Voltages for Champ/ Stinger.

[TIMBO]

Hi guys, I put together two small amps and i was wanting some conformation on the voltages i have( are they in the ball park for these amps)I have both amps on the one chassis using the same PT.( switchable to have only amp on at a time) An odd thing i found was that both have 4 and 8 ohm sockets but when connecting a 4ohm speaker to the 4 ohm socket at full dime it was not very loud but connecting to the 8 ohm socket the loudness was what i was expecting for these amps.( checked the wiring was correct) Any ideas or can i just leave the 4 ohm speaker connected to the 8 ohm socket?? Thanks

[sluckey]

Your champ 6V6 is idling at 20.5 watts. Seems very hot to me. The loudness issue is probably due to having part of the OT secondary shorted because of the shunt switching jacks. Disconnect the switch terminal on both speaker jacks and the loudness should behave properly (and louder too). Do the same on the Stinger.

[TIMBO]

Thanks sluckey, The champ circuit is a standard one other than the choke being added. What would i need to do to dial it down? Thanks

[sluckey]

You could use a higher value cathode resistor. Or you could drop the screen voltage. Or, if you like the sound, just be prepared to replace the power tube more often.

Did you look at those speaker jacks? If they are really wired as shown you put the OT at risk when wailing away.

[TIMBO]

Yep, Gave them the snip but a bit early in the morning to give it ago. Looked at some other amps with multipul taps and they weren't shunted to ground.Thanks again

[TIMBO]

New Findings, Removed 1K screen resistor and replaced with 10k .New readings pin 3 - 408v, pin 4 - 387v, pin 8 - 23.5v. Also removed the ground shunts on the speaker taps only to get high pitch squeal on Champ. Disconnected the 22k NFB and got rid of the squeal. Where do i go from here?

[PRR]

> Where do i go from here?

Swap OT primary wires.

[TIMBO]

Thanks PRR, That did the trick. I still don't understand that when you follow a schem that tells you that the Blue wire is connected to the B+ and the red is connected to pin 3, you would think it would work. Is there an explanation for this?? As it has happened to me a couple of times!!May be on this side of the world the electricity has reverse polarity :huh:Thanks


One thing i forgot mention was when i have the amp on standby i do get a vibration and i not sure if it is the PT or the Rect tube , is this a concern?

[jojokeo]

I still don't understand that when you follow a schem that tells you that the Blue wire is connected to the B+ and the red is connected to pin 3, you would think it would work. Is there an explanation for this??

That's actually backwards from normal. It may have worked from the amp/person that built that particular schematic and/or w/the OT that was used. It has to do w/ the polarity of the windings and when reversed it gives positive feedback rather than negative feedback. This means that signal frequencies are being increased rather than reduced (cancellations) from negative feedback and that's what causes the oscillation/squeel that you experienced & heard.
There's a member "Hotblueplates" - blue goes to plate. His name helps you to remember this proper hook-up. (I like word associations like this to help w/ memory recall).