Just acquired a C-31v CHEAP

[quartersaw]

This preamp is nearly identical to my C-35, visually. It does not have balanced outputs, or a digital volume display, and it sounds very smooth. It also did not come with a remote, but my C-35 remote works with it just fine. Looks to me like the C-35 might've been an upgrade of the same model.
Interestingly, it seems to have a much quieter noise floor at idle compared to my C-35, and C-39.The only caveat is that the left channel plays weaker than the right, which can be 'cured' with the balance control.
Any ideas about a fix for the volume?
Caps, maybe?
All feedback is appreciated!

 

[clinic-audio]

Hello
Do you have audio signal generator ?
Is it true with all inputs ?
Volume control is drived with a big IC . I don't think it is the gulty part and if it still available ...
I saw that you are in NY
Call RYAN at AC he will help you

 

[quartersaw]

Hello
Do you have audio signal generator ?
Is it true with all inputs ?
Volume control is drived with a big IC . I don't think it is the gulty part and if it still available ...
I saw that you are in NY
Call RYAN at AC he will help you

Just plugged the CD player into the AUX sockets, and it is much better.
Thanks, Patrice!

 

[c_dk]

There are two versions of the C31V. 1st generation used the Toshiba attenuator that drove some of us crazy with the noise, ticks, that accompanied the steps. This was the same attenuator as used in the CR7 and MAC4300. 2nd generation used the Alps motor driven volume control as was used in the C35 and C37 as well as many later units.

According to my schematic the ER series was the Toshiba chip version FH the Alps.

As for channel issues that will need some bench time to discover the cause.

I have done numerous A/B trials between recapped and non recapped c30,31,and 35s.....all parties even non owners have been extremely positive about the recapped units. Well worth the 4-5 hours of tech time after your channel is is solved.

 

[quartersaw]

There are two versions of the C31V. 1st generation used the Toshiba attenuator that drove some of us crazy with the noise, ticks, that accompanied the steps. This was the same attenuator as used in the CR7 and MAC4300. 2nd generation used the Alps motor driven volume control as was used in the C35 and C37 as well as many later units.

According to my schematic the ER series was the Toshiba chip version FH the Alps.

As for channel issues that will need some bench time to discover the cause.

I have done numerous A/B trials between recapped and non recapped c30,31,and 35s.....all parties even non owners have been extremely positive about the recapped units. Well worth the 4-5 hours of tech time after your channel is is solved.

I just can't get over the quiet noise floor. I'm happy with it as is!
The serial is ER1852, so it looks like the Toshiba attenuator.

 

[quartersaw]

There are two versions of the C31V. 1st generation used the Toshiba attenuator that drove some of us crazy with the noise, ticks, that accompanied the steps. This was the same attenuator as used in the CR7 and MAC4300. 2nd generation used the Alps motor driven volume control as was used in the C35 and C37 as well as many later units.

According to my schematic the ER series was the Toshiba chip version FH the Alps.

As for channel issues that will need some bench time to discover the cause.

I have done numerous A/B trials between recapped and non recapped c30,31,and 35s.....all parties even non owners have been extremely positive about the recapped units. Well worth the 4-5 hours of tech time after your channel is is solved.

My C-35 should be redone, but in the c35 service manual, the ratings for the electrolytic caps is not mentioned in the parts list, oddly enough.
This C31v just might have had some work done as it is absolutely dead quiet. On the other hand, the backup power supply looks like it needs service. The preamp does not 'remember' its previous settings. (The C-35 doesn't either)

 

[c_dk]

Sounds like both your units need some repair tech time followed by some restoration tech time. Remember there is a difference.

 

[quartersaw]

Sounds like both your units need some repair tech time followed by some restoration tech time. Remember there is a difference.

My repair work ends with caps, generally. W/O any real test equipment, diagnostics turns into a guessing game, and I've been wrong more than I've been right. As a suggestion, it would be fruitful for some of us who are so motivated, to know what a good, basic 'kit' would be for doing diagnostics, and repair. Perhaps, you could make some suggestions, if I may impose? I would like to 'increase my reach' in terms of what I am able to do from a maintenance standpoint with my older Mcintosh gear. It may turn out to be impractical, or even foolish, but it never hurts to ask...

 

[c_dk]

Let's see, a variac, ocsiliscope with the correct probes, a distortion analyser, at least 2 maybe 3 multimeters......and enough curiosity to stick to it.

There always is more but those are the basic basics.

As I type this I am watching the "Count" and his guys doing their thing with cars and bikes.

They are marketing restoring cars, they are not pounding metal to fix the latest fender bender. Restoration or tech work, similar but really different.

Today I had on my repair tech hat to take apart and repair a Dual 505 motor, get a Pioneer table to hold speed and dismantle a MA6700 to install new glass.

Then I put on my restore hat while listening to a a set of original Time Windows and wondering why they sounded so poor with a Hafler amp but great with a pair of 60 year old restored W5Ms. Now what to do with the Hafler?

Monday a restored MAC4100 will enter the mix. It does not end.

 

[BilboBaggins]

I've had some gear like that. The older speakers were much more efficient, so the hafler might just be one of those amps best for efficient speakers. A lot of Sansui gear I've had is like that to some degree. I avoid hooking Sansui gear to hungry speakers, although others don't seem to notice that.

 

[quartersaw]

Let's see, a variac, ocsiliscope with the correct probes, a distortion analyser, at least 2 maybe 3 multimeters......and enough curiosity to stick to it.

There always is more but those are the basic basics.

As I type this I am watching the "Count" and his guys doing their thing with cars and bikes.

They are marketing restoring cars, they are not pounding metal to fix the latest fender bender. Restoration or tech work, similar but really different.

Today I had on my repair tech hat to take apart and repair a Dual 505 motor, get a Pioneer table to hold speed and dismantle a MA6700 to install new glass.

Then I put on my restore hat while listening to a a set of original Time Windows and wondering why they sounded so poor with a Hafler amp but great with a pair of 60 year old restored W5Ms. Now what to do with the Hafler?

Monday a restored MAC4100 will enter the mix. It does not end.

Thanks for the information! I'll start pricing around to see if this is doable for me.

 

[damacman]

Personally, I gave up on that about 15 years ago. I found that the time it took me to conjure up all that I'd forgotten since high school electronics, put it to use to solve problems, etc. was just too great. And, if I wasn't doing it everyday then I forgot nearly as much as I remembered the next time a project came around. Regardless, I have no "inventory" so to speak of parts required to make general electronic repairs - other than a huge stash of bulbs and tubes.

I'll swap bulbs, replace glass, clean pots, do light electrical repairs, and do cosmetic restoration but the tough electrical troubleshooting - no thanks. Now, I just take it to Cornell Smith (The Audio Doctor - he's local to me). His rates are very fair, he's quite competent, and he has the parts in stock. What's not to like? I spent ten hours futzing around with an intermittent MR77 a few years ago before finally throwing in the towel. Cornell found the problem, repaired it with McIntosh replacement parts he had in stock, and aligned the tuner to spec in three hours. Bargain. It sounded sublime.

QS - you'd be money and time ahead investing the money you would in a bunch of test equipment (that takes years to know your way around btw) and put that same money towards finding a competent tech near you. Here at AK, if you read enough "re-cap" threads, you begin to wonder - did this unit actually meet spec after all these components were replaced blindly? Who actually verified that? That's what separates the technicians from parts replacers - the big picture.

OTOH, if you elected to enroll yourself in an electronics course at a local community college, read books on the topic, etc. then you could learn the trade and how to put the tools to work to help you solve the problems. But, it'll take you ten years at minimum to be considered competent. Nothing worth doing is ever easy.

Patrice, Chris, Cornell, EchoWars - you have my utmost respect.

 

[quartersaw]

Personally, I gave up on that about 15 years ago. I found that the time it took me to conjure up all that I'd forgotten since high school electronics, put it to use to solve problems, etc. was just too great. And, if I wasn't doing it everyday then I forgot nearly as much as I remembered the next time a project came around. Regardless, I have no "inventory" so to speak of parts required to make general electronic repairs - other than a huge stash of bulbs and tubes.

I'll swap bulbs, replace glass, clean pots, do light electrical repairs, and do cosmetic restoration but the tough electrical troubleshooting - no thanks. Now, I just take it to Cornell Smith (The Audio Doctor - he's local to me). His rates are very fair, he's quite competent, and he has the parts in stock. What's not to like? I spent ten hours futzing around with an intermittent MR77 a few years ago before finally throwing in the towel. Cornell found the problem, repaired it with McIntosh replacement parts he had in stock, and aligned the tuner to spec in three hours. Bargain. It sounded sublime.

QS - you'd be money and time ahead investing the money you would in a bunch of test equipment (that takes years to know your way around btw) and put that same money towards finding a competent tech near you. Here at AK, if you read enough "re-cap" threads, you begin to wonder - did this unit actually meet spec after all these components were replaced blindly? Who actually verified that? That's what separates the technicians from parts replacers - the big picture.

OTOH, if you elected to enroll yourself in an electronics course at a local community college, read books on the topic, etc. then you could learn the trade and how to put the tools to work to help you solve the problems. But, it'll take you ten years at minimum to be considered competent. Nothing worth doing is ever easy.

Patrice, Chris, Cornell, EchoWars - you have my utmost respect.

I agree, and the guys who do it for a living, forgot more than I will ever know, but there is that part of me that wants to give it a go, for better, or for worse.
I read books on vacuum tube electronics back in the '60's, but if you asked me about that topic today, I'd be hard pressed to give concrete answers.
My gut tells me that the potential investment in quality equipment will lead me to walk away, but I still have the curiosity to at least take a peek....

 

[c_dk]

I going get on a soapbox to point out it was McIntosh owners that expected, that demanded that McIntosh dealers provide exemplary service. It was the dealers, sometimes kicking and screaming who were bound by their McIntosh dealer agreements to honor that expectation.

Customer support both through word of mouth and their checkbook, along with a number of like minded manufacturers, allowed McIntosh and those few other suppliers to push forward the idea of quality service.

Obviously Terry and CJ need to be added to the list but I know there are dozens, maybe dozens of dozens of techs throughout AK that need local support and are not mentioned. I read throughout AK the complaints over and over about members local techs not making the grade.......would anybody make their grade?

It is my opinion that the reason Mac products are held in such high regard is based on those efforts decades ago to make it a special product line, the effort the early principles built into the company to grow that reputation.

If McIntosh owners are not going to demand that level of service today from their local dealers and techs, and yes the short sighted present management, the future value of their audio "investment" it is their own fault. McIntosh owners should demand more.

Who better to lead this rediscovery of our standard setting audio expectations than those who contribute to this forum.

 

[quartersaw]

I going get on a soapbox to point out it was McIntosh owners that expected, that demanded that McIntosh dealers provide exemplary service. It was the dealers, sometimes kicking and screaming who were bound by their McIntosh dealer agreements to honor that expectation.

Customer support both through word of mouth and their checkbook, along with a number of like minded manufacturers, allowed McIntosh and those few other suppliers to push forward the idea of quality service.

Obviously Terry and CJ need to be added to the list but I know there are dozens, maybe dozens of dozens of techs throughout AK that need local support and are not mentioned. I read throughout AK the complaints over and over about members local techs not making the grade.......would anybody make their grade?

It is my opinion that the reason Mac products are held in such high regard is based on those efforts decades ago to make it a special product line, the effort the early principles built into the company to grow that reputation.

If McIntosh owners are not going to demand that level of service today from their local dealers and techs, and yes the short sighted present management, the future value of their audio "investment" it is their own fault. McIntosh owners should demand more.

Who better to lead this rediscovery of our standard setting audio expectations than those who contribute to this forum.

Without the support of the membership within this forum, my ship would have sunk just off of the dock.