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rod elliott's P27/M27 or P03 + preamp?

Started by yoyoy_kun, September 20, 2013, 02:24:26 AM

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Roly

Quote from: phattlikely bigger than even Roly's junk yard collection. :P

ROFL!   :lmao:


Heatsinks.  This;
http://www.jaycar.com.au/productView.asp?ID=HH8555
Diecast Black Heatsink
* Size 150(L) x 75(H) x 46(D)mm
* No flange
* Thermal resistance 0.784°C/W

Or this;
http://www.jaycar.com.au/productView.asp?ID=HH8566
Versatile Heavy Duty Heatsink - 72mm Long
- Allows horizontal & vertical mounting.
- Thermal resistance 2.2° C/W.
- Length 72mm
- Undrilled.

Or this;
http://www.jaycar.com.au/productView.asp?ID=SY4085
Thermal resistance - 1.1ºC/W
Dimensions - 118(W) x 110(L) x 64(H)mm

Or this;
http://www.jaycar.com.au/productView.asp?ID=HH8532
Fan Assisted-Type Heatsink - 254mm Long
Assembly Type Cooling Mode Rating (approx)
Single Length Convection 0.83° C/W
Tunnel Assembly Convection 0.70° C/W
Tunnel Assembly Fan Assisted (single) 0.35° C/W
Tunnel Assembly Fan Assisted (dual) 0.30° C/W


To work out if a given heatsink will be sufficient you need to know how much power will be dissipated in each transistor, the maximum allowable chip temperature, the thermal resistance (in °C/W) for the chip to case (from the particular transistor datasheet), the thermal resistance of any insulator used between the transistor and the heatsink, and the thermal resistance to ambient of the heatsink under consideration, and finally the ambient temperature expected.

You add all the thermal resistances together, multiply by the number of watts to get the number of degrees differential between the chip and ambient, then add the ambient.  If the resulting chip temperature is higher than permitted then you need a heatsink with a lower thermal resistance.

You keep repeating this process with different heatsinks until you find one that will give you an acceptable chip temperature with the highest ambient you will encounter.

Ideally a heatsink should be able to cope with the worst case situation, but a thermally controlled fan can provide a backup in extreme situations.


{and a Perreux is certainly worth fixing - great amp.  :tu: }
If you say theory and practice don't agree you haven't applied enough theory.


Roly

(The Alaxan PDF won't load for me.)

The first thing you are looking for is a low thermal resistance in ºC/W, that is degrees temperature rise per watt of input power.  If the heatsinks don't specify their thermal resistance (naughty) then you are looking for the largest surface area of fins, bigger is better, and where this is equal or similar, for black anodising.  For best results the fins on a heatsink should be mounted vertical.

You may be able to recover a suitable heatsink from a junked TV, monitor, or computer, or failing that it is possible to make up a heatsink by stacking and bolting together scrap aluminium extrusions, taking case to maximise the fin area and minimise the distance the heat must travel between chip and fins.

Most fans these days are pretty low power, and electrically quiet, so you shouldn't need a separate supply, 'tho it would be a good idea to fit, say, a 100uF 12-16V right across the fan.  Modern fans are not tolerant of excessive voltage.
If you say theory and practice don't agree you haven't applied enough theory.

yoyoy_kun

#18
here is the link

http://www.alexan.com.ph/index.php/downloads

then download the Product List 2012..

yoyoy_kun

also, can anyone know if d1266 is complementary with d2058?
i need to replace this with an amp that was given to me, there were suposedly 4 transistor but the other 2 has been removed, the d1266 and d2058 was left...
i cannot find this parts here, can anyone suggest any substitute...

Roly

Annnn, Bnnnn, Cnnnn, Dnnnn are short forms for 2SAnnnn, 2SBnnnn, etc.

http://www.digchip.com/datasheets/search.php?pn=2SD1266

http://www.digchip.com/datasheets/search.php?pn=2SD2058

(That link still won't download the PDF.  Never mind; you know what you are looking for.)
If you say theory and practice don't agree you haven't applied enough theory.

J M Fahey

Back to chassis construction, forget galvanized sheet and go for aluminum sheet.

*MANY* advantages:

1) it's easier to work than steel

2) can be left as-is, it won't rust, doesn't *need* paint, galvanizing, or anything else.
Simply brushing it along one way with steel wool will give it a cool, "satin brushed" finish same as cool Hi Fi equipment.

3) you can use simple "woodworking type" hand tools, such as simple drills, files, X-Acto knives, sandpaper, etc.

4) you can have it cut to size and folded 90º bends to make simple "U" shaped chassis (that's all you need) in easy to find "tin shops", the kind which custom make galvanized steel tanks, chimneys, cattle feeding vats, rain gutters, air conditioning conduits, etc.

FWIW this is a 200W Power amp I made in 1972 (big power way back then)



Looks good, huh?

Now look inside:



1) a simple U shaped chassis, 2mm aluminum

2) no PCB but eyeletted boards, (I had been building Fender clones up to that point, and that's what I was used to)

3) lots of heatsinking **outside** (an often forgotten "small" detail)

As you see, a Pro looking (and sounding) product can be made with simple tools and a little outside help.

FWIW, I always visited galvanized steel shops with a couple "longnecks" under my arm (fine wine bottles) and "casually forgot" them there.

Workers sure were happy to cut and fold my aluminum after a couple visits  :lmao:

4) I forgot: all holes you see were either 10mm (pots/jacks/toggle switches/neon light) or 4mm (mounting screws, pop rivets if needed, TO3 transistors, etc.) except the 13mm fuse holder which was punched with a hand tool .... but you can simply file it.

And the front panel is printed on glossy (magazine cover type) paper under transparent acrylic for protection.

Roly

If you say theory and practice don't agree you haven't applied enough theory.

yoyoy_kun

ill try to find that aluminun plates, but i think its hard to find it here... hopefully if there is, i can buy portions... all i can see that is available here are L-bar and square pipe... and i think that the alu's are more expensive?
ive been thinking if i would put front woodwork + steel/alu body or the u-type...

i know it is the 2sdnnnn, what im asking if it is posible to subtitute any trnsistor? because its not available here, for example can i use 2sc3847, because the pcb is made to fit also for larger transistors...

regards

Roly

Quote from: yoyoy_kunif d1266 is complementary with d2058?

http://www.digchip.com/datasheets/search.php?pn=2SD1266

http://www.digchip.com/datasheets/search.php?pn=2SD2058

Not complementary, they are similar NPN transistors.


The 2SC3847 looks like a very capable transistor, 800V, 10A, 80W, 30hfe; get that heat away from them and they could roar.

http://www.digchip.com/datasheets/search.php?pn=2SC3847
If you say theory and practice don't agree you haven't applied enough theory.