'E'-Choke

Neal · Post by **Neal** » Wed Nov 30, 2011 6:02 pm

D1 is a 1N4007, 1000v...

I'm using the latest diagram Mike except my C1 is still the original 1uF, the 1K resistor seems to be working OK...

Mike H · Post by **Mike H** » Wed Nov 30, 2011 7:00 pm

Nope, can't see what's going on ....

Mike H · Post by **Mike H** » Wed Nov 30, 2011 11:19 pm

I'm going to have to try simulating this and see if any clues occur

Mike H · Post by **Mike H** » Wed Nov 30, 2011 11:21 pm

What is the transformer Voltage used with this, and what is the load impedance?

Neal · Post by **Neal** » Thu Dec 01, 2011 11:21 am

Voltage off the rectifier is 468, this is dropped to 450 IN, OUT is 424, draw 240mA so load 1766R....

Mike H · Post by **Mike H** » Thu Dec 01, 2011 12:42 pm

Neal wrote:if I put a cap directly on the input.

Current config is now SS rec > 50uF > 75R dropper > 50uF > Regulator > 250uF

I presume this means no 10R between input and the previous 50uF?

Mike H · Post by **Mike H** » Thu Dec 01, 2011 1:28 pm

Well have tried simming it, with the following assumptions:

Transformer secondary appears to be 500VAC, guessed at 90 Ohms DCR

Bridge SS rectifier, reservoir = 50uF
Then 75R > 50uF
Then 'IN' of E-choke, no input resistor.
No resistor on 'OUT', straight into 250uF then the load of 1766 Ohms.
MOSFET is IRFP240, meaning 200V Vds.
'CG' is 50uF.

Test circuit as below:

Mike H · Post by **Mike H** » Thu Dec 01, 2011 1:44 pm

The results come out as:

Bottom plot:
Green = rectifier out / reservoir.
Pink = post 75R, 2nd 50uF, aka 'IN' of E-choke.
Red = 'OUT' of E-choke.
Blue = reverse Voltage across D1. (The current is negigible even if it was "leaky".)

Middle plot:
Violet = Voltage across MOSFET M1 (limited to 200V by inernal Zener).
Grey = current through MOSFET, = internal Zener current.

Top plot:
Green = current through 'CG'.
Blue = current through varistor & R3.
Ochre = current through ZD2, this is because of M1 Zenering.

So can't see how D1 is being destroyed, unless circuit is not exactly as drawn?

Neal · Post by **Neal** » Thu Dec 01, 2011 2:17 pm

Neither can I mike...its working fine at the moment, no input 10R or one on the output....I still have that to do. The VDR is the RS 289-6780 one rated 45vdc 35vac....could that be an issue? C1 is 1uf.

I've made up my second one to fit to K5881 so will see how that gets on...

Neal · Post by **Neal** » Thu Dec 01, 2011 2:40 pm

Ah ha!

The original diodes where BAV21, 200mA, 250v....its these that are blowing (I had three)....the 1N4007 should therefore be OK with R6@10K...

Mike H · Post by **Mike H** » Thu Dec 01, 2011 2:51 pm

THAT makes sense. Did think of that but had assumed you must have upgraded them already. Alrighty then

With the problems we had with R3, so had to increase it, I then thought hang on 250PIV for D1 isn't going to be enough, hence the change to 1N4007.

Neal · Post by **Neal** » Fri Dec 02, 2011 2:46 pm

Thanks for your help Mike.

E-Choke is up and running in my WAD 5881 PP, initial reaction to the sound was not good, far too bright and little bass then I realised I forgot to up the o/p cap from 50uF so lumped another 100uF on there and the balance was restored...

Mike H · Post by **Mike H** » Fri Dec 02, 2011 2:59 pm

Also get rid of the fuse

Or put your caps after it

Better again replace with 10R and put you caps after

Neal · Post by **Neal** » Fri Dec 02, 2011 3:56 pm

Already done!

Mike H · Post by **Mike H** » Fri Dec 02, 2011 10:06 pm

Awl-righty then

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