[marchewd]

Hello everyone,
     I just noticed a problem with my Cornet2 tonight.  Everything has been fine for the last month or so since I completed the C2.  However, the output from the L channel is about double the output of the R channel now.  I still get a weak signal from the R channel (it is not completely dead).  I swapped the IC's from the turntable first (L to R and R to L), then tried every combination of swapping the cables from the TT to my Cinemags to the C2 and every combination still resulted in a low sound from the R channel, so it has to be something in the C2, since it was replicated with each cable swap.  Any clues what I should be looking for, or what it might be?

Thanks,
Dan

[Bill Epstein]

Measure the voltages at the points marked on the board, i.e., 150volts at R204, 354volts at R107, etc., compare them to the left and report back.

[mingles]

Try using different tubes to rule that out. If you swap the 12AX7's does the problem still exist?

[marchewd]

Thanks for the replies.  I haven't had time to pull the C2 out to test the voltage.  I swapped the 2 tubes and it made the R channel have a little bit more volume, but not much; so I do not think it is a tube issue.  I will post the voltages of the L and R side of the board hopefully tonight or tomorrow.

Dan

[ecir38]

If your voltages are good check that the pins for the tube sockets are OK. I lost the left channel on a amp once due to the pins not being tight on some cheap sockets. I used a small scratch all to bend them in some. The funny thing is I didn't have this problem with all the tubes I tried but tightening them fixed my problem for all tubes.

[marchewd]

Okay,
    I finally had a chance to check the voltages:

R107 (365v) is 357v
R219L (155v) is 165v and R219R is 169v
R212L (150v) is 148v and R212R is 151v
R211L (330v) is 327v and (300v) is 297v; R211R (330v) is 327v and (300v) is 298v
R204L (150v) is 147v and R204R is 154v
V200 is only 5.55v
V201 and V202 are only 5.56v

Hope this helps and hopefully someone can maybe decifer what is going on with my C2.

I am using a Brimar 5Z4G rectifier, RCA 5814a 12AU7, and a matched pair of New Sensor Mullard 12AX7's.

Thanks,
Dan

[tubesforever]

Just a couple of other things to try.  It could be an issue with a switch and not the board.

First the voltages all look fine although I will comment about the heater voltage below. 

Did you use the mono switch?  If so snap it back and forth a couple of times to make sure the wipers are engaged properly. 

Second flip the wiper that controls your preamps selection for the phono section and try another input on the preamp.  I had a preamp source switch that went bad and lost most of one channel's signal. 

Third, I like my heater voltage around 6.175 volts.  You might want to adjust the resistors to get that up just a bit.  You will pick up more bass response.  I think I am under .2 ohms from what the original part called for.  I might be a little less than that like -.3 to -.5 ohms.  I can double check mine if you would like.

Your issue sounds like either the tube fried on just one side....or a switch went south. 

[marchewd]

I figured it was a faulty tube(s) since the problem just started happening.  But, it was odd because the right signal level only came up a bit when I swapped the tubes around.  Sucks since the New Sensor tubes were brand new!!!!  Oh well.  I am on the road this weekend, so I cannot switch out the 12AX7 tubes until Sunday night.  I'll let you know if that helped.  I didn't put the mono switch in.  I will have to check out the resistors.  Which one would I decrease?  Could I just parallel another resistor to the one that needs changed?  If so, what value should I try?

Thanks again,
Dan

[WGH]

I will have to check out the resistors.  Which one would I decrease?  Could I just parallel another resistor to the one that needs changed?  If so, what value should I try?

Thanks again,
Dan

The calculations for finding the correct resistor value to bring your heater voltage to 6.3 V can be found here:
http://www.audiocircle.com/index.php?topic=41430.msg369374#msg369374
There is also a photo of parallel resistors in the same thread.

Wayne