Overload Board

Anything goes here, but abusive posts will be deleted.

Re: Overload Board

Postby kf1z » Wed Oct 20, 2010 2:14 pm

I just have to ask....

Have you checked the voltage at the output of each of the regulators?
User avatar
kf1z
Senior Contributer
 
Posts: 558
Joined: Sat Mar 18, 2006 7:07 am
Location: Ely, NV.

Re: Overload Board

Postby K9ACT » Wed Oct 20, 2010 4:57 pm

kf1z wrote:I just have to ask....

Have you checked the voltage at the output of each of the regulators?


They are all nominal.

js
K9ACT
Class E Enthusiast
 
Posts: 146
Joined: Sun Jun 27, 2010 12:03 am

Re: Overload Board

Postby K9ACT » Wed Oct 20, 2010 7:33 pm

Are we chasing a spook or did I miss something you said?

If .8v is based on 12/45 x 3, where does the 3 come from?

My guess is that it is the voltage one should see at TP! with 45 volts.

If I am only running 30, why would I expect to see 3 v at TP1?

30/45 x 3 = 2 so shouldn't I be setting the Volts at TP1?

Jack
K9ACT
Class E Enthusiast
 
Posts: 146
Joined: Sun Jun 27, 2010 12:03 am

Re: Overload Board

Postby kf1z » Wed Oct 20, 2010 8:34 pm

You need to set TP1 to 3 volts at your full operating current.

doesn't matter what power level you are operating, or what voltage your carrier is.

3 volts at TP1 is your target.



I told you that 0.8 volts for your transmitter (your carrier voltage actually) is not valid..
That you needed to set TP1 for 1.2 volts, with 12 volts a the input.

This is ONLY a preliminary setup, along with the other PRELIMINARY setup steps, so that whn you key your transmitter while it is connected to the OL board, the OL board parameters are somewhere near right, and the OL won't shut off the transmitter while you are making final adjustments.

The 3 volts is a voltage setpoint for the current/voltage tracking circuits in the OL board.
If you look at all the other adjustments, they are also 3 volts. ( and 0 volts )
User avatar
kf1z
Senior Contributer
 
Posts: 558
Joined: Sat Mar 18, 2006 7:07 am
Location: Ely, NV.

Re: Overload Board

Postby kf1z » Wed Oct 20, 2010 8:52 pm

I just double checked my ol board.

With only a 20 volt carrier I can easily adjust TP1 from 0 to 4.25 volts with R702
With a 40 volt carrier, from 0 to over 8 volts.

So you should have no trouble hitting the required 3 volts with a 30 volt carrier voltage,
User avatar
kf1z
Senior Contributer
 
Posts: 558
Joined: Sat Mar 18, 2006 7:07 am
Location: Ely, NV.

Re: Overload Board

Postby K9ACT » Wed Oct 20, 2010 10:05 pm

kf1z wrote:I just double checked my ol board.

With only a 20 volt carrier I can easily adjust TP1 from 0 to 4.25 volts with R702
With a 40 volt carrier, from 0 to over 8 volts.

So you should have no trouble hitting the required 3 volts with a 30 volt carrier voltage,


OK, then something is broken. I have checked and rechecked every thing on the board and can't find anything else amiss.

Strangely though, between postings, I set the voltage to 2 at 30v and 7A and it runs with full modulation. I ran my robot till I got bored, had a short QSO and thought I had fixed it. I don't know why it now works at 2v but it never faulted so I have no idea if the board is working or just passing it through.

js
K9ACT
Class E Enthusiast
 
Posts: 146
Joined: Sun Jun 27, 2010 12:03 am

Re: Overload Board

Postby K9ACT » Thu Oct 21, 2010 7:22 pm

I am not an engineer and not inclined to question proven designs but as I see this, the 1M and 100k pot make an 11:1 divider. It looks like the max voltage at TP1 can never exceed 1/11th of the voltage at the input.

Ergo... at 30V I should see no more than 2.7V which is very much like what I see.

What am I missing?

js
K9ACT
Class E Enthusiast
 
Posts: 146
Joined: Sun Jun 27, 2010 12:03 am

Re: Overload Board

Postby kf1z » Thu Oct 21, 2010 9:08 pm

What your missing Jack...

Is that test point TP1 is not at the divider...

It is AFTER an amlifier stage ( op-amp) you're going to see a sum or difference voltage
derived from the voltage level at each of it's inputs at TP1



I have to wonder... you had originally not connected the -18 volt supply...
Means that the op amps etc that were expecting to see a -12 and +12 supply, only saw the +12
I wonder if that could damaged something....?

Other than that, maybe check TP3 see if you get expected results there.... you should be able to set it for 3 volts in stand-by with R720.
If not... check D703 for orientation etc...
User avatar
kf1z
Senior Contributer
 
Posts: 558
Joined: Sat Mar 18, 2006 7:07 am
Location: Ely, NV.

Re: Overload Board

Postby steve_qix » Fri Oct 22, 2010 8:01 am

Ok, I see the situation.

The O/L board, in its default condition, is more or less designed around voltages between 40 and 50 VDC at carrier. You can EASILY make it work with other voltages. The 1meg dropping resistor is just a little big for 30V operation. Parallel another 1M or 2m or 1.5m or whatever you have lying around the shack across the existing 1m resistor. Preferably, use a stable resistor like an old meter multiplier or a metal film resistor. This will allow you to adjust the voltage at TP1 to be a real 3 volts. Don't make the total resistance too small (not under 500k).

Current: The board can be adjusted to run with between about 5 and up to 10 amperes without modification. If you want to run MORE current, put a shunt across the high voltage modulated DC input and output on the overload board. I have used these overload boards with transmitters running 25 amperes at carrier using a shunt.

Settting the current zero and current gain pots to get the output you want (3V at TP2) involves a bit of pot balancing, but it is not overly complex. The idea is to get 0 volts at TP2 with no current, and about 3 volts (or slightly less) at TP2 with normal carrier level current. Both the current gain and current zero pots will effect the zero current output.

You can set these pots experimentally, which is how I do it. Do the initial setup of the current zero and current gain pots. Make sure you have 0V at TP2 with no current. Run current through the sensor (transmit at normal power) and measure the voltage at TP2. If it's at 3 V, buy a lottery ticket :D Otherwise, adjust the current gain one way or the other, kill the carrier, and re-zero the current zero - 0V at TP2 with no current. Transmit again. Did the output voltage at TP2 move in the direction you wanted (higher or lower, depending)? If so, and it's not where you want it, keep adjusting the current gain in the same direction, kill the carrier - re-zero, etc.. If the voltage moved in the wrong direction, adjust the current gain in the opposite direction, kill the carrier, re-zero, etc.

Keep balancing the current gain and current zero adjustments until you get it right. It usually only takes a few tries.

IMPORTANT ADVISE NOTE (this is highly recommended): Even though there is a 1k resistor and a capacitor to ground at both TP1 and TP2 - RF can STILL GET INTO THE OP AMPS if you have a lot of RF in the shack, or a radiating souce (like a coil) nearby. RF getting into the op-amps WILL completely skew your measurements, and they will be meaningless. Put a 10k resistor in series with TP1 and TP2 if there is any question about RF. Solder the 10k resistors right into the TP holes, and have them simply stick out above the board. Makes a handy place for your meter probes, and keeps the RF out of the board. Note also, if you are using a meter like a Simpson 260, compensate for the small voltage drop across the resistors in your readings. EG you may lose .2 volts or whatever. Add the drop to your readings.

Regards,

Steve
Visit the class E web site at:

http://www.classeradio.com
User avatar
steve_qix
Class E Guru
 
Posts: 434
Joined: Fri Jan 31, 2003 11:03 am
Location: Townsend MA

Re: Overload Board

Postby kf1z » Fri Oct 22, 2010 8:26 am

I don't know if you saw my earlier post Steve....

I was able to get over 4 volts at TP1 with only 20 volt carrier.
I just had to try it, to see if his lower carrier voltage was the issue.


I'm thinking Jack still has a problem there, but I suppose if he tries lowering the value of the 1meg resistor,
and it solves the problem, then good!
User avatar
kf1z
Senior Contributer
 
Posts: 558
Joined: Sat Mar 18, 2006 7:07 am
Location: Ely, NV.

Re: Overload Board

Postby K9ACT » Fri Oct 22, 2010 8:41 am

Thanks for confirming this. After discussing this with K9WEK who recognized the problem almost immediately, I put a 4.7M across the 1M and it did exactly as he expected.

I now get all the right numbers except that bloody Current Zero. With no current, I can get -10.5v with TP4 grounded and near zero ungrounded but with power I always end up with 2.something for zero when I get 3v under power.

I will work on it some more but it's getting rather exasperating.

For some reason, it is now running at full power and 150%+ modulation without faulting or blowing fets so it seems like that insurance policy that is never needed.

js
K9ACT
Class E Enthusiast
 
Posts: 146
Joined: Sun Jun 27, 2010 12:03 am

Re: Overload Board

Postby steve_qix » Fri Oct 22, 2010 9:00 am

Hi Jack,

For the moment, forget about grounding TP4, etc. Put the current gain pot somewhere - maybe half way, and adjust the current zero for 0 VDC at TP2. Run power through it and see what you get (read the part about the RF, above). There's a procedure I outlined above that I use to set these boards up. Just get to 0V with no current first - all else can be set from there.
Visit the class E web site at:

http://www.classeradio.com
User avatar
steve_qix
Class E Guru
 
Posts: 434
Joined: Fri Jan 31, 2003 11:03 am
Location: Townsend MA

Re: Overload Board

Postby K9ACT » Fri Oct 22, 2010 9:40 am

Just for the record, I assume by "zero" you mean as near as possible as in 10's of mV. The pot is very touchy and getting less the 100mv +/- is a challenge.

If you mean it should go to ground then I do have a problem.

js
K9ACT
Class E Enthusiast
 
Posts: 146
Joined: Sun Jun 27, 2010 12:03 am

Re: Overload Board

Postby kf1z » Fri Oct 22, 2010 9:56 am

K9ACT wrote:Thanks for confirming this. After discussing this with K9WEK who recognized the problem almost immediately, I put a 4.7M across the 1M and it did exactly as he expected.


js


Glad the parallel resistor helped...

Still a curious thing that my board works fine at 20 volt carrier, with the origional 1meg resistor.

But yours doesn't work with 30 volt carrier.

I still think something's up... what exactly, I don't know.


One thing I wonder, is where are you connecting the negative lead of your meter? To a ground pad on the OL board? or somewhere else?
User avatar
kf1z
Senior Contributer
 
Posts: 558
Joined: Sat Mar 18, 2006 7:07 am
Location: Ely, NV.

Re: Overload Board

Postby K9ACT » Fri Oct 22, 2010 12:48 pm

kf1z wrote:
Glad the parallel resistor helped...

Still a curious thing that my board works fine at 20 volt carrier, with the origional 1meg resistor.


Me too. I tried spice modeling the front end but haven't gotten it to work yet.

>I still think something's up... what exactly, I don't know.

I do too but I can't argue with success but it's only partial success.

Problem with the current zero is that when I zero it and then key the transmitter, what was 3v is now lower and bringing that back up to 3 and then unkey, the zero becomes 2.something and the zero pot has very little effect. Like 2.2 to 2.8 but I can't get it anywhere near zero.

I forgot to try the 10R trick and will do that next.

>One thing I wonder, is where are you connecting the negative lead of your meter? To a ground pad on the OL board? or somewhere else?

Ground pad on OL board.

Speaking of meters, I do not have an efficiency meter connected and assume this causes no problem.

js
K9ACT
Class E Enthusiast
 
Posts: 146
Joined: Sun Jun 27, 2010 12:03 am

PreviousNext

Return to General Chit-Chat

Who is online

Users browsing this forum: No registered users and 1 guest

cron