test gear questions - Page 1
Forum section: electronics / beginners

author: p.larner
author_rank: Frequent Contributor
timestamp: December 20, 2023, 02:20:18 pm
content: questions about a solatron 7075,firstly what fluke or other makes have the same readout resolution,ie number of digits after the decimal point,and B can i use this to measure pcb power rails to help locate a shorted cap etc,by using the voltmeter or resistance ranges?,dont know a lot about it as its still in the post,cheers+ merry xmas all.

author: p.larner
author_rank: Frequent Contributor
timestamp: December 20, 2023, 08:57:44 pm
content: can noboby give any answers on this?.

author: Vovk_Z
author_rank: Super Contributor
timestamp: December 21, 2023, 06:15:45 am
content: You mean use ohmmeter with a lot of resolution to find a short circuit? Or what?I'm not sure it is convenient. Do you have it now? Have you tried it?At the end what works for you is good for you.Do you mean ceramic caps or which type? Ceramic (or other) caps can often be checked by usual DMM with 0.01 R resolution.I guess the name of this topic is too general. Try to be a bit more specific and I guess you'll have more answers.

author: p.larner
author_rank: Frequent Contributor
timestamp: December 22, 2023, 01:11:58 am
content: i realy wanted to know if the Solartron 7075 Schlumberger Digital Voltmeter a 9 digit meter,if so it should be ok for finding shorted caps ie tants on power rails etc,it will arrive in about 5 days,slow post this time of year,this was the item number ebay.266562163509

author: Gyro
author_rank: Super Contributor
timestamp: December 22, 2023, 10:18:36 am
content: First, you need to download, read, and understand the manual. Long scale meters are complex beasts an you do need to understand them. Specifically, the 7075 isn't a 9 digit meter, it comes from a 'phase' when Solartron thought it would be a good idea to always have the decimal point in the same place in the display window, so you get different numbers of digits before and after it depending on range, you don't get all 9 lit at the same time...http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=06_Misc_Test_Equipment/Solartron/Solartron_7075

author: shapirus
author_rank: Super Contributor
timestamp: December 22, 2023, 03:19:49 pm
content: Quote from: p.larner on December 22, 2023, 01:11:58 amwhile that device sounds like a gorgeous bench multimeter for a lab (as long as it's in a good working condition), that's not what you require to find shorted caps (or other components) on a PCB.what you need is:1) a multimeter with a quick reacting (ideally quick beyond human sensitivity, i.e., feeling like instant) continuity tester (buzzer) to identify the points which are shorted when they shouldn't be -- a slow one will work too, but you'll soon want to throw it out of the window;2) a CC/CV power supply that can be used to apply (typically low) voltage between the shorted points that you find;3) a thermal camera (better) or a can of liquified gas (cheaper) to identify the component(s) that heat up when you apply voltage -- those will be the shorted ones;4) all kinds of clamps, connectors and wires to make yourself a convenient tool kit.

author: Gyro
author_rank: Super Contributor
timestamp: December 22, 2023, 05:07:56 pm
content: The 7075 is capable of low resistance measurements (I don't know whether the resistance converter is an option), but you need to use Kelvin connection to do it (there is a section on measurement techniques in the manual). You need to source a hard to find Solartron specific input plug/lead first though (I don't see one included in the listing, or any other listings at the moment).First things first, you need to fix the fault (intermittent display) and any others that may be hiding. The loose lid implies that somebody has been in there before you.You got it cheap though, you just need to be prepared for the work ahead.

author: Testtech
author_rank: Regular Contributor
timestamp: December 23, 2023, 09:57:01 pm
content: The other thing to consider is that the 7075 has a very slow reading rate at the higher resolution settings. Instruments like this are not really suited to service and diagnostic roles.

author: p.larner
author_rank: Frequent Contributor
timestamp: December 31, 2023, 10:35:58 am
content: well it finaly landed,couple of issues,firstly it makes a stink from near the mains input connector/filter so suspect a rifa dying,can i replace that with a hv blue x type cap,or just remove it altogether?,second issue is if i tilt the unit a relay clicks and a few of the displays vanish,i suspect a poor ribbon connector as its repeatable,or a dry joint etc,will look at it later when new binding posts get delivered to fit to the front panel as the original input plug is unobtainium.

author: factory
author_rank: Super Contributor
timestamp: December 31, 2023, 11:13:13 am
content: Quote from: p.larner on December 31, 2023, 10:35:58 amThe correct input plug isnotunobtainium, it is very much still made, do some research on the forum & you'll find out about it.David

author: p.larner
author_rank: Frequent Contributor
timestamp: December 31, 2023, 04:49:07 pm
content: david,trust me i am not willing to spend £100+ for the connector,its getting binding posts fitted.

author: tggzzz
author_rank: Super Contributor
timestamp: December 31, 2023, 05:09:58 pm
content: Quote from: p.larner on December 31, 2023, 04:49:07 pmAnd trust me, the existing connector is sufficient to enable you to test the 7075 sufficiently to determine whether (or not) it is worth flipping to 4mm terminals.

author: p.larner
author_rank: Frequent Contributor
timestamp: December 31, 2023, 07:33:42 pm
content: Well ive just tested the voltage rails for ripple,i am using my fluke 83v set on acv,black lead to zerov tp and the other lead to the different voltage testpoints :tp 1 -21v ripple=104mv tp2 -30v ripple=102mv tp3 -18v ripple=108mv tp4 +30v ripple=111mv tp5 +18v ripple=18mvdo they look ok or should i be checking cap uf+esr?.

author: tggzzz
author_rank: Super Contributor
timestamp: December 31, 2023, 08:14:39 pm
content: Quote from: p.larner on December 31, 2023, 07:33:42 pmRTFserviceM.

author: p.larner
author_rank: Frequent Contributor
timestamp: December 31, 2023, 10:28:32 pm
content: The service manual only gives rail test voltages+ or- no ripple mentioned,the caps all read under 1 ohm esr apart from c119 on the psu pcb,this is a 1uf/250v cap tho so i expect a highish esr reading,it reads about 6 ohms,the binding posts will be here tue so will fit those and test it then,i will leave the input filter cap for now as its a pig to get at.