Today's progress wiring things up. Bar the heater wiring, the EL34 sockets and the ECC83 sockets are completely wired up. I've got to make another small notch in the central support so the heater wiring can pass through avoiding close proximity to the rest of the wiring to the sockets. I've also got two slim pieces of MDF that I will use as side panels which ought to help brace things as well as provide a mounting point for the input socket and speaker outputs.
Mid way through the day.
Done for the day.
Mid way through the day.
An externally hosted image should be here but it was not working when we last tested it.
Done for the day.
An externally hosted image should be here but it was not working when we last tested it.
Side panels cut and fitted along with the input socket. Speaker output sockets will be fitted when they arrive tomorrow.
Heater wiring probably isn't the best as it's my first go at it and it is definitely quite difficult, especially with stranded wire. All that is left to sort now is the heater wiring to the input valve.
An externally hosted image should be here but it was not working when we last tested it.
Heater wiring probably isn't the best as it's my first go at it and it is definitely quite difficult, especially with stranded wire. All that is left to sort now is the heater wiring to the input valve.
An externally hosted image should be here but it was not working when we last tested it.
Daft question, should the feedback loop come from the 8ohm tap on the output transformer or the 16ohm tap? I'll be using the 8 ohm tap and the components in the feedback path are set to suit that which makes me think it should be the 8ohm tap but the documentation doesn't make that bit clear.
Thanks Alan. Very helpful. Just sorted the speaker output sockets now. Just need to wire them up and the heater to the EF86 and it's done. In it's current form at least.
All of the wiring is now complete. Decided that I'd used excessively thick cable to the heater on the ECC83 so I dropped down a size for the EF86 as it has fairly low current draw. 4mm banana terminals fitted and only the 8 ohm tap wired up. I'll tie off the 16 and 4 ohm taps.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Went through the whole thing today with my father and spotted only one mistake. Went from pin 6 on V3 to C11 and pin 6 on V4 to C10 which was backwards. I also decided to rewire the heaters on V2 and V3 as the gauge of wire was more than needed.
Re-ran the unloaded test this evening and checked the voltages, all fine with no issues. Then tested with the valves in place. B+ peaks at 496V which is a tad close to the 500V rating on C15 but it falls back to around 450V pretty quickly. Other voltages seemed fine, the valves glow seemed normal and the transformers remained cool but there was quick a lot of buzzing and my dummy load got very hot fairly quickly which was a tad worrying as there was no input connected. I didn't have enough test gear connected for me to feel comfortable leaving it run any longer at that stage. I've got the feeling that it may be oscillating. I will be testing it again tomorrow but with a lot more test gear connected including a scope across the output.
An externally hosted image should be here but it was not working when we last tested it.
Re-ran the unloaded test this evening and checked the voltages, all fine with no issues. Then tested with the valves in place. B+ peaks at 496V which is a tad close to the 500V rating on C15 but it falls back to around 450V pretty quickly. Other voltages seemed fine, the valves glow seemed normal and the transformers remained cool but there was quick a lot of buzzing and my dummy load got very hot fairly quickly which was a tad worrying as there was no input connected. I didn't have enough test gear connected for me to feel comfortable leaving it run any longer at that stage. I've got the feeling that it may be oscillating. I will be testing it again tomorrow but with a lot more test gear connected including a scope across the output.
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