chinacave
Its Like a Jungle Sometimes; It makes me Wonder
All -
I debated whether to post this in 'Tubes' or the Marantz-specific section - but ended up here. Hopefully some of the folks over in the Marantz section will read this.....
I have been asked by a pal to fully restore a classic system for him - I am 99% finished with his 3 McIntosh MC-40's and am turning to two 7C and a single Marantz Consolette (Mono) pre-amp.
Obviously these are highly regarded, super-quality engineered and constructed units, He was for many years a pro audio consultant and supplier to NYC and North East recording and mastering studios, and uses a 3-chanel system now to listen to original master recordings.
I am NOT an experienced or qualified tech, but I am careful and deliberate, and have rebuilt a few monbloc amps and pre-amps. He does not want collector-status restorations - he wants reliable use and good / great performance from these units. One of the 7C's seems to have been under the knife before, with several cuts in one of the ground buses and a broken tape selector switch (more on this in a later post) The Consolette has been home to some critters in the past (since evicted), so these are not super-pristine collector units to begin with...
So I'd appeal to the AK reader-ship for experience and advice, especially any who have done something similar to the same or similar units.
My starting point is the VERY detailed restoration / update article by Walt Jung and Chuck Hollander in the 1/1981 'Audio Amateur' titled " Modifying the Marantz 7C / A classic preamp gets a modern overhaul" [Are these guys still reachable? I haven't thought of that till right now..] I have a copy, not sure if fair use would allow me to scan and post it, it does not seem to be posted on the 'net that I can find....
The article has a detailed discussion of parts quality and their effects, and notes more / better regulation of the power and filament supplies, but mostly follows the original circuit, using better grade than available in the 1960's of the same value. I believe this was one of the first articles in the 'POOGE' series, a term coined to mean "Progressive Optimization of Generic Equipment" -I assume that between 1981 and 2013 there might be better STILL components to consider?
- Has anyone here restored either a 7C or a Consolette? What parts did you choose, which, if any, did you keep from the original unit (I just read that the 'bumblebee' caps in the 7C might have been specially specified or sourced Mylar units less prone to failure or leakage that the more common paper type(?)
- The article recommends metal film resistors, specifically RD60D and RN70D made then by Corning I think. So far I have only found the 1/2W version of these to be available, along with the CFP Dale series at Mouser. But they do not seem to be available in many of the values I will need. I want to do this right and not just use any old resistor type, but also don't need or want to spend $5.00 for each one...(it would be a plus to have them all from the same series so they look the same, for visual reasons, but not strictly necessary...) ANY pointers / advice / direction / reasonable screeds - rants would be welcome!
- The parts list in the service manual notes most resistors as Carbon Comp., with some noted as 'deposited carbon' Were the later ones a special type at the time, and should I use something different or specific at those locations? I can post both the schematic and the parts list later - They seem to be at cathode and plate locations for the 12AX7's
-Should I even ask about capacitors? In the Mac amps I used Solens, reasonable cost, reasonable size, test and sound fine in my feeble experience and looking at how freaking PACKED the tone control networks are on these puppies, smaller size will be a distinct advantage. (I am almost done with restoring a Sprauge TO5 cap tester, now I have to be sure I am using it correctly so I might actually rely on leakage measurements to test the existing possibly super-spec Mylar caps. )
-The article goes into more depth than I currently can understand about correct and balanced RIAA compensation, I do not have the test gear or the knowledge to test this, so I will just carefully match the L-R component values and call it good - (I try and do this in any case on all the parts) -
-They also suggest upping the wattage rating an parts (IE if schematic calls for 1/2 watt, use a 1 watt unit) for reliability as well as sonics / stability - Good plan?
As always, and like many here, I really appreciate and value the pointers, help, advice and good cheer in this here forum.
I debated whether to post this in 'Tubes' or the Marantz-specific section - but ended up here. Hopefully some of the folks over in the Marantz section will read this.....
I have been asked by a pal to fully restore a classic system for him - I am 99% finished with his 3 McIntosh MC-40's and am turning to two 7C and a single Marantz Consolette (Mono) pre-amp.
Obviously these are highly regarded, super-quality engineered and constructed units, He was for many years a pro audio consultant and supplier to NYC and North East recording and mastering studios, and uses a 3-chanel system now to listen to original master recordings.
I am NOT an experienced or qualified tech, but I am careful and deliberate, and have rebuilt a few monbloc amps and pre-amps. He does not want collector-status restorations - he wants reliable use and good / great performance from these units. One of the 7C's seems to have been under the knife before, with several cuts in one of the ground buses and a broken tape selector switch (more on this in a later post) The Consolette has been home to some critters in the past (since evicted), so these are not super-pristine collector units to begin with...
So I'd appeal to the AK reader-ship for experience and advice, especially any who have done something similar to the same or similar units.
My starting point is the VERY detailed restoration / update article by Walt Jung and Chuck Hollander in the 1/1981 'Audio Amateur' titled " Modifying the Marantz 7C / A classic preamp gets a modern overhaul" [Are these guys still reachable? I haven't thought of that till right now..] I have a copy, not sure if fair use would allow me to scan and post it, it does not seem to be posted on the 'net that I can find....
The article has a detailed discussion of parts quality and their effects, and notes more / better regulation of the power and filament supplies, but mostly follows the original circuit, using better grade than available in the 1960's of the same value. I believe this was one of the first articles in the 'POOGE' series, a term coined to mean "Progressive Optimization of Generic Equipment" -I assume that between 1981 and 2013 there might be better STILL components to consider?
- Has anyone here restored either a 7C or a Consolette? What parts did you choose, which, if any, did you keep from the original unit (I just read that the 'bumblebee' caps in the 7C might have been specially specified or sourced Mylar units less prone to failure or leakage that the more common paper type(?)
- The article recommends metal film resistors, specifically RD60D and RN70D made then by Corning I think. So far I have only found the 1/2W version of these to be available, along with the CFP Dale series at Mouser. But they do not seem to be available in many of the values I will need. I want to do this right and not just use any old resistor type, but also don't need or want to spend $5.00 for each one...(it would be a plus to have them all from the same series so they look the same, for visual reasons, but not strictly necessary...) ANY pointers / advice / direction / reasonable screeds - rants would be welcome!
- The parts list in the service manual notes most resistors as Carbon Comp., with some noted as 'deposited carbon' Were the later ones a special type at the time, and should I use something different or specific at those locations? I can post both the schematic and the parts list later - They seem to be at cathode and plate locations for the 12AX7's
-Should I even ask about capacitors? In the Mac amps I used Solens, reasonable cost, reasonable size, test and sound fine in my feeble experience and looking at how freaking PACKED the tone control networks are on these puppies, smaller size will be a distinct advantage. (I am almost done with restoring a Sprauge TO5 cap tester, now I have to be sure I am using it correctly so I might actually rely on leakage measurements to test the existing possibly super-spec Mylar caps. )
-The article goes into more depth than I currently can understand about correct and balanced RIAA compensation, I do not have the test gear or the knowledge to test this, so I will just carefully match the L-R component values and call it good - (I try and do this in any case on all the parts) -
-They also suggest upping the wattage rating an parts (IE if schematic calls for 1/2 watt, use a 1 watt unit) for reliability as well as sonics / stability - Good plan?
As always, and like many here, I really appreciate and value the pointers, help, advice and good cheer in this here forum.
Last edited:
