845 Project

[pre65]

Hi-using bits left from the now dismantled PT15 monoblocks i have started my new project,an 845 power stage.

This is to be driven from my existing 300b single ended amp with an 2-1 interstage transformer replacing the output transformer.

This is my first attempt at anything HIGH voltage and also using the breadboard technique.The hardware is now mounted on the ply bases (thanks DTB) and now i can start to work out where all the wires should go.

The 845 heater is DC and i have just managed to get 10V from a 9V toroid and 1N5820 diodes + cap.

The power supply is 360-0-360 transformer via a hybrid bridge rectifier (high voltage silicon diodes and 6D22s damper diodes with raised heater voltage).Because of the high voltage i have made the power supply circuit board from 2mm teflon sheet and used turret tags for the connections.

Thanks to Nick G,Darren and Andrew I for the help in getting the details of the circuit sorted and making me so aware of the dangers of circuits with high voltages (900-1000V) .So many components that are "happy" up to 600v are just not safe at 1000V !!!

My choke for example is rated at 1.5KV,which was fortunate and the power supply caps are in sets of 3,each rated at 400V.

http://i111.photobucket.com/albums/n...readboards.jpg



Philip

[Ali Tait]

Looking good Phillip,Look forward to your impressions of the sound.

[pre65]

Hi-i have powered up both of the amps and there seem to be no obvious problems.

HT is around 950 V,which is about what was predicted.

Next job is to mod the 300b amp wiring to provide the signal to the interstage transformer (ie disconnecting the output transformers).

http://i111.photobucket.com/albums/n...rogress001.jpg


Philip

[Cobblers]

Phil,
So you're still with us in the land of living then

What does the lightbulb do?

[pre65]

Ah-the lightbulb !!

The lightbulb is an unmistakable indicator of power in the amp !

I had the holders and bulbs left over from the PT15 project (where they were the cathode resistors) and i wanted to make sure i did not forget that power was applied.

I really did it just for DTB.


Philip

[Cobblers]

Originally Posted by pre65

Ah-the lightbulb !!

The lightbulb is an unmistakable indicator of power in the amp !


Philip

The impression you gave last night was that your burnt charred corpse was going to be the best indicator of that

[pre65]

I shouldn't joke about that sort of thing really because one must be so careful of 1000V ,more so as it's DC.

There are 3 things i must consider

1-Safety
2-Safety
3-Safety

If i croak it who will keep an eye on Ian ?

[Dave the bass]

Originally Posted by pre65

I shouldn't joke about that sort of thing really because one must be so careful of 1000V ,more so as it's DC.

There are 3 things i must consider

1-Safety
2-Safety
3-Safety

If i croak it who will keep an eye on Ian ?

Add to the above...

4-Blast Shield
5-A recent Will stating all contents of home to be left to DTB!

Glad to see you're being a sensible chap with those big toys.

Hang on ... the lights just dimmed a bit here in Central Lundun Village. You still with us Phil?

DTB

[pre65]

Now ready for final test procedure.

That will have to be tonight now.

http://i111.photobucket.com/albums/n...300bSETamp.jpg



Philip

[Richard]

Wonderful, don't forget the sunglasses - is that an asbestos mat it's all laid out on?