soundcraft series 800B power supply build

[iampoor1]

Oh I'm well aware of those manufacturers!  They are too expensive though! I got this desk for $200 untested and had it shipped from South Carolina to Baltimore for $100 through an app called uShip which is like an Uber for shipping. It looked like it had been sitting for a long time so I cleaned it up and looked over all the modules, nothing looks burnt or broken.  These 1083 kits are only $15+$15 for the ones pictured and $11x4 for the smaller ones and I have a box of assorted toroids that a local factory threw out.  I'll test the regulators under load that's good advice  Ohm's law.. what a thing. 

lets see how many degrees C/W these heat sinks need to be. Whats the specific heat of aluminum? How many watts we talking?

Reasonable enough. Thanks for the heads up about uship, that looks like it could come in handy!

The power one HD15 6amp supplys are available for around 40$ used on Ebay all the time. They are properly designed, and have the heatsinks, so I think thats pretty hard to beat, once you factor in the cost of heatsinks I wonder how the cost will compare.

Ultimately dissipation and heatsink size will depend on what transformer you are using. Oh and if you want an evil fan in your power supply or not.  ;D

 

[abbey road d enfer]

lets see how many degrees C/W these heat sinks need to be. Whats the specific heat of aluminum? How many watts we talking?

This is not how it works. Using the specific heat of the material will just give a time-constant (how long it takes for the heatsink reaches a given temperature). What you need is calculate the heat transfer, which depends on the effective area and the radiation coefficient.

 

[buildafriend]

This is not how it works. Using the specific heat of the material will just give a time-constant (how long it takes for the heatsink reaches a given temperature). What you need is calculate the heat transfer, which depends on the effective area and the radiation coefficient.

Ah thanks! I'm not as versed in thermodynamics as I am in electronics troubleshooting. That's helpful advice

 

[buildafriend]

pinout data

 

[buildafriend]

Experimented with the +17VDC rail
It was run under load with a 4.1A 27 Ohm antique rheostat as to supply 4A to the load.
Used an 8"L x 2" W x 0.5" T aluminum bar as a poor mans large heat sink, it gets warm, but I do not have a thermometer to test with. regardless, it seems to work okay.
Under load the transformer sags more than the regulator dropout.
Unloaded xfrmr secondaries are +17AC ( transformer says the tap is for 15VAC, but they are almost always a few volts above the rating )
17x1.41=24VDC post rectifier
When the circuit is loaded with a 4 ohm dummy load this sags down to 18VDC post rectifier pre regulator, then giving me 2V of dropout on the regulator when the output is set to +16VDC. That's not enough for +17VDC
16VDC would be okay, but maybe I'll up the transformer voltage rating to give me a little more pressure? Not sure yet. moving along.. 
There seems to be about  0.5V change due to heat changes. with a fan on it it runs higher VDC, without a fan on it it runs lower VDC