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Old 11th January 2017, 10:37 AM   #71
tfboy is offline tfboy  United Kingdom
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Jem, I haven't offered this as it would just get too complicated. I'm fairly sure all the parts are available from Mouser or Digikey. We would save on postage, but it's too much work for me to sort out and allocate components for every package.

I'm updating the first post now I have final pricing for the boards
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Old 11th January 2017, 10:41 AM   #72
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Originally Posted by tfboy View Post
Jem, I haven't offered this as it would just get too complicated. I'm fairly sure all the parts are available from Mouser or Digikey. We would save on postage, but it's too much work for me to sort out and allocate components for every package.

I'm updating the first post now I have final pricing for the boards
Thought that would be the case, it's just that I always seem to end up ordering from three different places and then find a cheaper source! However, the BOM is quite small in this case anyway, so I should cope ok.
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Old 11th January 2017, 10:50 AM   #73
tfboy is offline tfboy  United Kingdom
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Thanks. It's just relatively complex as it stands with the various permutations of bare, assembled and with/without regulators.

When I did this last time, I spent days on sorting out the logistics and accounting. I'm hoping to streamline now with new tools for sending out the proforma invoices...

Still, the post office hates me!

Edit: first post now updated. Please re-read it for all details, final pricing, instructions, etc. Thank you
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Old 11th January 2017, 11:12 AM   #74
AndrewT is offline AndrewT  Scotland
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Originally Posted by jemhayward View Post
Are there any plans to group buy the through hole components? Has anyone found a single source for all the bits, e.g. Farnell, and collected the parts numbers. I always seem to end up buying from multiple sources and then I find out I could have done a better deal at XYZ...
first board used the melf power input current limiting resistors.
These are reputed to have extra overload capability compared to ordinary smd resistors.

On my second board I swapped out the smd/melfs for 600mW leaded resistors.
A pair of series connected 1r0 giving the equivalent of 2r 1.2W have a rated current capacity of 770mA and the short term transient overload will be at least double that. They will survive start up from cold repeatedly.
The pair of metal film resistors standing upright on the PCB fit onto the two melf solder pads.
Whereas the tiny melfs will be much less and ordinary smds even lower.
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Old 11th January 2017, 11:30 AM   #75
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Andrew, did you have a problem with the first board MELFs burning or are you just being cautious?

Has anyone done/shared a Front Panel Designer layout for the inputs and output side?
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Old 11th January 2017, 12:01 PM   #76
AndrewT is offline AndrewT  Scotland
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I just thought that adopting a low rated smd for current limiting did not make any sense. So I changed it to a resistor type that can survive start up.
And there's space next to the input capacitors to make the change.

There is a lot of discussion that ordinary smd are not suitable in this location, because of the current demand at start up. Melf improves things a little bit. Why use 1/8 W, or 1/4W when one can use 1.2W with the same formed helix around the ceramic substrate?
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Old 11th January 2017, 12:28 PM   #77
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Thanks, Andrew. I appreciate your conservative engineering philosophy and advice.
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Old 11th January 2017, 12:33 PM   #78
AndrewT is offline AndrewT  Scotland
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Maybe better would have been for me to substitute in the opposite direction and used an ordinary smd 1/8th W and tested to destruction.
But that is not my preferred test method.

Has anyone got any data for the input current limiting resistor lifetimes?
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Old 17th January 2017, 08:08 AM   #79
tfboy is offline tfboy  United Kingdom
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Order has been placed with Quick Circuits, SMD components are being sourced and boards are being manufacturered.

I'll report back once I have an ETA - should be end January / beginning Feb.
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Old 17th January 2017, 08:41 AM   #80
tfboy is offline tfboy  United Kingdom
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Order for regulators now placed too.
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