Quote from: J M Fahey on May 13, 2011, 05:30:24 AM
That Randall amp needs those .27/.62 ohm resistors as shown in the schematic.
It was an old trick (also used by others such as Acoustic) to even the current sharing.
You have a length problem here.
Those 49mm long ones are way too much.
In 22 mm/5W:
1) you can use a 5W .27 ohm without a problem because it dissipates less than one half what the .62 ohm does.
Why did they use a 5W then? because buying a smaller one costs practically the same and simplifies bulk ordering (as from Ohmite)
2) substitute each .62 ohm with two .33 ohm ones in series.
Mount them this way:
In your hand, put two of them vertical.
Each of them will have an upper lead and a lower one.
Twist upper leads together, solder and clip them.
Now you have a nice vertical .66 ohm, 10W resistor.
Open it slightly into an inverted "V" shape and insert free legs into the PCB.
Done.
Sounds like a plan. But for the 0.60 ohm 7 watt power resistors, what about just getting vertical mount power resistors that are in stock and available in either 0.47 or 0.68 ohm and both are 7 watts like the schematic calls for? Are these too far from the specs in either direction?
such as these:
http://www.mouser.com/catalog/specsheets/XC-600039.pdf