BluegrassDan

Another PCB check - PSU with Transformers
« on: August 09, 2019, 12:51:54 AM »
Hey all,

Do you all see any issues with this layout?

This is for an external tube PSU with three transformers mounted on the board. I've only used toroids and chassis mount EI before, so I'm curious to know if there will be any problems with these flat-pack PCB mounted transformers.

In case it's hard to read...The circuits L to R: 12.6V, 48V, and 240V.
« Last Edit: August 09, 2019, 12:56:05 AM by BluegrassDan »


BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #1 on: August 09, 2019, 12:53:59 AM »
And a 3d view, just for fun!

ruffrecords

Re: Another PCB check - PSU with Transformers
« Reply #2 on: August 09, 2019, 04:03:04 AM »
I would recommend beefing up the tracks from the tracks to the diode bridge on the 12.6V supply and also its 0V and 12.6V tracks.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #3 on: August 09, 2019, 08:29:28 AM »
Do you foresee any issues with those three transformers laid out the way they are so close together?

ruffrecords

Re: Another PCB check - PSU with Transformers
« Reply #4 on: August 09, 2019, 10:44:28 AM »
Do you foresee any issues with those three transformers laid out the way they are so close together?
I think their proximity is not a problem as long as they are properly rated.

I am a little concerned about the convoluted mains tracking between them. There are usually ( country specific) creepage and clearance rules for mains wiring which applies equally to PCB layouts of mains carrying conductors. I would be tempted to rotate the 12.6V transformer to bring the mains connections closer to the those of the other transformers.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

moamps

Re: Another PCB check - PSU with Transformers
« Reply #5 on: August 09, 2019, 04:09:22 PM »
This is for an external tube PSU with three transformers mounted on the board. I've only used toroids and chassis mount EI before, so I'm curious to know if there will be any problems with these flat-pack PCB mounted transformers.

Three transformers are too heavy for a single board.
Beginners should avoid designing the mains connection (especially 230V) on PCBs. It's too dangerous.
 

BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #6 on: August 09, 2019, 06:07:41 PM »
I can always go back to a transformer design off the PCB. Anyone else?

Re: Another PCB check - PSU with Transformers
« Reply #7 on: August 09, 2019, 08:03:56 PM »
I don't know the weight of the transformers and it's possible they'd be fine with enough mechanical support from stand-offs if they're light.  You could always increase the board thickness up one level.
I'd also be concerned with the clearance issues and proximities to the edges of the AC traces though - and a couple of holes for mechanical supports look a tad too close to my eyes.
I wouldn't necessarily give up on having the transformers on board, but I would lay this out as if it needed to pass all regional  regulatory safety issues.   
👍

BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #8 on: August 10, 2019, 01:23:53 AM »
Okay. Abandoning the three transformers for the fear of MAINS on the PCB. Switching back to toroidal mounted on the chassis.

How about this version?

BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #9 on: August 10, 2019, 01:24:48 AM »
And the 3D view.


ruffrecords

Re: Another PCB check - PSU with Transformers
« Reply #10 on: August 10, 2019, 05:09:59 AM »
Couple of points. First I think your big electrolytics are too close to the fins of the heatsink. Electrolytic cap life is very temperature sensitive so try to keep them cool. Second I still think you need to beef up the main power carrying tacks. There are chunky currents flowing to and from the electrolytics and the diode bridge. Attached is a pic of one of my power supply boards. Look at the red flooded areas on the bottom of the PCB.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

ruffrecords

Re: Another PCB check - PSU with Transformers
« Reply #11 on: August 10, 2019, 05:11:57 AM »
By the way, which PCB layout program are you using.? The 3D renderings are great.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #12 on: August 10, 2019, 07:14:54 AM »
You don’t think 80mil 2oz traces will be beefy enough for the 12.6v? All the rest are 50 mil.

Matador

Re: Another PCB check - PSU with Transformers
« Reply #13 on: August 10, 2019, 11:36:29 AM »
Looks like KiCAD.

Calculate the currents in those traces, and how much heating you can tolerate,
and the length, andd you'll find many free calculators for track width.  80 mil can do about 4 amps across 10 inches with a 10C rise above ambient.

BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #14 on: August 10, 2019, 11:49:58 AM »
Yes. Kicad.

The max current rating will be in the neighborhood of 2.6A for the 12.6v heaters. My four channel tube circuit draws 1.89A on the heaters. Transformer rated for 4A on the heaters, or thereabouts. Although I’m still deciding on which toroid brand to use. Don-Audio has nice ones, but they’re expensive and service/communication has been dreadfully slow.

ruffrecords

Re: Another PCB check - PSU with Transformers
« Reply #15 on: August 10, 2019, 01:48:48 PM »
You don’t think 80mil 2oz traces will be beefy enough for the 12.6v? All the rest are 50 mil.

I had not realised you are using 2oz copper in which case ignore me.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

ruffrecords

Re: Another PCB check - PSU with Transformers
« Reply #16 on: August 10, 2019, 01:54:25 PM »
Yes. Kicad.

Looks like Kicad has come a long way. I first tried it, must be 10 years ago, and I was reasonably impressed, especially as it runs natively on Linux and is open source etc. I even started a yahoo group for Kicad users which is still going. Despite that I never really used it - I got hooked on the much simpler freePCB program which was more than adequate for the basic tube designs I was doing back then. But now I would quite like to make some front panels using aluminium substrate PCBs and use silk screening for the legend. That way you can make some seriously low cost front panels.

I guess I need to spend some time getting up to speed on it again.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Audio1Man

Re: Another PCB check - PSU with Transformers
« Reply #17 on: August 10, 2019, 02:17:57 PM »
Hi Dan
The first layout with transformers needed 8mm spacing primary to secondary and needed to be corrected.

The 2nd layout without the transformers needs to have routing updated as the CHARGE & DISCHARGE CURRENTS for the storage caps will cause extra HUM. The caps must be CHARGED to the terminals and DISCHARGED from the terminals. You have a TEE wiring and this is extra impedance in the path.

I would also look @ a way to reduce the loop area from TX, rectifiers & storage caps to reduce hum fields.
Duke

BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #18 on: August 10, 2019, 03:07:12 PM »
Uggh. I started trying to lay this out as I would on a turret board, then started making adjustments to fit everything to the dimensions I need.

Another thing I can do it heatsink to the side of the chassis, which has fins. Wanted to make it all tidy on one board, though.

BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #19 on: August 10, 2019, 03:48:46 PM »
Hi Dan
The first layout with transformers needed 8mm spacing primary to secondary and needed to be corrected.

The 2nd layout without the transformers needs to have routing updated as the CHARGE & DISCHARGE CURRENTS for the storage caps will cause extra HUM. The caps must be CHARGED to the terminals and DISCHARGED from the terminals. You have a TEE wiring and this is extra impedance in the path.

I would also look @ a way to reduce the loop area from TX, rectifiers & storage caps to reduce hum fields.
Duke

Specifically, the two big caps on the left?


 

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