Need some guidelines on how to do safe diagnose to Bench Powersupply TSX3510P - Page 1
Forum section: electronics / repair

author: ia2115
author_rank: Newbie
timestamp: December 19, 2019, 04:42:55 pm
content: HeyIm pretty new to this repair stuff, and i got these two pretty advanced bench powersupply for free.Both aint working, one did blow the fuse when tried so now i know something is wrong and may shortcurcit.How do one diagnose this without powering it on and measure components?Hope for some basic guidelines, and /or equipment suggestions to help me in this quest to find the faulty components, or at least to find out if this is just to throw outThe company behind was so kind to send me their Servicemanuals, and schematics for it.Kinds RegardsJan

author: PKTKS
author_rank: Super Contributor
timestamp: December 19, 2019, 05:58:12 pm
content: Well nobody....Let me put this way: You have conflicting things.- new does not match advanced stuff- safe and new hardly fit- even experienced techs get dizzy w/SMPSSafe: you need to power it via VARIAC+BULBsNew: implies you need a lot of research to basic steps in troubleAdvanced SMPS: means you will need to understand how it worksI would recommend what I do first:- EXHAUSTIVE VISUAL INSPECTION (please repeat that 5 times)- mains critical components testing OFF BOARD BEFORE POWER- scan for dead shorts of critical points BEFORE POWER UPThen you can try power (via VARIAC)and very carefully see what happensMostly 2 things:- it won't soft start- it just smokes againthing goes onPaul

author: ia2115
author_rank: Newbie
timestamp: December 19, 2019, 07:40:24 pm
content: Hey PaulThanks a lot for this answer, i will also only do visual inspections. And maybe do some very limited measurements on components.. but ye surely its for advanced repair techs on this kind of equipment.So unless i can see very visual defects, i will leave this to techs who knows their stuff.But for now im just happy to have a clue on how someone like you would take this on as more pro as i amRegardsJan

author: m3vuv
author_rank: Super Contributor
timestamp: December 19, 2019, 08:18:29 pm
content: Did you forget to post the make and model,also whether its an smps or linear,i would like to help but cant find my crystal ball!!

author: JFJ
author_rank: Regular Contributor
timestamp: December 19, 2019, 11:38:15 pm
content: Quote from: ia2115 on December 19, 2019, 04:42:55 pmIf the service manual is the same as the attached pdf file, then it includes a useful main PCB test procedure (from page 16 onwards).

author: coromonadalix
author_rank: Super Contributor
timestamp: December 19, 2019, 11:42:08 pm
content: Seems an switch mode, they are tougher to diagnose, take some internal photos for us, if it is an smps, you'll have to dig into the main mosfet circuitry, check for shorts ... remove the main transistos / mosfets, sometime you get bad tests / impedances results because you may have some signal coupling x formers, or drive resistors.Try to find all the parts numbers, the main ic's who could drive the psu ... it could give you some insightsIn these case the last protection to blow is the fuses ...My first approcah would be ask for an schematic, if its available under an non disclosure agreement ?loll got me while posting

author: coromonadalix
author_rank: Super Contributor
timestamp: December 19, 2019, 11:46:01 pm
content: Ok seems an phase / triac controlled section with an smps section too aaaand an linear section.First guesscheck TC1 the triaccheck Q1 Q2 2sk1524 mosfetsYoure lucky in a way they are xformer coupled, it will contain some damagesIts based on a uc3825 pwm icI would check for any burnt resistors, low values ones, or flame proof ones / higher wattages ones.And yes as written, check the page 16 and up for tests / check procedures

author: macboy
author_rank: Super Contributor
timestamp: December 20, 2019, 02:54:49 pm
content: This is a switching power supply with linear post-regulation. It's quite a complex design, but the OP is lucky to have a very good service manual with excellent circuit descriptions, block diagrams, testing and troubleshooting tips, and schematics with parts lists. Few service manuals much better, maybe only pre-90's HP ones.The TRIAC mentioned by coromonadalix is used in a soft-start circuit. At power-up, a PTC limits initial current into the large filter capacitors, and a short time later the TRIAC shorts the PTC, providing essentially a direct path.I'd recommend using a "dim-bulb" tester when powering the questionable supplies. A variac to limit voltage can cause strange behavior with switching supplies, while not actually limiting current per se. The dim bulb tester (a 100 W or so incandescent light bulb in series with the load) limits short-circuit current and power to the load, while allowing most power supply type circuits to operate normally when they have no faults and no load.Beware that a significant portion of the internal circuitry (and at least one very large heatsink) is connected to mains and can have very high voltages present, without the benefit of transformer isolation. This is a major shock hazard.

author: ia2115
author_rank: Newbie
timestamp: December 22, 2019, 07:59:25 am
content: loads of pictures taken of the unit in question, in case someone can use them to point out places of interest

author: Shock
author_rank: Super Contributor
timestamp: December 22, 2019, 12:41:31 pm
content: Decide which one you are repairing first (i.e. do they both have blown fuses?) and attach the service manual to make sure we have the correct one is a good place start.

author: ia2115
author_rank: Newbie
timestamp: December 22, 2019, 01:53:00 pm
content: I concentrate on the one who blows fuses, will try measure shorts on Triacs and mosfets. The other psu is doing other wierd stuff, clapping some relays.. but as a non pro the basic measurement of components, is something i can do without destroying thingsThis Service manual attached is the one support from Aim-TTi send me. So with that i can go hunting and do the basic measurements and teste specified in the documentations.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 22, 2019, 02:14:15 pm
content: You could start it with the light bulb trick and a variac, at least you shoud have dc voltage to the vrect + and vrect - test points, since you have a full bridge rectifier.Test your 120 - 240 v switch just in case ...120 vac rectified should be around 170vdc240 vac rectified should be around 340 vdc ??oh you have an pseudo ground point at the junction of c9 and c10, sometimes it will become your ground reference for some measurements, it could be a ground point up to the 2 main mosfets Q1 an d Q2.You have many small regulators section, a main 5vdc to check, a 12vdc one, some negatives ones too, see page 8 for auxiliary suppliesIm trying to find where the pj4-1 pj4-2 and pj4-4 connections goes .... page 5 of the service manual give a rough example of the psu circuitry.You have 6x fuses near T1 the aux transformer

author: ia2115
author_rank: Newbie
timestamp: December 28, 2019, 06:27:22 pm
content: looking myself blind on schematics, cant find TC1 the triac , only TS1..