Valhalla Scientific 2701C DC Voltage/Current Calibrator - Page 1
Forum section: electronics / testgear

author: MikeDombo
author_rank: Unknown
timestamp: April 22, 2015, 04:02:30 pm
content: Hey EEVBlog!I recently acquired a Valhalla Scientific 2701C calibrator from eBay for $300, which I think is a good deal. The device has similar accuracy to the EDC MV-106, but with more range and 1 more digit of resolution.I will be posting teardown photos and videos when I have them.If anyone has the full manual, that would be amazing since the most complete one I could find online is still missing the schematics and calibration procedures.The photos are too big to post here, so they're on my website here -http://mikedombrowski.com/projects/valhalla-scientific-2701c-dc-voltagecurrent-calibrator/I didn't take out the front panel board because I would need to remove the main board and transformers. The main weight is in the transformers and the case. The case is aluminium, but isn't used for any heatsinking. I really think they should have made this whole thing out of plastic or I guess a thinner metal. I do really like that the handles and the side of the case extend to protect the knobs and binding posts.The backside of the main board only has a resistive voltage divider and a single 10 ohm shunt resistor.The label on the intel chip in the digital section is the IT-2 option that adds current function for 120mA. It is just an EPROM.Annoyingly, it requires a key to calibrate it.Let me know if you want any pictures of certain components closer up.

author: HighVoltage
author_rank: Super Contributor
timestamp: April 22, 2015, 04:19:26 pm
content: 300$ for a Valhalla Scientific 2701C calibrator seems to be very good.Is it working correctly?Looking forward to your tear down pictures.

author: TiN
author_rank: Super Contributor
timestamp: April 22, 2015, 05:31:54 pm
content: Good deal. Waiting for photos too!I guess someone need tell Dave to make separate volt-nut section on forums, since our team just got one more

author: Vgkid
author_rank: Super Contributor
timestamp: April 22, 2015, 05:55:16 pm
content: Cool, add another member waiting for pics.

author: jlmoon
author_rank: Unknown
timestamp: April 22, 2015, 06:55:58 pm
content: and another one.....

author: MikeDombo
author_rank: Unknown
timestamp: April 22, 2015, 07:36:53 pm
content: Quote from: HighVoltage on April 22, 2015, 04:19:26 pmIt does seem to be working well, verified with a HP 3457A. One of the two is slightly out and I don't know when either was last calibrated. But it really was only out be a bee's dick on some ranges.

author: ltz2000
author_rank: Regular Contributor
timestamp: April 22, 2015, 07:46:45 pm
content: Quote from: MikeDombo on April 22, 2015, 04:02:30 pm2701C calibration procedure

author: MikeDombo
author_rank: Unknown
timestamp: April 22, 2015, 08:01:20 pm
content: Quote from: ltz2000 on April 22, 2015, 07:46:45 pm

author: MikeDombo
author_rank: Unknown
timestamp: April 22, 2015, 09:22:27 pm
content: The photos are too big to post here, so they're on my website here -http://mikedombrowski.com/projects/valhalla-scientific-2701c-dc-voltagecurrent-calibrator/I didn't take out the front panel board because I would need to remove the main board and transformers. The main weight is in the transformers and the case. The case is aluminium, but isn't used for any heatsinking. I really think they should have made this whole thing out of plastic or I guess a thinner metal. I do really like that the handles and the side of the case extend to protect the knobs and binding posts.The backside of the main board only has a resistive voltage divider and a single 10 ohm shunt resistor.The label on the intel chip in the digital section is the IT-2 option that adds current function for 120mA. It is just an EPROM.Annoyingly to calibrate the 2701C requires a key to calibrate it.Let me know if you want any pictures of certain components closer up.

author: Len
author_rank: Frequent Contributor
timestamp: April 22, 2015, 09:25:01 pm
content: Quote from: MikeDombo on April 22, 2015, 07:36:53 pmThe industry standard is half a bee's dick, so you'll need to get one of them calibrated.

author: MikeDombo
author_rank: Unknown
timestamp: April 22, 2015, 09:26:21 pm
content: Quote from: Len on April 22, 2015, 09:25:01 pmyep, that's what I figured.

author: TiN
author_rank: Super Contributor
timestamp: April 23, 2015, 04:30:56 am
content: Remarked LM399Thanks for photos, may I steal them with proper references to your site given?

author: Vgkid
author_rank: Super Contributor
timestamp: April 23, 2015, 04:46:32 am
content: Thanks for the teardown pics.

author: HighVoltage
author_rank: Super Contributor
timestamp: April 23, 2015, 07:24:51 am
content: Thanks for your great picturesIt seems this unit is still in production:http://valhallascientific.com/instruments/calibrators/model-2701c/And the price is $18,660.00 USD? (at Transcat)Is that real?http://www.transcat.com/valhalla-scientific-2701c-2701c

author: MikeDombo
author_rank: Unknown
timestamp: April 23, 2015, 12:12:22 pm
content: Quote from: TiN on April 23, 2015, 04:30:56 amPlease do steal them.

author: MikeDombo
author_rank: Unknown
timestamp: April 23, 2015, 12:15:15 pm
content: Quote from: HighVoltage on April 23, 2015, 07:24:51 amAccording to the Valhalla site they still make this model, but are on to the 2nd or 3rd rev and mine is still the first.That transcat price is one of the reasons I bought it for $300, I figured I couldn't pass up that kind of deal.

author: MikeDombo
author_rank: Unknown
timestamp: May 09, 2015, 02:41:50 am
content: So I'm thinking about modding the 2701C to replace the calibration/operation keylock switch with a regular rocker switch. I especially want to do this because I do not have the key. I have tracked the keylock to a c&k Y series dual pole with 2 positions. In operation mode the switch connects its 8 and 1 connections and its 4 and 5. In position 2 which is calibration mode, it connects 1 to 3 and 5 to 7. These respond to E32-37 labeled on the top side silkscreen. I should be able to replicate the functionality with a regular rocker, maybe with a light to indicate calibration mode as well.What type of switch would I need to make this work?Let me know if you have any thoughts about this mod.

author: quarks
author_rank: Frequent Contributor
timestamp: May 09, 2015, 10:27:45 am
content: if it is working 300$ is a very good pricethe 2701C is a very good piece of gear, I like mine very muchit also seems to be a great candidate for an upgrade with LTZ1000

author: MikeDombo
author_rank: Unknown
timestamp: May 10, 2015, 08:58:56 pm
content: Quote from: quarks on May 09, 2015, 10:27:45 amWould the LTZ1000 be a drop-in replacement for what I assume is an LM399 that is the current reference? Would the surrounding circuitry have to be changed/removed in any way?To remind you here is the voltage reference.

author: barnacle2k
author_rank: Regular Contributor
timestamp: May 12, 2015, 07:05:05 pm
content: Quote from: MikeDombo on May 10, 2015, 08:58:56 pmDrop-in? - No!Changing/removing: Yes, all of it.You'd need to add a daughter board.

author: Theboel
author_rank: Frequent Contributor
timestamp: May 13, 2015, 02:26:28 am
content: I spot in ebay this valhalla offer for under 500USD include shipment to my country (Indonesia) thats very atractive but my question is not are they work but are they work in spec ?so let me ask if anybody know how much the cost for calibration this kind off equipment in USA

author: nadona
author_rank: Regular Contributor
timestamp: May 13, 2015, 09:05:05 am
content: Theboel:PM sent.