chinacave
Its Like a Jungle Sometimes; It makes me Wonder
A good friend of mine has entrusted me to refurbish some of his audio gear over the winter. He was a distributor / importer of pro audio / studio gear from the 60's -'00's & has a wonderful set-up. Has not been really used for many years, hence my labor input.
He has already been most generous in letting me help him clear out some of his spare units and speakers.
I need all of your help and knowledge here!
First up are three Mac MC-40's
They all work, and only one shows any signs of even a hint of flaky behavior, even with the tubes they were put away with. (Unit #01397 has -156v dc on Pin 5 of V6 - all the other voltages are withing 10% or so of specified...)
I will be doing a complete re-build, and would like to solicit opinions. experience, rants etc on how best to approach this, and what your experiences has been with these or similar amps.
I understand from a post here that the large black Sprauge, I think,.22uf coupling caps should stay, but that all the stripped ones should be replaced.
A few random questions for the Gurus, Sensei and wizards here, in no particular order.
-Should I wire in a grounded 3-wire power cord or leave the 2-wire configuration (I plan to use a new, non-crusty one)
-Should I replace the power supply caps with the same value, or increase in size, and if so, all positions or only after C16A?
- What rectifiers does everyone suggest using?
- On two of the three amps - there are yellow apparent capacitors that seem wired in parallel with C8 & C9, yet they are not on the schematic, and have no markings - will detach one and measure - weird...
-I'd like to replace the press-fit RC input Jack, any advice on how to remove the sucker?
- Inrush limiter on the input line?
-Also the sockets - do you suggest keeping existing, cleaning and re-tensioning, or drill the rivets out and replace with new?
-The owner would like me to get a base-line set of tubes fro one amp so as to have a consistent set with which to compare the re-worked units - short of grabbing something quick from Antique Electronics, is there a preferred set / brand for each position?
- I have the owner's and service manual, but cannot find a Sams for this - it seems that there is none (checked on Sams website..) what would really be helpful if anyone has annotated it already is a labeled photo of both sides of the tagboard - and as one of the units seems to have been cooked with heat, should I get a replacement tagboard of the same size (assuming I can source one?
-ANnnnnnd the obligatory question about what are the 'right capacitors and resistors to use. I assume you all have done some / much experimenting in this area - I / we do not want to break the bank with silver-foil in extra-virgin olive oil caps rolled by Druids under a full moon, but would like to use better than 716P orange drops......And should I *really* keep the existing caps at C8 & C9...... Metal film resistors or carbon comp?
Anything else I am missing?
Photos & progress reports to follow......
Some of the other gear after the Macs are two Marantz 7C and an 8B... Threads on those to follow when I get to them....
Thanks!
CC
He has already been most generous in letting me help him clear out some of his spare units and speakers.
I need all of your help and knowledge here!
First up are three Mac MC-40's
They all work, and only one shows any signs of even a hint of flaky behavior, even with the tubes they were put away with. (Unit #01397 has -156v dc on Pin 5 of V6 - all the other voltages are withing 10% or so of specified...)
I will be doing a complete re-build, and would like to solicit opinions. experience, rants etc on how best to approach this, and what your experiences has been with these or similar amps.
I understand from a post here that the large black Sprauge, I think,.22uf coupling caps should stay, but that all the stripped ones should be replaced.
A few random questions for the Gurus, Sensei and wizards here, in no particular order.
-Should I wire in a grounded 3-wire power cord or leave the 2-wire configuration (I plan to use a new, non-crusty one)
-Should I replace the power supply caps with the same value, or increase in size, and if so, all positions or only after C16A?
- What rectifiers does everyone suggest using?
- On two of the three amps - there are yellow apparent capacitors that seem wired in parallel with C8 & C9, yet they are not on the schematic, and have no markings - will detach one and measure - weird...
-I'd like to replace the press-fit RC input Jack, any advice on how to remove the sucker?
- Inrush limiter on the input line?
-Also the sockets - do you suggest keeping existing, cleaning and re-tensioning, or drill the rivets out and replace with new?
-The owner would like me to get a base-line set of tubes fro one amp so as to have a consistent set with which to compare the re-worked units - short of grabbing something quick from Antique Electronics, is there a preferred set / brand for each position?
- I have the owner's and service manual, but cannot find a Sams for this - it seems that there is none (checked on Sams website..) what would really be helpful if anyone has annotated it already is a labeled photo of both sides of the tagboard - and as one of the units seems to have been cooked with heat, should I get a replacement tagboard of the same size (assuming I can source one?
-ANnnnnnd the obligatory question about what are the 'right capacitors and resistors to use. I assume you all have done some / much experimenting in this area - I / we do not want to break the bank with silver-foil in extra-virgin olive oil caps rolled by Druids under a full moon, but would like to use better than 716P orange drops......And should I *really* keep the existing caps at C8 & C9...... Metal film resistors or carbon comp?
Anything else I am missing?
Photos & progress reports to follow......
Some of the other gear after the Macs are two Marantz 7C and an 8B... Threads on those to follow when I get to them....
Thanks!
CC
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