Category: Power Supply

4-65a filament supply mono block

Today made more progress as managed to build one of the 4-65a raw filament supplies. They weigh a ton so decided to build monoblocks for all filament power supplies as well as the main amp.

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4-65a filament raw choke input

The power supply is built on a piece of wood. This is a fast method for breadboarding the amp which provides fantastic results. I’m using PTFE sleeved wire for the first time. This is rated 600V and 10A, sufficient for the requirements here.IMG_3577

 

The common-mode choke is built under the capacitor arrays to reduce wire length and optimise space use.

The choke and 200VA transformers are bolted directly to the board.
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The Schottky rectifier bridge is mounted on an 4mm alumminium angle which is primarily used as heat sink and also the solid structure helps to mount the first capacitor array very close to the bridge.

Tested the supply with a dummy load of 3R3 50W. Ripple is only 53mVpp which will be dramatically reduced by the Rod Coleman filament regulator.

Edit (28th December 2012)

Just made a minor adjustment of the output voltage by the addition of R1 and R2 and fuse F1 was increased to 2A to avoid blowing it at full load when switched on:

4-65a filament raw choke input

4-65a filament supply

One of the good things about Christmas is that I always managed to get some proper time for working on my projects. This year is devoted to my belated project: 4-65A SE amplifier. We bid farewell to our family guests so had this evening a bit of time to start preparing the filament raw supply for the 4-65A.

This will be a heavyweight amplifier. Too much iron, but 100% DHT and no capacitor in the signal path, a promising design.

A couple of hours were sufficient to prepare some of the key components: a pair of common-mode chokes winded on ferrite rings, capacitor arrays and a Schottky bridge mounted on an aluminium sink:

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The raw filament supply circuit follows the standard design recommended by Rod Coleman to use the filament regulator boards. I managed to get a nice pair of 10mH@3.5A chokes made by JMS transformers which is the same company that provides the custom-made split bobbin transformers:

4-65a filament raw choke input

 

The 10mH choke will help reducing the current pulses and the input capacitance, which is less than 3mF. This circuit will provide 12V @ 3.5A with a ripple current of 31mV peak to peak maximum.

4-65a HT +300V supply

First breadboard of the 4-65a SE amplifier. Will start this long project with tuning the HT supplies. Will need a +600V, +300V and +100-150V supplies to be stacked.

4-65a 300V supply

Here is a simple breadboard using metal rails over an old wooden frame I had around. Oil caps will be glued temporarily and damper tubes will be fit later:

+300V HT supply (breadboard)

 

A snapshot of first test….

First tests