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: > <CAOT1cQLOjZ0=Xs_+nQ+MzAODboZG5ar0f8G_PydxJ=oj6gr...@mail.gmail.com> > Content-Type: text/plain; charset="UTF-8" > > Hello Folks, > > I'm coming back to this after a few days of prodding etc. and there has > been some progress. The fault has been tracked down to the A3 input board > and it points at a crack in the board or a joint. Here is the sketch: > After a good clean of the switches and re-seating all boards etc. the 5370 > sprung back into life with almost-in-spec performance of 102.xx ns with > it's own 10 MHz. Trouble is it didn't last - after a while and triggered by > sliding some switches around it went back to the 14 ns. Fiddling with the > BNC's may have the same effect, i.e. there is a mechanical element to it > all. > Turns out that running it with the front panel removed I can make it go > from 14 to 102 ns by slightly bending the A3 board, certainly while it is > cold. After a while this trick doesn't work anymore, my suspicion is > whatever crack/gap is causing the trouble has expanded too far to close it > tight. After cool-down we're back to square one. > I notice there are a few SMD components on that board, right in the middle > where it would bend most - basically on the reverse side of the switches. > Capacitors and resistors I expect. I wonder if it is worth going over the > solder joints of all these carefully. > What has stopped me so far are 2 questions: > Am I the only one with this observation or has anybody come across this > before? > Secondly the solder on these SMD's is coated with a black substance. > Clearly this could be removed somehow but it is probably there for a > reason. Has anybody re-touched joints like these before? > On an instrument like this it is very much a case of "proceed with care" > and I'd hate to do more damage by rushing in. > > On a related subject: last year there was a discussion over redesigning the > input board(s) for the 5370 / 5345. Did this get off the ground? If my A3 > packs up completely... > > Thanks in advance for any suggestions, > > Thomas. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.