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Re: HP8640B RF Fails Several Seconds After Power Up
开云体育works for me, although seems the condensation is worse with canned air, may be my imagination.搁别苍é别 On 3/1/22 12:42 PM, Jim Ford wrote:
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Re: HP8640B RF Fails Several Seconds After Power Up
开云体育Say, anybody know any disadvantages of using freeze spray as a duster or a duster as freeze spray?? Turn one upside-down to make it work as the other, of course.? TIA. Jim Ford Sent from my T-Mobile 4G LTE Device -------- Original message -------- From: Flannel Tuba <flanneltuba@...> Date: 3/1/22 12:12 PM (GMT-08:00) Subject: Re: [HP-Agilent-Keysight-equipment] HP8640B RF Fails Several Seconds After Power Up @Jim: I too am a big fan of freeze spray. It can really root out faults that would otherwise be very difficult to diagnose with bench equipment, especially intermittent issues like this. I gave each of the regulator sections a nice dose of freeze spray, without any revealing results, except for the one drawback of such techniques, namely the condensation that can result after cooling the boards, which in this case would throw the regulators off until they'd dried off. Ordinarily, I avoid freezing entire sections of a circuit at once, preferring to freeze each component separately with a nice steady and directed drip from the freeze can. This not only helps eliminate the condensation issue, but saves on the freeze spray, which is not inconsequentially pricy. Unfortunately, without any extender cards, it's nearly impossible to just freeze a specific component at a time, so, firehose freeze spray it is! Anyway, it didn't expose any temperature sensitive issues on the regulator cards. @George: I definitely plan to re-flow all of the TO3 connections, and clean the sockets and pins. Even if it doesn't fix this issue, it's good hardware hygiene in any case. I'll put all of the power transistors on a curve tracer too, and run them through a wide temperature sweep. None of them generated any notable heat while in circuit, but a flakey P/N junction can decide to fail at relative room temperatures. I will say, the day this failed, the temperature in my shop (uninsulated barn actually) was probably in the mid 40°s, F. Admittedly a silly temperature to be aligning a receiver, but it was intended to be a rough alignment. I was bored, what can I say? @Dave: As long as I've had this 8640, is has always been positioned horizontally, so I would hope this would preclude the possibility of the lubricant creeping into the electronics. I do agree that the behavior of the 44.6V supply floating high when the oscillation stops, seems like the regulator's reaction to being underloaded, perhaps when the circuits it supplies, take a nap. Thanks for the tips on where these los might reside.? |
Re: HP8640B RF Fails Several Seconds After Power Up
@Jim: I too am a big fan of freeze spray. It can really root out faults that would otherwise be very difficult to diagnose with bench equipment, especially intermittent issues like this. I gave each of the regulator sections a nice dose of freeze spray, without any revealing results, except for the one drawback of such techniques, namely the condensation that can result after cooling the boards, which in this case would throw the regulators off until they'd dried off. Ordinarily, I avoid freezing entire sections of a circuit at once, preferring to freeze each component separately with a nice steady and directed drip from the freeze can. This not only helps eliminate the condensation issue, but saves on the freeze spray, which is not inconsequentially pricy. Unfortunately, without any extender cards, it's nearly impossible to just freeze a specific component at a time, so, firehose freeze spray it is! Anyway, it didn't expose any temperature sensitive issues on the regulator cards. @George: I definitely plan to re-flow all of the TO3 connections, and clean the sockets and pins. Even if it doesn't fix this issue, it's good hardware hygiene in any case. I'll put all of the power transistors on a curve tracer too, and run them through a wide temperature sweep. None of them generated any notable heat while in circuit, but a flakey P/N junction can decide to fail at relative room temperatures. I will say, the day this failed, the temperature in my shop (uninsulated barn actually) was probably in the mid 40°s, F. Admittedly a silly temperature to be aligning a receiver, but it was intended to be a rough alignment. I was bored, what can I say? @Dave: As long as I've had this 8640, is has always been positioned horizontally, so I would hope this would preclude the possibility of the lubricant creeping into the electronics. I do agree that the behavior of the 44.6V supply floating high when the oscillation stops, seems like the regulator's reaction to being underloaded, perhaps when the circuits it supplies, take a nap. Thanks for the tips on where these los might reside.? |
Re: Scoping the Power Rails [8566B]
Additional thoughts on the REF unlock - If it appears whenever the 8566 has been off long enought for the oven to cool down, that is an indication that either the 10 MHz Ref oscillator has drifted significantly and may need re adjustment to 10MHz, or the internal 100MHz reference (located next to the M/N section) needs adjustment - you should check both.
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So try the following: 1) Confirm the 10Mhz reference is on frequency and adjust if necessary. 2) Once #1 is done, check the 100 MHz reference and adjust if necessary. Note that the adjustment process is complex but for these purposes, you only need to confirm that the loop is locked and the VCO control voltage is close to the specified lock voltage. Once you have solved the YO unlock issue, you can go back and do a through job. Cheers! Bruce Quoting Matt Huszagh <huszaghmatt@...>: To add to Bruce's answer: the REF unlock can occur when the OCXO oven is |
Re: Scoping the Power Rails [8566B]
Yes - Matt is correct - I forgot to advise about the warm up time - also there is o real problem about the battery - plan on replacing it but it will not cause YTO unlock.
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Cheers! Bruce Quoting Matt Huszagh <huszaghmatt@...>: To add to Bruce's answer: the REF unlock can occur when the OCXO oven is |
Re: HP 1727A CRO: Problem with the vertical output amplifier.
I think my best course of action is to make a replacement circuit on a drop-in PCB, I have the tools and skills to do so. The online store I contacted regarding a replacement IC did not have any.
Another thing I wanted to ask you people is how thick the trace should be. The best I can get mine is 1.5-2mm, is this normal? |
Re: Scoping the Power Rails [8566B]
To add to Bruce's answer: the REF unlock can occur when the OCXO oven is
warming up. If the unit has been plugged in (doesn't need to be powered on, since the oven supply is active anytime the instrument is connected to mains) more than ~10min or so and the annunciator is still there, that's an indication there's an issue. FYI although the oven supply is always present when plugged in, the oscillator supply isn't. You'll need to power on the unit to see the 10 MHz signal. I would start by just checking to make sure this 10 MHz signal is present. You don't need to open the instrument, it's available on the back panel. Any oscilloscope should be able to tell you whether the reference signal is present or not. I got a ref unlock on an 8340 (same reference as the 8566) and it was caused by a dead reference. If the reference is dead, you can test the rest of the instrument by providing an external 10 MHz reference. Check the manual to ensure the power level is appropriate. If you're not getting a 10 MHz signal, before ultimately implicating the reference, you should ensure all interface signals to the reference (including both the oven and oscillator supplies) are correct. If the reference is present but you still see the REF unlock that will require some additional troubleshooting. Good luck, Matt |
Re: HP 410B probe wire
You're absolutely right about that.? I checked one of mine and OHMS/AMPS is, indeed, shielded.? Apologies for the misinformation. Thanks, Barry - N4BUQ From: "Askild" <megafluffy@...>
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Re: HP 410B probe wire
Bob Albert
The 410C is different.? The 410B has regular wire for Ohms, Commnn, and (except for the resistor) DC.? Well the DC may be shielded (not coax).? The AC probe is fancier with filament voltage for the tube. Bob
On Tuesday, March 1, 2022, 10:53:02 AM PST, Askild <megafluffy@...> wrote:
Hi, Just checked my HP 410C, and only Common is regular wire,? both Ohms/Amps and DCV are coax. Regards, Askild On Tue, Mar 1, 2022 at 6:49 PM Bob Albert via <bob91343=[email protected]> wrote:
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Re: Scoping the Power Rails [8566B]
So the REF unlock will be a major problem - you need to fix that before addressing the YTO unlock. Be sure the internal REF (10 MHz) oscillator is on frequency and that the INT/EXT switch is set properly and there as a good BNC connection between the INT and EXT reference BNCs (this assumes you are using the internal reference.
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I thought there was an LED for the M/N section (I'll have to check - don't have the cover off an 8566 right now) - or you could post a close up of the REF + M/N modules - As I remember, there is at least one LED there. The REF unlock is much more likely the problem than any power supply noise. Cheers! Bruce Quoting Jinxie <paul666@...>: @Bruce |
Re: HP 410B probe wire
Hi, Just checked my HP 410C, and only Common is regular wire,? both Ohms/Amps and DCV are coax. Regards, Askild On Tue, Mar 1, 2022 at 6:49 PM Bob Albert via <bob91343=[email protected]> wrote:
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Re: Scoping the Power Rails [8566B]
@Bruce
I only had very little time this evening to investigate further, I'm afraid. Not even enough time to try shortening the ground clip lead! I will try out everyone's suggestions in due course, however. As things stand, I was able to observe that the screen is showing three errors in all now: Battery, YTO Unlock and REF Unlock. I don't recall that last one being there previously. There are three LEDs lit on the stack of modules criss-crossed by the press-on patch leads. I think these are the ones you were referring to: ON=PLL3 Lock ON=PLL1 Lock ON=HET As I say, all three are lit. Can't see any LED for PLL2, though! After trying everyone's suggestions I plan to work through the steps suggested in the troubleshooting & diagnostics manual. It's probably going to be above my pay-grade, but nothing to lose by at least trying I guess. |
Re: HP 410B probe wire
Bob Albert
Don't forget the resistor in the DC probe.
On Tuesday, March 1, 2022, 05:00:07 AM PST, n4buq <n4buq@...> wrote:
COMMON and OHMS/AMPS is regular probe wire.? DCV is shielded (coaxial).? ACV is shielded with two conductors (triaxial). Thanks, Barry - N4BUQ From: "Askild" <megafluffy@...>
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Re: HP8640B RF Fails Several Seconds After Power Up
开云体育If you are working from a scan of 08640-90017 that doesn’t have schematics, you can find those same schematics in military manual “TM 9-4935-601-14-7&P”. It is written for serial number prefix 1324A, the same as 08640-90017. ? Study of the Service Sheets reveals that the +44.6V rail is used by:
? A9 drives the FM varactor diode in the oscillator.? If the diode is inadvertently forward-biased, the increased loss may cause the oscillator to stop.? Meanwhile, depending on details inside A26U1, it might stop drawing power when its input disappears, causing the +44.6V rail to lose most of its load and overshoot.? This is speculation on my part. ? An oscillator problem the 8640 is well known for is that if the instrument was stored facing down, lubricant at the back of the oscillator migrates forward, fouling the electrical connection of the cavity plug.? Treatment consists of storing the instrument for a while facing up. ? HTH, Dave Wise ? From: [email protected] <[email protected]>
On Behalf Of Flannel Tuba via groups.io
Sent: Monday, February 28, 2022 7:22 PM To: [email protected] Subject: Re: [HP-Agilent-Keysight-equipment] HP8640B RF Fails Several Seconds After Power Up ? I have not checked for bad solder joints on the pass transistor. I will give all of them a close inspection tomorrow afternoon.? |
Re: HP 410B probe wire
COMMON and OHMS/AMPS is regular probe wire.? DCV is shielded (coaxial).? ACV is shielded with two conductors (triaxial). Thanks, Barry - N4BUQ From: "Askild" <megafluffy@...>
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Re: HP 410B probe wire
Hi, So please check how many of them are coaxial.? Or maybe someone else has the correct answer. Regards, Askild On Tue, Mar 1, 2022 at 3:39 AM saipan59 (Pete) <saipan1959@...> wrote: I believe the most important feature of "probe wire" is that it have very fine strands, so that it doesn't break internally with a lot of flexing. |
Re: 8350B *restoration adventure?*
Yves, that data is very helpful, thank you so much! Helps a lot indeed ;) ? PD Lothar, I always look for 'best offer' auctions on eBay, but the shipment and customs still very heavy. It's a disadvantage to live in Europe for this hobby :D |
Re: OT: Help with Galep-5 problems
开云体育Conitec got in touch with me and guided me through some things to try. ? Switching to different USB port solved the problem! ? Thanks David ? From: [email protected] <[email protected]> On Behalf Of Kuba Ober via groups.io
Sent: 28 February 2022 05:47 To: [email protected] Subject: Re: [HP-Agilent-Keysight-equipment] OT: Help with Galep-5 problems ? I have that programmer. Chips on order from a reliable source. Will report as soon as I get them. ? Cheers, Kuba
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