[TV MAN]

I did a full power up last night and - it works! Actually, pretty good! I was pleasantly surprised. I brought it up on a variac using some Raytheon 6L6gcs and a 5R4gyb. It came up flawlessly. I did some voltage measurements. Bias is rock solid. I set it blindly to -41v. B+ with the 5R4 was 430v when I tested it on the 1st filter cap.


I later did some swapping around, trying a 5U4, 5AR4, Russian 5Z3 (says 5U4c on it), and my solid state rectifier. The 5U4 was 5v higher than the 5R4 (about 435v), and the 5AR4 added about another 5-8v, putting me at 440-445v. The 5Z3 was about the same as the 5AR4, just a couple-three volts lower. The solid state put me at about 465v. Our line voltage jumps around, which affects the final B+. Ran it for a couple hours with the 5Z3 on and off, and it settled at around 450v. Not 100% sure if the 5Z3 is up to the task, but has held it's own so far. I could lay my hand on the power trans without a violent retraction, and the output trans was just over room temperature. That's after running for an hour.


Soooo - how does it sound?? My first impression - very solid, much like a Dynaco Mk. I was bench testing it with some 'junk' odd impedance bookshelf speakers and it drove them very well. I later connected a much better Yamaha speaker and sounded crisp and clear, smooth bass. I did hear some light static tho at zero volume. Guessing it's my cheap 6GH8a, or a "not well tightened" ground screw. I didn't hold my ear to the speaker, but no notable obvious hum or distortion in a quiet room. I haven't run any power tests, scope tests or really even actually set the bias yet. I did take note that it sounded a little more crisp and solid with solid state rectifiers, sounded a little softer with the 5R4 & 5U4. Another note, I left out the little 390pf feedback(?) cap simply because AES must have given me 2 extra 22pf caps and NO 390pf. So, I'll reorder later. It may have very little effect anyway.


However, back to the power supply: I noted the 5AR4 and 5Z3 gives it a soft start, with the B+ not going much over 465-70v. However, the solid state shoots it to 510-20v, and the 5U, 5R shoots it right to 500v, so if I use either of those, I either need to up my input cap to 525v, add a CL90 or something. I'd probably be OK with the 5U4. My input cap is a modest 22uf at 500v. I'm a little mixed about an inrush current limiter - they always have a "hot" smell, and I don't like that. But, if need be, then need be. I'm inclined to either leave the 5Z3 or try to find a couple robust 5AR4 tubes. In the future, I'll probably go solid state.


I started construction on it's twin sister. Going a lot faster since I have a workable pattern to follow. Got almost all of the physical parts (trannys, sockets, etc. ) mounted. I'll post back in later with some power measurements and distortion tests. Got a square wave gen coming soon, right now, only have an old school AF generator, which only generates a sine wave.