you just have a slightly smaller headroom. This is analog circuitry, so there's still sound.
If the desk isn't booting, or is acting up, it's likely more an issue regarding the 5 or 12V supply.

Regarding noise, this is more related to how much noise is in the supply. Originally you have the loooong umbilical cable runnng to the desk - this is a perfect opportunity for noise to creap into the DC. Therefore it has to be filtered as the first thing inside the desk - hence the power distribution board with the big caps.
But from what I read, switch mode powersupplies are potentially less noisy than linear powersupplies.
By using a small circuit of about 7 components (for each rail) and the two seperate 15V supplies, I get a much cleaner DC supply (at least as far as my oscilloscope tells me....). As an added bonus, I can get both rails to 16V.

However - BE CAREFUL.
I think I just managed to fry the ad8803/ad8804 chips on two of my faderboards.... You really want to be careful with the 5V supply. As I belive I have the circuit for the +/-16V ready, my next step will be filtering the 5 and 12V supplies, and maybe add a bit of protection, to avoid having it go above 5 and 12.

[RJH_MUSIC]

I think you just conformed my suspicion. My problems were most likely the +5 supply or 12 vdc supplies. Would 6 amps make that much difference? I read that the LPS-152 +5 supply form the d8b puts out 22 amps and the Meanwell only puts out 16. I also think the sense is important because of line drop. Since I want to extend the BFC to 50 feet, line drop would be an issue without a power supply that can offer sense. SO the REL-150 +5 single output at 30 amps might work well. Gotta wait 3 weeks for it to be delivered.

Forgive me as i am not an engineer so "Rail" to me is Greek. Do you mean that + is one rail and - is the other? How do you get the second power supply to be -16v? just reverse the wires for + and -?

Which power supplies are you using?

I finished fabrication of the new 2 RU remote CPU on Sunday so i will post some pictures tonight.

[arjepsen]

I think you just conformed my suspicion. My problems were most likely the +5 supply or 12 vdc supplies. Would 6 amps make that much difference? I read that the LPS-152 +5 supply form the d8b puts out 22 amps and the Meanwell only puts out 16. I also think the sense is important because of line drop. Since I want to extend the BFC to 50 feet, line drop would be an issue without a power supply that can offer sense. SO the REL-150 +5 single output at 30 amps might work well. Gotta wait 3 weeks for it to be delivered.

Forgive me as i am not an engineer so "Rail" to me is Greek. Do you mean that + is one rail and - is the other? How do you get the second power supply to be -16v? just reverse the wires for + and -?

Sorry - yes. "Rails" refer to the positive and negative supply.
First supply PLUS goes to +16. First supply MINUS goes to ground.
Second supply PLUS also goes to ground. Second supply MINUS goes to -16
did that make sense??

Which power supplies are you using?

I finished fabrication of the new 2 RU remote CPU on Sunday so i will post some pictures tonight.

Meanwell LRS-35-15. They're a little less than half the size of the 5 and 12V supplies.