General Resistance RTD-100 Teardown and repair.

[Vgkid]

I have always wanted an rtd calibrator / milliohm box. Well it finally happened , and here is what I got...
I will apologize , my pics didn't turn out too well. I can't use my lab(packing stuff up , to move it into the unheated garage) plus my mom is recovering from knee surgery , don't want to risk it.
I included a variant image of this unit.

[Vgkid]

For this , the tear down will be first , and a short overview on the theory will be later.
**I will add a few more pics as I go through the unit**
After seeing the outside of the unit , lets look at where the output terminals should be.

We are presented with one gold binding post , most likely a Pomona 3770. The other 3 binding post are missing , they look to have been cut  from their wires. The binding post sense leads are connected to the source leads by a gold binding post link( judging from other pictures)

The first 3 decades follow the conventional decade resistor layout , except the '1' position on the 10-Ohms range is its lowest setting. The resistor for this represents the difference between 10 Ohms , and the rest of the lower shunted mill-ohm values.

The milliohm range represents a large shift in the expected values in a decade resistor. These occur by shunting a resistor , with varying resistors in series. This will give a range that will increment by a desired amount.    This will be explained more later.

[bitseeker]

Cool. Following along...

[mnementh]

Some fuckwit defiled a laboratory-grade resistance box with dikes to harvest $6 a few $$ worth of banana jacks...

Where is the [Punch him in the DICK!!!] button on my keyboard? I need it RIGHT NOW!!!

mnem
Don't forget to use silver-bearing solder when you restore; keep it as original as possible.

[Vgkid]

Unless that other banana jack is able to be cleaned , I will need to grab  4-3770 thats like 45bucks. I can't wait to test it.

[Kosmic]

Unless that other banana jack is able to be cleaned , I will need to grab  4-3770 thats like 45bucks. I can't wait to test it.

There's also the Mueller BU-P3770. Supposed to be similar to the Pomona but cheaper. You can find them on arrow for 8$ shipping included.

[Vgkid]

Unless that other banana jack is able to be cleaned , I will need to grab  4-3770 thats like 45bucks. I can't wait to test it.

There's also the Mueller BU-P3770. Supposed to be similar to the Pomona but cheaper. You can find them on arrow for 8$ shipping included.

I see digikey stocks them , might need to add them to my resistor order.
Arrow is a painful site to use , if you don't know part numbers.

[bitseeker]

Arrow is a painful site to use , if you don't know part numbers.

Yep, it sure is. But sometimes (not always) they have the best price. The free overnight shipping is nice as well.

[mnementh]

Crap. I had no idea they were that expensive now. 

Good single-contact jacks like that were a couple bucks from ECG; I figured that thing was probably coeval with them.

mnem
*Sigh* I sound just like my grandmother... "Kids are fuckwits. Cars are ugly. Stuff costs more."   

[Kosmic]

Crap. I had no idea they were that expensive now. 

Copper is expensive now. Brass binding post are cheaper.

[Vgkid]

Filed a small amount off the end of the binding post , and it looks to be gold plated brass. I will tell more tomorrow. I will also get some better pics , hopefully. taking pics out side.
Correct , gold plated brass .