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Author Topic: Dentron W2-PEP Power Meter Repair  (Read 6061 times)
KE4LJH
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Posts: 9




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« on: July 07, 2013, 10:22:29 AM »

Steve / KE4LJH 07-07-2013

Dentron W2-PEP Watt Meter

Recently purchased this watt meter and all worked well for a few weeks.
Suddenly the forward power meter stopped working.

I am using about 600 watts dc to tune the amp up. All equipment is grounded
with  the  exception of the watt meter.

Could I have caused this by not having it grounded? Or, with the stray rf radiating from the ladder line?

I am using 600 ohm HB ladder line, there is some rf radiating into the shack

Any thoughts, comments or thinking you may have on how I might trouble shoot
And/or repair  this unit would be greatly appreciated.

I have the Dentron Matched set. MLA 2500, RT-3000 Coupler, W2-PEP
power  meter.  It would certainly be nice to keep all the components working.
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K8AXW
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« Reply #1 on: July 07, 2013, 11:45:48 AM »

LJH:  It's unlikely your meter was harmed by the ladder line.....

As with any question like, "why doesn't it work?" I suggest you get the schematic for this meter and simply see what components affect that right hand meter.  Go from there. 

Or, perhaps you could post the schematic on Photobucket or some similar place so we can view it and offer detailed suggestions instead of generic suggestions like "look at the schematic and fix it."



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K8AXW
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« Reply #2 on: July 07, 2013, 12:02:40 PM »

LJH:  Ok, I was able to find the schematic for this unit and the first impression I got was this has to be the simplest SWR meter I've ever seen!

If the Forward meter no longer works and the Reflected meter does, I would check CR1 first.  It is a diode used for rectification of some RF for the Forward meter circuit.

Off hand, it is the most delicate item and just might be the first thing to go if overloaded.... whatever.  Anyhow, this is what I would check first.

We can go from there.

Does the Reflected meter work?
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N4ATS
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« Reply #3 on: July 07, 2013, 01:16:50 PM »

I can fix it for you if you wish , ( www.N4ATS.com ) but the first question I have for you is why are you grounding everything? Is it because you are getting rapped by RF or is it just the famous old rumor , "grounding everything is a must". The reason I ask , I do MORE claims for people who ground everything and never do claims for those that don't ground anything and simply pull power and antenna connections when not in use.  (but the antenna of course is well grounded). Usually , in most all cases I have seen and wrote up , everything that's hooked to ground REGARDLESS if the power and antenna connections are pulled, is usually wiped out. I used to own a very large station (qrz.com) and NEVER lost a single item yet my towers have been hit multiple times. My Neighbor Jim N4IAT has had two claims I wrote , and everything WAS grounded BUT his antenna coax and power was unhooked. Lightning almost ALWAYS looks for the lowest potential and typically the "common radio operator grounding schemes" are the worst of the worst unlike TV and Radio radio stations who are live 24/7 and must ground but have tens of thousands invested into it.
« Last Edit: July 07, 2013, 01:28:54 PM by N4ATS » Logged
KE4LJH
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Posts: 9




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« Reply #4 on: July 09, 2013, 12:55:43 AM »

The Reflected meter deflects, although at this point it may need to be calibrated. I can't get it to match my other external power meter. But that is another matter.

I have checked the diodes with the multimeter diode function. Both Cr1 and CR2 appear to be ok. Voltage does flow and only in one direction.

Could I have just ruined the forward power meter by putting high power through the meter when the meter was set to the low power setting. The power setting is 200w/2000w. If this happened without me realizing it, I would have put about 600 watts through it on the low setting.

With this in mind, is there a way to test the meter itself to see if it has been damaged? I suspect I may have simply had the power setting in the low position and used to much power.
If you concur this might be the problem, then I am looking for a new meter replacement.

After looking at the schematic, I don't think it is complete. Perhaps it may have been for an earlier or other wise other meter that was manufactured. With a quick vew there are two more switches in the meter than are shown on the schematic. That is as far as I got. It might not match.

Thank you all for your comments.

Steve / KE4LJH

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KE3WD
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« Reply #5 on: July 09, 2013, 05:57:08 AM »

Don't overlook cleaning the switches.  Deoxit. 

Yes, dry/dirty switch contacts can indeed stop the show, as well as be responsible for erroneous readings. 


73
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K8AXW
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« Reply #6 on: July 09, 2013, 10:01:36 AM »

Yes, it is possible you smoked the meter by overloading it....although I have never actually experienced this.  I've overloaded my SWR/PWR meters several times and the meters to recover OK. 

WD:  I defer to your expertise on how he should check to see if his meter will deflect.  My methods are quite primitive and frankly can't recommend them.

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KE3WD
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« Reply #7 on: July 09, 2013, 11:42:25 AM »

Please, I'm just about trying to help the OP cover all bases towards solving the problem. 
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KE4LJH
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Posts: 9




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« Reply #8 on: July 10, 2013, 01:41:51 PM »

The schematic found on the internet does not seem to match this unit. It has far more components. The unit also has a remote coax box to keep cables off the desk and on the floor. There is circuitry in the remote box as well.

I have checked all the diodes with the multimeter. Voltage flows in one direction only.

The meters deflect when touched with the multimeter probes in diode mode to send a small voltage through the coil.

Don't know where to go from here.

Steve ke4ljh
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N4ATS
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« Reply #9 on: July 10, 2013, 02:16:22 PM »

Looking at the actual manual schematic , it is as simple as you can get as far as technical design. CR-1 and CR-2 are Germanium Diodes so in Diode Check you should see about .325 and in REV , open. R1 and R2 are balance / current limiters. I'll bet if CR1 and CR-2 are OK , C1 or C2 are dirty OR S1 needs cleaned. If NO meter appears to be moving , T1 may have an issue. Of course C3 and C4 must not be shorted either.

PS to test the meter movement it self (quick test) , go to diode check on the DVM , put the probes across the actial meter movement , it should move pretty well.
« Last Edit: July 10, 2013, 02:22:35 PM by N4ATS » Logged
KE3WD
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« Reply #10 on: July 10, 2013, 03:11:40 PM »

Now that you've eliminated all the other components, check the REV/NORMAL switch. 

Just because something is brand new doesn't necessarily rule out dry or dirty switch contacts, or perhaps a defective switch.  A shot of deoxit and exercise switches doesn't take long, and should be followed through at this point. 

 
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