Repair or hack options for Z-IV Developing timer.

[Christiaan Phleger]

I'm having some problems with my Zone IV Developing Timer, the one with the temp unit and that changes with the temp shifts. It started getting a bit tweaky, nothing new every now and then it would need the wires jiggled, but this time I noticed one of the phone plugs was cracked, the one that goes to the temp unit. I've properly replaced the plug, but the wires had a layer of oxidization and I fear that the whole stretch might be corroded. Problem here is that the non-plug end ends Into the unit, and I can't figure out how to replace the cord. I've read that Calumet/ZoneIV does not repair these anymore, and although the Timer Unit is still good and works in normal time, I'm also thinking that I maybe could just figure out a replacement temp sender. If anybody has any electronics ideas for me to try I'd be very stoked. I've printed with this timer for 10+ years and out here when it gets hot it really helps keep the consistency of my prints. I've also considered designing a new one, I don't think it would be as hard considering the advances in chips and such.

 

[resummerfield]

About one year ago I bought a replacement probe for this timer from Calumet. They probably still sell them.

 

[Nicholas Lindan]

What sort of sensor does it use: RTD or thermocouple - and then what sort of RTD (Pt, Iron, NTC, PTC) or thermocouple (K, E...)?

 

[Christiaan Phleger]

According to the original operation manual, it has Quote;

" The electronic design utilizes state of the art microchips in a careful and conservative circuit configuration. My component selection includes gold signal connectors, military-style tantalum capacitors, sealed 'cermet' controls, precision metal-film resistors, and temperature-stable polycarbonate timing capacitor."
"The temperature-sensing unit is a black epoxy casting in the shape of and inverted U, with the temperature-sensing thermistor embedded in the lower front edge..."
"We've used precision curve-confroming thermistors so that the temperature sensors are not only accurate, but identical (and therefore interchangeable"

This 'interchangeable' sensor is what I think I need. I talked to Calumet and they're going to look on the shelf to see if one is still around, but I think that may not have much hope. The unit is good and solid, and I don't think I'd be hurting any patent issues by perhaps figuring out some other way to get the temp info to the unit.

 

[resummerfield]

Zone VI made at least 2 separate designs of this probe. The one I obtained from Calumet is a stainless steel cylinder of 0.25-inches diameter x 7.0 inches long.

 

[Christiaan Phleger]

Wow, that's totally different than mine, which is the black chunk of epoxy. I managed to get mine to go properly, I replaced the phone connector again, and cleaned the whole temp unit. When I did that, the little lever had corrosion on the magnet part, and I cleaned that as well as re-magnitized it with a strong magnet. Fiddling with that lever in place and with the magnet in the proper position, I think made the sensors internal switch move correctly, and now the timing unit responds correctly to tempetarure shifts. I'm still thinking about replacing it with something better. I have no idea why this timer wasn't more popular, or why another manufacturer hasn't done another one, they are great in use.

 

[Richard T Ritter]

They both had the same type of sencor in then. It was a 68 degree thermocouple.

 

[Christiaan Phleger]

Aha!
What's a 68 degree thermocouple?

 

[lee]

they were very expensive when sold new. I seem to remember over $300 for a timer. I have one now. I like it.

lee\c

 

[Nicholas Lindan]

According to the original operation manual, it has Quote;

... temperature-sensing thermistor ... interchangeable ...

Sounds pretty generic:

http://www.ussensor.com/prod_inter_precision.htm

Prices vary greatly: 5 cents to 20 dollars, common DO-xx or bead styles are about 1 dollar.

It sounds like it may be a thermistor and a trim circuit encapsulated in epoxy.