Tektronix TDS 380  Power Supply - Page 1
Forum section: electronics / repair

author: Rico75
author_rank: Newbie
timestamp: January 30, 2024, 07:10:05 am
content: Hello everyone, Im Rico and Im writing from Nz.I need your help guys about my Tek TDS380.Couple days ago, I've received the replacement for the IC DALLAS and alsothe flat circuit I have bought on Ebay.My plan was to change the DALLAS and the flat circuit and check the power supply (caps).Unfortunately, I had some problems, first, desoldering the Dallas has been a challenge and i broke some pits.Second i made a huge mistakeon the power supply circuit and as result now I have to change some components.I have downloaded all the service manual and schematics from internet but I'm not able to find the Power supply schematic.Could you please guys help me to find the schematics?Thanks guys!Have a gday

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: January 31, 2024, 05:05:59 am
content: The service manual lists the PSU as just a single component, as you would see for a singular resistor. Because of this, I would think Tek never actually released the schematics of the PSU.Perhaps the TDS380 uses an off-the-shelf PSU.However, I think the PSU troubleshooting flow chart in the service manual may help.https://w140.com/tekwiki/images/4/41/070-9436-04.pdfGo to PDF page 135, or the manual page 6-43.

author: CaptDon
author_rank: Super Contributor
timestamp: January 31, 2024, 02:45:31 pm
content: Check the thread on Tek TDS400 or TDS420, they may use the same supply. Tektronix bought off the shelf supplies and I think some identical supplies were used by LeCroy. I am thinking LeCroy included the power supply schematic. Between blowing up your power supply and damaging the circuit board trying to remove the Dallas N.V.R. chip it sounds like you'll have the unit totally destroyed soon. I gave a TDS420 to guy here on EEVblog. It had a blown 'unobtainium' green ceramic hybrid in the power supply. He managed to make one good scope out of two bad ones and did an extensive thread with pictures here on EEV.

author: Rico75
author_rank: Newbie
timestamp: February 05, 2024, 05:11:33 am
content: Hi,sorry for late reply.I enclose pics you can see below.I guess the problem is bit bigger that what I hoped .Q3its died but I was able to read the sigle .CR72its died but I was able to read the sigle.C12its okT2as you can see from the pic its damagedVR9I have no idea ...The resistors over there I've no idea.I have tried to identify any LeCroy oscilloscope with similarPower Supplybut I didn't find no one.

author: Rico75
author_rank: Newbie
timestamp: February 05, 2024, 05:13:06 am
content: This the pics.Gday guys!

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: February 05, 2024, 07:20:27 pm
content: That looks like quite a destructive failure. Usually if a PSU failed like that, most of the time I wouldn't even bother trying to fix it as there are a billion things that could have possibly gone wrong. So I just buy a replacementBut since this is the PSU of a scope, I think that replacement is not a really real option.I think the failure here was the transistor that shorted, and caused a huge mess on the board. But this is just a guess.Try checking other components in the vicinity and see if any of those have possibly failed.Before replacing parts, take A LOT OF PHOTOS. Sometimes when you power it back on again, something else will burn and you don't know the value of that component, or what that component is at all. Photos will really help you.Edit: I think the 3 burnt resistors are 10 ohm 1% resistors. Maybe 1/2 watt.