Author Topic: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]  (Read 25735 times)

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Offline dr.diesel

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #25 on: July 28, 2016, 04:27:08 pm »
Sorry, my bad, fixed above.


Offline dr.diesel

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #26 on: August 03, 2016, 11:48:56 am »
Finally got around to replacing the caps and attempting to clean the switches, and all I did was make it worse,  :palm:

Last night's run:

308uV - Peak to Peak
56uV - Standard Dev

I used the same method and dunked the face of the instrument in IPA, toggling the switches, got lots of dirt out in the process.  I'd really like to take the switches apart to properly lubricant, but on this unit that would really be a PITA.  I can see over 1mV of deviation just by touching the most significant digit switch handle.

Offline HighVoltageTopic starter

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #27 on: August 03, 2016, 09:01:00 pm »
Finally got around to replacing the caps and attempting to clean the switches, and all I did was make it worse,  :palm:

Last night's run:

308uV - Peak to Peak
56uV - Standard Dev

I used the same method and dunked the face of the instrument in IPA, toggling the switches, got lots of dirt out in the process.  I'd really like to take the switches apart to properly lubricant, but on this unit that would really be a PITA.  I can see over 1mV of deviation just by touching the most significant digit switch handle.

Great that you got out the dirt with IPA.

But make sure to add some kind of high quality contact lubricant, like I did and then blow the excess with some air pressure.
(Some lubricant will exit the back housing)
After that, you should not see any changes anymore, when you touch any of the switches.

I repeated this process of cleaning and lubrication a few times, until the reading was stable for all switches in all positions.
Now I can touch the switches even harder and the values stay stable and do not move anymore.

There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline USMC_Spike

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #28 on: December 23, 2016, 12:29:31 am »
@ High Voltage Can you tell me, when you soaked your front panel
pots in ISO, did you fill a pan with ISO and put it face down in it
and let it soak?

Or did you pour it in from the face?

Same with the MG chemicals too
after you were finished.

@ Dr. Diesel What was the logging meter for lack of a better term that
you used that gave you a read out of the measurements and dates?

Thanks,

Spike
Cheers,

USMC_Spike
 

Offline dr.diesel

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #29 on: December 23, 2016, 12:38:22 am »
@ Dr. Diesel What was the logging meter for lack of a better term that
you used that gave you a read out of the measurements and dates?

Thanks,

Spike

Keithley 7510.

Offline HighVoltageTopic starter

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #30 on: December 23, 2016, 09:52:18 am »
@ High Voltage Can you tell me, when you soaked your front panel
pots in ISO, did you fill a pan with ISO and put it face down in it
and let it soak?

Or did you pour it in from the face?
Spike

I placed it face down in to the cleaning alcohol until the air had completely escaped.
And then I moved the wheels a lot and I mean a lot until all the dirt was out
In between I blew it out with air pressure

This might sound brutal but it worked very well.
And based on the dirt inside the alcohol, it was very effective

I repeated this procedure with a second unit and had the same success.
Both of them are working perfectly right now.

Good luck


 
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Offline USMC_Spike

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #31 on: December 25, 2016, 01:52:29 am »
This is good information for me and probably many other people.

I've had one of these for about a year now and it's never worked
properly, nor had I found good readable information about it.

With your postings I'm confident now that I can get the problems
with my unit worked out. 
Cheers,

USMC_Spike
 

Offline Assafl

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #32 on: December 25, 2016, 11:50:19 am »
This is good information for me and probably many other people.

I've had one of these for about a year now and it's never worked
properly, nor had I found good readable information about it.

With your postings I'm confident now that I can get the problems
with my unit worked out. 


Yes - BTW They do have a data sheet which has calibration information. They do not publish schematics.

They also do exist as a Company (called Calibrators Inc.) and while they don't seem to answer their official email address they answer their phone and do stock spare parts.

I called them and replaced a bad LCD (25$) on a DVC-350a I got for 15$ (listed as-is for parts) on ebay. Altogether I spent about 80$ including shipping to Israel. My device is from the GE days (mid 80s) - Have never seen a company that makes the same electronics for 30 years. I wonder how they source the old parts?

 

Offline Messtechniker

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #33 on: December 25, 2016, 01:03:56 pm »
Have never seen a company that makes the same electronics for 30 years. I wonder how they source the old parts?
I have seen special time related manufacturing agreements with subcontractors
(hopefully) guaranteeing supplies for 10, 20 or even 30 years.
Agilent 34465A, Siglent SDG 2042X, Hameg HMO1022, R&S HMC 8043, Peaktech 2025A, Voltcraft VC 940, M-Audio Audiophile 192, R&S Psophometer UPGR, 3 Transistor Testers, DL4JAL Transistor Curve Tracer, UT622E LCR meter
 

Offline USMC_Spike

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #34 on: December 25, 2016, 07:07:09 pm »
And sometimes with companies, depending on the company, they have their contracted manufacturer make a lot
of parts and they warehouse them.  (expensive).  The audio company Audio Research Corporation comes to mind.
I bought some new replacement knobs for a pre amp that hand not been manufactured since the 70s.

Can you post their phone number I will need two things, the bezel and one of the small vertical holders
for the bezel...someone man handled mine and sheared off the bezel pin at the top along with
cracking the bezel.  Unscrew from the bottom, rotate forward from the bottom and the
bezel rotates and lifts out.

For the first time since I've had the calibrator, it works.  Who every handled it, had one ground
not connected and the ground from the pot floating.

Can you post the phone number? Or did you use the phone number listed on the  data sheet?

I've got to order two pieces.

Thanks,

Spike
Cheers,

USMC_Spike
 

Offline Assafl

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #35 on: December 25, 2016, 08:25:15 pm »
I think you are right and that they actually stock all these very old parts. Quirky QIP (zig zag DIP) multiplexers... Or they buy from Rochester...

The phone number I have is: 401-769-0333
 

Offline USMC_Spike

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #36 on: December 25, 2016, 09:00:42 pm »
Thanks Assafl, appreciate the phone number for them.

Also I didn't know they made even smaller calibrators.
The DVC-8500 is pretty small, but I saw pics of the
DVC-350a and that looks to be pocket sized.

Can you post a link to a data sheet for that?

Thanks,

Spike
Cheers,

USMC_Spike
 

Offline Assafl

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Offline IconicPCB

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #38 on: December 25, 2016, 10:31:15 pm »
What might the attenuator resistors be ?
specification and supplier?
 

Offline HighVoltageTopic starter

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #39 on: December 26, 2016, 10:36:36 am »
What might the attenuator resistors be ?
specification and supplier?
They are probably custom made.
I have looked and found nothing, when I repaired my first unit.

DVC-350A
There is one on eBay Germany right now
But it seems to have a broken display and is too expensive
http://www.ebay.de/itm/290660105128
See pictures below

DCV-9500
I have looked for a long time but have never seen one for sale
Well, I have not even seen a real picture of it.
But it has some impressive figures:

Part number DVC 9500
• UNPRECEDENTED Calibration Accuracy < +/-0.0005% error or < +/- 5 PPM
• Less than 3 PPM / deg C temperature drift
• 13 types of Thermocouples output simulations
• Both a +/-20 Volt and +/-2 Volt Range ( programmable bipolar operation )
• Direct TOUCH PAD INTERFACE FOR INTUITIVE HUMAN INTERACTION
• Compact rugged aluminum case that takes up very little precious bench top space
• Digital Output Vernier control down to 1uV steps
• Settable limit controls to protect devices.
• Automatic standby function protects device under test
• Six (6) Manual/Automatic set points per output range
• Programmable Dwell time between set points
• Tellurium-Copper binding posts reduce thermal EMFs to <1uV
• Source 25ma Voltage output with 13 thermocouple ranges




There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline Assafl

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #40 on: December 26, 2016, 11:36:05 am »
I got a DVC350 for about 20$ with a totally black display. Verified it worked - and purchased the LCD for 25$. Shipping to Israel doubled the price.... My DVC8500 is stuck in customs for a fortnight. Sorry I have to wait....

As for the DVC350 - it doesn't use a resistor ladder: It uses an AD1403A 2.5V regulator and a CMOS multiplying D/A (an Exar MP7614) to create the output voltage steps. It then uses various op-amps to get the voltage to get the voltage to a 1.2 or 12V range (or for Hex 1 or 10V range), and to operate the current limit. 

Further control of the display is an ICM7211NIPL, an EPROM, and an Intersil CDP1802A CPU and various multiplexers I think from Harris in QIP packages (I could not find them anywhere).

Power supply is a RC4193 (I think when Raytheon still made chips) with a support array of components (as switching power supply circuits were back in the day).

Overall the DVC350 is pretty linear - if quite noisy (my comparison is unfair - a saturated standard cell - a boat anchor but stable as a brick). The last digit drifts quite a bit as well. But I find I use it quite a bit more than I expected. Whenever I suspect a dubious reading I use it to validate my setup is okay. Were it to generate accurate AC it would be even more useful. 
« Last Edit: December 26, 2016, 11:40:06 am by Assafl »
 

Offline Arjan Emm

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #41 on: December 26, 2016, 03:07:37 pm »
I also bought a datel 8500 half a year ago. The cord was also really bad, replaced is it first. Switched it on and measured all digits perfectly with my fluke 187 and the cal nob at 0. But after 10 minutes of playing with, it went nuts, voltages are all over the place. It now gives only negative voltages and only roughly close to the settings, 20-30% off. For example +19.999 volt gives -24.8V and -19.999 gives - 24.8V.
The switches feel really smooth.
Any ideas what could be wrong? I find it really hard to troubleshoot a device without a schematic.
 

Offline Assafl

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #42 on: December 26, 2016, 03:43:17 pm »
Did you check the LM399 to see that it has the correct voltage?

Also did you check that the shorting bars are well tightened in the back?

When something goes wild like that it usually is a contact or something the blew up (I did have a tantalum give up the magic smoke in the DVC350).
 

Offline Arjan Emm

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #43 on: December 26, 2016, 04:24:01 pm »
Thanks, i didn't measure the lm399 it self, but the 10 v reference on the back measures 12.4 V. 
the shorting bars are very tight and the contacts look clean.
There seem to be many tantaliums in there, does it make sense if they fail after 10 minutes before being powered off for probably years?
Edit: The lm399 measures 7.0250V on the fluke, not 6.95.
« Last Edit: December 26, 2016, 06:25:43 pm by Arjan Emm »
 

Offline Vgkid

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #44 on: December 26, 2016, 07:54:35 pm »
The 7.025v seems good. With that 12v instead of the 10v look into anything involving the reference amplifier. Also how do the voltage  supplies look?
If you own any North Hills Electronics gear, message me. L&N Fan
 

Offline Assafl

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #45 on: December 26, 2016, 08:38:55 pm »
Received mine, replaced the cord (kept a 110V cord as it can be damaged if plugged into 220V) - the cord disintegrated because of the hot transformer. The rest of the wiring is PTFE so could care less if it is hot... The only other damage is the knob cap (for the potentiometer).

It is right on calibration (much less than 100uv deviation). No output changes touching or wiggling the levers. It does need 10 minutes or so to settle some initial drift. After that the 6th digit (on the HP34401A) is pretty stable at the 10V range +- 1 digit. I'll let it settle overnight.

What's up with not having a tapped voltage transformer for 100, 110 and 220V??? Is it a mil-spec thingy?
 

Offline Assafl

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #46 on: December 27, 2016, 07:45:34 am »
What might the attenuator resistors be ?
specification and supplier?

They are marked R1 R2 R3... Also marking is 2307 (the two large resistors have the same marking). The resistors seem to be potted on one side. So maybe wirewound? The switches are gold flashed levers from Cherry. Potentiometer is a Claro USA.

Chip codes are 86 (the LM399) to 1988 (for the 714 and transistors). So 1988 could be the manufacturing year - albeit - If they keep long stock then chip dates may not reflect manufacturing date...

Since the "big" electrolytic caps from Japan (Nichicon) are end mounted axial, they also have the extensions.

The transformer is mounted on two metal spacers to the PCB - it was completely loose and pushed some of the TO220 sideways (but no damage was done).

Apart from the 110V cable which seemed to have lost the plasticizer (it became somewhat sticky on the outer section and the insulation was falling apart on the inside section - usually means the plasticizer is gone) the rest seems to be almost mil-spec to the letter - I say "almost" as the transformer mount is not mil-spec and the TO220 heatsinks are not anchored, and the end mounted electrolytic caps have 2-sided adhesive mount but would usually need a shock mount. Also not having a manufacturing date code probably means no real mil-spec...
 

Offline Assafl

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #47 on: December 27, 2016, 08:03:30 am »
Thanks, i didn't measure the lm399 it self, but the 10 v reference on the back measures 12.4 V. 
the shorting bars are very tight and the contacts look clean.
There seem to be many tantaliums in there, does it make sense if they fail after 10 minutes before being powered off for probably years?
Edit: The lm399 measures 7.0250V on the fluke, not 6.95.

I just measured - the 10V on my unit measures 10.00004V. It is within the uncertainty of the HP34401A.
 

Offline USMC_Spike

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #48 on: December 27, 2016, 10:32:03 am »
My DVC-8500A is getting better.  It reads close to what it should be after
cleaning everything and then plugging the wireing (grounding) back in.

So I almost have it dialed back to zero...but it wanders about 0.000,010
on my 34401A. 

My main filters are Orange Siemans from 1978 date code. Most of the
resistors on the main board are carbon comps, sadly.  The others are
looking like bulk foil, behind the cherry switches and then along
the side next to cal pots down to the power inlet are other bluk foil
resistors. 

Anyone know about the front panel pot?  How would a precision 10 turn work there?
or a conductive plastic vs. cermet?  I'm almost sorry now that I touched the R46 zero
offset pot....

--Spike

I"ll have to read the brochure again as I'm not to sure how to send a voltage...

I guess for a clean voltage reference, I could use my HP339A and set it for 60 Hz at
the 19.999 voltage? and I'd hook it up where is what I was wondering?

Any guidance appreciated.

Thank,

Spike
Cheers,

USMC_Spike
 

Offline Assafl

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Re: DATEL Voltage Calibrator DVC 8500, Repair [SUCCESS]
« Reply #49 on: December 27, 2016, 12:40:39 pm »
So I almost have it dialed back to zero...but it wanders about 0.000,010
on my 34401A. 

I wouldn't expect it to be accurate enough to match (let alone be better) than the HP34401A. Although it uses the same voltage reference - the LM399 - the HP34401A uses a combination of precision components combined with procedures (e.g. the auto zero) to compensate for the rest of the system. The Datel is good - but I wouldn't expect it to be as good - just look at the specs.

Quote
I"ll have to read the brochure again as I'm not to sure how to send a voltage...

I guess for a clean voltage reference, I could use my HP339A and set it for 60 Hz at
the 19.999 voltage? and I'd hook it up where is what I was wondering?

Do you mean for calibration? They suggest using a DC reference voltage and using it with a DVM connected as a null meter to ensure the voltage is identical. So you'd connect the - together (- of Datel and - of DC source together) and connect the + of the Datel to the DVM + and the + of the source to the DVM.

You are basically looking for 0v on the DMM (so that the voltages are identical on the Datel and the reference). The advantage to this scheme, is that if you use your HP34401A - you can use the full precision of the 120mV range (100nV resolution). Which is nice but can drive one nuts as the numbers will flutter about with noise and drift).

If you have a 34401A I am not sure that is needed. Their calibration instruction require 100uV resolution - since you can utilize the long precision 6.5 digit (or better - use the computer link and get about 7 digits) mode that gives you the required resolution at full scale. You may want to use a voltage such as 11.999V instead of 19.999V to take advantage of the higher resolution of the HP34401A at that value (10uV at 12V range and not the 100uV at the 120V range). Of course calibrate the zero at the mV range. Let it warm up at least 15-30 minutes. It does drift a bit at power up.
 


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