6.3v indirectly heater valve PCB (possible group buy?)

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Andrew
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6.3v indirectly heater valve PCB (possible group buy?)

Post by Andrew » Thu Mar 01, 2012 8:08 pm

Nick and I have been chatting about doing a PCB for 6.3v DC heater circuit that could provide up 1 amp of pure DC, so that's 3 valves like a ECC88/83/12AY7/5751 and a whole host of 330mA values etc or one 6N6P/5687 etc from the one single PCB.

The circuit uses pretty much standard components, to keep the cost down, but has excellent ripple rejection, probably in the excess of 80db, the Spice sim say no AC component what so ever!

It is set for 6.3v without need for adjustment and is also designed to isolate the valve's heater from the nasties on the output of the 3 legged reg equally, it also isolates the reg from any feedback from the heaters; for high gm valves I found this very effective.

At the moment, we have no idea of cost but the process would be similar to the start up boards, if you remember how we did those?

The PCB would require an external 9v feed from, say, a toroid. The TX will probably be the most expensive part, roughly £8 or £9 from Rapid, I would guess, but don't hold me to that. The remaining parts, excluding PCB will probably be less than that, but I don't know for sure yet.

If the design has enough interest I will build first a prototype on strip board and post the measurements here, so we all know what we're getting, then we will do the artwork for a run of PCBs.

The idea is you buy the parts on the BOM yourselves and Nick, or myself, supply the PCB and any parts that cannot be sourced direct in a single buy from Rapid; this is designed to be easy.

Please register any interest or post comments on the design below; there's always room for improvement.

Andrew
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Post by IslandPink » Thu Mar 01, 2012 8:22 pm

Ah ..
I see you two have been chatting in the last couple of days !
How big is this board likely to be, because I've been thinking of building something a bit more hefty in case I need to double-up on 6N6P's ?
Would be interested though .
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Post by Andrew » Thu Mar 01, 2012 8:28 pm

Well I was thinking it might be handy for you Mark, but I count for a few myself.

Re size, not that big, I imagine, can't say for sure, until we lay it out, biggest parts are the two 10000uF caps and the heatsink.

One per 6N6P would be ideal, in your case.

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Post by ed » Thu Mar 01, 2012 8:36 pm

don't know if you chaps have seen this:

http://www.classicvalve.ca/tubepcb-1.html#HEATER

I bought the Rod Coleman 1 and 5 amp kits before I saw this, but I bet there isn't much in it. The cvd boards certainly look versatile though, even for indirectly heated???.
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Post by Paul Barker » Thu Mar 01, 2012 9:13 pm

Andrew if the 1086-5 was switched for the 1086 adjustable with necesary changes to ADJ components, does everything which follows remain the same?

I was thinking to use it for the 01a 5v filaments, British 2v filaments and 10y 7.5v 1.25A filaments.

What do you think?

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Post by Andrew » Thu Mar 01, 2012 9:34 pm

Yes everything stays the same, perhaps a resistor value tweak....

For simplicity, we were trying to avoid an adjust circuit, we discussed it and we decided not too, but, yes, it could be done, if there were sufficient interest, I guess?

Having said that, a combination of the right LED, choose your poison as it were, either red, green or blue, plus a diode or two could easily net you the right voltages for your needs and would be, in my humble, better than a pot.

For example, roughly, two red LEDs and a 1N4148 and you have a 7.5v reg. A 5v reg just needs two 1N4148 diodes, maybe just one 1N4001 and one 1N4148. The only problem would be 2v. Perhaps a 3.3v reg chip might do it?

If we did the PCB with slots for two LED and a couple of diodes then those that don't need them could just put in a wire link.

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Last edited by Andrew on Thu Mar 01, 2012 9:45 pm, edited 2 times in total.
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Post by Andrew » Thu Mar 01, 2012 9:37 pm

ed wrote:don't know if you chaps have seen this:

http://www.classicvalve.ca/tubepcb-1.html#HEATER

I bought the Rod Coleman 1 and 5 amp kits before I saw this, but I bet there isn't much in it. The cvd boards certainly look versatile though, even for indirectly heated???.
I need to study it more, there's some subtleties in there, but I'm more comfortable with having a FET after the reg. Having said that, there's always room for improvement.

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Post by Paul Barker » Thu Mar 01, 2012 10:04 pm

Andrew wrote:
Having said that, a combination of the right LED, choose your poison

If we did the PCB with slots for two LED and a couple of diodes then those that don't need them could just put in a wire link.

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Post by Cressy Snr » Thu Mar 01, 2012 10:08 pm

I'd certainly be interested in these modules
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Post by IslandPink » Thu Mar 01, 2012 10:10 pm

So you've got a couple of 10,000/16V caps and a regulator, is that in TO-220 style ?
Are rectifiers a package or discreet diodes ?
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Post by Andrew » Fri Mar 02, 2012 7:54 am

Current plan is per diagram a KB 2 Amp bridge, like this one.

http://www.rapidonline.com/Electronic-C ... iers-66255

Can support both on the PCB if folks prefer. But I am inclined to think a diode bridge will be fine here and hope the bread board experiments will show this.

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Post by Andrew » Fri Mar 02, 2012 10:24 am

PS. You can add a soft start, by changing the time constant of C1, R1 and R5 as I have them drawn above - this gives the same sort of behaviour as the circuit Ed referenced tho' its an entirely different topology.

Though with indirectly heated valves this is an unlikely failure mode.

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Post by JamesD » Fri Mar 02, 2012 1:59 pm

I'm in for at least six boards - maybe more.

James

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Post by Mike H » Fri Mar 02, 2012 4:18 pm

In case anyone else was wondering, TIP142 is a power darlington, but the symbol is for a thyristor :D
 
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Post by Andrew » Fri Mar 02, 2012 5:07 pm

Mike H wrote:In case anyone else was wondering, TIP142 is a power darlington, but the symbol is for a thyristor :D
Glad you spotted that Mike, bit of a hack really isn't it? But its the right spice ".model" just the wrong symbol.

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