Info on a WATERS dummy load watt meter.

[Knightt150]

I have a WATERS DUMMY LOAD WATT METER 10, 100, 300, 1000 model 334A. After 50 years mine begin to fail, I was checking my 45w out Johnson Ranger the reading went to about 10watts.  I do not have any kind of schematic on the meter after checking all the componats in the meter circuit I could not find anything wrong. My guess is the pickup or what ever you want to call it inside the can is going bad, should it show open as read with my ohm meter, where could one be purchased?

John W9BFO

[Pete, WA2CWA]

The schematic shows two non-inductive resistors (total resistance 52 ohms) in series from the input connector to ground. At the junction of both resistors, the anode of a diode is connected. The load is oil-cooled.

[WQ9E]

John,

It was sold by B&W and you will find the manual for it on edebris under B&W:  http://bama.edebris.com/manuals/b&w/

You definitely shouldn't read an open circuit for the input but hopefully it is a wiring fault and not a failed resistor.

[Knightt150]

Thanks everyone for the help, I have not checked the input but that can of oil is sealed I would guess she is a lost cause.

John W9BFO

[w1vtp]

Sounds like it may have opened up.  If it is not going to be repaired, this would be a good time to replace it with an upgrade.  The attached photo is of my Bird 500 watt oil cooled load.  I picked it up at NearFest for $100.  I see from your QRZ photo you have a Bird watt meter so that should be a good match.  That particular load is a 500 watt continuous duty load and is good into the GHz.

gl es 73, Al

[Pete, WA2CWA]

You could try building or buying a 50 ohm dummy load of appropriate wattage and attaching it to the input connection with a T- connector. Other side of T would go to rig. Lift the diode connection from where it's presently connected to the internal dummy load and connect it to the input connector. Most likely you'll have to recalibrate each range and probably have to diddle with some of the fixed resistor values. Almost nothing is a lost cause if you get creative.

[Jim, W5JO]

John, if you have not taken it out of the case do so.  You will find the connector is soldered to the inside case containing the oil and can be stood on the front side while you unsolder the connector with a very large iron.

Once the connector is off you can drain the oil and possibly make repairs.  The manual shows two resistors in series so I am betting the may be 25-35 watt versions of non-inductive types.  If they are you can get some that may work from MFJ for a reasonable price, provided they fit of course.

Their catalog shows they have some 22 ohm, 35 watt continuous types, PN 113-1220.  A quick check of their website shows them to be 22.50 each.  If I am not mistaken when you remove that connector, the hole will be large enough to fit those inside  and if the mounting is the same or can be made to work, you would be in business.  While in there I would think about replacing the diode.   A 1N256 or replacement would work or there are some more modern types to use.

That thing was assembled and it can be disassembled so it wouldn't hurt to try.   Just some thoughts.

[Pete, WA2CWA]

Jim: Isn't the 1N-256 a silicon rectifier. Wouldn't you want a germanium diode replacement if that was necessary?

[Jim, W5JO]

Jim: Isn't the 1N-256 a silicon rectifier. Wouldn't you want a germanium diode replacement if that was necessary?

You may be right Pete, I was thinking the 256 was used in the Drake W-4 type meter but it may be something.  I am going to use the age excuse please.  Maybe the 1N295???

[Pete, WA2CWA]

1N295 is also a silicon diode. How about the good old germanium 1N34 or 1N64. That's what I've used in all RF detecting projects over the years.

[Jim, W5JO]

They would work for sure Pete however am not sure about availability.  Drake went to the latter in the W4 and they seemed to have good luck with them.