DHT Heater Group Buy notes.

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Nick
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#16 Re: DHT Heater Group Buy notes.

Post by Nick »

To quote Andrew
The TLV431 should just drop in, the voltage pre-regulator, the LD1085, is referenced from the TL431
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#17 Re: DHT Heater Group Buy notes.

Post by Andrew »

Nick wrote: Mon May 21, 2018 10:07 am To quote Andrew
The TLV431 should just drop in, the voltage pre-regulator, the LD1085, is referenced from the TL431
Yep, the whole unit is referenced off the TL device, no need for other changes.
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#18 Re: DHT Heater Group Buy notes.

Post by RhythMick »

Ok I'll build a 26 version as soon as the TLV431 arrive and report back. Thanks.
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#19 Re: DHT Heater Group Buy notes.

Post by RhythMick »

Is the Vref an internal parameter of the device?

My bad. For some reason I thought it was set externally. Probably because a pin is labelled REF and the datasheet diagrams show Vref external to the device. Of course REF is the voltage at the resistor junction. Doh.

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#20 Re: DHT Heater Group Buy notes.

Post by Andrew »

The TL series have internal references, the output of the actual device is relative to this reference, which in turn is set by the potential divider on the REF pins.

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#21 Re: DHT Heater Group Buy notes.

Post by RhythMick »

Thanks Andrew, the penny dropped last night. Just my inexperience.
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#22 Re: DHT Heater Group Buy notes.

Post by RhythMick »

26 board working perfectly thanks.

LD1085P and D44H11 mounted to heatsink remotely and wires running from legs to terminal blocks to PCB vias.

Single heatsink, ambient temperature was 20 degC now 50 after about 5 minutes. Watching to check its stable. When mounted in the amp the heatsink will be mounted on copper sheet.
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#23 Re: DHT Heater Group Buy notes.

Post by RhythMick »

Multimeter measures 115mV AC at the simulated filament (resistor). What's normal? Might be better scoping it.
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#24 Re: DHT Heater Group Buy notes.

Post by Andrew »

RhythMick wrote: Thu May 24, 2018 8:32 pm Multimeter measures 115mV AC at the simulated filament (resistor). What's normal? Might be better scoping it.
115mv :shock: that's huge, are you certain it's all ok? The AC component should be tiny, like less than 2mV (from memory) please have look at the FFT graph/imagess in the group buy for reference.

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#25 Re: DHT Heater Group Buy notes.

Post by IslandPink »

Multimeter ? :roll:
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#26 Re: DHT Heater Group Buy notes.

Post by RhythMick »

Yeah I'll scope it. Work went crazy just at the wrong time.
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#27 Re: DHT Heater Group Buy notes.

Post by IslandPink »

Andrew, have you got a BOM or BOM's for the board ?
& can you confirm the Kemet part C2220C474J5GACTU is the non-epoxy part ?
I need to get a few more and label them !
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#28 Re: DHT Heater Group Buy notes.

Post by izzy wizzy »

IslandPink wrote: Sun Jun 16, 2019 12:23 pm Andrew, have you got a BOM or BOM's for the board ?
& can you confirm the Kemet part C2220C474J5GACTU is the non-epoxy part ?
I need to get a few more and label them !
And to add to what Mark has asked, are these https://www.ebay.co.uk/itm/181883201906
the same as these https://uk.farnell.com/kemet/c2220c474j ... dp/1679460

From what I can makeout from the datasheet http://www.kemet.com/Lists/ProductCatal ... 0G_SMD.pdf, it isn't these that have the epoxy layer so was that another type of part?

Cheers,
Stephen
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#29 Re: DHT Heater Group Buy notes.

Post by Andrew »

Those caps in standard form can can become fractured due to expansion and contraction; basically the "ends" fall off under the heat.

The epxoy version was created for environments where this fracturing was percieved to be a problem.

When I subbed the non expoy for the epoxy one, thinking they'd be the same, but Mark felt the sound changed with epoxy in the current path.

The epoxy one has a differnt part number. The part number in your BoM, Stephen, is the non expoy version. I can get a number tonight, but we'd both be looking at copies of the same file.

I wouldn't buy off ebay, well not for that part, given the hassle it caused me; that part of the circuit is very component sensistive.
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#30 Re: DHT Heater Group Buy notes.

Post by izzy wizzy »

Thanks Andrew. That has clarified it for me.
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