audio-talk

The thing with the hybrid bridge like I use,and the way Steve did it with a GZ rectifier is the slow start up which will bring the diodes up to max without a "jolt" ! (?) Or would an inrush limiter on the transformer primary help ? Are their any bad things about inrush limiters ?? Hi Phil...

OK, I think we're all on the same page again now. I've just read back through the whole thread, and Nick did suggest shunt resistors about two weeks ago, followed shortly by Mike spelling out exactly why they are needed. So apologies to you both, I should have just gone with the resistors when you s...

Ahh, A bit of googleing found this To elaborate a bit more on that PIV problem, I might add that the reason for swamping the series diodes with a high value resistor is because the reverse resistance of diodes of the same type number can vary radically. Three diodes of a four-diode series string ma...

The 10M were just what I was going to use in the 813, not suggesting that would be best in this case. I know, and I appreciate the suggestion. Sorry if I'm coming across as negative. Do you think I'm worrying unnecessarily about low inductance in this application? I did find some thick film high vo...

Still not sure why the diodes went, the caps you had should have balanced the charge. I found some high voltage thick film resistors for the 813 project on farnell, maybe higher than you need http://uk.farnell.com/jsp/search/productdetail.jsp?sku=1292582 I agree. I think I will try re-connecting th...

Thanks Philip The BY255 is rated 1300V, the STTA512D I am using is rated almost as high (1200V) and is ultra fast/soft recovery ( plus I have just ordered another batch) Do you think the BY255 will be that much more robust? What transformer RMS secondary have you run with the BY255, and how many did...

Next job on the list is to re-build the rectifier bridges. As per the discussion earlier in the thread, I would like to try adding a resistor across each of the diodes, to ensure that the voltages are shared equally across them. But the resistors will need to have a high voltage rating - I have foun...

OK, I just wanted to work through the numbers to check that my rule of thumb was OK. I'll assume your transformer secondaries are 350V MJ's rule of thumb is: Minimum current (mA) = Vrms / L In your case Imin = 350 / 27 = 13mA My rule of thumb was to use a 27K resistor. If this was bleeding across a ...

Thanks for this Colin, I think I will be using this company

pre65 wrote:OK then-I will be using some 27H @ 200ma chokes and 27K bleeder resistor.(or a near practical equivalent)

Hi Philip
Just out of interest, what HT voltage and load current are you aiming for?
And can you remind us where you got those chokes, they sound pretty useful.
Cheers

Mike
If you want, you could simulate small 'voltage tweaking' caps before the choke in the choke input case and see how quickly the current in the transformer reverts to the cap input waveform.

Ah, Nick got there first

No, I don't think there's any problem with excess current capacity. The minimum current that needs to be drawn is governed by the inductance of the choke. The equations are in MJ, but I think a reasonable approximation is that if you have a 10H choke, then a 9K bleed resistor would shunt enough curr...

Just a quick post to say that I am going on holiday for a week, so may not be posting much. I will try to log on and read, but typing on an iPod touch isn't the slickest thing in the world

Just to clarify, using a choke in a PI filter on a cap input supply does not confer the same benefits as a choke input supply. I keep coming back to PSUD, but again if you model the two types of supply and then look at the voltage/current in the transformer, you will see how much better the choke in...