Salas hotrodded blue DCB1 build

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I am currently planning my case work.

I have two large alu heatsinks that will form the side walls - but as the plan is to have enough width in the centre channel for the trafo (approx. 100mm diameter) this puts the heatsinks to far from board mounted mosfets at the side. The base alu plate (5mm but could go thicker) will be butted to heatsinks and the join made with a alu right angle. Presuming I use thermal grease etc. do y'all think I will get sufficient heat transfer to my sinks if the mosfets are mounted to baseplate?

Is the 2nd level hotrod with passive cooling possible with this kind of construction?
 
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Meaning 3R3 current setting power resistors. That will put about 10-12W on each side sink when using a 15-0-15 Vac transformer. Yes your sinking plan should prove sufficient. But move the gate stopper resistors from the board to directly on the MOSFETS gate pins if you will need cable extensions to them. Wire from each resistor's input side pad of the now empty gate stoppers board positions.
 
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Meaning 3R3 current setting power resistors. That will put about 10-12W on each side sink when using a 15-0-15 Vac transformer. Yes your sinking plan should prove sufficient. But move the gate stopper resistors from the board to directly on the MOSFETS gate pins if you will need cable extensions to them. Wire from each resistor's input side pad of the now empty gate stoppers board positions.

Thanks very much.

Build going well so far (except insufficient packing on the heatsinks and mishandling in transit meant that one ended up with dog ears and had to be returned for exchange). Just selecting and sourcing the 0.22uf cap - have a couple of options, can see Wima MKP10 is well liked, and will get that to try as well. Will start with Audionote tantalum resistor for 220r but also have Shinkoh to try - though it is 2w version so will have go in as a soldier.

Might try LDR down the way but for starters will use regular 20k pot.

Still digging through this thread. And enjoying the number of AndrewT posts on this project. No doubt I will be back with more questions if I can't find for myself what I need to learn.

Too many projects, not enough time, not enough pocket money!
 
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LDR is popularly well liked but it can add some THD of its own since it has light sensitive elements with some non linear capacitance and voltage coefficient. Starting with a regular 20k pot is a safe way you will establish a subjective reference to compare other solutions in the future.

Yes, AndrewT was frequent in these threads and he was using a DCB1. He had also built it for friends as he had mentioned. R.I.P.
 
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2sk170 matched pairs

I have read near the beginning of the thread that the lower of the matched pairs should go to the middle.

But as I have 2 pairs of identical closely matched pairs (at least that is what they are labelled and I have not measured them myself) to get the best result should I keep the identical pairs together or swap so that I have 2 pairs that are the same?

(reading across the quad)

7.85 - 7.85 - 7.84 - 7.84

or

7.85 - 7.84 - 7.84 - 7.85

I think I read that the identicals should remain together rather than make similar pairs ? but can't now find that post.

Thanks in advance
 
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Avoid it, it will allow too much extra heat on the MOSFETS. It can even exceed 35V reservoir capacitors voltage spec when on "healthy" mains. Higher withstanding ones will be usually fatter and if not fitting you will have to reduce their choice in capacitance value.

You can use power resistors in series with the outer AC inputs on the PCB's Tx connector to drop the incoming voltage if you must use it. But increasing a big transformer's impedance is negating its dynamic benefit over a smaller one and producing heat on those resistors.

What you need for a DCB1 in Australia is a 230V primary transformer with 15+15V dual secondaries. Exactly like for Europe. Some 50VA size core will be more than enough with the typically 170-190mA mild hot-rod PSU bias current when using 10R setting resistors that most builders find a happy compromise.

Here is a made in CZ example from a major stockist (AU$): 0050P1-2-015 | 2 Output Toroidal Transformer, 50VA, 2 x 15V ac | RS Components
 
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Hi Salas, Thanks for the info, that should do the trick & quite unbelievably, cheaper than F/Bay.
Now sorry for the nob question, but normally I never, never work with 240 AC, How do I connect up the wires!!:confused::confused:

Cheers


Its datasheet shows brown to live, blue to neutral (primary side colours to the mains plug).
Mains earth third wire from the plug just tie it to the chassis with screw and nut for safety.

Secondary side colours to the electronics:
Black and yellow put them together to the middle input of the board's AC connector.
Put red to one of its corner inputs, orange to its other corner input. No matter which.

https://docs-apac.rs-online.com/webdocs/15bd/0900766b815bd18d.pdf
 
Apologies if this is answered elsewhere but I have not been able to see it.
I have the black Hypno boards. I am intending to use foil caps for the .22uF caps and the ones I am using have an indication for open foil end. Would it be better to connect this end to the + or the -, or does this not matter?
KR
Keith.
 
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If it matters in this case, the lower impedance point in the positive section is the (-) and in the negative is the (+) to orient the outer foil ends of those Vref bypass capacitors.

With bigger sized capacitors mainly, the outer foil becomes less susceptible to external interference when connected to the lower impedance side of the circuit.