Help needed to identify   component in TDS460 power supply - Page 1
Forum section: electronics / repair

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 28, 2017, 10:55:56 pm
content: Hi All,I had for years a TDS460 that was given to me by a friend, but today, it did not work.After checking, the fuse was blown.I changed it, and of course, it blew again.After searching, I dismount the power supply. The output caps were fine, but one of the inrush current limiteris in bad shape. The diode is a GI506 ( 600V, 3A), but what is the current limiter ?Or what could be a good choice ?Thanks

author: Armadillo
author_rank: Super Contributor
timestamp: December 29, 2017, 01:18:17 am
content: Oh no!, you didn't have the opportunity to read this;https://www.eevblog.com/forum/repair/it's-not-always-the-capacitors-lecroy-lt342l-repair/msg1320619/#msg1320619Likely now a few components; fuse, varistor, main switching transistors + driver transistor, maybe the green module ETC...The picture component is the Varistor [metal oxide varistor]. Try [130L10 from little fuse].https://www.ebay.fr/itm/Lot-of-5-GE-130L10-130V-4-5KA-Metal-Oxide-Varistor-MOV-Radial-Leads-NOS/132252400791?hash=item1ecadb7c97:g:ancAAOSweW5U27pAEdit: if I remember correctly, you don't need the varistor after the conversion.Though I experienced this problem with the lecroy autorange circuit, I suspect your power supply is somewhat similar to it.BTW, be careful the heatsinks are LIVE.Regards;Armadillo;

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 29, 2017, 01:42:17 am
content: Yeah, the SG40 is the NTC inrush limiter, the red thing is a MOV. Originally, neatly wrapped in fiberglass, for whatever reason, clearly a bit cooked here!Replace with whatever voltage rating is suitable -- if you're 240V, a 130V MOV will be a little exciting.Tim

author: Armadillo
author_rank: Super Contributor
timestamp: December 29, 2017, 01:57:00 am
content: Quote from: T3sl4co1l on December 29, 2017, 01:42:17 amIf I remember correctly, that varistor is wired in series to Diode and wired to the autorange circuit black module for switching 120 volts power supply.The 130L10 is the exact component used in the oscilloscope I mentioned.Though 240v types sounded logical, yeah you can experiment with it.But even after you changed the varistor, you must check all other components before powering it on "Safely". Otherwise is money in the drain.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 29, 2017, 05:35:08 am
content: This is strange,In the service manual, it is said that the power source can be up to 250Vrms. There is no EU version. The US and EU are the same. In fact this unit was purchase in California where my friend was living.On the board, it is written 120/220V.But the big caps are rated 250V. This is a little bit short for 240V Rms operation. Normally, one should, I believe, have 400V.But this may be the reason why at the end there was a failure on the MOV, if it was rated to 130 V. Here the main is 240 V .The bad thing is that I just yesterday had an order on Mouser for some components. I had to top up to 50€ to avoid shipping costs, and had a hard time to find things to buy.By the way, to verify the power supply, I can probably just remove the bad MOV, and run it as it is, dont you think ?

author: floobydust
author_rank: Super Contributor
timestamp: December 29, 2017, 05:47:26 am
content: The PCB has the input voltage, frequency, and current written on it.Looks like 2A fuse for 220V and 4A FOR 120V input, just need to see if a jumper change is needed.

author: Armadillo
author_rank: Super Contributor
timestamp: December 29, 2017, 06:42:30 am
content: Quote from: JacquesBBB on December 29, 2017, 05:35:08 amIf I am not wrong, the MOV and a series diode connects to the centre, in between the 2 bigger capacitors.if you still cannot understand, unfortunately this repair will be difficult for you.Better send to the repair shop.Happy hunting.!

author: Belrmar
author_rank: Regular Contributor
timestamp: December 29, 2017, 09:33:27 am
content: Check if the caps are in series or paraleled, i have a pc power supply that confused me a bit , it has 200v caps but they are in series so i am safe

author: lihach
author_rank: Contributor
timestamp: December 29, 2017, 10:36:38 am
content: Good afternoon . I have such a block of kicking on my table. I can give the denominations of any interesting detail. But I very much ask you to give me a clear photograph of the resistor R- 25 or its denomination. I've been looking for someone who can help me in this matter for a long time. I really hope for your help.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 29, 2017, 11:04:57 am
content: Here is the picture.It should be 1.33 k (E48 value), and this is what I measured with the meter.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 29, 2017, 11:12:32 am
content: Quote from: Belrmar on December 29, 2017, 09:33:27 amYes, this is what I checked this morning the hard way.I was indeed confused as I measured on board the capacitor and found the double value, from which I assumed they were in parallel.I then wanted to be sure, at it makes much more sense like that.In addition, I found that one of the caps was not in good shape so I will replace both.

author: lihach
author_rank: Contributor
timestamp: December 29, 2017, 01:29:44 pm
content: Thank you very much. I no longer hoped that somewhere I can find such information. Because this requires disassembling the device. I am ready to answer all your questions. Why did you come to repair your power supply unit?

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 29, 2017, 02:37:11 pm
content: Thanks,I am glad my picture could be useful to others.My problem ( at least !) is the shortcut that occurred in the varistor, as you see in the picture.My problem is to identify this component. Obviously we have exactly the same board, but the component isenclosed in the small fiber glass packet yellow packet, in front of the big caps.Armadillo says that it is a 130L10 varistor from little fuse.Quote from: Armadillo on December 29, 2017, 01:57:00 amBut to be sure, I would appreciate if you can have a peek beneath the yellow fiber glass and tell me the references of thecomponent.If it looks too complicated, do not mind, as the value of this part should not be that critical, and it is not even sure that the label will be readable.

author: lihach
author_rank: Contributor
timestamp: December 29, 2017, 03:09:35 pm
content: I'll take it out and give you a photo

author: capt bullshot
author_rank: Super Contributor
timestamp: December 29, 2017, 03:27:17 pm
content: For 230V operation you can simply remove the varistor and the automatic input voltage switching module - they are not needed here.The automatic input voltage switch does nothing but to connect the input rectifier as a voltage doubler for 115V operation. AFAIR, the MOV and the series diode are part of this automatic switch, so they are not required for 230V only operation.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 29, 2017, 04:40:35 pm
content: Thanks for this information.If I just remove the varistor and diode, can I leave the switching module as it is ?

author: lihach
author_rank: Contributor
timestamp: December 29, 2017, 06:06:22 pm
content: here is a varistor photo

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 29, 2017, 07:00:11 pm
content: Thanks,That is great ! it is thus V150LA20BP, slightly different than the one mentioned by Armadillo.Even if I am in France, my friend is in the US and may get back the scope some time.I can then try to restore it completely.The part is available, for examplehttp://uk.farnell.com/littelfuse/v150la20bp/varistor-80-0j-150vac/dp/1057190

author: lihach
author_rank: Contributor
timestamp: December 30, 2017, 09:54:56 am
content: Here is drawn for understanding the regulator circuit voltage divider. Maybe someone will come in handy.

author: capt bullshot
author_rank: Super Contributor
timestamp: December 30, 2017, 10:42:04 am
content: Quote from: JacquesBBB on December 29, 2017, 04:40:35 pmYou should also remove the module. I did so because the MOV and the module looked quite crispy, and I wouldn't run the scope on 115V anyway. If the input fuse blows repeatedly, check the main primary side switching transistor. I had to replace it because it was shorted, it's an bipolar transistor, don't know the type anymore. I replaced it with transistor a already had as a spare for repairing an ancient TV (the main horizontal deflection transistor, something like a BU508). The specs would be similar (switching BJT with low gain and low Vce sat).Edit: your supply appears to look somewhat different from that I remember, the components of the automatic input voltage switching module appear to be on the PCB, not inside a potted module as it was for me. So you can't easily remove the module since there isn't a module. From the schematic lihach posted (thanks a lot for that), I'd say you'd require the MOV to protect whatever (maybe the main caps) from asymmetric voltage if the autorange circuit isn't removed.Still check the main transistor, it was the reason to blow the fuse for my power supply. Nothing else was defective, I just removed the autorange module since it looked broken and the MOV looked toast like yours.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 30, 2017, 05:47:33 pm
content: Quote from: lihach on December 30, 2017, 09:54:56 amThanks !This is extremely useful.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 30, 2017, 05:54:21 pm
content: Quote from: capt bullshot on December 30, 2017, 10:42:04 amThanks a lot ! I am glad the components I ordered did not arrived yet.I checked the Q1 transistor. The one with the big heatsink. I suppose this is the one you referred to. It is a MotorolaMJW16010A NPN 15A /500V large beast.http://pdf.datasheetcatalog.com/datasheet/on_semiconductor/MJW16010A-D.PDFIt was totally shorted !Too bad I send today my order to RS for the varistor ans the caps.I will post additional pictures of the board for possible futur use. The reference board isTektronix 119-3939-01

author: Twoflower
author_rank: Frequent Contributor
timestamp: December 30, 2017, 06:12:30 pm
content: Maybe that might be a trick of the lens but the right big cap (C2) looks a bit bulged in your first picture. Any chance for you to check if it is still alive and kicking?

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 30, 2017, 06:44:03 pm
content: I have removed the big caps to check the circuit.They seem to be relatively OK, although when I checked one, it seems to me that the first time, it did not look right.I wonder if this is the effect of the heat.When I desoldered them, I had to heat the pins. I tested them immediately, and one did not look right.But after they cooled, they both look right ( ESR 0.23R, cap roughly in range : one 616uF instead of 680 uF)Nevertheless, As I had dismounted them, I decided to change them all and ordered the pieces. I should have them in a few days.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 30, 2017, 08:53:11 pm
content: Quote from: capt bullshot on December 30, 2017, 10:42:04 amI have a brand new S2000A which has quite similar characteristics as the BU508, but somewhat less Amps than the MJW16010A (8/15 vs 15/20 collector current ) . Do you think I can use it ?It looks indeed quite identical as the BU508 (see the attached datasheet)otherwise, I can order a STMicroelectronics HD1750FX NPN Transistor, 24 A, 800 V, 3-Pin ISOWATT218FXhttps://fr.rs-online.com/web/p/transistors-bipolaires/8772671/that I can get in a short time.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 30, 2017, 10:59:06 pm
content: Hmm, might work. Worried about the longer switching time, and maybe the lower hFE (but hFE isn't too high on the MJW part, either, so maybe the circuit will deal with that just fine).Tim

author: capt bullshot
author_rank: Super Contributor
timestamp: December 31, 2017, 11:20:06 am
content: Quote from: JacquesBBB on December 30, 2017, 08:53:11 pmI'd give it a try. The maximum Ic shouldn't be reached in such a circuit. If you can achive that some way, watch it for getting not too hot when running the scope.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 31, 2017, 01:45:15 pm
content: Thanks for the comments.Finally, I have ordered the MD2310FX (14A/21A)http://www.st.com/content/ccc/resource/technical/document/datasheet/5c/99/f7/04/f3/61/4b/37/CD00073553.pdf/files/CD00073553.pdf/jcr:content/translations/en.CD00073553.pdfAs I wish also to reduce the noise of the scope, thus to reduce the heat dissipated by the power supply, and regulate the fan accordingly. I hope that this transistor will dissipate less than the previous one.

author: shakalnokturn
author_rank: Super Contributor
timestamp: December 31, 2017, 03:30:26 pm
content: I've substituted the main primary transistor on the similar PS-1690 PSU with BU508AF and 2SD1887 without problems the BU508AF giving slightly better switching times.Make sure you check the emitter resistor before powering-up again, failure to do so can lead to alotof extra work.

author: lihach
author_rank: Contributor
timestamp: January 02, 2018, 11:28:17 am
content: Here I present the edited scheme of the power filter and the high-voltage part of the power unitBe careful the circuit is drawn for yourself so there may be inaccuracies

author: navales314
author_rank: Newbie
timestamp: January 02, 2018, 01:02:52 pm
content: Quote from: Armadillo on December 29, 2017, 01:18:17 amHelp needed! My power supply didn't work it is two weeks ago i found it cracked ic cr18818 but i can't found at any store.have a similar of this?Sent from my SM-J105B using Tapatalk

author: Armadillo
author_rank: Super Contributor
timestamp: January 02, 2018, 02:05:33 pm
content: Quote from: navales314 on January 02, 2018, 01:02:52 pmRelax. I suggest you create a new thread with detailed description of your problems and photos.Many people can help you.

author: navales314
author_rank: Newbie
timestamp: January 02, 2018, 02:24:36 pm
content: Help neededMy power supply didn't work it is two weeks ago i found it cracked ic CR18818 but i can't found any store have a similar of this or same pinout ic CR18818?Sent from my SM-J105B using Tapatalk

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: January 02, 2018, 02:38:26 pm
content: Please use this thread only for matters related to the TDS460 power supply.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: January 02, 2018, 02:48:35 pm
content: Quote from: lihach on January 02, 2018, 11:28:17 amThanks a lot for the effort ! This is great work.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: January 05, 2018, 10:48:51 pm
content: I have now received the components I ordered, and proceed to the remounting of the scope.I replaced all the electrolytic caps, except the 4700uF which I had not received yet.They were OK, anyway.I put the MD2310FX. I had to drill an additional hole in the heatsink for that as it is slightly larger than the previous one.I put a BY500-600 diode in series with the V150LA20BP.Put the power on,and everything is working again.Thanks to all for the help, and in particular to lihach for providing the right value of the varistor, and to capt bullshot for telling meabout the potential problem of the MJW16010A transistor.

author: capt bullshot
author_rank: Super Contributor
timestamp: January 06, 2018, 10:36:57 am
content: Congratulations, good job!