C47 or C34V, with MC452?

[damacman]

I had an old Yamaha TOTL CDP that had difficulty reading certain tracks on discs. I did what one is never supposed to do - turned up the gain on the laser ... ever so slightly. As I performed this modification with nothing more than a screwdriver and my calibrated wrist (I gave it about 1/64th of a turn), I accepted that the laser could fail any hour or day thereafter.

That was 15yrs ago and the machine is still going ... not that I'm condoning such lunacy here ...

 

[Couldbfishin]

I did what one is never supposed to do - turned up the gain on the laser ... ever so slightly. As I performed this modification with nothing more than a screwdriver and my calibrated wrist (I gave it about 1/64th of a turn), I accepted that the laser could fail any hour or day thereafter.

That was 15yrs ago and the machine is still going ... not that I'm condoning such lunacy here ...[/QUOTE]

Damacman- and I thought I didn't have the right tools..funny. You have the touch.

Couldbfishin

 

[damacman]

I did what one is never supposed to do - turned up the gain on the laser ... ever so slightly. As I performed this modification with nothing more than a screwdriver and my calibrated wrist (I gave it about 1/64th of a turn), I accepted that the laser could fail any hour or day thereafter.

That was 15yrs ago and the machine is still going ... not that I'm condoning such lunacy here ...

Damacman- and I thought I didn't have the right tools..funny. You have the touch.

Couldbfishin[/QUOTE]
I actually do have a pretty nice Kenwood o-scope, but on that day it was like - well, it ain't working anyway...

 

[77Bronco]

I’ll chime in here to say...I’ve recently had Chris (c_dk) restore a number of pieces for me recently. I’m super pleased with everything so far that he has done. But the one night/day difference piece was the c33 he did.

There was a bad switch, but along with that he returned a pretty good bag of electronics along with the broken parts.

He’d have to chime is as to exactly what he did....but I am beyond happy with the results.

So....here is to hoping your 34v will come back and garner some praise.

 

[c_dk]

I prefer to proceed cautiously about a recap solving all ills.....Even though on most all occasions positve results are experienced after a recap has been done.

You first have to bench test. Solve any semiconductor or mechanical issues (including switch cleaning) if there and then a recap cap be done to improve the SQ.

Power supply cap issues and such should turn up during the bench stress test, same with dirty switches and controls. Yes many times a physical examination will turn up a leaking cap but often all will look well until the unit is stressed and no longer will output the correct signal.

 

[Couldbfishin]

Chris (c_dk), I didn't realize you were offering to rebuild my C34. I would have considered it as you do sound like you would give it the personal touch and not rush through the rebuild. You also sound experienced at the C33/C34 rebuild.

I am calling the repair a re-cap, I am not suggesting that is all that AC will do. For what I know they will do a thorough bench test before they do any repairs. I don't know one way or the other. But I can ask next week about the time my C34 arrives there. I do suspect they wouldn't spend as much time on it as you would, as they are about turn-over as most businesses are. They do have a good reputation, so I am not concerned that they won't do a good job.

What all should a thorough bench test entail? I ask for my education, but others following this thread would benefit from it also.

Thanks Chris.
Couldbfishin- Gerry (Gary)
Houston, TX

 

[Couldbfishin]

I don't think I posted a photo of the C34, CR-7 and MCD 7000 in this thread, so I thought I would do it now.

Thanks again for everyone's contributions.

 

[c_dk]

Looking at the position of the variable loudness compensation control at 12:00 I would expect the system to be very bass heavy at any volume control level over 9:00.

Plus with the two bass controls turned up.......those passive radiators should be really flapping around. Typical passive radiators are tuned to have a bass band pass at right about the frequencies you are boosting.

Hope that very non neutral setting was not used when you were making the SQ evaluation.

 

[kevzep]

Chris is right, you shouldn't be needing to do that with the loudness and EQ to make things sound normal,. and certainly not to assess the SQ of anything in the system.....
Was this the case, or were you just having a bit of fun......?

 

[Couldbfishin]

These photos were taken when I first hooked the C34 up and was using the Dynaco ST70 as a test amp. I think at the time I was using KLH 5's or JBL 110s as the speakers. I usually start a function test with every control in the flat position and then make adjustments to test the function of pots, switches, etc. These same photos were later used when I posted the initial thread asking for advice on an amp to buy, to use with the C34 and the MCD 7000. I had not purchased the MC452 yet. When I tested the MC452, I put all controls in the flat position and tested with the JBL150s. Later, when the C34 was back upstairs on my work table I tested it again in neutral or flat positions with the the MC40s with KLH 5's and 20's.

So, no, the controls were not at this setting when I tested the C34 with the MC452 or with the MC40 mono-blocks. The controls were all at the neutral or flat positions for those tests.

Good eyes though guys. Thanks for watching out for me.

 

[Couldbfishin]

Here is a photo of the two MC40 mono-blocks I used to do the most recent tests with the C34. I had disconnected the C20 preamp and wired the C34 to test it again without taking it downstairs and hooking it back up to the MC452. I thought if it had similar issues with the MC40s as with the MC452, then it was a confirmation that the problem was with the C34 and not with the speaker selector box and a second pair of speakers. The C34 still sounded like it had no high or low frequencies and not clear but murky. Not technical terms I know, but it just didn't sound good. On that basis, I didn't bother to hook up to the MC452 again. I decided to send it off for repair.

I am also attaching a photo of the C34 and MCD 7000 taken during the previous test using the Dynaco ST-70 amp. Note the dial settings are the same as in the picture you were looking at earlier. I was rotating the dials and pushing the buttons, to see if they were functioning and if they needed cleaning.

Now that I think about it, I did notice the C34 was sounding bad back then, and mentioned it in a thread and someone commented it might be the ST-70. But since then I have heard the same issues using the C34 with the MC452 and the two MC40 mono-blocks. So, that is three separate amps, or sets of amps, hooked to different speakers, with only the C34 as a constant, and in all cases it didn't sound 'right'.