Overload Board

[K9ACT]

Steve,

I sort of misread your last question but my answer is the same. I thought I saw RF deck in your question and I was just trying to clarify.

Where things stand at present is/are that the only adjustment that seems to have any effect on the fault level is the Current Gain.

Any level above about 2.5v at TP2 faults with modulation. At 2.3 I can modulate all day at 150%. As I move from there to 2.5, the allowable mod level drops to near zero at 2.5. This is of course, zeroing after each change.

The above applies whether I modulate a resistor or the RF deck.

js

[steve_qix]

I didn't hear anything about the PWM filter. Where is the filter in the mix?

[K9ACT]

I didn't hear anything about the PWM filter. Where is the filter in the mix?

The Overload Board is between the PWM filter and the load. Actually at the node L2, C2 and D Limit.

js

[K9ACT]

Yo Steve,

It's your turn. I am still stuck at 2.3v

js

[steve_qix]

Hmmmmmmmmmmmmmmmmm..... like "The Thinker" (that is a famous piece of art - looks like he's sitting on - well, you know), I've been pondering the problem

We need to know if the voltage and current track correctly. With 3V (or maybe a little more at TP3) at TP1 and TP2 with current and volage, and 0V at TP1 and TP2 with no current or voltage, set Vthresh so that there is 0 Volts at TP3 (when there is 0 V at TP1 and TP2). Now operate with normal current and volage, and with no modulation, reduce the carrier level at the PWM generator board, and make maybe 5 different measurements at TP1 and TP2 with various settings of the carrier level, and also note the output voltage and current along the way from normal duty cycle to something less than 10%.

This will tell if the current and voltage values, as the board sees them, track - at least going down.

Let us know !

Thanks and Regards,

Steve

[K9ACT]

I hope you take this as the humor intended but me thinks "The Thinker" needs to flush and try again.

I normally get back to you within minutes of reading your suggestions but after about ten readings, I thought it might be clearer if I sit down to the board and take it word by word but I still can't get past the first sentence. In fact not beyond a few words.

What is meant by current and voltage vs normal current and voltage?

I don't understand how I can get 0 at 1 and two if I have just made sure I had 3 under load.

i am lost.

js

[steve_qix]

Ok, let's try this again

I guess the first thing is to determine if the voltage and current sensors track.

This involves taking a series of measurements at TP1 (voltage) and TP2 (current) at various current/voltage levels, while the transmitter is operating.

So, set everything up for normal board operation. This means with no voltage or current, have 0V at TP1 and TP2, and with normal operating current and voltage you get a little more than 3V at TP1, and as close as possible to 3V at TP2.

Now, using the carrier level pot on the PWM generator board, adjust the modulator output voltage. Can you get 50 or 60V output from your modulator without tripping the overload? If so, do so (both 50v and 60V) and measure the voltage at TP1 and TP2 with both voltages.

Do the same thing with 40V output, 40V output and 20V output.

This will tell if the current and voltage values, as the board sees them.

Hope this makes more sense. The previous note was slightly confusing - but I've been involved in a rather intense intense software development project for the past week or so, so the brain is definitely operating in the mostly right brain zone - and left brain functions (such as clear communications) are not getting full airplay

Let us know how the measurements come out!

Thanks and Regards,

Steve

[K9ACT]

Postby steve_qix


>Can you get 50 or 60V output from your modulator without tripping the overload?

I believe so but the fuse in the Variac blew at about 50V so I assume the board didn't fault first.

>If so, do so (both 50v and 60V) and measure the voltage at TP1 and TP2 with both voltages.

Upon further consideration, this puts a serious stress on my stuff here.
60v into 5 ohms is 12A and 720W. Even with a fan on my 100W dummy, I wouldn't want to run it long enough to make the measurements and of course, I can't use my 200W RF deck as a load.

>Do the same thing with 40V output, 40V output and 20V output.

Is this still useful without the 50/60v numbers? Remember, I am running at about 30V carrier.

js

[steve_qix]

Whatever you can get 40v, 30v, 20v, 10v into the resistor. All of those readings will be great - measured at TP1 and TP2.

Include the modulator output voltage, current (if available) and the voltage at TP1 and TP2 for each measurement point.

[K9ACT]

HERE ARE SOME NUMBERS....

MOD V A TP1 TP2

30 6.9 3.00 2.2

25 5.8 2.54 1.8

20 4.6 2.0 1.38

15 3.4 1.54 1.02

10 1.0 .95 .59

This was done into the RF deck with a 50 ohm load. The current meter is on that deck so it was easier to get to than with the 5 ohm load on the modulator.

js

[steve_qix]

Ok, interesting ! Is it possible to set the overload board such that you have 3v at TP2 with normal current (and 0V at TP2 with no current) and make the measurements again? The voltage and current are more or less tracking, but it will be much more useful to see what happens when the board is set up with its design values.

Let us know !

Thanks and Regards,

Steve

[K9ACT]

With 3/0 v at TP2



Mod V A TP1 TP2

30 6.9 3.001 3.062

25 5.5 2.45 2.44

20 4.8 2.03 1.99

15 3 1.4 1.19

10 2.2 .996 .910

To reiterate the problem, if I go back to 30V as above, any modulation will fault the board.

With 2.3/0v at TP2 I can modulate all day. Mileage varies between the two points.

js

Why are there nice neat columns in the preview but they are all scrunched together in the posting?

jjs