Help with gain problem with Cornet

RogueAngel · « **on:** 21 Oct 2003, 03:19 am »

I've built the octal version of the cornet. All was fine after I solved the final hum problem.

After about an hour of listening, the right channel started losing gain compared to the left channel. It's now about 10 to 12 db difference between channels.

After checking for differences between channels I've found the the voltage at R11 is the only appreciable difference between the two channels. The right channel is reading about 70 volts the input to R11 and the left channel is reading about double that. All the other voltages are close.

Is this an indication that V3 has a problem on one side?

The quality of the sound from both channels is great, but the gain difference is very much bothering me.

Any other ideas about what could be wrong?

hagtech · « **Reply #1 on:** 21 Oct 2003, 05:39 am »

I'd guess you have a problem with V2. Check all your resistor values. Check voltages at plates of V1 and V2. Should all be around 150V. The cathode follower outputs should be a few volts above this.

Lemme know what you find.

jh

RogueAngel · « **Reply #2 on:** 21 Oct 2003, 12:21 pm »

Problem fixed, bad joint at the V3 cathode. It read 0 between the PCB and the socket on the DMM, but I resoldered it and the voltage came up to 154. The channels about equal now.