Replacing Resistors in Mc240

drillher

Super Member
I plan to replace some or all of the resistors in my Mc240.What is the best way to desolder the old resistors from the solder lugs without damaging the lugs?Should I clip the old lead and suck up old solder and twist new lead over the old and re-solder,or should I remove all of the old resistor leads before crimping the new lead to the lug and resoldering?Thanks,
Dave
 
The Hakko 808 is excellent at removing as much solder first before getting into the mechanics of the mounting turrets and wire wraps. Here's an AK thread on this desoldering tool.

The turrets can be broken so it pays to use as little force as possible in removing the old wires. Clip the old resistor out first, then remove as much solder as possible. Then use a pair of pliers to slide off the loop of wire. Usually this involves the capacitor's wire from the other side as many of the resistors appear to have been mounted first before the capacitors were added - I'm guessing about that but that's what the sequence may have been.

Try not to put much pressure on the turrets. Preform the new resistor leads with loops first before mounting them. Also, for consistency, pay attention to the orientation of the color bands so they remain consistent with McIntosh build standards.

Cheers,

David
 
Thanks David.When I replaced the coupling caps a few years ago I clipped the old cap leads and sucked away as much old solder as possible and then twisted new cap lead over the the old leads.It will be some work to remove my coupling cap leads over the old cap leads and resistor leads.I will be careful...Jim McShane is going to supply me with the new resistors.
 
It will be some work to remove my coupling cap leads over the old cap leads and resistor leads.
That's why I replaced the resistors at the same time I replaced the coupling caps. Total outlay for the resistors (Vishay/Dale metal films from Mouser) was less than $10; so why not ?!?
Jim McShane is going to supply me with the new resistors.
Out of curiosity, what sort is he sending you ?
 
I will post here when I find out which type.In retrospect,replacing the caps and resistors together would be the way to go.I bought one of the sprong loaded solder suckers.Is the desoldering tool way easier?
 
Out of curiosity: What is your goal here? Do you want more modern sound from your mac, or are you just trying to replace out of spec resistors?
 
I'm trying to replace the out of spec.resistors.I upgraded the bias supply and the main power suppy had been done a few years before I bought the amp.I replaced the bumblebee coupling caps when I did the bias suppy about 4 yrs.ago.I plan to replace the Black Beauties with K40 caps when I go back in.I have read that they are usually good,but can become leaky.The amp.sounds nice as it is now,except I notice more detail in the left channel,which propms me to go in and measure voltages and change the B.B. coupling caps.
 
The resistors from Jim McShane are a mixture of Premium carbon film,carbon comp.,premium metal film,metal film and wire wound.The wire wounds are the 12k 3 watt resistors.Jim is great to deal with.
 
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