No, you should figure out why it isn't working with the secondary grounded. Actually, I can tell you why - you had the secondary grounded at both ends, shorting the output resulting in virtually no volume. You've just got to figure out how that happened.
Inspect the binding posts, and make sure that one of them isn't somehow making contact with the plate on which it is mounted. Power off the amp and disconnect the speaker from the problem channel. Use you ohm meter and verify that both binding posts show infinite resistance with respect to the chassis ground. If you see no resistance to ground, unsolder the white and yellow wires going to the OPT and check them again. That will tell you which one is causing trouble. It's probably the red binding post.
You should solve the problem, but there are not that many possibilities. I don't know exactly how that amp is wired, but I suspect that your positive speaker terminal (normally unearthed) is shorted to your chassis.
Sheldon
Oops, didn't see that Ty had posted the same thing.
That was my fear. It came to me in a dream last night that after all the work I did getting a good ground for the chassis plate and switches, I bet I grounded the binding posts. So, I'll follow your advice and pull out the ohm meter, and finding the offending connection. Finding shorts is my new favorite past time!
Success! I checked all the binding posts and pretty much all of them were grounded through the chassis plate (I'm surprised it played at all). I pulled the posts and wrapped a little electrical tape around the posts where they go through the plate. After that, no more grounding. I've only been able to listen to my cheap/junkie speakers so far but hopefully tomorrow I'll get it set up into the main rig for some listening.
Special thanks to all you guys for walking me through this and helping; couldn't have done it without you!
Special thanks to all you guys for walking me through this and helping; couldn't have done it without you!
Glad you sorted it all out.
Your binding posts look very similar to the Kobiconn parts I like to use (Mouser 164-19B2-EX). If they are the same type, you can drill a pair of 1/2" diameter holes in the chassis. Space the holes exactly 3/4" apart. The front and back pieces of the post assembly have circles molded into the plastic that fit into the holes you drill. It guarantees that no metal part of the binding post can touch the chassis, yet holds the posts securely. Maybe a thing to look at the next time you build something.
Thanks for the checkout info
Finished my Tubelab SSE amp the other day. On first try, it only had audio on one channel, and the side that did work was week.
Everything looked good, so I turned to the checkout by Ty. I quickly found that the cathode voltages were both low on the 12AT7 (.9V). The plate voltages were low too. My next check was to look at the CCS resistors. I found I had swapped the 1K and 330 Ohm resistors. While I was poking around, I also noticed I had not soldered a wire going to the coupling cap.
After those two quick fixes, the amp has worked perfectly. Thanks for the checkout info, I would have been lost without it.
Also, thanks Bruce for the awesome design. I'm amazed that a complete noob like myself could build a tube amp first time around that sounds so good. We've listened to it continuously for the past two days. Even my wife thinks it is awesome.
Actually, she is probably just glad it's finished....
Finished my Tubelab SSE amp the other day. On first try, it only had audio on one channel, and the side that did work was week.
Everything looked good, so I turned to the checkout by Ty. I quickly found that the cathode voltages were both low on the 12AT7 (.9V). The plate voltages were low too. My next check was to look at the CCS resistors. I found I had swapped the 1K and 330 Ohm resistors. While I was poking around, I also noticed I had not soldered a wire going to the coupling cap.
After those two quick fixes, the amp has worked perfectly. Thanks for the checkout info, I would have been lost without it.
Also, thanks Bruce for the awesome design. I'm amazed that a complete noob like myself could build a tube amp first time around that sounds so good. We've listened to it continuously for the past two days. Even my wife thinks it is awesome.
Actually, she is probably just glad it's finished....
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.