03-29-2013, 08:46 PM
I know, I was an idiot on the last problem. That mute switch was giving me problems from the get go. I mentioned earlier in the post that after a while running the volume would drop. Let it cool down and great for a while, this was before the muting fiasco. Well it is now fixed at that lower volume and a little distorted. Voltage measurements are all over and low. The following were taken at 105V AC, I failed to check my variac setting. I did afterwards move it up to 110 but didn't change the values given below by more than a few volts.
Measurements were taken to ground with my trusty VOM and a few confirmed with a fluke.
Some highlights:
6L6s Plates running about 240V should be 290V
G2 running at 250V on both tubes should be 300V.
6Q7 First audio Plate running 100V should be 70V Double checked and with new 110V AC reads 105V. The only high voltage.
6J5 Driver audio Plate running 180V should be 260V
6K7s 1st and 2nd IF Plates running 170V should be 250V
G2 running at 73V should be 90V
6A8 Osc Plate running 130V should be 250V
Grids 3/5 running 75V should be 90V
Grid 2 running 125V should be 225V
Cathode to ground 2V no spec.
6A8 Mixer Plate running 200V should be 250V
Grids 3/5 running 75V should be 90V (corrected previous value)
Grid 2 running 75V should be 90V (corrected previous value)
6U7 RF amp Plate running 210V should be 250
G2 running 75V should be 90V
I should note that on powering up and measuring with the meter in place the first voltage to hit is well in excess of 300V, closer to 400V but then drops to the readings indicated. The rectifier tests excellent.
Any ideas gang? Schematic: http://www.nostalgiaair.org/PagesByModel...013235.pdf
Jerry
Measurements were taken to ground with my trusty VOM and a few confirmed with a fluke.
Some highlights:
6L6s Plates running about 240V should be 290V
G2 running at 250V on both tubes should be 300V.
6Q7 First audio Plate running 100V should be 70V Double checked and with new 110V AC reads 105V. The only high voltage.
6J5 Driver audio Plate running 180V should be 260V
6K7s 1st and 2nd IF Plates running 170V should be 250V
G2 running at 73V should be 90V
6A8 Osc Plate running 130V should be 250V
Grids 3/5 running 75V should be 90V
Grid 2 running 125V should be 225V
Cathode to ground 2V no spec.
6A8 Mixer Plate running 200V should be 250V
Grids 3/5 running 75V should be 90V (corrected previous value)
Grid 2 running 75V should be 90V (corrected previous value)
6U7 RF amp Plate running 210V should be 250
G2 running 75V should be 90V
I should note that on powering up and measuring with the meter in place the first voltage to hit is well in excess of 300V, closer to 400V but then drops to the readings indicated. The rectifier tests excellent.
Any ideas gang? Schematic: http://www.nostalgiaair.org/PagesByModel...013235.pdf
Jerry
A friend in need is a pest! Bill Slee ca 1970.