back after an amp free week.
Temporarily replaced the metal screws with plastic ones and continued to operate, relatively successfully, upside down.
I checked the voltages on a number of occasions and compared with spec voltages. Readings as follows:
pins 3,4,5 spec 13.5, 6.3ac, 6.3ac, my readings, approx 14v dc on all three pins on all valves, or if measured as ac, 30v ac.
pins 7,9 spec 370, 375, my readings, approx 350dc on all pins 7 and 9.
While measuring the voltage on pin 9 valve 2 the volume suddenly came back on the left channel. Problem solved, I thought, a loose connection between pin and socket, but after listening to music through the amp for the last three days ( a lot of old mono recordings) I noticed that the left channel was very quiet again.
Swapped speakers and inputs again, problem stayed in the left channel, tried checking for loose connection between pin 9 and socket but no change this time.
At this point my intention is to build - rebuild the two amps, the dynaco and the dynakit. I have a choice of 3 sets of pcbs:
1. original dynaco boards with new r5 as they were out of spec.
2. replica boards with surface traces like the original dynaco.
3. troublesome boards with an internal short between trace and chassis mounting screw(s)
Any advice on quiet left channel trouble shooting, discrepacy between spec and measured voltages on pins 4 and 5 and finally which boards to use in the build - rebuild?
The components for one build are obviously already on the problematic boards. They include ceramic disk capacitors in positions c1,c2,c6,c7. I assume this is not an issue as the original dynaco components in these positions were ceramic disks. Would that be right?
Thanks for reading and to anyone who takes the time to respond.