Guildline 9730CR oil bath, under the cover+manual&cct.

[lowimpedance]

So seeing the DIY oil bath thread reminded me of a Guildline 9730 at work and thought some might like to see some pictures of under the covers.
So what is under the covers .............. well not that much really. See the photo's from the top is of course the bath with the strirrer/heater and cooling coil assembly with a temp sensor ! (a 390 ohm resitance) in a TO-39 case.
 Underneath is the compressor at one end and the stirrer motor and temp control at the opposite end so basically thats it. 
This unit has reached BER  , and now becomes spares for the other still operating Guildlines.

[lowimpedance]

More pics.

[Vgkid]

Thanks for the teardown. Surprised they used a Fluke decade potentiometer instead of the ESI Deca-stat.

[lowimpedance]

Indeed it was a surprise ,the dials are slightly different to ESI dials so generally stand out as not being from ESI. And to note the other Guildline baths at work actually have ESI pots instead. Perhaps the Flukes were to expensive  .

[Vgkid]

I was thinking that maybe it was because the two were competitors. Then I realized, that they are  not really that close.
@ lowimpedance
Can you take off the cover of that decade potentiometer. I'm curious is they used regular flat mica PWW resistors or Flkes usual teal cylindrical resistors.

[zlymex]

From the 8th photo, the Fluke one is a RHEOSTAT, a varistor with two terminals, rather than a potentiometer or a voltage divider.

I had a manual of Fluke 50A/M Decade potentiometer but they are not the same. The file is too large to attach.

[lowimpedance]

I was thinking that maybe it was because the two were competitors. Then I realized, that they are  not really that close.
@ lowimpedance
Can you take off the cover of that decade potentiometer. I'm curious is they used regular flat mica PWW resistors or Flkes usual teal cylindrical resistors.

Okay the cover is off and what do we see................ Mica resistors and what appears to be fibre glass switch wafers with gold plated contacts all wrapped up in a plastic sheet of poly 'something',  ethylene perhaps  .

[Vgkid]

Thanks. Interesting that they did not use ceramic switch wafers. My ESI's use Centralab's. Set up so that each wafer uses 2 rotary contacts in parallel to minimize switch contact resistance.
So it runs it in the 2+2+2+2+2+1 arrangement. I haven't seen a cylindrical coax decade that uses 9/10 individual resistors of that range. Yet...

[lowimpedance]

And just for comparison here we have the ESI version of a 12K ohm rheostat.  (missing the dials!)
Construction a little bit different in the switch wafers are ceramic and there is a trimpot at the bottom. But of course still mica card resistors.

[Vgkid]

That is how my DB655 is set up(w/o the potentiometer), Always wanted an 877. They went for to much money, even broken .

[lowimpedance]

I have an DB877, a very nice bit of gear. I like the coaxial arrangment, (I could spend hours just turning the dials : )

[zlymex]

So it runs it in the 2+2+2+2+2+1 arrangement.

Fluke used this arrangement in its 335D varistor too.

I also found out a photo of an ESI bridge that employ a bare potentiometer/varistor (photo right)

Edit: add ESI DekaStat instruction sheet(with schematic diagram)

[ace1903]

Thanks for nice pictures.
Does someone has schematic? I mostly do embedded programming so I am fascinated by this pure analog design.
Any insight in temperature control loop? Does the cooling system run all the time and temperature stabilization is achieved by balancing current through heater?

[lowimpedance]

Thanks for nice pictures.
Does someone has schematic? I mostly do embedded programming so I am fascinated by this pure analog design.
Any insight in temperature control loop? Does the cooling system run all the time and temperature stabilization is achieved by balancing current through heater?

Here is the only documentation I could find, hope its of interest.

[dacman]

The compressor should be either always on or always off depending on the desired temperature.  (For standard resistors, it will be on.)  Temperature is then controlled by turning the heaters on and off.  The power of the heaters should be set so that the on/off times are approximately equal (for the 9730CR).

[Vgkid]

Thanks for that information loZ. Similiar to what dacman said, I have seen in thermally controlled chambers there the cooler is running continuously (for certain temp zones) and the heater power is varied in order to maintain a constant temperature. Similiar to how I have peltiers run. Where they have a heater that is constantly on(power varied if needed) and the peltier element is ramped up/down .