4 4 0 wiring help needed

[mehfuzhoss]

finished building the amp. all tubes are installed with a 8 ohms spkr connected. when i power up the amp it blows the 1A fuse. i have checked for wiring closely; no short found. ground wires are okay. i pictured the power switch wiring and the OT wiring. any suggestions/comments!

[Colossal]

Take a look at your main power switch and see if it seems right to you. Look at the diagram I drew and tell me if that looks the same as how your switch is wired.

https://ampgarage.com/forum/viewtopic.php?f=6&t=32595

[johnnyreece]

I'm with Colossal on this one: It appears that your switch is set to directly short your mains, which would definitely blow a fuse in short order.

[mehfuzhoss]

i wired it according to the diagram colossal provided me.

[mehfuzhoss]

if you could tell me which color wire goes to which pole of the power switch. that will be helpful. thanks

[pompeiisneaks]

I'm not 100% sure, but I think per that switch you've got the wiring off 90 degrees, i.e. the black and the orange sides should be on either right side two pins or left side two pins, BUT I don't know for sure. A simple test would be to desolder the switch, then put your DMM on continuity mode and put one lead on the top left pin, and the other on the bottom left, then toggle the switch, One way of the switch should give off an audible beep, if it does, those two are designed to be a matched pair. Most switches I've seen have the long sides as the 'matched' ones for DPDT switches, you've got it wired like the short ones should line up, and I think you're creating a dead short across mains.

~Phil

[sluckey]

Just swap the black and the blue wires.

[Colossal]

if you could tell me which color wire goes to which pole of the power switch. that will be helpful. thanks

I am not telling you because you need to learn this! Figure out how the switch works. If your brain hurts, it means you are learning. It is a Double Pole Single Throw switch. If you have a multimeter, put it into Beep/Continuity mode and test the poles for yourself to see which are connected when you throw the switch.

As stated above, you are shorting the mains.

[pompeiisneaks]

Just swap the black and the blue wires.

woot that means I was right

I agree with Colossal, you should use the technique I mentioned with your multi-meter on continuity mode to figure out how the switch works. but Sluckey gave you the shortcut.

~Phil

[mehfuzhoss]

Yaaay. my amp works now. Thank you guyz a bunch....

now two more issues: -

- the pilot light stays off but the amp is making sound ? how can this be!
- hum noise at volume 0. and becomes very noisy as i turn up the volume. when i turn the eq knobs the noise level/type changes at the same time. when the volume is set to max, the noise level is worst.

the amp seems really really loud for a 2 watt design. i have a 20 watt and this one is pretty close to that db level...im guessing

and the bias pots - should i set them to middle position ? please help me on this one as well.

Thanks again, i wouldn't make it to work without ur help.

[sluckey]

Wrong pilot light, wiring error, bad pilot light.

[Colossal]

Wrong pilot light, wiring error, bad pilot light.

Pilot light probably got smoked during it's trip down Main street

[mehfuzhoss]

it is a 120v pilot light wired to the heater wires through two black resistors as shown in the pic. i am okay with not functioning. does a bad pilot light cause any issue!

shown with two red arrow on the picture.

[Colossal]

it is a 120v pilot light wired to the heater wires through two black resistors as shown in the pic.

Your heaters run at 6.3VAC. Your pilot light is 120VAC. Therein lies the problem.

[sluckey]

Pilot lamp should connect to the power switch, same lugs as black and white wires.