Dosy TC-4002PSW Schematic/help needed

[dss56]

I have a used
Dosy TC-4002PSW
Would anyone out there have a schematic/ info on calibrating this meter. I think the watts are off a bit and would like to get it calibrated or adjusted to what my other meters say for watts from the same radio when keyed up using a dummy load.

thanks

 

[nomadradio]

That meter has been made with more than one circuit board in it. The trimpots that serve to set each scale's calibration are marked clearly in some versions.

Not so clearly in other versions.

We use Bird meters that have had the elements checked for accuracy. The meter being calibrated goes in line with the dummy load, and the trimpots set to match the Bird's reading.

If the trimpots are labeled "20w", "200w" etc, it's not a big deal.

And if they're labeled "R4", "R5" and such you'll have to trace each wire from the range selector to the trimpots to identify what each one does.

Here is the only manual I have for those. Pretty sure the circuit board in this one is bolted to two screws against the back panel, with the main wire from the "input" coax socket passing through the center of a doughnut-shaped toroid coil on that pc board.

Don't ever remember seeing a diagram for any other version.

We learned the hard way to make sure that the coax sockets are properly grounded to each other. Some versions simply rivet the coax sockets to the painted rear panel. Doesn't penetrate the paint to the metal back panel. I have some pics of what we do to bond the ground side of the coax sockets to each other and to the pc board. I'll upload them to post here when I get the chance.

73

 

[dss56]

Thanks for the info I will open it up tomorrow and see if I can decipher the power meter section. much appreciated

 

[nomadradio]

Oh, one more detail.

The meter may say "4000" Watts, but the antenna switch is good for about one thousand.

Don't push it harder than that, even if the coax-socket grounds are good.

73

 

[dss56]

Thanks but will never get that close to 1k watts mostly run stock and do repairs on radios mostly very little amp work so think im safe watt wise.

 

[W4KVW]

I once owned one of those & had it calibrated.It was a Bad Joke & the readings always changed from day to day & usually every day.It was far from Accurate but I learned that it did not have a PEP reading circuit in it so it is impossible for it to read PEP.I replaced it with an Autek WM-1 & I could not be happier.If I get these meters in stuff that I buy I now use them for targets at the gun range since they are perfect for that & they catch those bullets just fine & don't waste my time or energy.Don't expect accuracy but they do just fine for an SWR meter but are expensive just for that purpose.

SIX-SHOOTER

 

[Tallman]

Here.

 

[Wire Weasel]

Ha! I just picked up one of these as I was in need of a basically useful external meter just for 11 meter purposes. Got at a good price and looks like new. Power and SWR is accurate to other known readings on present radio and gear. Didn't work with Vertical Ant. plugged into Vertical position on rear connector (you can use any of them). So when I looked inside the factory foil trace from the SO239 center to the switch was completely missing LOL. So that would never work. Easy matter to solder a heavy wire from board point to switch pin. Also the Modulation function is dead. Bumped around the Mod Adj Pot but no effect. No big deal. Shocked that these things cost $260 these days. Not too many years ago they were $125 new.

 

[whiteastro]

That same meter I have been using on my bench as my main meter for my talking radio and it has served me well for about 3 or 4 years with no real problems. When I received it I took it to my local guy starting a shop and he adjusted it to match his Bird equipment. If my memory is correct the trim pots are in the back on the left. Left to Right is Low ( 20 ) Middle ( 200 ) R/H ( 2000/4000 ) but I would check them for markings. The modulation pot if I remember correct is towards the front on the right. The guy never adjusted that and it always read conservative or stingy which P-ed me off so when I took a radio to DTB Radio to have work done he set the modulation at 100% so when I got home I adjusted my Dosy to read the same and have been happy with it ever since. Now I have 3 Dosy meters all reading the same. If you are just going to be a user of radios the Dosy will probably serve you just fine if you don't rough house it. But If you are thinking of repairing for other people I would go with Bird as others have said. The only reason I bough other Dosy meters was to get the frequency read out for checking radios and a Finer break down on the SWR scale. I'm not Only a Nut but a Nut for Accuracy also. ( On a Budget ) LOL