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Not directly HP related but this is where the knowledge is. I am starting to repair an IFR-1200S that had an incident.   A 150 uF 15V tantalum went up in smoke. What is the best solvent to remove the residue on the rest of the PCB. Isopropyl does not take all of it off? Want to get it all clean before I replace parts and continue the repair. Thanks Dave?
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Try Acetone.? I use it with q-tips and a rag.? Don't pour it on the equipment as it may melt some things.? Just dampen the q-tip or rag with it.? ?Have good ventilation and no open flames!!? That includes space heaters. Bill
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Make certain it is a wooden steam Q-tip. ?Acetone will melt the plastic ones.
Ken
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On 6Apr, 2020, at 11:37 PM, Bill via < ko4nrbs@...> wrote:
Try Acetone.? I use it with q-tips and a rag.? Don't pour it on the equipment as it may melt some things.? Just dampen the q-tip or rag with it.? ?Have good ventilation and no open flames!!? That includes space heaters. Bill
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Thanks guys, Good reminder on wooden Q tips. ? There is also Xylene. (Goof off) I shall go at it slowly. ?No rush Might have to wait as it’s sort of hard to just pop over to the local store as many are shut down.? Might also try Ultrasonic. ?
Thanks
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On Apr 6, 2020, at 10:38 PM, Bill via groups.io <ko4nrbs@...> wrote:
? Try Acetone.? I use it with q-tips and a rag.? Don't pour it on the equipment as it may melt some things.? Just dampen the q-tip or rag with it.? ?Have good ventilation and no open flames!!? That includes space heaters. Bill
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What a mess - it really did a number on that board section. I agree that acetone would be a pretty good solvent for some of the char, but unfortunately, it may not clean it all off. Some is likely carbon particles (from burning up the coating) and Ta oxides (from the cap guts) splattered onto (and into) the surfaces, and no conventional solvent will dissolve it. The good news is that even if you can't get it spic and span, any remaining residue probably won't hurt the circuit operation after cleaning and repair.
Besides some solvent action, good mechanical scrubbing should help. I'm not sure if your comment about IPA is a question (will it work?) or a statement (tried and it doesn't work). I'd start with IPA, if you haven't already. Paint thinner or acetone are logical next steps. Acetone may be a little too intense to leave on for very long.
Presuming you don't want to remove the board from the RF assembly, which appears to have its feed-throughs soldered to the board, the trick is to be able to work on board cleanup without getting anything bad into the RF. IPA and acetone would probably be best then, since they're miscible with water and will evaporate quickly, while paint thinner would be a bit messy and slow to depart.
If the board can be readily removed, you have more options such as aqueous washing with detergents, and some gentle abrasive action such as an opaque toothpaste worked with - of course - an old toothbrush, to scrape off the particles that aren't too tightly embedded in the surfaces. Regardless of the solvents and methods, I always use old toothbrushes for scrubbing. Higher intensity solvents may dissolve or degrade the bristles and heads, so you have to work fast in some cases.
Another option, if you have access to the appropriate equipment, is to skip solvents altogether and do purely mechanical cleaning, like with a soda or walnut shell blaster.
Good luck.
Ed
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May I suggest using a glass fiber pen/brush for removing burnt-in particulate matter and charring?
I've used them in the past to clean corrosions caused by leaking batteries.?
Regards
Jan
What a mess - it really did a number on that board section. I agree that acetone would be a pretty good solvent for some of the char, but unfortunately, it may not clean it all off. Some is likely carbon particles (from burning up the coating) and Ta oxides (from the cap guts) splattered onto (and into) the surfaces, and no conventional solvent will dissolve it. The good news is that even if you can't get it spic and span, any remaining residue probably won't hurt the circuit operation after cleaning and repair.
Besides some solvent action, good mechanical scrubbing should help. I'm not sure if your comment about IPA is a question (will it work?) or a statement (tried and it doesn't work). I'd start with IPA, if you haven't already. Paint thinner or acetone are logical next steps. Acetone may be a little too intense to leave on for very long.
Presuming you don't want to remove the board from the RF assembly, which appears to have its feed-throughs soldered to the board, the trick is to be able to work on board cleanup without getting anything bad into the RF. IPA and acetone would probably be best then, since they're miscible with water and will evaporate quickly, while paint thinner would be a bit messy and slow to depart.
If the board can be readily removed, you have more options such as aqueous washing with detergents, and some gentle abrasive action such as an opaque toothpaste worked with - of course - an old toothbrush, to scrape off the particles that aren't too tightly embedded in the surfaces. Regardless of the solvents and methods, I always use old toothbrushes for scrubbing. Higher intensity solvents may dissolve or degrade the bristles and heads, so you have to work fast in some cases.
Another option, if you have access to the appropriate equipment, is to skip solvents altogether and do purely mechanical cleaning, like with a soda or walnut shell blaster.
Good luck.
Ed
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Have you tried the IFR group as well - there are people who have this stuff and might be able to help.
Not directly HP related but this is where the knowledge is.
I am starting to repair an IFR-1200S that had an incident.
 
A 150 uF 15V tantalum went up in smoke.
What is the best solvent to remove the residue on the rest of the PCB. Isopropyl does not take all of it off? Want to get it all clean before I replace parts and continue the repair.
Thanks
Dave?
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Thanks Nigel, I have found the IFR group. I should have looked first. ? Thanks
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On Apr 7, 2020, at 2:50 AM, nigel adams via groups.io <nigel.adams@...> wrote:
?
Have you tried the IFR group as well - there are people who have this stuff and might be able to help.
Not directly HP related but this is where the knowledge is.
I am starting to repair an IFR-1200S that had an incident.
<IMG_0884.jpeg> <IMG_0886.jpeg>
A 150 uF 15V tantalum went up in smoke.
What is the best solvent to remove the residue on the rest of the PCB. Isopropyl does not take all of it off? Want to get it all clean before I replace parts and continue the repair.
Thanks
Dave?
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Thanks everyone for the great suggestions.? I will try them all. Starting with the simpler ones then moving up.? The RF board is just a simple D/C to DC power supply.? I shall report back.?
Thanks Dave
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On Apr 7, 2020, at 2:41 AM, Jan Weber via groups.io <jancarlweber@...> wrote:
? May I suggest using a glass fiber pen/brush for removing burnt-in particulate matter and charring?
I've used them in the past to clean corrosions caused by leaking batteries.?
Regards
Jan What a mess - it really did a number on that board section. I agree that acetone would be a pretty good solvent for some of the char, but unfortunately, it may not clean it all off. Some is likely carbon particles (from burning up the coating) and Ta oxides (from the cap guts) splattered onto (and into) the surfaces, and no conventional solvent will dissolve it. The good news is that even if you can't get it spic and span, any remaining residue probably won't hurt the circuit operation after cleaning and repair.
Besides some solvent action, good mechanical scrubbing should help. I'm not sure if your comment about IPA is a question (will it work?) or a statement (tried and it doesn't work). I'd start with IPA, if you haven't already. Paint thinner or acetone are logical next steps. Acetone may be a little too intense to leave on for very long.
Presuming you don't want to remove the board from the RF assembly, which appears to have its feed-throughs soldered to the board, the trick is to be able to work on board cleanup without getting anything bad into the RF. IPA and acetone would probably be best then, since they're miscible with water and will evaporate quickly, while paint thinner would be a bit messy and slow to depart.
If the board can be readily removed, you have more options such as aqueous washing with detergents, and some gentle abrasive action such as an opaque toothpaste worked with - of course - an old toothbrush, to scrape off the particles that aren't too tightly embedded in the surfaces. Regardless of the solvents and methods, I always use old toothbrushes for scrubbing. Higher intensity solvents may dissolve or degrade the bristles and heads, so you have to work fast in some cases.
Another option, if you have access to the appropriate equipment, is to skip solvents altogether and do purely mechanical cleaning, like with a soda or walnut shell blaster.
Good luck.
Ed
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Well to be fair, yours was a pretty general question that certainly
applies here too.
-Dave
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On 4/7/20 10:02 AM, Dave Miller wrote: Thanks Nigel,
I have found the IFR group. I should have looked first. ?
Thanks
Dave
On Apr 7, 2020, at 2:50 AM, nigel adams via groups.io
<nigel.adams@...> wrote:
? Have you tried the IFR group as well - there are people who have
this stuff and might be able to help.
------------------------------------------------------------------------
*From:* [email protected]
<[email protected]> on behalf of Dave Miller
<ve7hr@...>
*Sent:* 07 April 2020 03:55:29
*To:* [email protected]
<[email protected]>
*Subject:* [HP-Agilent-Keysight-equipment] Hints on removing burned
tantalum residue
?
Not directly HP related but this is where the knowledge is.
I am starting to repair an IFR-1200S that had an incident.
<IMG_0884.jpeg>
<IMG_0886.jpeg>
A 150 uF 15V tantalum went up in smoke.
What is the best solvent to remove the residue on the rest of the PCB.
Isopropyl does not take all of it off? Want to get it all clean before
I replace parts and continue the repair.
Thanks
Dave?
--
Dave McGuire, AK4HZ
New Kensington, PA
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What a mess and unfortunately it happens. In addition to the various cleaning hints at least with nicad batteries I have found they do leave conductive stuff. Even though the boards been cleaned. In between traces can conduct and creates all sorts of strange effects. I ran into this in a HP 3586 selective voltmeter. After figuring out the traces were conducting I used a sharp knife to remove some of the top layers in a 2 layer regulator board. That fixed it. The stuff had leaked below the top surface. Regards Paul.
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On Tue, Apr 7, 2020 at 07:02 AM, Dave Miller wrote:
I have found the IFR group
Hi Dave: If you could post the links you found, that would be great. There appears to be many things associated with the names IFR and Aeorflex Cheers and best wishes. Roy
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Hi Roy,
I have been getting some good information?there. Dave
On Tue, Apr 7, 2020 at 07:02 AM, Dave Miller wrote:
I have found the IFR group
Hi Dave:
If you could post the links you found, that would be great.
There appears to be many things associated with the names IFR and Aeorflex
Cheers and best wishes.
Roy
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Guys,
Just in case it helps, the names Marconi Instruments / IFR / Aeroflex / Cobham / Viavi are all
historical parts of the same company from 1998 onwards.
With regards to IFR, this operation was/is still located in Whichita, Kansas, although much of the former operation no longer exists. The only historical records and knowledge will be with the group you found already.
On the Marconi side, mostly UK, there are extensive records as a very good archive of manuals, catalogues, photographs and uFiche were kept.
There are some IFR manuals in the UK archive but not much else.
A lot of those manuals are somewhat specific to aviation/aerospace rather than general purpose test instruments.
Much of what a lot of us seek is knowledge/experience on the products as well as information - whilst there are those of us left who can do so, i’m sure we will gladly help where possible.
Regards
Nigel
Hi Roy,
I have been getting some good information?there.
Dave
On Tue, Apr 7, 2020 at 07:02 AM, Dave Miller wrote:
I have found the IFR group
Hi Dave:
If you could post the links you found, that would be great.
There appears to be many things associated with the names IFR and Aeorflex
Cheers and best wishes.
Roy
--
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Dave,
I do quite a bit of work on IFR service monitors, and have seen this problem many times, both with tantalum and aluminum electrolytics.? I use alcohol and toluene as solvents, and find that I usually have to remove and clean under the components in the affected areas - remove the ICs and clean them and the area under them, and unsolder one lead of the axial parts like resistors and lift them up vertically.? I sometimes use Q Tips to clean, but usually use a solder flux brush that has had the bristles cut short to do the scrubbing. Replace any affected pots.? Early IFR boards are usually not silkscreened, so the tinned surface may stay discolored even after cleaning, but that does not seem to be a problem.? Getting all of the goo off of the areas between the traces is important, though.? In my experience, less thorough cleaning will allow leakage current to continue to flow, which may affect performance.? Be careful doing this, particularly with the blue boards used in early IFR products - they are quite fragile.? I use a Hakko vacuum desoldering tool with good results.
Also, any of those little axial inductors that feed the capacitor that failed are highly suspect: the overcurrent that the capacitor failure causes will often result in shorted turns within the inductor.
Lastly, Viavi has pretty much forgotten about anything labelled IFR - I doubt you will get any assistance from them at all.
Good luck with your repair - Kurt
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Hi Kurt, Thanks for great suggestions. ? I tried the following on the board and am ready to replace capacitor and start testing.? 1) Isopropyl Alcohol and Q tip. Mixed results.? 2) Xylene (goof off) is really good at getting grunge off caps near the epicentre.? 3) Ultrasonic cleaner with soapy water solution. Then?flushed with?clean water. This seems to do a nice job Attached is a picture. Much better than before. Baked the unit for a couple of hours at 40C to dry.? Will let stand for at least a day.?
On Apr 8, 2020, at 8:28 AM, Kurt Swanson <kurt2135@...> wrote:
?Dave,
I do quite a bit of work on IFR service monitors, and have seen this problem many times, both with tantalum and aluminum electrolytics.? I use alcohol and toluene as solvents, and find that I usually have to remove and clean under the components in the affected areas - remove the ICs and clean them and the area under them, and unsolder one lead of the axial parts like resistors and lift them up vertically.? I sometimes use Q Tips to clean, but usually use a solder flux brush that has had the bristles cut short to do the scrubbing. Replace any affected pots.? Early IFR boards are usually not silkscreened, so the tinned surface may stay discolored even after cleaning, but that does not seem to be a problem.? Getting all of the goo off of the areas between the traces is important, though.? In my experience, less thorough cleaning will allow leakage current to continue to flow, which may affect performance.? Be careful doing this, particularly with the blue boards used in early IFR products - they are quite fragile.? I use a Hakko vacuum desoldering tool with good results.
Also, any of those little axial inductors that feed the capacitor that failed are highly suspect: the overcurrent that the capacitor failure causes will often result in shorted turns within the inductor.
Lastly, Viavi has pretty much forgotten about anything labelled IFR - I doubt you will get any assistance from them at all.
Good luck with your repair - Kurt
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Dave,
This looks way better, and might now work, but if it was mine I would clean on it some more.
Looking at your hi res photo, there is still some crud around the anode of CR8, around the pin 1 and pin 16 end of U3, as well as what appears to still be? crud hiding under both U2 and U3.? As I mentioned before, I would also consider the pots suspect, particularly after immersion cleaning.? The symptoms of incomplete cleaning usually manifest themselves as instability, particularly at elevated temperature and / or humidity.
As I also mentioned, this type of failure is common on IFR units of this vintage - the record here currently stands at 5 caps that were shorted simultaneously in an old FM/AM 1000S that had not been turned on in over 10 years.
Again, good luck with this repair - Kurt
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?
OT:? ? question? ?Aeroflex 3416 6 GHz Signal Generator,? ?No RF output? ? ?& Service Man. for 3410 - 3416 series
? ?Apologies, I will post this on the Marconi group,?
? ? ? ? but thought I might ask here, for the moment.
hi Dave, Nigel, & others who might know something about Aeroflex or its IRF /Marconi version ?
I have an Aerolflex IFR 3416 (digital) Signal Generator ?( of the 3410 Series ) that has No RF output, and I'd like to try to repair it.
a)? I fear that the RF final GaAs Mesfets are blown (dead short so far...)
They are HexaWave HWF1681RA ?or H 1681 ceramic (?), but I can not find them anywhere !
b)? Trying to find the Service & Maintenance manuals P/N: 4680/111 (or 468880/111 ?)? & P/N: 46882/500.
? ? ? ? ? ?Cobham wanted ~ $200 for the Service Man., but can't afford anything close to that.
I do have the Op Man, but that has little hardware info in it (" replace the main PCB... ").
Anyone ?
thank you,
rick
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Sounds like you don't have a manual/schematic, but if you can look at the actual circuit and poke around for measurements, look for how the MESFETs are biased. If the sources are grounded, then there should be a negative gate bias supply somewhere, going into the circuit (it's also possibly generated locally, like with an ICL7660). If this bias supply is lost, the MESFETS (depletion-mode devices) will be full-on, and have very low resistance, which can be self-destructive, depending on the design. Good designs should include protection against this event, by disconnecting the drain DC supply or having some sort of intrinsic current limiting at a non-destructive level.
If the sources are degenerated and self-biased, there's no need for a negative gate bias supply. You should be able to find the source resistors and bypass caps, which will be adjacent the MESFETs, to tell if this is the case.
I'm not familiar with the parts you mentioned, but if you can find a datasheet, you can at least figure out how they should be set up. There are some enhancement-mode RF MOSFET types, but I don't know if any go to multi-GHz. I found some of these inside a power amplifier (+30 dBm 1 GHz) in my noise generator.
So anyway, measuring very low MESFET channel resistance in an unpowered circuit doesn't necessarily mean they're shot - they need to be properly biased first. If it turns out they are some kind of enhancement-mode parts, then that's a different story.
Good luck.
Ed
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So I looked up this HexaWave HWF1681RA - definitely a MESFET. If it turns out they're shot, you may be able to find NEC brand equivalents. I vaguely recall that I have some amplifiers that have NEC-something-something-8001 or 8002 types that have similar Idss specs. I don't recall the exact part numbers, but you may find a bunch searching NEC/CEL (California Eastern Laboratories - their US distributor way back when).
Ed
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Dave McGuire
