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In Reply to: RE: I had a nice talk with Doc Hoyer. posted by Tre' on February 25, 2015 at 13:24:30
I asked him that mainly because of the filter cap rating and he said you want to be sure you have a 500v rated filter cap..The other thing I was concerned with was the rating of the OPT and he said he has never had any issues with destroying either the power trafo or OPT...
Of course if a lot of people do this and he's BSing,maybe he figured he will get a ton of Mac trafos to rebuild ROFL.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
Edits: 02/25/15Follow Ups:
Damage aside, wouldn't all the operating points (for all the stages) be changed and the MC30 wouldn't be a MC30 anymore?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
It is a curious thing, as the plate voltages are going to pop up, but not the bias supply voltage. Since the output stage relies on reasonably predictable current being drawn through the bias supply, I would be kinda wary of these changes.
Good point
You may have to adjust R30 but that is very easy to do because Mac amps work on the bias tracking which goes up or down with the plate B+ on the tubes.I set all my Mac amps up with a variac and a voltmeter..Take an Mc60.After a rebuild and changing the old selenium out to a silicon you just run your variac up until you have 435vdc on the plate and you want minus 47 on G1..If if's higher than that,you just change the resistor feeding the C minus voltage until you get minus 47v.It may be minus 45 but I go for minus 47.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
Edits: 02/25/15
You would still have the same circuitry of course and even tho operating voltages would change,it would still be relative to the existing components that are already in the circuit so the sound may change for the better even.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
You have only altered the voltages on the other side of r28. The half wave rectifier generated voltages would be the same. Everything is all out of whack. Doc needs a hearing test.
Maybe so but lets try it anyway.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
Check this out
Edits: 02/25/15
Did you look at the plate voltage on the 6L6s? It's 435v on there and on the Mc60s on the 6550s it's only 430v. They made so many different versions of the Mc30s and Mc60s and it can drive you nuts with the changes.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
~!
The Mind has No Firewall~ U.S. Army War College.
Sure nuf Ken.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
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