Tektronix DPO4000 / MSO4000 powersupply - Page 1
Forum section: electronics / testgear

author: darkstar49
author_rank: Frequent Contributor
timestamp: December 28, 2015, 01:27:01 pm
content: Hi,does anyone have an idea of the pinout of the power connector in the DPO/MSO4K series from Tek?? (connector J780 in the service manual if I remember well)Here's a pic of the power supply of a DPO4034, from some old article "took apart my DPO4034", and btw, if someone has a pointer to that (deleted ?) article and/or the pics of it, I'd be glad to have it, and not just the reference found on Google (I can use Google, too... ;-)https://lh6.googleusercontent.com/-MGC5TYg8DGE/TOculVi4FbI/AAAAAAAAG5w/4XMXITf1UtA/w756-h567-no/DSC00661.JPGI'm in particular interested in the RTS (or R1S ??) and 12V_S lines, what are these good forThe labeling 12V_S suggests remote sensing, but that doesn't match with RTS (green cable)Any hint/info/idea is welcome !!

author: darkstar49
author_rank: Frequent Contributor
timestamp: December 29, 2015, 09:02:37 pm
content: PSU pinout seems relatively clear... but I'm missing many secondary voltages on the J890 pads, 12V is obviously present (as provided by the PSU), 10.8v as well, but 17V shows 0V, and all smaller voltages (1,5V, 3.3, 5V, etc...) show irrelevant values...So it looks like the "voltage regulator part" of the mainboard is more of less dead... now given the price of a DPO4034 mainboard, it's probably worth a try finding out what's wrong, especially as the components on that part are far less "exotic" than on other parts of the mainboard...I'm thus calling for a miracle... should someone have the schematics of a DPO4000's mainboardI guess this could even be worth some money... ;-

author: RayeR
author_rank: Contributor
timestamp: January 06, 2016, 01:45:21 pm
content: Hi dude, I just have a PSU accident yesterday on our DPO4034.I turned the scope on, it displayed bootscreen as usual but within ~3s something popped inside and sceen went black. I disassembled the cover and checked the fuses. The big one 6,3A was OK but small one F2 (beside the big cap) blew off. I found why - the MOSFET Q5 was shorted and on bottom side below Q5 there are 2 blown SMD resistors. I cannot read theirs value. Please could you help me to read/measure the values?See this photo:http://rayer.g6.cz/1tmp/tek-psu-bottom.jpg- I think it's obviout which ones I meanAnd here photo of whole PSU and back side of scope:http://rayer.g6.cz/1tmp/tek-back.jpgDid you have a luck with service schematics? I didn't googled any yet, just a service manual but no schematics there.I'm also interested what are the output voltages in case I will need to replace whole PSU - there are 2 fat cables labeled VOUT and RTN and 2 normal cables 12V_S and RTS and they are not connected with first pair - is it some isolated auxiliary 12V rail?Thanks for any help.

author: RayeR
author_rank: Contributor
timestamp: January 06, 2016, 06:53:44 pm
content: OK, one fried kindly looked for resistors in his scope, it's 2x10R as current sense in source of MOSFET. I found other dead components: MOSFET, IC 3842B, one SMD schottky diode 1A/40V. I just ordered the components hope it will work then...

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: January 06, 2016, 07:36:45 pm
content: Hi,I suspect that12V_S is the sense lead. It will be connected to the +12V (VOUT) rail at the load.RTS is the return sense. It will be connected to the RTN lead at the Load.If you test the board out of unit you should connect VOUT -> 12V_S and RTN -> RTS.These extra connections are called remote sense.Regards,Jay_Diddy_B

author: RayeR
author_rank: Contributor
timestamp: January 07, 2016, 12:17:02 am
content: OK, thanks for explanation. So if I'll not success with PSU board repair I can just replace it with another powerfull 12V supply. Even it may be usefull to enable 12V battery powering for floating or in the field measurement

author: RayeR
author_rank: Contributor
timestamp: January 11, 2016, 05:00:08 pm
content: Hi, today arrived the components that I ordered for repair, I replace them (IC, FET, F2, Rsense, 1 schottky diode 40V/1A and elyts around) and the scope is working again

author: tautech
author_rank: Super Contributor
timestamp: January 11, 2016, 06:24:44 pm
content: Quote from: RayeR on January 11, 2016, 05:00:08 pmOn first power up after repair be sure to use a Dim Bulb tester to limit the current available and not fry all your new parts.

author: dodge bullets
author_rank: Newbie
timestamp: September 09, 2018, 03:18:11 am
content: I am in the process of troubleshooting my DPO4034 (see the bottom of my post) when I came across this thread.I assume that since this has set idle for a couple years that everyone has repaired their issues, but others might be interested in what I have to say about this power circuit.My device has problems other than the power supply, so I hope this will assist those with power issues. My unit will power up, the fans will spin, both of the 12VDC supplies from the power supply are present and applied to the Main Board. There are several test points labeled on the board denoting all the different supplies. I have all of them including: +5, +3.3, +2.5, +1.8, +1.5, -5, and -12.The power supply basically only supplies the two +12 volt supplies. With the supply disconnected, the three large red wires (VOUT) reads 47 Ohms to the yellow wire (12V_S). The three black wires (RTN) measures 10 Ohms to the green wire (RTS).My unit fails to fully turn ON, or so it seems. The LCD display backlights flash as soon as the power switch is either activated or opened. The display never has any video present (flashlight pointed into the screen proves it) and the XGA output doesn't have any output either if I use an external display. I have to assume it has a problem with one of the large BGA chips. One more important fact, the LED behind the indicators fail to light. For instance, ff you select channel 1-4 there is no indicator to show that you selected it.I found this scope in the recycle bin at work, so I have no idea what the original owner did to it. I do think I was the first to open it up. I haven't had any luck finding information that assists my plight.I was thinking if I had the schematic I might figure out which chip to replace or reflow, but I guess they never released it to the web. I couldn't even find a definite part number. The manuals you find says "671-5960-00", but the numbers stickers on the board say either "870-0001-02" or "872-0001-70". Neither of these has any matches on the web searches I tried. I am almost at the point where I toss it into a reflow oven and hope for good results.I wonder if there is someone out there with schematics to assist me. If not then, I suppose I could be persuaded into selling my power supply or perhaps the entire scope for parts and not for the outrageous prices I saw on eBay.