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E4401B No 50MHZ Cal signal
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I dont have the service manual or CLIP for E4401B but I was scratching my head since Mike said the VCC for VCO
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comes from a MUX. I am sure I have never seen such a thing and it would be a bad practice to turn on/off the? VCC of a? chip by a MUX. Sampling it for ADC and self test makes a lot more sense. Still I suspect if that second LO was dead or unlocked, the instrument would have generated an error message of some sort On Mon, Apr 1, 2019 at 03:58 PM, Mark Bielman wrote:
Michael, |
开云体育Mark, ? The documents I am using are E4401-90474 “Service Guide, ESA Spectrum Analyzers” and the CLIP for “1.5 GHz RF (75 Ohm) E4401-60100. ? -- Mike ? ? From: <[email protected]> on behalf of "Mark Bielman via Groups.Io" <mbielman@...> ? Michael, |
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Yes, those are the ones I am using as well. My CLIP is quite hard to read. (poor scans) and my PDF reader cannot search for text. (graphics files I guess)
I have simply ignored the test points on the schematic! On the PCB I see things like "1st LO Ref" and such. But I agree that the CLIP is not great but we'd be lost w/o it! Don't give up. Mark |
开云体育Found the problem! ? C448 had failed short. ? Many, many thanks to all the guys who contributed to this thread – especially Mark and AmirB.? You guys pulled my head out of the rabbit hole with that MUX nonsense.? I’m so glad it was something as simple and easy to fix as a bad cap.? I had fears of bad ASICs, and other such unobtanium floating through my head. ? If anyone is interested in my fault-finding approach this evening, read on. ?Otherwise, please accept my thanks – this group has been very helpful to me. ? My probing the other day had shown no signal at R525, and when I was unable to see anything resembling an 800MHz source signal (due to bad probing) I started checking every voltage I could find, which led me down the rabbit hole with 2ns_VCO_Vcc and the MUX nonsense. ? After listening to Mark B and Amirb (and the many others who contributed to this thread) I had a more organized plan of attack for tonight.? After double-checking the supply voltages, I started working from the other end of the 50MHz signal path (the 1/16 divider).? I confirmed the presence of the 800 MHz 2nd VCO by making an ad-hoc RF probe with a loop of wire connected to my SDR Play, I then walked all the way through the 50Mhz path.? After seeing signal on one side of R523, and no signal on the other side, I began to suspect C448.? A quick power-down and check with a multimer confirmed my suspicion.? I may not know one end of a MUX from another, but I do know that capacitors should not act like low-value resistors.? I pulled the cap, and the analyzer started to behave itself.? Little did I realize I was so close to the problem when I probed R525 the other day!? ? I have a replacement cap on order.? I assume it’s purpose is part of a filter along with L55 and R523 to clean up the 50MHz signal.? The analyzer would probably function reasonably well without it, but I may as well replace it while I have the RF module open. ? Cheers, ? Mike Williams AG5QX ? ? From: <[email protected]> on behalf of "Mark Bielman via Groups.Io" <mbielman@...> ? Yes, those are the ones I am using as well. My CLIP is quite hard to read. (poor scans) and my PDF reader cannot search for text. (graphics files I guess) |
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The number one tool of anyone fixing modern
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electronics should be an ESR meter of the Dick Smith variety. Arguments about about ESR vs capacitive reactance are numerous, but immaterial. When a capacitor goes bad, its ESR will usually be 2 to 100 times higher than normal. Shorted capacitors will also be obvious, as the ESR meter will show their ESR to be 1/4 (or less) the normal value for a capacitor of that value. Capacitors are the least reliable part made today. Also, use your eyes, and scan the field. If almost all of the capacitors used are, say, Nichicon, and you find one or two that are YooSun, or Samson, or Jokcon, or something else weird, it means the supply line for Nichicons of that value was blocked up for some reason, and purchasing bought what they could find. -Chuck Harris Michael Williams wrote: Found the problem! |
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On Tue, 2 Apr 2019 07:41:18 -0400, you wrote:
The number one tool of anyone fixing modernPlugged in a Tektronix 7000 series counter (7D15 to be exact), on an extender. It wasn't working. I had the room lights dim for whatever reason, hopefully to see anything that was unhappy. Everything was fine, but the scope wasn't happy. Even the little LED on the main board of the counter was glowing a nice cheerful red. Wait a minute, *what* LED? I don't remember an LED on that board.... TUrned up the lights a bit, and saw one of the dipped tantalums glowing a nice cheerful red. Not quite the way you want to find that out. No smoke, no smell, just rather gray and glowing. Harvey
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Hi
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Or treat yourself to a thermal imaging device i have found it to br very useful. On 02/04/2019 07:53 pm, Harvey White wrote:
On Tue, 2 Apr 2019 07:41:18 -0400, you wrote:The number one tool of anyone fixing modernPlugged in a Tektronix 7000 series counter (7D15 to be exact), on an |
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Sorry to barge in with this, but I have my sights on a 4411B (I assume it is similar to the 4401B being discussed here) that has a message on the startup screen that says "Align RF Skipped, No align signal". Is it possible this is just being caused by some setting being wrong, or could it be a similar problem as discussed here?
I am new to these units and considering getting one (~cheap) for the barn. Any insight into this appreciated. Thanks. |
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Hello Alex,
Everything is automated during alignment so no settings will affect this. Sounds like the unit has an issue and yes similar to discussions here. It's easy to check - with a cable from 50 MHz out to RF In, use the I/O menu to enable the 50 MHz signal... it would be displayed if it's working. (set Center Frequency to 50 MHz and Span to, say 10 MHz) If it's not there or very low, then you have a faulty component in that signal path. Good Luck! Mark |
开云体育Hi Alex, ? Based on my experience with the 4401B, there could be a number of causes: ? * Blown front end * Faulty 50 MHz internal test signal * Bad mixers or * IF issues ? You really can’t tell from just the error message.? The service manual will help you identify which major component/board is the likely cause.? Once you have that, you will need the CLIP to determine the problem in that component.? To trace down the issue in the signal path, you will need active RF probes as Amir has mentioned, and test equipment capable of measuring the 1st and 2nd IF stages.? This is where I am currently stalled on my 4401B, while I wait for more capable equipment to arrive. ? Depending on the price of the unit, and your needs, it could be an interesting learning experience on RF probing and troubleshooting.? However, if you are looking to have a functional unit that you can start using soon, you should probably keep looking. ? Cheers, ? Mike ? ? From: <[email protected]> on behalf of "Alex via Groups.Io" <hpagilentgroup@...> ? Sorry to barge in with this, but I have my sights on a 4411B (I assume it is similar to the 4401B being discussed here) that has a message on the startup screen that says "Align RF Skipped, No align signal". Is it possible this is just
being caused by some setting being wrong, or could it be a similar problem as discussed here? |
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Thank you Mark and Mike for the insightful answers.
Unfortunately I don't have access to this particular unit yet, I only saw the error message on one of the pictures sent to me. The selling price is around the $500 mark shipping to FL included. Normally I would feel adventurous in trying to find and ultimately fix this problem, but given the big complexity of these units in this case I am not so sure I really want having to go into the jungle from the get go. Unless someone more experienced in these ESA units thinks the price would still be a good deal, I guess will wait for the next one. Or would anyone care to suggests a counteroffer I could send that would make sense and minimize my risk given the unknowns? BTW wanted to ask what is the "CLIP" that has been mentioned several times in this thread? Sounds like an extension to the service manual, or some sort of diagnostic hardware. Maybe I should think of getting it ahead of purchasing one of these units. Can't even find a PDF service manual yet. Thanks again. |
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The CLIP stands for "Component Level Information Package" Beginning in the 1990's ( for the most part) HP/Agilent stopped publishing what we all used to know as full up service manuals. At that point in time most of the service manuals only? had test and adjustment info but not schematics , no board part locators nor parts list . For roughly the next 10 years if you wanted schematics you had to purchase a CLIP ( at a price of $250-$500 !!!) . Trouble shooting trees as we knew them disappeared all together for the most part . After 2000 they even stopped ( for the most part) publishing the CLIPS. Typically CLIPS do not cover GHZ level RF circuits, YIGS etc. Most do not cover the power supplies and CRT ( or LCD) display units both of which HP had stopped making and were 3rd party drops ins.
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Dave manuals@... On 4/15/2019 10:28 AM, Alex wrote:
Thank you Mark and Mike for the insightful answers. --
Dave Manuals@... www.ArtekManuals.com |
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For what it is worth, and to give you guys an idea I have a good background servicing Motorola and other brands of LMR 2-way radio equipment for over 40 years. I use a R2001H service monitor on the bench as most of my customers with big radio fleets are still on analog. Besides the R2001H (1GHz), for tracing I do have a Fluke 85 RF probe, which has a upper -3dB limit of 500MHz, and among other scopes have a Tek 2465B with P6137 400MHz probes, and several 1.1GHz frequency counters which I check and recal as needed with a 10MHz rubidium oscillator. Plus the obligatory 3468, 3478 and several 974/975 handheld DVMs. Not sure that would stack the odds enough in my favor towards being prepared to find the RF problem in that 4411B.
But just in case I would definitively check C448 first, although I doubt will be this lucky. |
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On Mon, Apr 15, 2019 at 07:43 AM, ArtekManuals wrote:
The CLIP stands for "Component Level Information Package" Beginning in Thank you Dave. Do you have anything available for the 4411B in terms of service aid literature? Maybe its time to make another purchase from you. |
开云体育Sadly, C448 was not the actual culprit.? When I replaced what I thought was the defective cap, the malfunction returned. ? At this point, I suspect the 1st IF mixer, or the amplifier post-mixer.? I am waiting on the tools to properly probe the signal path to know for sure.? Once I have the equipment to test, and have more info, I will post it here. ? -- Mike ? From: <[email protected]> on behalf of "Alex via Groups.Io" <hpagilentgroup@...> ? For what it is worth, and to give you guys an idea I have a good background servicing Motorola and other brands of LMR 2-way radio equipment for over 40 years. I use a R2001H service monitor on the bench as most of my customers with big
radio fleets are still on analog. Besides the R2001H (1GHz), for tracing I do have a Fluke 85 RF probe, which has a upper -3dB limit of 500MHz, and among other scopes have a Tek 2465B with P6137 400MHz probes, and several 1.1GHz frequency counters which I
check and recal as needed with a 10MHz rubidium oscillator. Plus the obligatory 3468, 3478 and several 974/975 handheld DVMs. Not sure that would stack the odds enough in my favor towards being prepared to find the RF problem in that 4411B. |
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