SQLGuy said:
Magnetic contacts would, in most cases, be non-stainless ferrous metals. That means they would be prone to oxidation, especially if being repeatedly heated, cooled, and exposed to arcs.
Also, magentic materials lose magnetism when heated. High current relay contacts that rely on the magnetism of the contacts themselves might become bad connections under high current.
Thanks for the explanation, and yes it makes sense.
Fotios
+ and - 9V for the analog section seems a little low. Why not use dual 15 V supplies for more headroom ?
At the risk of being accused to be too precise: 39 uf is a value that is hard to get. 47 uf is a more common value. Please adjust the layout to accomodate for 47 uF or even 100 uf.
At the risk of being accused to be too precise: 39 uf is a value that is hard to get. 47 uf is a more common value. Please adjust the layout to accomodate for 47 uF or even 100 uf.
I finished designing the power supplies (thanks to the recent threads on shunt regulators). Here's the PDF, and the BOM has been updated.
Bill of Materials
Bill of Materials
Attachments
Been working on this layout for months. Hard to see what's going on in a PDF, since it's a six-layer board, but here it is anyway, for the curious.
A 500KB PDF file
A 500KB PDF file
exciting!
looking forward to the progression of construction pics and listening reports when you get to the end ...
mlloyd1
(who is another babylon 5 fan - even time i see the phrase "And so it begins ..." i hear kosh's voice and the last season's theme music.
what a great show ... )
looking forward to the progression of construction pics and listening reports when you get to the end ...
mlloyd1
(who is another babylon 5 fan - even time i see the phrase "And so it begins ..." i hear kosh's voice and the last season's theme music.
what a great show ... )
jwb said:And so it begins.
That transformer I specified is useless. Digi-key says it's 16VAC in parallel, but it's not. It's 16VAC on one secondary, and 35VAC on the other. The correct transformer is Tamura 3FD-416. Sorry for the error.
Here are the manufacturing images for the board, in a 1MB PDF file. The pages, in order, are the outline, the silkscreen, the top solder mask, metal layers 1 through 6, and the bottom solder mask.
http://octothorpe.barelyconnected.net/~jwb/preamp/gerber.pdf
Here are the manufacturing images for the board, in a 1MB PDF file. The pages, in order, are the outline, the silkscreen, the top solder mask, metal layers 1 through 6, and the bottom solder mask.
http://octothorpe.barelyconnected.net/~jwb/preamp/gerber.pdf
Attachments
I had 10 boards made, although I only plan to build two units myself. I will sell the boards to forum members for the low, low, insanely low price of $125, shipped in the USA or Canada, if anyone is interested. That's my cost. Anyway I'll post it over on the market forum later after I prove that the boards are error-free.
One design note: I found that you can't allow the -9V regulator to operate when the +9V regulator is disabled. The CS3318 draws infinite current in this state. Luckily my negative shunt regulators are inherently limited to 200mA of current, so I don't think the chips were damaged or destroyed in my testing.
The good news is all four regulators work great, and nothing smokes when the unit is powered on.
The only real construction difficulty was mounting those Jensen transformers. Their #30 stranded leads are very difficult to strip properly, and sticking a #30 stranded wire in a #30 drill hole is painful.
The good news is all four regulators work great, and nothing smokes when the unit is powered on.
The only real construction difficulty was mounting those Jensen transformers. Their #30 stranded leads are very difficult to strip properly, and sticking a #30 stranded wire in a #30 drill hole is painful.
First clear pic of my baby. Power supplies working great. Need to write software now.
Bigger picture here
Bigger picture here
Attachments
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