DHT Heater using VCCS - PCB or Kit (Possible Group buy)

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Andrew
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#1036 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by Andrew »

There's two more large smoothing caps on the "big" boards to deal with the extra incoming AC ripple, but if you're not using them for high current heaters, its just wasted money.

The "small" ones will do 300B and everything downwards, the big ones are really for 2A3, nothing will do a GM70 without serious hacking.

Andrew
Last edited by Andrew on Sun Feb 03, 2019 12:23 pm, edited 2 times in total.
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Max N
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#1037 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by Max N »

Andrew wrote: Sun Feb 03, 2019 12:03 pm
Max N wrote: Sat Feb 02, 2019 4:33 pm Hi Andrew.
This is probably a long shot - do you have any kits or boards still available?
Or does anyone have any that they want to sell?
Cheers
Max
How many, Max? I have the so called "small" PCB in stock?

Andrew
I'd like 4 pcbs please Andrew. Also happy to buy any components for the boards if you have surplus stock you want to get rid of.
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#1038 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by Andrew »

The "small" ones will do 300B and everything downwards, the big ones are really for 2A3, nothing I have will do a GM70 without serious hacking.

Andrew
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pre65
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#1039 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by pre65 »

Andrew wrote: Sun Feb 03, 2019 12:22 pm
nothing I have will do a GM70 without serious hacking.

Andrew
I thought mine were reasonably standard ? :?

GM70 & GK71 heaters the same (or very similar).
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Andrew
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#1040 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by Andrew »

pre65 wrote: Sun Feb 03, 2019 12:29 pm
Andrew wrote: Sun Feb 03, 2019 12:22 pm
nothing I have will do a GM70 without serious hacking.

Andrew
I thought mine were reasonably standard ? :?

GM70 & GK71 heaters the same (or very similar).
No, that's all yours and Mark's own work, Phil. I disown it. ;)
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#1041 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by IslandPink »

But seriously ( folks ) do you have a residual gripe about the GK-71 application ? - after all, it seemed to be merely a matter of feeding it with a 24V SMPS and making sure one or two caps on the board were 35V rated, as I remember ( and the heatsink up to scratch ) ?
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#1042 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by Max N »

Andrew wrote: Sun Feb 03, 2019 12:22 pm The "small" ones will do 300B and everything downwards, the big ones are really for 2A3, nothing I have will do a GM70 without serious hacking.

Andrew
I'd like 4 pcbs please Andrew. Also happy to buy any components for the boards if you have surplus stock you want to get rid of.
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#1043 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by Andrew »

IslandPink wrote: Sun Feb 03, 2019 12:44 pm But seriously ( folks ) do you have a residual gripe about the GK-71 application ? - after all, it seemed to be merely a matter of feeding it with a 24V SMPS and making sure one or two caps on the board were 35V rated, as I remember ( and the heatsink up to scratch ) ?
I've no gripes at all, they are your boards, after all. I was just, perhaps a bit tongue -in-cheek, pointing out that it wasn't what I designed.
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#1044 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by RhythMick »

Max N wrote: Sun Feb 03, 2019 12:53 pm
Andrew wrote: Sun Feb 03, 2019 12:22 pm The "small" ones will do 300B and everything downwards, the big ones are really for 2A3, nothing I have will do a GM70 without serious hacking.

Andrew
I'd like 4 pcbs please Andrew. Also happy to buy any components for the boards if you have surplus stock you want to get rid of.
Max I have 6 spare (small) boards from Andrew which I plan to use shortly. I'm going to be putting in an order (either Farnell or RS) soon so let me know if you need components. We're unlikely to cross any significant price points but you never know - plus I have spares of some items.

Same applies if anyone else needs components for the boards.

EDIT - there are some savings to be had. For example the Panasonic caps are £1.78 <10, £1.05 between 10 and 24
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#1045 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by RhythMick »

Andrew - Farnell no longer stock the 470k CC TE 1/4W. They have the 1/2W equivalent in stock, but only 203 and not restocking I think. I'm going to be ordering at least 18 at 35.8p. Next price point is 50 at 25.6p
https://uk.farnell.com/neohm-te-connect ... ?st=Carbon

Similar with 1K - 1/4W awaiting delivery, 1/2W in stock
https://uk.farnell.com/neohm-te-connect ... dp/1265117

Any reason not to use the 1/2W versions ? Don't think it will be a problem room wise.

EDIT 2 - the big cost is the surface mount caps.
1+ = £4.87
50+ = £3.45

I need 12, I guess we're unlikely to get to 50 but let me know anyone who needs them.

EDIT 3 - Andrew I happen to have plenty of 1N4004 in stock, I assume no harm using those in place of the 1N4001 ?
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#1046 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by Andrew »

The 1N00x diodes should be fine, can't see why not?

The correct 470K CC resistors are available from RS, does that help? I suspect the 1/2 watt ones will be fine as well, if a little over-kill.

Yep, the caps cost a fortune, pity as I just bought 24 for a a mini buy.

Andrew
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#1047 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by RhythMick »

Andrew wrote: Tue Feb 12, 2019 4:11 pm The 1N00x diodes should be fine, can't see why not?

The correct 470K CC resistors are available from RS, does that help? I suspect the 1/2 watt ones will be fine as well, if a little over-kill.

Yep, the caps cost a fortune, pity as I just bought 24 for a a mini buy.

Andrew
Thanks yes I was just looking at RS and doing a price comparison. I'm going to place orders tonight, so if anyone wants to jump on the bandwagon let me know SOON.

The caps are half the price on RS, but need to be back ordered. EDIT - unable to be back ordered, Mouser and Digikey show them as 52 week lead time.

OK I'm going to order the 1/4W CC resistors from RS as they are in stock and cheaper even than bulk buying from Farnell. Everything else looks right from Farnell.
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#1048 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by Ali Tait »

I’ve eight small boards coming from Andrew for my Pinnacle OTL build. In retrospect I should perhaps have requested large boards so I could use the chassis as heat sink.

Given I will be using the small boards, and there will be four mounted inside each monoblock chassis, I’m a little concerned that heat may be a problem, so to minimise this what’s the minimum input I could get away with to run a 300b?

Other possibilities could be drilling to bolt the top of the heat sinks directly to the chassis with some thermal paste, this would act as the fixing rather than some nylon pillars and presumably increase dissipation.

Or perhaps make up some boards for the amps to sit on with cut outs and pc cooling fans fitted.

Some advice from the panel would be much appreciated.
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#1049 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by RhythMick »

Ali Tait wrote: Tue Feb 12, 2019 10:19 pm I’ve eight small boards coming from Andrew for my Pinnacle OTL build. In retrospect I should perhaps have requested large boards so I could use the chassis as heat sink.

Given I will be using the small boards, and there will be four mounted inside each monoblock chassis, I’m a little concerned that heat may be a problem, so to minimise this what’s the minimum input I could get away with to run a 300b?

Other possibilities could be drilling to bolt the top of the heat sinks directly to the chassis with some thermal paste, this would act as the fixing rather than some nylon pillars and presumably increase dissipation.

Or perhaps make up some boards for the amps to sit on with cut outs and pc cooling fans fitted.

Some advice from the panel would be much appreciated.
I used the large boards and mounted the heatsinks on 2mm copper sheet (my chassis is wooden) at the back of the amp. I can't see how you would do that with the small boards. If you're concerned with heat then a small silent fan might be a good idea, along with suitable holes for airflow. Although I haven't wired them in yet, I have mounted 2 fans at the back of my cupboard and put a circuit together which uses thermistors in the amp to automatically control the fan speed. The fans themselves are very cheap and small.

The board needs I think about 4v to regulate, so you'll need about 9v peak, or 6.3v RMS transformer. I use a 7v with my 45s, which are 2.5v 1.5A. 300Bs with a 6.3v transformer should dissipate MUCH less heat than my 45s and I haven't had a problem with 12 boards in the amp (4 45s, 4 26s, 4 71As). Yes they are mounted to vertical copper sheets, but still.
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#1050 Re: DHT Heater using VCCS - PCB or Kit (Possible Group buy)

Post by IslandPink »

I made some notes on heater tests for the 45. 5.62AC in was clean for 2.5V DC out.
http://www.audio-talk.co.uk/phpBB3/view ... 6&start=90
Another data point is that for GM70, with 23.8V DC in, 19.2V DC out is clean.
I think you can come down from 9V AC in, to about 8V AC or maybe slightly more. Transformer needs modelling with typical 245+AC unless you want to visit Andrew I or Dave :D
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