Daiwa makes a great SWR/Watt meter, and my version is the CN-901HP. The CN-901HP is a legal limit HF meter. (They do make others with other designations for other uses.)
A few months ago the PEP function just stopped working. Searching Google found no help. I called the folks who take care of USA repairs, and learned they wouldn't repair my meter. The only solution they offered was to send them my meter and $94, plus pay the shipping, and they would send me back a refurbished meter.
Uh...... no.
(At this point, let me say this. The description that follows assumes a lot of things. It assumes you know how to solder safely. This is not an all-details-included teaching moment, so if this info sounds foreign to you, don't fool with your meter. Send it to Daiwa for the swap. Mainly this is what I did to fix what was wrong with my meter, and it may not apply to your situation at all. If you have any uncertainties about trying to replicate what I did, just don't do it. Just. Don't. Above all else, be safe, and observe your own limitations.)
I opened the meter, and found that two resistors, R6 and R15, had smoked and died. Visually, that was the only issue, so I decided to replace the resistors and see what happened. I found a schematic online, and identified these as 1/4 watt, one was 100 ohms, one was 390 ohms. eBay seller jsac1234 had large packs of both of these, delivered, for less than $10.
The two bottom tab screws holding the front panel to the meter box:
The last screw you have to remove holds the circuit board to the side of the box. Here it is:
You've now got all the screws out. The only thing still connecting the circuit board to the meter box is a pair of wires, one red, one black. Just leave these alone, the wires are long enough you can remove the circuit board while leaving them attached on each end.
That is all that is involved in removing the board that needs repair. Once that last screw is out, the board just slides out. R15 and R6 can be seen in the top left corner. Daiwa was kind enough to label the board "R15" and R6".
Pick the first resistor you want to replace, roll the board over, and use a Sharpie or a felt tip pen to mark the solder connections that need to be removed. No matter how much experience you have doing this sort of stuff, it's still easier than it should be to un-solder the wrong component.
Unsolder those two joints, and pull away the molten solder with either Chem-Wik or a solder sucker of some sort.
Okay, most of the hard part is done. Now, roll the board over, drop the new resistor in place, bend the legs (on the back side) in a bit so it stays in place, and solder the two holes around the leads.
With soldering complete, R15 is done!
Repeat the above removal/replacement process with R6.
At this point, all the hard stuff is done.
Reverse the disassembly process, and then put the meter into service to make sure the PEP function now works. Volia! Success!
Okay, now that I've made it sound super simple, here are the other things you may need to know.
Don't be afraid to open the meter box and take a look. You already know the meter doesn't work, and the worst case is you'll spend $94 and shipping for a fix.
The process described above can be used for any problem with any of the Daiwa SWR meters. Exactly how many screws may change, screw locations may vary, and which resistor has died may be different. The problem may not involve resistors, or any part with an obvious failure. But, as you can see from the photo below, spotting the evil culprits in my meter isn't all that hard if you compare them to good resistors.
The items you'll need to do this fix are pretty simple.
- Solder (I used 3.3%, rosin, .031" diameter from Kester)
- Chem-Wik Solder braid (or some vacuum solder sucker tool)
- Small Phillips screwdriver
- Good lighting
- Solder iron (I used a 500W Weller)
- Needlenose pliers (not a have-to-have, but helpful for inserting the new parts)
Since there were no how-to disassemble videos online that I could find, I'm hoping this helps someone else get their Daiwa apart and then back into service.
One last thing: It's kind of small, but here is the schematic I found.
