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PWM outboard problem?

PostPosted: Sat Oct 01, 2011 3:33 pm
by W3FJJ
Hi, I just finished wiring the QIX PWM today, I tested the PWM generator and
the Shut Down Board, and they are working. I'm now testing the Output
Board with an 8 ohm resistor Load. I turned it on with only the 13v dc ,that goes to LM7805
and LM7812, and No HV DC. My output voltage meter and current meter
went up, I quickly turned it off. I was not expecting any voltage/current output. Any Idea whats going on? I don't think that is normal unless
it needs the HV to operate properly? Thanks-Chuck


Re: PWM outboard problem?

PostPosted: Sun Oct 02, 2011 8:41 am
by W3FJJ
Did find a problem, duh, I had a solder blob across pins 4 and 5 of the opto-isolator.

She seems to be working Fine!!

Now on to building the RF Deck...

Re: PWM outboard problem?

PostPosted: Fri Oct 07, 2011 1:27 am
by Gilly
Hi Chuck

All looks good....
Its interesting to see how others build their equipment....
On the Output filter board whats the little coil and resistors for....there appears to be a ceramic capacitor across the parallel resistors ? or maybe its the way the photo is taken....
The 2 inductors are quite close .... nearly touching .... maybe others might want to comment....
I separate my inductors as this photo etc:

How many Watts is your dummy load....mine is appox 6 Ohms by 100watts and when testing gets HOT real quick ! :D

Have you decided on a circuit for the sequencer yet ?


Re: PWM outboard problem?

PostPosted: Sun Oct 09, 2011 6:35 am
by W3FJJ
Hi Wayne, Nice job on your construction! I like see pics of others constructions too.

Good Eye there, I reused a filter board, for my PWM filter, it already had a couple
torriods glued to it, which I had trouble getting off the board, so I left them on the board, but
they are not being used.

The Resistors and ceramic capacitor are not on the board, but hooked across the current Meter, as Current shunt
and bypass cap. I need to buy a single current shunt, instead of that mess, which still is not they right value...

I have two 8.5 ohm 300 watt resistors that I used as a dummy load., They maybe inductive, Not sure if thats going to be problem when I test it under
full power, and freq sweep...

I built a Homebrew version of w2drz sequencer circuit, here's pic, it is mounted under the PWM filter..
There's extra an IC socket and transistor/pot. I originally was going to build vfo circuit on that board, but that's going in another cabinet.. 73, Chuck


Re: PWM outboard problem?

PostPosted: Mon Oct 10, 2011 4:41 pm
by Gilly
Hi Chuck

Just a bit concerned about your Output Filter Inductors......being close.... :?
If it was my PWM would mount the right inductor on the side of the case .... this would give more separation and also place both at 90 degrees to each other.....

This is a quote from Steves WEB site:

In this implementation, the PWM filter inductors are held in place between 2 pieces of plexiglass. The filter inductors generate very little heat, so any convenient method of mounting may be used. The inductors should be sufficiently separated from each other to prevent coupling between the inductors.

I'm sure Steve will come across this post and comment.......