Hi Chris,
No, they weren't anything to do with supply rail sensing as far as I could see. I could imagine them stopping the supply rail sensing from working properly though!
On page 41 of the the service manual (actually for the M-1.5 but same schematic) you can see the -12V regulator at the bottom of the page. The resistors in question are R58,R60. I've just noticed that in an earlier version of the schematic only one of the resistors are fitted.
I was hesitant about leaving them disconnected but after discussing it with another engineer as well, I can't see that they were serving any useful purpose.
No, they weren't anything to do with supply rail sensing as far as I could see. I could imagine them stopping the supply rail sensing from working properly though!
On page 41 of the the service manual (actually for the M-1.5 but same schematic) you can see the -12V regulator at the bottom of the page. The resistors in question are R58,R60. I've just noticed that in an earlier version of the schematic only one of the resistors are fitted.
I was hesitant about leaving them disconnected but after discussing it with another engineer as well, I can't see that they were serving any useful purpose.
Hi Chris,
Thanks for the link.
R58 looks like it's there to provide a load for the regulator, and to possibly help discharge that supply when power is turned off. It is a bizarre thing to see from my point of view. R60 and R58 together seem to work by spreading the load current across the other supplies.
Thinking about how Carver designs work, I find it dangerous to change many things. These may have a role in discharging those rails so that the voltage control will track if the load is intermittent. In any event, I know those engineers well enough to tell you that everything they do had a purpose.
I'm thinking that even though removing these eliminated a thump, there is something else going on and that this is not a cure, just a temporary "work around". If it were me, I'd put these back using new parts and go find the real problem.
-Chris
Thanks for the link.
R58 looks like it's there to provide a load for the regulator, and to possibly help discharge that supply when power is turned off. It is a bizarre thing to see from my point of view. R60 and R58 together seem to work by spreading the load current across the other supplies.
Thinking about how Carver designs work, I find it dangerous to change many things. These may have a role in discharging those rails so that the voltage control will track if the load is intermittent. In any event, I know those engineers well enough to tell you that everything they do had a purpose.
I'm thinking that even though removing these eliminated a thump, there is something else going on and that this is not a cure, just a temporary "work around". If it were me, I'd put these back using new parts and go find the real problem.
-Chris
Hi Chris,
Thanks for your thoughts. My thinking on it is that they were put there as a 'workaround' which now seems to be unnecessary. If those resistors were going to ground or even to the closest rail I could perhaps understand them. From -12V to -125V is just bizarre. Even more so that there isn't anything similar on the positive side. I'm also looking at the resistor that bypasses the regulator and I don't get that either but I'm going to leave it alone as it's not causing any trouble!
Having monitored the rails, they actually collapse more evenly now than they did with them fitted.
Ultimately although you may not agree, I have decided to leave them without the resistors fitted as the amps seem to be happier that way. Time will tell if the decision comes back to bite me!
Now, if only I could solve the cross-conduction problem in my own amp design I'd be happy!
Chris
Thanks for your thoughts. My thinking on it is that they were put there as a 'workaround' which now seems to be unnecessary. If those resistors were going to ground or even to the closest rail I could perhaps understand them. From -12V to -125V is just bizarre. Even more so that there isn't anything similar on the positive side. I'm also looking at the resistor that bypasses the regulator and I don't get that either but I'm going to leave it alone as it's not causing any trouble!
Having monitored the rails, they actually collapse more evenly now than they did with them fitted.
Ultimately although you may not agree, I have decided to leave them without the resistors fitted as the amps seem to be happier that way. Time will tell if the decision comes back to bite me!
Now, if only I could solve the cross-conduction problem in my own amp design I'd be happy!
Chris
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