Re: [time-nuts] 5370B Input Board Repair [WAS: 5370B Question / help needed]

[Thomas Allgeier]

Hi Don,

Yes, my thinking is they may have feared problems and opted for the 
adhesive, but I'm only guessing. Wouldn't have been my first choice for this 
piece of kit.


I don't think you can get this stuff off one joint at a time, but definitely 
one component at a time which is what I have done. The adhesive is 
physically between the component and the pads and unless the component is 
removed you won't be able to clean up the pad ready for soldering. After all 
this messing about with these SMD's it is probably better fitting new parts 
anyway, otherwise you may well be back into the intermittent fault situation 
fairly quickly.


Kind regards,
Thomas.

Message: 6
Date: Wed, 19 Jul 2017 18:16:42 -0600
From: djl <d...@montana.com>
To: Discussion of precise time and frequency measurement
<time-nuts@febo.com>
Subject: Re: [time-nuts] 5370B Input Board Repair [WAS: 5370B Question
/ help needed]
Message-ID: <2138b5104f5a250430c2ed46a755d...@blackfoot.net>
Content-Type: text/plain; charset=UTF-8; format=flowed

Could it be that someone thought adhesive would be less prone to
cracking from stress than solder?
Also, do you think that the adhesive could be cleaned one end at a time
and replaced with solder?
I'm admittedly too lazy to look/try just now.
Don



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Re: [time-nuts] 5370B Input Board Repair [WAS: 5370B Question / help needed]

[John Allen]

Thanks! Didier! 73, John K1AE

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Didier Juges
Sent: Wednesday, July 19, 2017 1:35 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] 5370B Input Board Repair [WAS: 5370B Question / help 
needed]

That is very good information. I will add your email to the 5370 page on my
web site.

Didier KO4BB


On Jul 18, 2017 4:02 AM, "Thomas Allgeier" <th.allge...@gmail.com> wrote:

> Hello All Again,
>
>
>
> I’ve got my 5370B going now and in the process made a “discovery” which I
> thought might be worth sharing:
>
> The A3 input board is a through-hole PCB with a few SMD capacitors and
> resistors on the reverse of the “switch area”. It turns out that on my 5370
> (2410A00777) these components are not soldered, but fitted with conductive
> adhesive. I first thought it was solder with a black coating but under a
> microscope it is clear that it is not solder at all. Most probably it is a
> mixture of epoxy and silver particles, or a similar compound. So no going
> over joints with a fine iron…
>
> Inspecting all this carefully under the microscope I discovered that the
> “joints” on 2 resistors (R23 and R56) had cracked. As you know this board
> gets heat from the hybrid amplifier IC’s and due to the way the board is
> mounted to the front panel I guess it sees thermal stressing when the
> instrument warms up and cools down. While this obviously lasts a long time
> it looks that on my unit the adhesive has eventually cracked in places.
> (Vigorous switch activation and pressing / pulling on the switch handles
> also won’t be helpful in this respect…) One of the resistors just fell off
> at the slightest touch with fine tweezers.
>
>
>
> Anyhow, after removing the offending components, cleaning the pads of the
> adhesive, and soldering replacements in place, we have a perfect 99.9x ns
> with the 10 MHz on the commoned inputs. Happy days!
>
>
>
> So if any of your 5370’s have the kind of intermittent fault I described
> (and one or two other people seem to have reported) or instability that
> seems to originate from the A3 board – check the joints around the SMD’s.
>
>
>
> I wonder why / how it ended up having the adhesive instead of solder –
> were earlier / later instruments the same, or was this a build change
> introduced at a certain period?
>
>
>
> Hope the above is of help to somebody else,
>
> Thomas.
>
>
>
> Message: 1
> Date: Sat, 15 Jul 2017 21:54:47 +0100
> From: Thomas Allgeier <th.allge...@gmail.com>
> To: Discussion of precise time and frequency measurement
> <time-nuts@febo.com>
> Subject: Re: [time-nuts] 5370B Question / help needed
> Message-ID:
> 

Re: [time-nuts] 5370B Input Board Repair [WAS: 5370B Question / help needed]

[djl]

Could it be that someone thought adhesive would be less prone to 
cracking from stress than solder?
Also, do you think that the adhesive could be cleaned one end at a time 
and replaced with solder?

I'm admittedly too lazy to look/try just now.
Don


On 2017-07-19 07:09, Gary Neilson wrote:

This is very interesting, I have a 5370B that has the same behavior as
yours. I will take the input board out again and give it a good
inspection. BTW, what did you use to clean the adhesive from the pads
?

Thanks
Gary

On 7/18/2017 2:41 AM, Thomas Allgeier wrote:

Hello All Again,



I’ve got my 5370B going now and in the process made a “discovery” 
which I thought might be worth sharing:


The A3 input board is a through-hole PCB with a few SMD capacitors and 
resistors on the reverse of the “switch area”. It turns out that on my 
5370 (2410A00777) these components are not soldered, but fitted with 
conductive adhesive. I first thought it was solder with a black 
coating but under a microscope it is clear that it is not solder at 
all. Most probably it is a mixture of epoxy and silver particles, or a 
similar compound. So no going over joints with a fine iron…


Inspecting all this carefully under the microscope I discovered that 
the “joints” on 2 resistors (R23 and R56) had cracked. As you know 
this board gets heat from the hybrid amplifier IC’s and due to the way 
the board is mounted to the front panel I guess it sees thermal 
stressing when the instrument warms up and cools down. While this 
obviously lasts a long time it looks that on my unit the adhesive has 
eventually cracked in places. (Vigorous switch activation and pressing 
/ pulling on the switch handles also won’t be helpful in this 
respect…) One of the resistors just fell off at the slightest touch 
with fine tweezers.




Anyhow, after removing the offending components, cleaning the pads of 
the adhesive, and soldering replacements in place, we have a perfect 
99.9x ns with the 10 MHz on the commoned inputs. Happy days!




So if any of your 5370’s have the kind of intermittent fault I 
described (and one or two other people seem to have reported) or 
instability that seems to originate from the A3 board – check the 
joints around the SMD’s.




I wonder why / how it ended up having the adhesive instead of solder – 
were earlier / later instruments the same, or was this a build change 
introduced at a certain period?




Hope the above is of help to somebody else,

Thomas.



Message: 1
Date: Sat, 15 Jul 2017 21:54:47 +0100
From: Thomas Allgeier 
To: Discussion of precise time and frequency measurement

Subject: Re: [time-nuts] 5370B Question / help needed
Message-ID:

Re: [time-nuts] 5370B Input Board Repair [WAS: 5370B Question / help needed]

[Didier Juges]

That is very good information. I will add your email to the 5370 page on my
web site.

Didier KO4BB


On Jul 18, 2017 4:02 AM, "Thomas Allgeier"  wrote:

> Hello All Again,
>
>
>
> I’ve got my 5370B going now and in the process made a “discovery” which I
> thought might be worth sharing:
>
> The A3 input board is a through-hole PCB with a few SMD capacitors and
> resistors on the reverse of the “switch area”. It turns out that on my 5370
> (2410A00777) these components are not soldered, but fitted with conductive
> adhesive. I first thought it was solder with a black coating but under a
> microscope it is clear that it is not solder at all. Most probably it is a
> mixture of epoxy and silver particles, or a similar compound. So no going
> over joints with a fine iron…
>
> Inspecting all this carefully under the microscope I discovered that the
> “joints” on 2 resistors (R23 and R56) had cracked. As you know this board
> gets heat from the hybrid amplifier IC’s and due to the way the board is
> mounted to the front panel I guess it sees thermal stressing when the
> instrument warms up and cools down. While this obviously lasts a long time
> it looks that on my unit the adhesive has eventually cracked in places.
> (Vigorous switch activation and pressing / pulling on the switch handles
> also won’t be helpful in this respect…) One of the resistors just fell off
> at the slightest touch with fine tweezers.
>
>
>
> Anyhow, after removing the offending components, cleaning the pads of the
> adhesive, and soldering replacements in place, we have a perfect 99.9x ns
> with the 10 MHz on the commoned inputs. Happy days!
>
>
>
> So if any of your 5370’s have the kind of intermittent fault I described
> (and one or two other people seem to have reported) or instability that
> seems to originate from the A3 board – check the joints around the SMD’s.
>
>
>
> I wonder why / how it ended up having the adhesive instead of solder –
> were earlier / later instruments the same, or was this a build change
> introduced at a certain period?
>
>
>
> Hope the above is of help to somebody else,
>
> Thomas.
>
>
>
> Message: 1
> Date: Sat, 15 Jul 2017 21:54:47 +0100
> From: Thomas Allgeier 
> To: Discussion of precise time and frequency measurement
> 
> Subject: Re: [time-nuts] 5370B Question / help needed
> Message-ID:
> 

Re: [time-nuts] 5370B Input Board Repair [WAS: 5370B Question / help needed]

[Thomas Allgeier]

Hello Gary,

The adhesive doesn't come off with solvent - I am afraid very careful 
scraping with a pointy scalpel under the microscope was what did it. That's 
what makes me think it is epoxy-based. Touching it with a hot iron also 
doesn't seem to have much effect. Once cured it probably can only be 
mechanically removed. But it is not immensely strong, I guess the metal 
filler means it can be kind of crumbled off bit by bit. Make sure you really 
get all the debris removed as of course it is conductive and would easily 
cause trouble elsewhere.


I hope you get yours going!

Kind regards,
Thomas.

Message: 3
Date: Wed, 19 Jul 2017 07:09:58 -0600
From: Gary Neilson <g...@deepskyridge.com>
To: time-nuts@febo.com
Subject: Re: [time-nuts] 5370B Input Board Repair [WAS: 5370B Question
/ help needed]
Message-ID: <addd510a-1c2e-ef77-2dba-78497ab16...@deepskyridge.com>
Content-Type: text/plain; charset=utf-8; format=flowed

This is very interesting, I have a 5370B that has the same behavior as
yours. I will take the input board out again and give it a good
inspection. BTW, what did you use to clean the adhesive from the pads ?

Thanks
Gary


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and follow the instructions there.

Re: [time-nuts] 5370B Input Board Repair [WAS: 5370B Question / help needed]

[Gary Neilson]

This is very interesting, I have a 5370B that has the same behavior as 
yours. I will take the input board out again and give it a good 
inspection. BTW, what did you use to clean the adhesive from the pads ?


Thanks
Gary

On 7/18/2017 2:41 AM, Thomas Allgeier wrote:

Hello All Again,



I’ve got my 5370B going now and in the process made a “discovery” which I 
thought might be worth sharing:

The A3 input board is a through-hole PCB with a few SMD capacitors and 
resistors on the reverse of the “switch area”. It turns out that on my 5370 
(2410A00777) these components are not soldered, but fitted with conductive 
adhesive. I first thought it was solder with a black coating but under a 
microscope it is clear that it is not solder at all. Most probably it is a 
mixture of epoxy and silver particles, or a similar compound. So no going over 
joints with a fine iron…

Inspecting all this carefully under the microscope I discovered that the 
“joints” on 2 resistors (R23 and R56) had cracked. As you know this board gets 
heat from the hybrid amplifier IC’s and due to the way the board is mounted to 
the front panel I guess it sees thermal stressing when the instrument warms up 
and cools down. While this obviously lasts a long time it looks that on my unit 
the adhesive has eventually cracked in places. (Vigorous switch activation and 
pressing / pulling on the switch handles also won’t be helpful in this 
respect…) One of the resistors just fell off at the slightest touch with fine 
tweezers.



Anyhow, after removing the offending components, cleaning the pads of the 
adhesive, and soldering replacements in place, we have a perfect 99.9x ns with 
the 10 MHz on the commoned inputs. Happy days!



So if any of your 5370’s have the kind of intermittent fault I described (and 
one or two other people seem to have reported) or instability that seems to 
originate from the A3 board – check the joints around the SMD’s.



I wonder why / how it ended up having the adhesive instead of solder – were 
earlier / later instruments the same, or was this a build change introduced at 
a certain period?



Hope the above is of help to somebody else,

Thomas.



Message: 1
Date: Sat, 15 Jul 2017 21:54:47 +0100
From: Thomas Allgeier 
To: Discussion of precise time and frequency measurement

Subject: Re: [time-nuts] 5370B Question / help needed
Message-ID:

[time-nuts] 5370B Input Board Repair [WAS: 5370B Question / help needed]

[Thomas Allgeier]

Hello All Again,



I’ve got my 5370B going now and in the process made a “discovery” which I 
thought might be worth sharing:

The A3 input board is a through-hole PCB with a few SMD capacitors and 
resistors on the reverse of the “switch area”. It turns out that on my 5370 
(2410A00777) these components are not soldered, but fitted with conductive 
adhesive. I first thought it was solder with a black coating but under a 
microscope it is clear that it is not solder at all. Most probably it is a 
mixture of epoxy and silver particles, or a similar compound. So no going over 
joints with a fine iron…

Inspecting all this carefully under the microscope I discovered that the 
“joints” on 2 resistors (R23 and R56) had cracked. As you know this board gets 
heat from the hybrid amplifier IC’s and due to the way the board is mounted to 
the front panel I guess it sees thermal stressing when the instrument warms up 
and cools down. While this obviously lasts a long time it looks that on my unit 
the adhesive has eventually cracked in places. (Vigorous switch activation and 
pressing / pulling on the switch handles also won’t be helpful in this 
respect…) One of the resistors just fell off at the slightest touch with fine 
tweezers.



Anyhow, after removing the offending components, cleaning the pads of the 
adhesive, and soldering replacements in place, we have a perfect 99.9x ns with 
the 10 MHz on the commoned inputs. Happy days!



So if any of your 5370’s have the kind of intermittent fault I described (and 
one or two other people seem to have reported) or instability that seems to 
originate from the A3 board – check the joints around the SMD’s.



I wonder why / how it ended up having the adhesive instead of solder – were 
earlier / later instruments the same, or was this a build change introduced at 
a certain period?



Hope the above is of help to somebody else,

Thomas.



Message: 1
Date: Sat, 15 Jul 2017 21:54:47 +0100
From: Thomas Allgeier 
To: Discussion of precise time and frequency measurement

Subject: Re: [time-nuts] 5370B Question / help needed
Message-ID: