Author Topic: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A  (Read 5016 times)

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Offline Jwalling

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I've got a customers DSO8104A on my bench that won't self calibrate. CH1 has a bad/blown pre-amp - it's input impedance from the attenuator is way too low (The calibration routine doesn't even detect that the coax cable is connected from CH1 to the AUX OUT connector, and "common" calibration fails). The cal log is attached.

Luckily I have a few scrap 54831B/32B acquisition boards around as they use the exact same preamp. Once again though, I don't have the needed equipment or expertise to do the repair as there's a large GND pad underneath the chip. The chip is entirely made of ceramic; whether this requires more delicate handling and heating to keep it from cracking is unknown. It looks like the "cap" of the chip is bonded to the bottom ceramic plate where the die lies; I'm hoping the cap doesn't fall off as I have no idea what material holds it together. Hopefully not glue!

I'm going to have Louis Rossmann do the repair work again like he did in this thread:
https://www.eevblog.com/forum/repair/looking-for-someone-who-can-replaceswap-tek-tds694c-trigger-chips-for-$/msg1186021/#msg1186021

Does he read this forum? Let's find out!

Pictures of the good chip on the scrap donor board, and the bad chip on the board to be repaired are attached as well.

Jay

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Offline vze1lryy

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Sure. Might use the zm-r6200 if more precise heating is required for the ceramic. Send it in.
Louis Rossmann
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Offline Jwalling

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Excellent. Will get it shipped out to you tomorrow. Thanks!
Jay

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Offline tooki

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[...]I'm going to have Louis Rossmann do the repair work again like he did in this thread:
https://www.eevblog.com/forum/repair/looking-for-someone-who-can-replaceswap-tek-tds694c-trigger-chips-for-$/msg1186021/#msg1186021

Does he read this forum? Let's find out!
Why on earth is this a public post? You could have sent him a PM, or an email, or called his office... nothing about this needed to be public.
 

Offline Toasty

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Because someone else might have this problem and need assistance.  Just a thought. :)

T
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Offline KE5FX

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Why on earth is this a public post? You could have sent him a PM, or an email, or called his office... nothing about this needed to be public.

Much the same could be said of your post.

One difference is that the result of Louis's repair attempt will make for an interesting follow-up. 
 
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Offline RGB255_0_0

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Would be cool if he live streams it  :-+

Also would be interesting to know if it's the most expensive piece of equipment he'd have worked on - besides priceless data recovery.
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Offline Jwalling

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[...]I'm going to have Louis Rossmann do the repair work again like he did in this thread:
https://www.eevblog.com/forum/repair/looking-for-someone-who-can-replaceswap-tek-tds694c-trigger-chips-for-$/msg1186021/#msg1186021

Does he read this forum? Let's find out!
Why on earth is this a public post? You could have sent him a PM, or an email, or called his office... nothing about this needed to be public.

This is a forum about repairing equipment.

This particular thread is about documenting a repair on a piece of equipment, specifically an Agilent DSO8104A. Of particular interest to some (not you) may be the difficulty of replacing a chip entirely made out of ceramic with an unknown bonding agent that may or may not survive the process.

With a little bit of luck, I'm hoping to see a Youtube video made of the repair process; this may interest some people (not you) as well.

With a little more luck, I'm hoping for a successful repair.

If you don't want to read this thread, then don't. I'm pretty sure no one is forcing you to read this (I'm not), but correct me if I'm wrong. Or not.
Jay

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Online Cyberdragon

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Louis has his own forum, but I think it's a paid subscription. He probably stays over there rather than coming here and having "4chan" find him.

EDIT: WAIT A MINUTE...is vze1lryy actually Rossman? If it is, I need to slap myself. (employees of his don't count, my point still stands)
« Last Edit: August 19, 2017, 11:35:46 pm by Cyberdragon »
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Why on earth is this a public post?


marketing
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Offline retiredcaps

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EDIT: WAIT A MINUTE...is vze1lryy actually Rossman?
He is.
 

Offline Armadillo

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #11 on: September 16, 2017, 12:55:46 am »
What's Up with this work? Any updates?
 

Offline bigeblis

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #12 on: September 16, 2017, 07:02:03 am »
I've got a customers DSO8104A on my bench that won't self calibrate. CH1 has a bad/blown pre-amp - it's input impedance from the attenuator is way too low (The calibration routine doesn't even detect that the coax cable is connected from CH1 to the AUX OUT connector, and "common" calibration fails). The cal log is attached.

Luckily I have a few scrap 54831B/32B acquisition boards around as they use the exact same preamp. Once again though, I don't have the needed equipment or expertise to do the repair as there's a large GND pad underneath the chip. The chip is entirely made of ceramic; whether this requires more delicate handling and heating to keep it from cracking is unknown. It looks like the "cap" of the chip is bonded to the bottom ceramic plate where the die lies; I'm hoping the cap doesn't fall off as I have no idea what material holds it together. Hopefully not glue!

I'm going to have Louis Rossmann do the repair work again like he did in this thread:
https://www.eevblog.com/forum/repair/looking-for-someone-who-can-replaceswap-tek-tds694c-trigger-chips-for-$/msg1186021/#msg1186021

Does he read this forum? Let's find out!

Pictures of the good chip on the scrap donor board, and the bad chip on the board to be repaired are attached as well.

Sorry, English may not be very good.
I've done this work. You need a far infrared auxiliary heating platform to heat the bottom of the PCB board. I'll heat it at 180 degrees, and then use the hot air gun over the top to heat it up to 260 degrees to remove the chip.
Note: never hold the upper part of the film to move it, especially when the temperature is very high. Otherwise, the chip will be scrapped immediately. Only the bottom ceramic substrate can be clamped to move the chip.
It is impossible to use only a hot air gun to disassemble the chip, and I have damaged the two chips.
 

Offline Jwalling

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #13 on: September 16, 2017, 09:36:01 am »
What's Up with this work? Any updates?

The boards were received on 8/21/17.
Last update on 8/30/17 is "It's still in progress. It's proving to be difficult. We will keep you posted once we have any news."

So nothing yet...
I'll probably shoot them an email this coming week.
Jay

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Offline KE5FX

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #14 on: September 16, 2017, 06:03:18 pm »
What's Up with this work? Any updates?

The boards were received on 8/21/17.
Last update on 8/30/17 is "It's still in progress. It's proving to be difficult. We will keep you posted once we have any news."

So nothing yet...
I'll probably shoot them an email this coming week.

Watching the TDS 694C repair, I was surprised that his idea of preheating was "stick the board in an oven for a while before putting it on the workbench."  I wouldn't be surprised at all if he's discovering the limitations of that particular process.
 

Offline Jwalling

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #15 on: September 16, 2017, 06:08:22 pm »

Watching the TDS 694C repair, I was surprised that his idea of preheating was "stick the board in an oven for a while before putting it on the workbench."  I wouldn't be surprised at all if he's discovering the limitations of that particular process.

I'm hoping you're wrong!
I let him know that one of the pre-amp hybrids on the donor board was known bad (put an X on it with a sharpie pen as well), and could be used to experiment with / get a heating profile.
Jay

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Offline Jwalling

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #16 on: September 21, 2017, 05:11:11 pm »
I just got an update.

Quote
"Apologies, that email was not intended for you.

We've replaced the chip you marked, but we don't really have a
way to test it."

Well, that's a relief!  :phew:

So it looks like it's all done. Just have to pay and hopefully it'll be back next week for further testing/repair.
Disappointed that there's no video.
Jay

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Offline Jwalling

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #17 on: September 28, 2017, 05:18:32 pm »
Update.
Got the board back today. It now will complete a calibration (no more cannot detect cable so you can't proceed) But it fails CH1 trigger and vertical. Cannot get any kind of a decent trace on the screen...

Further testing shows that there's a solder short on pin 20 to the large GND pad, see pictures. |O
Checked it in four wire REL mode on my Keithley 2000, it's 60uOhms, so it's definitely between the pin 20 pad and the GND plane (no way can it be the chip or at the other end of the trace).
The pad can be seen on the donor board.
It looks like it's going to be heading back to NYC :--

Question: Will performing the operation twice increase the likelihood of killing the chip? In other words are the heating effects cumulative?
Jay

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Online PA0PBZ

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #18 on: September 28, 2017, 06:02:49 pm »
Looks like you also have some excess solder between 20 and 21? What about sucking the pin(s) clean with litz wire? With a bit of luck the short will be removed I'd guess.
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Online TheSteve

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #19 on: September 28, 2017, 06:04:34 pm »
Preheat with a heat gun and use some really good solder wick possibly?
VE7FM
 
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Online PA0PBZ

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #20 on: September 28, 2017, 06:05:41 pm »
Preheat with a heat gun and use some really good solder wick possibly?

Solder wick, that was the word I was looking for :)

Also I was thinking if you suck it clean and then still have the short put a piece of kapton tape in between and a wire from the pin to the track...
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Offline Jwalling

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #21 on: September 28, 2017, 06:13:27 pm »
Looks like you also have some excess solder between 20 and 21? What about sucking the pin(s) clean with litz wire? With a bit of luck the short will be removed I'd guess.

I just measured pin 21 to GND and it's 1MOhm. Good spot though, I couldn't see it with my optical visors and never thought to look closer at the picture. A little flick with the end of an x-acto blade removed it. Not entirely sure it wasn't flux; there quite a bit of it remaining even after cleaning with some IPA.
Jay

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Offline wraper

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #22 on: September 28, 2017, 06:14:56 pm »
Preheat with a heat gun and use some really good solder wick possibly?
I'd say preheat the board if possible (borrow hot air from your wife), apply decent amount of tacky (gel) flux and solder the pad. Short will likely go away even without a solder wick.
 

Online PA0PBZ

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #23 on: September 28, 2017, 06:16:01 pm »
Looks like you also have some excess solder between 20 and 21? What about sucking the pin(s) clean with litz wire? With a bit of luck the short will be removed I'd guess.

I just measured pin 21 to GND and it's 1MOhm. Good spot though, I couldn't see it with my optical visors and never thought to look closer at the picture. A little flick with the end of an x-acto blade removed it. Not entirely sure it wasn't flux; there quite a bit of it remaining even after cleaning with some IPA.

So one non-existing problem solved :) If I compare the amount of solder with the IC above it he didn't really hold back...

Pins 30 and 31 are also looking very suspicious on the picture.
« Last Edit: September 28, 2017, 06:17:59 pm by PA0PBZ »
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Offline Jwalling

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #24 on: September 28, 2017, 06:17:59 pm »
Preheat with a heat gun and use some really good solder wick possibly?

Another good idea! I've got a nice tiny nozzle for my hot air station. Thanks Steve, I'll give that a try tomorrow.
Jay

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Offline vze1lryy

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #25 on: September 29, 2017, 04:55:03 am »
Why on earth is this a public post?


marketing

We honestly don't advertise or solicit this stuff since we don't do it... for the record, if someone mistakes any of my posts for marketing odd jobs, and you have something that is not a liquid damaged macbook.. from the horse's mouth here, you should not send it. If we are busy with "regular" repairs then the odd stuff people drop off(refrigerator PCBs/oscilloscopes/other weird stuff) winds up at the bottom of the pile... and steve will always kick my ass for taking in some refridgerator PCB/custom PCB/odd audio interface since we can't test it. usually flux is cleaned off in the ultrasonic but a Crest CP500D we bought for laptop boards is never going to fit this. No video since too busy by far over the past month to do any regular repair videos. I didn't do this one so not sure what it could be, I'll ask jason how he did it and take a look when it comes back... odd that it didn't work.

I'll take a 2nd look once it comes in. I'm sorry to hear it didn't work.
Louis Rossmann
Component level motherboard repair technician.
 
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Offline Jwalling

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Re: PING Louis Rossmann, you're needed in surgery! Repairing an Agilent DSO8104A
« Reply #26 on: September 29, 2017, 03:22:34 pm »
(Whining snipped)


We honestly don't advertise or solicit this stuff since we don't do it... for the record, if someone mistakes any of my posts for marketing odd jobs, and you have something that is not a liquid damaged macbook.. from the horse's mouth here, you should not send it. If we are busy with "regular" repairs then the odd stuff people drop off(refrigerator PCBs/oscilloscopes/other weird stuff) winds up at the bottom of the pile... and steve will always kick my ass for taking in some refridgerator PCB/custom PCB/odd audio interface since we can't test it. usually flux is cleaned off in the ultrasonic but a Crest CP500D we bought for laptop boards is never going to fit this. No video since too busy by far over the past month to do any regular repair videos. I didn't do this one so not sure what it could be, I'll ask jason how he did it and take a look when it comes back... odd that it didn't work.

I'll take a 2nd look once it comes in. I'm sorry to hear it didn't work.

Hi Louis,
Never-mind the whiners that have nothing to worthwhile to contribute.

I greatly appreciate the work you've done for me on that TDS694C some months back (and the one you now have in your possession), as well as on this DSO board repair project as well. Sometimes things go wrong; believe me I understand that! It doesn't help at all that you don't have any way to test after doing the re-work...

Anyway, I hope that you'll still be open to doing future repairs for me, but I understand this may be a bit out of your comfort zone. If not, then that's OK as well.

I'm going to try to reflow the pin/pad a bit and see if the short goes away, hopefully today, but if not, then tomorrow
Thanks.

Jay

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Offline Jwalling

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Well, I was unable to remove the short by reflowing the pad or using solder wick. So I attempted to break the connection by carving out the conductive material with an x-acto knife on the chip itself in the vertical half circle that runs down the edge of the chip. This was successful, so I cut the 1cm etch that runs to a via and put a wire from the via to the top of the chip where the silver conductive material goes under the top cap of the chip. This is where things went wrong. That silver material did not like being soldered - it sort of just disappeared.  |O

In hindsight, I should have used the x-acto knife to cut away the connection where the half circle solder point meets the PCB itself, then run the wire from the half circle to the via. Live and learn. :(

So the chip will need to be replaced again with another donor chip.

During all this screwing around, I also noticed the Teledyne RF relay was cooked. Measuring resistance at the BNC in 50Ohm mode at some vertical amplitude settings, the impedance was 285 Ohms. So it looks like someone overloaded the input when the scope was in 50 Ohm mode. That's replaced and all is well there now.
Jay

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Online TheSteve

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Ouch - I believe anytime you solder anything to a trace that is on ceramic you need to use silver solder.
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Offline wraper

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Ouch - I believe anytime you solder anything to a trace that is on ceramic you need to use silver solder.
FYI SMT resistors and capacitors are made from ceramic. Special leaded solder with added silver is thing of the distant past. Pads on remotely modern parts have nickel barrier on top of the silver protecting it from dissolving. It rather sounds that metallization was torn off by mechanic impact, and when soldered, was just washed away with liquid solder.
 

Online PA0PBZ

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Since it is unusable as it is now, try to decap it? If it doesn't work out at least you'd get some pretty pictures :)
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Offline Jwalling

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Since it is unusable as it is now, try to decap it? If it doesn't work out at least you'd get some pretty pictures :)

I probably will after it's replaced; I won't attempt to repair or re-use it, though. I've requested that he return the damaged chip with the boards when he send them back. Luckily I have more spares to replace it with!
Jay

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Offline Jwalling

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Update. Board is back after having the chip replaced again. Still failing cal. but somewhat normal waveforms can now be seen! I now believe that the pre-amp is operating correctly (Thanks Louis!). There's many more "PASSED" tests in the debug log. Before and after attached.

I now have a high impedance fault to figure out... Amplitude is way too high, and some distortion on top and bottom of square wave. Whoever blew this scope's input really meant business!

EDIT: Since the blowout occurred in 50 Ohm mode, I'm wondering if the scope sensed the overload and switched over automatically to 1M, thereby blowing something the 1M path as well? The Tek TDS700X input hybrids do this...
« Last Edit: October 12, 2017, 11:36:16 am by Jwalling »
Jay

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Offline Jwalling

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Obligatory chip porn as promised. This is the one I mucked up trying to remove the GND short and adding a wire.

The ceramic cap is bonded to the substrate using a material very similar to RTV. Must be a high temp version as no discoloration or burning is noted. It was a breeze to de-cap.
« Last Edit: October 11, 2017, 05:18:44 pm by Jwalling »
Jay

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Offline Jwalling

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One of these days, I'd love to get a microscope with the ability to take hi-res pictures. Not in the budget now...

If anyone in the US has a setup like that and wants to take some good pictures for us, I'll mail the chip for free!
Jay

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Online Samogon

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I can try Amscope x40 with 5mp camera
 

Offline Armadillo

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Something like this would be at ~X50 or X70, can't remember.
Was trying to get good depth of field but my lighting was at the max.
 

Offline AF6LJ

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Good deal Jay, sounds like you are well on the way to having that scope back on the road.   :-+ :-+
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Offline Jwalling

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I can try Amscope x40 with 5mp camera

PM sent. Thanks.
Jay

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Offline Jwalling

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Still working on the DSO.

In other news, Louis has performed another successful trigger chip swap on a TDS694C for me.  :-+
This one failed to trigger on CH1 and CH2 with two obviously burnt chips in U1823 and U1813. While U1833 wasn't obviously blown, it had a very slight brownish color to it, so I didn't trust it. The board was repaired by using the spare chip from the previous repair back in April, and placed in U1823.

EDIT: wrong picture posted.
Jay

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Offline AF6LJ

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 :-+ :-+
Good deal.
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Online Samogon

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Jay, got your chip today
Here are some snapshots from may Amscope 45 with barlow lense x2 and 5MP camera.
I have articulating arm which is extremely shaky on x90 magnification. Hard to get focus
 
« Last Edit: October 21, 2017, 06:02:58 am by Samogon »
 
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Offline AF6LJ

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Nice shots, thanks for posting them.  :-+
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