Car Audio Classifieds! banner

Resistor bank and test board build log 56K Nightmare

1K views 14 replies 9 participants last post by  Rolex 
#1 ·
I've been working on a resistor bank for testing some early 1990's amps and in the process decided to make a test board with some equipment I wasn't using.

here's where I've been and where I am:

Yes, thats a Power Series heat sink


using plexi as my "board"


Eight 100watt 8ohm resistors.
laying down placement right now



board out lines laid:




now for the holes:


mock it up;










 
See less See more
12
#3 ·
At this point I didnt want to lug around the bank from place to place and due to the fact that resistors work by transforming their input into HEAT I figured some cooling would be needed since the Fosgate heatsink would not be dissipating it since I used plexi as the board. And a few monitoring gauges would be nice, so.....













 
#8 ·
Couldn't the plexi be flipped over and heat conducting paste be used between the resistors and the RF heatsink? Or is the inside of the case not smooth enough?
Or am I looking at this wrong?
 
#9 ·
Thanks for the interest guys.

To answer a few queistions:

What does this do / what is it for?

- I'm not sure if CACO has the same issues as other forums where "clamping" an amp for power output is always scrutinized, but....
To be properly done using a VOM and Amp clamp then you have to use a resitor to load the amp down and not a speaker. This is because since a speaker is reactive the load presented to the amp changes as the speaker moves. The resistors present a constant load to the amp thus the measurement is accurate. Simply put, if you "clamp" an amp with speaker on it the power measurement you get is not accurate, PERIOD.

What value resistors are you using?

I used eight 100 watt 8 ohm resistors with a 5% tolerance.
I will be able to test the following.

8 channel mode
-- 8 x 100 watts @ 8 ohms

4 channel mode
-- 4 x 200 watts @ 4 ohms
-- 4 x 200 watts @ 16 ohms

2 channel mode
-- 2 x 400 watts @ 2 ohms
-- 2 x 400 watts @ 8 ohms

1 channel mode
-- 1 x 800 watts @ 1 ohms
-- 1 x 800 watts @ 4 ohms

Could you flip the plexi, heat issues?

When I started the build I underestimated the possible heat issues that's why I used the plexi. The resitors are too tall to flip the board so that was not an option. Attaching to the heat sing would mean drilling and tapping it, not the route I wanted to go. What I should have done was used a piece metal as the board in order to draw the heat away from the resistors and transfer to the sink. The plexi board turned out so good I didnt wantto mess with it and found another way to cool it. Pics to come.

FYI, as you look at the board from top to bottom the gauges are Cyberdyne Volt, Volt, Temp and teh last is an amperage gauge.

This is a low amp board designed for my old school gear.

here are the rest of teh tools needed to properly "clamp"

 
#10 ·
once mounted the resistor bank will feed these studs so that the amps can then be connected via speaker wire:



Each pair of studs represents both sides of each resistor. Bridging is accomplished by the straps as seen here:



As shown here you know have 4 channels of 200 watts by 4 ohms.

And here is the fan that will be incorporated to cool the system.




this brings us current to where I stand on the project. More pics as progress is made. :)
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top