dvc 8500 calibrator repair - Page 1
Forum section: electronics / repair

author: Arjan Emm
author_rank: Regular Contributor
timestamp: February 07, 2016, 05:44:56 pm
content: I bought a dvc8500 for 20 euro on marktplaats a dutch version of ebay. The seller told me to replace the mains lead. And that was nessecery, it crumbled to dust when touching it. datasheat:https://www.google.nl/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwjqwbiNl-bKAhVCyxoKHRwYDyYQFggzMAI&url=http%3A%2F%2Fwww.calibratorsinc.com%2Fimages%2FDVC-8500_DATA_SHEET.pdf&usg=AFQjCNE-HX3LUku-j8pIM_wl_zpK4VN7kQ&sig2=jfMifnr3EGZTaiCQmXMBwwIt's a lm399 based voltage source from +- 19.999 Volt with decade switches to set it.I replaced the cord, powered it on en measured it's output with my Fluke 187. I set it to 12.345V and the fluke agreed! excellent, much more confidence in my 2nd hand fluke 187!Two minuts later the dvc died. Voltage dropped from 10.000 to 2.503V. 1.000 gives 0.2503 . so the decade setting part still works. But the powerspply it completely off.Does anyone have a schematic or a working device to share some voltage measurements?The dvc has also 4 clear test points, does anyone know what they should measure, they are numbered 1-4.

author: Vgkid
author_rank: Super Contributor
timestamp: February 07, 2016, 06:04:13 pm
content: Post up some pics.

author: Arjan Emm
author_rank: Regular Contributor
timestamp: February 07, 2016, 06:18:26 pm
content: The front pannel.The lm399.

author: Arjan Emm
author_rank: Regular Contributor
timestamp: February 07, 2016, 06:23:41 pm
content: And the power supply.The left elco measures 51Vdc and 0.1Vac. The right one 36Dc and 0.3Vac. The left pass transistor is quite a bit hotter as the right side counter part.

author: HighVoltage
author_rank: Super Contributor
timestamp: February 07, 2016, 06:26:02 pm
content: Wow, you got lucky with that price !There is one on ebay usa for $ 1000Probably an easy fix too.

author: Arjan Emm
author_rank: Regular Contributor
timestamp: February 07, 2016, 07:20:59 pm
content: Yeah definately a good price.Down side is there isn't a schematic available. And the pcb is double sidded and hand drawn. Not that easy for tracing out the schematic. actually impossible for me to figure out the powersupply exactly.

author: Vgkid
author_rank: Super Contributor
timestamp: February 07, 2016, 07:30:19 pm
content: Something does not look good about those orange capacitors, one looks like it is leaking.

author: Macbeth
author_rank: Super Contributor
timestamp: February 07, 2016, 07:42:41 pm
content: Quote from: Arjan Emm on February 07, 2016, 07:20:59 pmSurely this is just about the easiest type of PCB to reverse engineer? I would do it as a matter of course if no schematics available and it's a keeper. Use at as an opportunity to learn KiCad or something.But those electrolytics don't look good.

author: Arjan Emm
author_rank: Regular Contributor
timestamp: February 07, 2016, 07:55:03 pm
content: The black crap at the bottom of the electrolitycs is glue in all kinds of states of deterioration.The caps seem to measure fine, in or out of circuit. Those where the ones to replace at first thought but they seem fine..

author: HighVoltage
author_rank: Super Contributor
timestamp: February 08, 2016, 08:17:50 am
content: Not a schematics, but may be this block diagram one will help a little:www.calibratorsinc.com/images/DVC-8500_DATA_SHEET.pdf