Power Supply problems

[bouipoz]

I am currently building a small (2x 12AX7 1x EL84) amp but am having some issues with the power supply that I cant find the cause of.

For the record i am a beginner and this is a first build

The design is very simple, from the mains inlet to the PT primary, then the secondary (275V) to a bridge rectifier. Im using a 100R resistor for sag before the resevior cap. A 47u capacitor rated at 450V. This is in parallel with another three 22u capacitors that each have 1k resistors in SERIES with them- 15W for the cap feeding the power tube and 3W for the preamp tubes.

Simple eh?

The problem is that when i apply power to the circuit the reservoir capacitor gets VERY hot after just a few seconds and actually continues getting hotter once i turn the power off. The PT also gets quite warm.

I have checked it over and over again and cant find any reason for this.....

Any help would be greatly appreciated

[Amp Kat]

Try taking the 100 ohm resistor out of the equation and see if the problems go away.

[bouipoz]

sorry - i had forgotten to mention that

at first the 100ohm resistor was getting very hot as well so i did take it out but it didnt seem to change anything else....

to be specific i didnt remove the resistor i just bypassed it as was planning to make it switchable in and out of the circuit anyway

i recently noticed when there is power in the circuit (for the few seconds i dare to run it) i only read around 40v across the filter capacitors which doesnt make any sense.

when reading the voltage across the secondary of the transformer my multimeter broke- hopefully just a fuse

im running out of hair to pull out

[Euthymia]

Make sure the cap is in right way 'round. Also make sure you have the bridge connected correctly. It's possible for a newb to get either of them backwards, with the result being as you describe.

If it is in the correct orientation, disconnect the load downstream from the cap, leaving only it hooked up and measure the voltage.

Remove the cap from the circuit and check it with an ohmmeter.

[bouipoz]

i actually made that mistake to begin with- i had the reservior cap in with the positive terminal to ground and this caused the 3watt resistors to glow and smoke

ill look over the rectifier again more thoroughly but i dont THINK theres anything wrong with it

do you mean to disconnect the rest of the power supply leaving on the reservoir cap or disconnect the rest of the amp - at the moment the power supply isnt feeding any tubes i wanted to make sure it worked before i risked blowing any as i dont have spares

as for removing the cap and checking resistance- what would be the purpose of this? what sort of resistance should i be looking at?

[bouipoz]

so it turns out the diodes are backwards

FUCK

id have thought the cathode goes to ground... oh well sorry to waste your time

[Cygnus X1]

Don't sweat it.
I've done the same with no damage to anything.
Just fix it and continue.