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Hi there. I need some technical help to fix my Tweed Royal. Last night, I switched the amp on and didn't get any signal. The jewel light was on, but no sound. After looking around, I realized that one of my speaker wires became accidentally disconnected.
Unfortunately, it seems to have fried a lug on my rotary 4pol/3pos standby switch. In particular, it's the one where the wire (white) connects to the 470 ohm resistor/25 uf cap. There is also another 470 ohm resistor that is connected to the standby switch at this point.
I hooked the amp up with a voltage regulator and confirmed there was a short. It sparks at this point that I mentioned where the wire and the 470 ohm resistor connect to the switch. The lug appears quite loose. Along with the spark, there was a burning smell. It appears that this point became overheated and I suspect this has created the short in the signal. The fuse did not blow and there does not appear to be any other obvious visual signs of damage.
Replacing the switch appears like an obvious first step. Before I just order this part, is there anything else I can check in case I need to replace something else as well?

Hey there - bummer! let's see if we can get you up and running...


The loose speaker wire is probably a red herring (but maybe not). I've heard of output transformers melting down when a speaker is not connected for a long time, but have not heard a of bias resistor melting down because of this.


Need to figure out what burnt. Are there any scorch marks on anything at all? If it were me, I'd replace the 2 470r resistors and the 25uf cap too, since they are not expensive items and all connect to that point. I also would try both 6V6 tubes in another amp to see if they work. A bad 6V6 could take out the bias resistor like that.

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MasterDelayer/Reverbrador/Ampaholic/TopJacker

The speaker wire was disconnected for no more than 3-4 min, but that's the only thing that appeared different at the time. The amp has worked fine up until this point. And the lug that sparks on the switch is pretty loose compared to the others, as if the heat has fried this point. That's why I though it might need a new switch. But I don't want a bad tube to fry the next one as well! So I will check the tubes and make sure they're ok before using them again.
There are no scorch marks, but it does still spark at the point mentioned in the post when I take it off standby.
I may have an extra 470 ohm resistor, but it'll probably be more like 1w rather than 5w. I think I have extra 25 uf caps as well.

The switch needs to be replaced. I meant to replace the resistors in addition to the switch. 1w won’t work. You need a 5 watt.


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MasterDelayer/Reverbrador/Ampaholic/TopJacker

Got it. I will replace the 2 x 5W 470 ohm resistors, 1 x 25 uf cap, and standby switch. I'll also make sure the tubes are good. It may take a little while to get the parts, but I'll report back once everything is back together. Thanks for the guidance!

Ok - I just wanted to give a quick update. I just replaced the switch and everything is now working like it should and sounding geat. Thanks for the suggestions!