ZoneVI Devel. Timer Repair or Adjust?

[Peter Lewin]

My ZoneVI Compensating Development Timer is in desperate need of repair/recalibration/adjustment, and I wondered if anyone knows if this is even possible?

After seeing that recently developed film was significantly under-developed, I decided to check the compensating aspects of the timer. I placed the ZoneVI probe in a beaker of water measured at 68F using a Kodak thermometer, and compared the ZoneVI times with a stop watch. My assumption is that at 68F, the compensated time and real time should be the same, or very close. Instead I found that while the ZoneVI "real time" setting agrees with my stop watch, the "film" and "paper" settings are about 50% off, so that when the ZoneVI timer says, for example, that 4:30 has elapsed, the stop-watch elapsed time is only 3:00; if anything the error is slightly worse on the "paper" setting, almost a 60% difference.

My sense is that either there is a problem with the circuitry in the timer, or something has failed in the temperature probe. Any suggestions would be greatly appreciated, especially if the old "ZoneVI hands," Mssrs. Barlow and Ritter have any thoughts.

[Mark Sampson]

Richard Ritter is the go-to guy for most Zone VI devices. www.lg4mat.net.

[peter schrager]

I moved on from these devices and now just use common sense and a regular timer...I can print 15 almost identical images no problem. ..every printing session is different and there is never all the same factors involved ..
As an aside richard doesn't do electronic devices but maybe knows someone who can fix it

[Peter Lewin]

A quick status update: I cross-posted to APUG, and Ken Nadvornik responded with information about the internal pots for compensated and real time. I managed to get the error down from 50% to 5%, but couldn't go further because the compensation pot is now at its limit. I'm still hoping for some ideas to get the timer completely calibrated, and I sent an email to Richard Ritter.

In the meantime I have two choices: I can use the timer as a non-compensated timer in the Real Time setting, since that is accurate, and use the usual temperature correction factors for temperatures other than the standard 68F. My other choice to to scale my times upwards by 5%, so for example if I develop my HP5+ by letting the ZoneVI timer run to 12:36, I will actually be developing for the equivalent of 12 minutes. But it would be more pleasant to have the timer working correctly, without extra math.

[Kevin Crisp]

As almost anybody who repairs electronics will tell you, 90% of the time a capacitor has drifted out of spec. I suspect given the volume of the product, the circuit board isn't that hard to test and repair.

[Geary Lyons]

As almost anybody who repairs electronics will tell you, 90% of the time a capacitor has drifted out of spec. I suspect given the volume of the product, the circuit board isn't that hard to test and repair.

Kevin is quite right. I repair old audio tube amplifiers and pro-sumer reel-2-reel decks. Electrolytic capacitors from the 90's are well past their life expectancy. Get them replaced before they start leaking the corrosive electrolyte! Probably not high grade boards in the timer, so wouldn't take much corrosion to trash. No guarantee that is the problem, but it would be my first point-of-inspection!! Next would be PROM's, (programmable read only memory), and that will be, mostly likely, fatal without the code.

Cheers,
Geary

[neil poulsen]

I use mine almost religiously for paper and film developing.

A convenient way to check the unit is to do the same test, but plug a Gralab timer into the Zone VI timer's enlarger plug after setting it to say, ten minutes.

As you related, put the thermocouple into a water bath that's 68 degrees. Start the compensating timer and wait until 3 minutes has expired. The Gralab will automatically keep track of real time, while the compensating timer is keeping track of compensating time. Of course, the two timers will start and stop at exactly the same moments.

[Geary Lyons]

Just a thought. I use an RH Designs Stopclock Pro and have built my paper exposure process around it. So I know how unconsciously competent our chosen tools can make us. I think this compensating timer software is still available. It has a Zone VI emulator. Just in case!!

http://curtpalm.com/Software.html

Cheers,
Geary

[Doremus Scudder]

Don't rule out a defective temperature probe. These should be easy to replace.

As an aside, it would be nice to be able to repair and maintain these devices. Maybe one of the more technically-minded members here wouldn't mind offering a repair service? Or, is there somewhere we can send our timers for repair that I'm not aware of?

Best,

Doremus

[Drew Wiley]

Sometimes it's just grime that develops on the probe. Amidol stain is an obvious suspect. I just periodically scrub it off with a gentle nylon pots n' pan scrubber.
Official service for Zone VI items ended long ago. A specific reason I got pissed off at Calumet when they took over the line. But I'd much rather have something
simple like this than anything dependent on software.