BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #20 on: August 12, 2019, 07:14:10 AM »
Ok gents. Here is another version. No transformers. No mounted heatsinks.

Better?



BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #21 on: August 12, 2019, 07:15:50 AM »
And Kidac 3D.

Re: Another PCB check - PSU with Transformers
« Reply #22 on: August 12, 2019, 07:48:18 AM »
I think that looks pretty good Dan. 
One thing I noticed, and it may be that the resolution is too fuzzy to tell?  But on the TL783 to the left:  Does the bottom trace to the middle pin have enough clearance from the pin above?  Maybe bring it out a bit first before scooting it back? 
That's all I have to say 🙂

Matador

Re: Another PCB check - PSU with Transformers
« Reply #23 on: August 12, 2019, 10:43:31 AM »
Looks good!

Where did you get the heatsink outline?  I've been looking for a KiCAD library that has those.

Also, why no ground plane?

BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #24 on: August 12, 2019, 01:26:35 PM »
One more "FINAL" version. Needed to clean up the silkcreen and add two more mounting holes halfway.


BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #25 on: August 12, 2019, 01:28:01 PM »
And 3D.

Thanks, everyone, for all the help. I'm new to PCB design. This is just my second board.

Re: Another PCB check - PSU with Transformers
« Reply #26 on: August 12, 2019, 01:51:35 PM »
And 3D.

Thanks, everyone, for all the help. I'm new to PCB design. This is just my second board.

You should have seen my second board.  You should see some of my current boards for that matter! 
😊
 

BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #27 on: August 12, 2019, 02:07:58 PM »
Thanks, Duke. Especially for the phone call to clear things up!

Found a few unconnected traces even on thye FINAL version. It's like writing a thesis - never too many eyes can proofread it.

moamps

Re: Another PCB check - PSU with Transformers
« Reply #28 on: August 12, 2019, 02:22:48 PM »
One more "FINAL" version. Needed to clean up the silkcreen and add two more mounting holes halfway.

Do you really need C1, C12, and C (I don't see the number) across the secondaries?
R9 or R10 is redundant.
What's dissipation of D6? I't is IMO too small and too close to C9.

You can do that board on bottom layer only. Than use top layer to beef traces and make eventually ground planes.

BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #29 on: August 12, 2019, 03:23:30 PM »
R9 and R10 are two voltage dropping resistors, dividing 66k @4W between two 33k @ 2W resistors.

D6 is a GBU802. 8W, 200V. https://www.mouser.com/ProductDetail/Diodes-Incorporated/GBU802?qs=sGAEpiMZZMtQ8nqTKtFS%2FJolQOfQMTyVY01irg1iCuA%3D


BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #30 on: August 12, 2019, 03:42:22 PM »
Please help me understand ground planes. How would it help this design?

moamps

Re: Another PCB check - PSU with Transformers
« Reply #31 on: August 13, 2019, 02:56:23 PM »
R9 and R10 are two voltage dropping resistors, dividing 66k @4W between two 33k @ 2W resistors.
You can't replace 66k/4W resistor with two 33K/2W. Anyway you don't need so low values of these resistors just for heater bias.
Quote
D6 is a GBU802. 8W, 200V. https://www.mouser.com/ProductDetail/Diodes-Incorporated/GBU802?qs=sGAEpiMZZMtQ8nqTKtFS%2FJolQOfQMTyVY01irg1iCuA%3D
It looks good but I would put a small heatsink on it.

moamps

Re: Another PCB check - PSU with Transformers
« Reply #32 on: August 13, 2019, 03:09:42 PM »
Please help me understand ground planes. How would it help this design?

A (ground) plane is a concept taken from RF circuitry where it is used to isolate tracks (and get better stability) by shunting parasitic capacitors to the ground.  There is it possible because the input/output impedances are usually low, 50 or 75 ohms.
In audio spectrum it is used mainly to get lower impedance/resistance of common  signal distribution lines as ground, power tracks etc. If they are correctly implemented, they are good for EMI shielding too. In your case, you can implement three separate grounds,  which help to have lower hum or other problems, as Audio1Man already noticed. 
 

BluegrassDan

Re: Another PCB check - PSU with Transformers
« Reply #33 on: August 13, 2019, 03:30:14 PM »
You can't replace 66k/4W resistor with two 33K/2W. Anyway you don't need so low values of these resistors just for heater bias. It looks good but I would put a small heatsink on it.

Am I undermisstanding? Two 33k 2W in series cannot replace a single 66k 4W?

moamps

Re: Another PCB check - PSU with Transformers
« Reply #34 on: August 13, 2019, 03:48:48 PM »
Am I undermisstanding? Two 33k 2W in series cannot replace a single 66k 4W?
Yes, they can. My bad. I didn't decoded this part of the board correctly. Could you post the schematic of the whole power supply? 

ruffrecords

Re: Another PCB check - PSU with Transformers
« Reply #35 on: August 14, 2019, 03:19:45 AM »
You can't replace 66k/4W resistor with two 33K/2W. Anyway you don't need so low values of these resistors just for heater bias. It looks good but I would put a small heatsink on it.
Many tubes specify no more than about 20K resistance between heater and cathode. 66K and 22K give 25% HT heater elevation.

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 #36 on: August 14, 2019, 06:06:18 AM »
Many tubes specify no more than about 20K resistance between heater and cathode. 66K and 22K give 25% HT heater elevation.

Does this resistance should have the same value if one or more tubes are connected to the one heater power supply? What happens if this resistor is shunted with a capacitor? Is resistance Rhk always equal to Rh-ground?

Btw:
(Designing High-Fidelity Valve Preamps by Merlin Blencowe)

 

ruffrecords

Re: Another PCB check - PSU with Transformers
« Reply #37 on: August 14, 2019, 04:52:17 PM »
Does this resistance should have the same value if one or more tubes are connected to the one heater power supply? What happens if this resistor is shunted with a capacitor? Is resistance Rhk always equal to Rh-ground?
The resistor value is the same no matter how many tubes, The bottom resistor is always decoupled by an electrolytic so that at ac the heater and cathode are connected directly together.
Quote
Btw:
(Designing High-Fidelity Valve Preamps by Merlin Blencowe)


I am not sure where Merlin gets his 150K value from. I used to use a much higher values - something like 300K at the top and 100K at the bottom. But then I came across a number of data sheets where it was stated it should not be more than 20K so I changed the design. There is no obvious reason to make the resistor values high other than the small HT current of about 3.4mA at 300V HT. It is an unfortunate fact that the vast majority of data sheets do not specify this parameter so I choose to err on the side of caution.

In my latest designs I have reduced the HT voltage from 300V to 250V. With the tubes I use I can now dispense with heater elevation altogether. Which is handy because I can now use the heater supply for LEDs and relays instead of having to provide a completely separate supply for this purpose.

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 #38 on: August 14, 2019, 05:32:30 PM »
Just tried searching some tube data sheets to see if Rhk is specified. The only one I found was the EF86 which specifies 20K.

http://www.r-type.org/pdfs/ef86.pdf

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'

boji

Re: Another PCB check - PSU with Transformers
« Reply #39 on: August 14, 2019, 05:53:35 PM »
Quote
ground planes

Also speaking to the obvious, switching to a pour might free up real estate previously used by com traces, and may allow reduction in via count or bridge wires.


 

Related Topics

  Subject / Started by Replies Last post
4 Replies
1158 Views
Last post August 25, 2009, 10:42:03 PM
by CJ
6 Replies
1346 Views
Last post March 29, 2013, 07:33:11 PM
by JohnRoberts
3 Replies
614 Views
Last post April 30, 2018, 03:49:14 PM
by fazeka
12 Replies
410 Views
Last post August 03, 2019, 04:27:33 AM
by ruffrecords