Author Topic: Help needed to identify component in TDS460 power supply  (Read 3996 times)

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Offline JacquesBBB

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Help needed to identify component in TDS460 power supply
« on: December 28, 2017, 10:55:56 pm »
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 limiter
is in bad shape. The diode is a GI506 ( 600V, 3A), but what is the current limiter ?

Or what could be a good choice ?

Thanks

 

Offline Armadillo

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Re: Help needed to identify component in TDS460 power supply
« Reply #1 on: December 29, 2017, 01:18:17 am »
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/#msg1320619


Likely 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:ancAAOSweW5U27pA

Edit: 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.

 |O

BTW, be careful the heatsinks are LIVE.

Regards;

Armadillo;
« Last Edit: December 29, 2017, 01:46:38 am by Armadillo »
 

Online T3sl4co1l

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Re: Help needed to identify component in TDS460 power supply
« Reply #2 on: December 29, 2017, 01:42:17 am »
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
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Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline Armadillo

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Re: Help needed to identify component in TDS460 power supply
« Reply #3 on: December 29, 2017, 01:57:00 am »
- if you're 240V, a 130V MOV will be a little exciting. :)

Tim

If 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.

 

Offline JacquesBBB

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Re: Help needed to identify component in TDS460 power supply
« Reply #4 on: December 29, 2017, 05:35:08 am »
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 ?

« Last Edit: December 29, 2017, 05:40:32 am by JacquesBBB »
 

Offline floobydust

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Re: Help needed to identify component in TDS460 power supply
« Reply #5 on: December 29, 2017, 05:47:26 am »
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.
 

Offline Armadillo

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Re: Help needed to identify component in TDS460 power supply
« Reply #6 on: December 29, 2017, 06:42:30 am »
This is strange,

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 .


If 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.  :palm:
Happy hunting.!
 

Offline Belrmar

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Re: Help needed to identify component in TDS460 power supply
« Reply #7 on: December 29, 2017, 09:33:27 am »
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
 

Offline lihach

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Re: Help needed to identify component in TDS460 power supply
« Reply #8 on: December 29, 2017, 10:36:38 am »
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.
 

Offline JacquesBBB

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Re: Help needed to identify component in TDS460 power supply
« Reply #9 on: December 29, 2017, 11:04:57 am »
Here is the picture.

It should be 1.33 k  (E48 value),  and this is what I measured with the meter.
 

Offline JacquesBBB

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Re: Help needed to identify component in TDS460 power supply
« Reply #10 on: December 29, 2017, 11:12:32 am »
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

Yes,  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.

« Last Edit: December 29, 2017, 11:20:19 am by JacquesBBB »
 

Offline lihach

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Re: Help needed to identify component in TDS460 power supply
« Reply #11 on: December 29, 2017, 01:29:44 pm »
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?
 

Offline JacquesBBB

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Re: Help needed to identify component in TDS460 power supply
« Reply #12 on: December 29, 2017, 02:37:11 pm »
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 is
enclosed 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.
The 130L10 is the exact component used in the oscilloscope I mentioned.

But to be sure, I would appreciate if you can have a peek beneath the yellow fiber glass and tell me the references of the
component.
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.

 

Offline lihach

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Re: Help needed to identify component in TDS460 power supply
« Reply #13 on: December 29, 2017, 03:09:35 pm »
I'll take it out and give you a photo
 

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Re: Help needed to identify component in TDS460 power supply
« Reply #14 on: December 29, 2017, 03:27:17 pm »
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.
Safety devices hinder evolution
 
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Offline JacquesBBB

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Re: Help needed to identify component in TDS460 power supply
« Reply #15 on: December 29, 2017, 04:40:35 pm »
Thanks for this information.

If I just remove  the varistor and diode, can  I leave the switching module as it is ?
 

Offline lihach

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Re: Help needed to identify component in TDS460 power supply
« Reply #16 on: December 29, 2017, 06:06:22 pm »
here is a varistor photo
 

Offline JacquesBBB

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Re: Help needed to identify component in TDS460 power supply
« Reply #17 on: December 29, 2017, 07:00:11 pm »
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 example
http://uk.farnell.com/littelfuse/v150la20bp/varistor-80-0j-150vac/dp/1057190
« Last Edit: December 29, 2017, 07:04:14 pm by JacquesBBB »
 

Offline lihach

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Re: Help needed to identify component in TDS460 power supply
« Reply #18 on: December 30, 2017, 09:54:56 am »
Here is drawn for understanding the regulator circuit voltage divider. Maybe someone will come in handy.
 

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Re: Help needed to identify component in TDS460 power supply
« Reply #19 on: December 30, 2017, 10:42:04 am »
If I just remove  the varistor and diode, can  I leave the switching module as it is ?
You 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.
« Last Edit: December 30, 2017, 10:54:12 am by capt bullshot »
Safety devices hinder evolution
 

Offline JacquesBBB

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Re: Help needed to identify component in TDS460 power supply
« Reply #20 on: December 30, 2017, 05:47:33 pm »
Here is drawn for understanding the regulator circuit voltage divider. Maybe someone will come in handy.

Thanks !

This is extremely useful.
 

Offline JacquesBBB

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Re: Help needed to identify component in TDS460 power supply
« Reply #21 on: December 30, 2017, 05:54:21 pm »
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).

Thanks 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 Motorola
MJW16010A   NPN 15A /500V  large beast.
http://pdf.datasheetcatalog.com/datasheet/on_semiconductor/MJW16010A-D.PDF

It 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 is
Tektronix 119-3939-01
« Last Edit: December 30, 2017, 05:56:20 pm by JacquesBBB »
 

Online Twoflower

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Re: Help needed to identify component in TDS460 power supply
« Reply #22 on: December 30, 2017, 06:12:30 pm »
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?
 

Offline JacquesBBB

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Re: Help needed to identify component in TDS460 power supply
« Reply #23 on: December 30, 2017, 06:44:03 pm »
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.
 

Offline JacquesBBB

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Re: Help needed to identify component in TDS460 power supply
« Reply #24 on: December 30, 2017, 08:53:11 pm »
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).

I 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 ISOWATT218FX
https://fr.rs-online.com/web/p/transistors-bipolaires/8772671/ that I can get in a short time.
« Last Edit: December 30, 2017, 09:13:09 pm by JacquesBBB »
 


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