Datron 4708 problems - Page 1
Forum section: electronics / general

author: Fastah
author_rank: Contributor
timestamp: February 17, 2019, 11:36:43 pm
content: HiPlease help.Arrived Datron 4708 with AC functions only. Seller said "Working in good condition, powers up etc." but as I can see left display not working. After calibrator power ON I can set voltage and current on the right side of front panel and turn output ON and OFF, output voltage present but frequency is set to 1kHz permanently and green led on the 1kHz button is all ways ON. Many buttons on the left generate "bip" only. Only I can change on the left side is Guard and Sense leds OFF/ON. Spec, Error and Offset buttons not generate "bip", on press just shortly blink B (Bussy) on he right display, this confirm these three button are ok too. All other buttons on the left produce "bip" only.Any ideas?Where to start with diagnostic and repair?Thank you

author: jfphp
author_rank: Regular Contributor
timestamp: February 20, 2019, 09:56:54 am
content: Normaly the AC function of the 4708, like the 4200, needs a certain amount of time to stabilize the time base, VCO and phase lock loops. Only after a couple of minutes you have access to the frequency command.

author: Fastah
author_rank: Contributor
timestamp: March 18, 2019, 10:56:55 pm
content: HiAfter a long time I'm back...Warm-up time to stabilize calibratror is not a problem.I take a time for clicking randomly on keyboard and found combination when left side of keyboard is active.When I select AC-I 1A mode and try to switch output ON, calibrator automatic turn output OFF. After that left keyboard is active. This is only situation how to make active left side of keyboard. After that I can select AC-V mode and left keys still can change.I made three short videos to demontrate situation. Please see videos carefully.https://youtu.be/fa3UJlxFGXMhttps://youtu.be/qA5xPRH7Xdwhttps://youtu.be/2KvYP2_ydWgI think left keyboard is blocked because 4708A have a problem with output ON-OFF state recogniition or setting.Is this automatic return to OFF state in AC-I 1A without connection on calibrator sockets normal or not?Another detail, sometimes at AC-I 1A when I switch to ON state, ON led do not light up and beep is little different than, but after that left keyboard activate (visible on video). Not working display is different story.Any suggestion?Thank you

author: doktor pyta
author_rank: Frequent Contributor
timestamp: March 18, 2019, 11:55:06 pm
content: I think left display is trying to show You error/fail code just in that moments when You press '+' button.I suspect hardware failure. In my case it was worn out relay on the small HV board+ optocouplers.I don't know if the error code is stored in a queue available via GPIB but it is worth digging.If not it would be nice to have left display working.

author: CalMachine
author_rank: Frequent Contributor
timestamp: March 19, 2019, 01:46:28 am
content: I'm in agreement with pyta, your left display is not working. When turning on the output in current mode, with no load, there should be an 'ERROR OL' or something displayed on the left hand side. Also in current mode, (with the default frequency), you'll only be able to select the 100 Hz and 1 kHz frequency ranges. 10kHz-1MHz will result in an error. Also, in AC mode, you should hear a relay clicking upon each frequency range selection. I don't believe I'm hearing any?How come you're only attempting to turn the output on in current mode? Does it work in Volt mode?Final thoughts; a lot of your button presses the unit simply can't perform and will always result in an error.

author: Fastah
author_rank: Contributor
timestamp: March 19, 2019, 08:27:03 am
content: HiI can switch ON-OFF in voltage mode (video2 0:41-1:10) but in voltage mode I can controll left keyboard only if I select current mode 1A before and calibrator automatic switch to OFF... on lower current ranges calibrator do not switch OFF automatic and if I manual switch output OFF I can't control left keyboard too... I can control keyboard ONLY when calibrator switch output OFF automatic (AC-I 1A range)...I must try to repair display first...Thank you

author: doktor pyta
author_rank: Frequent Contributor
timestamp: March 19, 2019, 02:02:59 pm
content: Try one thing: short I+ and I- terminals in OFF state and then press output ON '+'.The error might be 'out of voltage compliance' when the output is open.

author: Fastah
author_rank: Contributor
timestamp: March 19, 2019, 07:55:48 pm
content: HiJust checked...When I short U+ and U- calibrator stay ON at AC-I 1A range. After that I press output OFF manualy and left side keyboard is blocked.I found another situations when left keyboard unblocked. In every situations calibrator automatic switch output OFF.a) AC-I - 100mA - U+ and U- no connection (automatic OFF - two beeps)b) AC-I - 1A - U+ and U- no connection (automatic OFF - two beeps)c) AC-V - 1V - Hi and Lo short (automatic OFF - three beeps)d) AC-V - 10V - Hi and Lo short (automatic OFF - three beeps)I'm not tested AC-V 100V and 1000V ranges but I think will automatic output OFF too and unblock left side of keyboard.Seems 4708 unblock left keyboard only after automatic OFF because voltage overload errors or no current errors on higher ranges.Thank you

author: Fastah
author_rank: Contributor
timestamp: March 31, 2019, 05:33:59 pm
content: HiToday found some free time and open Datron 4708 to inspect first of all why left display do not working ...On the top (pins side) of left display is visible very small glass cracking and two pins are curved and separated from display case. Display was damaged in transport because very poor packing. This damage is not visible without opening calibrator. Some stronger force was applied on the left display and glass cracked, air entered inside the display (no more vacuum inside) and display died.Left and right displays they are different colors because no more vacuum?Thank you

author: maginnovision
author_rank: Super Contributor
timestamp: March 31, 2019, 06:08:43 pm
content: Quote from: Fastah on March 19, 2019, 07:55:48 pmThose sound normal. On my 4000 if nothing connected to I+ and I- but current selected it shuts off for out of range. Same with shorting output terminals with V+ off, it's a short so it shuts off.You should see about the replacement display board from branadic if you haven't already done so.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 31, 2019, 06:57:20 pm
content: The display glass does not look that bad. To me it looks like a small piece one edge chipped off that would not effect the vacuum at all. This is more like during production not transport. It looks like the vacuum seal is a little further down in the picture, below the visible pins.The more troublesome parts could be pins loose.

author: Fastah
author_rank: Contributor
timestamp: March 31, 2019, 11:07:28 pm
content: I'm sure this display was broken because two pins loose... all voltages are ok.Inside display on the right side are visible some random placed silver shining dots visible on different view angles. This shiny dots are not visible on the right working display.Why segments (cathodes) on this display are dark, not white like on right working display? Maybe this signaling damage of display too?Maybe this display has some coating on the back side that would change color by signaling that it came air inside like on classic vacuum tubes?Thank you

author: Fastah
author_rank: Contributor
timestamp: April 01, 2019, 12:51:33 am
content: Quote from: maginnovision on March 31, 2019, 06:08:43 pmThose shot off situation is normal when no load and short voltage .But my question is why left keyboard is blocked when I manualy shut off output???What's difference between my maual Output OFF and calibrator's automatic Output OFF at this four situations?? That is the question. This is not normal.Thank you

author: maginnovision
author_rank: Super Contributor
timestamp: April 01, 2019, 02:51:19 am
content: Ah, I'm not sure. Check the user manual?http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Datron/Datron_4708_Autocal_multifunction_standard__calibrator_Operator_Manual.pdf

author: Fastah
author_rank: Contributor
timestamp: April 03, 2019, 09:16:30 pm
content: HiThe display has definitely gone. Broken nipple on the back.I temporary soldered one partialy working display.Calibrator on power on give Fail 6 (calibration ram error)Battery voltage is 3.5V.When switch to ACI 1A, calibrator automatic switch output OFF (without load) and give Error OL.Error OL is mystic unblock for left keyboard. Fail 6 block left keyboard.What first? Backup and check calibration ram?Thank you

author: Testtech
author_rank: Regular Contributor
timestamp: April 03, 2019, 11:49:47 pm
content: RE: The display plasma, the good news is it is the same part as used in the 106x series DMM.