C41 Phono issue

[bobschneider]

I appear to be having an issue with the phono input on my C41. The basic problem is that I have to turn the volume control way up to get a decent sound level - like past 1 o'clock to get the same volume I get at 8 o'clock with my other sources. I also get a low hum on the phono input when I turn the volume up to this level, which I don't get on the other inputs with the volume control at the same level.

I'm sure I've got the phono/aux switch on the phono position, and the sound is decent when I do turn it way up - no noticeable distortion, and the RIAA eq is obviously in the loop. I'm using an MM cartridge, not MC (a Shure V15 IV, but I have the same problem with a Stanton), and the TT and arm worked fine with a MC cartridge on my other system, so I don't think the problem is there.

I'm guessing that something is blown in the phono circuit. (Perhaps a prior owner put a line level source on this input with the switch on Phono?) I can solder if someone can let me know what might be blown (first stage gain transistors?), or I'd bring it in to a good repair shop if need be. In Houston if possible (the west side would be best), since I'd rather not ship it, but I do have the original boxes if I have to.

Thanks in advance.

[f1 fan]

Bob....I've got a C41 and no issues playing vinyl which I play alot of everyday, when playing the Rega P25 with the Exact cartridge the volume is normal like my other sources and no hum issues.

Dave

[MC352]

Just for the heck of it, flip that aux/phono switch back and forth one more time ,and try it.

[bobschneider]

Originally Posted by MC352

Just for the heck of it, flip that aux/phono switch back and forth one more time ,and try it.

Ok, I tried it. No signal at all when the switch is on Aux - very low level but fairly clean signal when it's on Phono. I'm 99% sure there's something wrong with the Phono circuit in the preamp - any suggestions for a good repair place in Houston?

[MC352]

Well, it was worth a shot. I don't know about Houston, but Terry DeWick can help you out, I'm sure.

His link is at the bottom of the page.

[f1 fan]

Bob...I don't know about Houston. Steve George or Terry DeWick here in Tn can help you. Steve is in Nashville while Terry in Knoxville. Steve's # is 615-451-4168, Terry can be located at the bottom of of this page. I'm sure Houston or Dallas has some repair centers. Go to the McIntosh home page for the nearest dealer.

Dave

[bobschneider]

Thanks again, guys. I'll go to Terry if I can't find someone local, or fix it myself.

I haven't been able to find a service manual or schematic for the C41, but I did find one for the MA6500, which is supposed to be a simplified version of the C41 with a power amp on a single chassis. That schematic shows that the only active elements in the phono stage are a NE5534AN low noise single op amp in each channel. I have some of those around, so I may just swap the op amps out myself before sending it out to a pro.

[MC352]

You might try the Berners site, to see if they have a schematic.

Berner's Site

[jdandy]

I had a C40 for thirteen years. It had the same phono/aux combo input as the C41. That was the only thing I did not like about my C40.

[miner]

Bammel TV & repair in Houston (off of 1960) is a certified McIntosh repair facility. I have never used them.