Marconi 2390 Spectrum Analyser with YIG fault - Page 1
Forum section: electronics / repair

author: SparkyBruce
author_rank: Contributor
timestamp: December 13, 2016, 10:33:55 pm
content: Hello,I have just got a Marconi 2390 22Ghz analyser that has a YIG fault with it. It works fine on the lowest "range" up to 2.9Ghz , and it appears to work above that just with a higher noise floor.Does anyone have a copy of the maintenance manual for this unit. (I have noticed that the ref out signal is not present either - but that might be a different issue).I do have a paper copy of the standard manual if anyone needs a scan of one.The unit has the TG option as well as the Quasi Peak option (02 and 08) so it is worth sorting out.( I also have a HiLO , AR 100HB , and a Holaday HI-6005 to look at over xmas).ThanksBruce

author: pe2ben
author_rank: Contributor
timestamp: July 12, 2020, 05:09:43 pm
content: Hello Bruce,I have purchase the IFR Marconi 2393a but i have not any manual at all.Would you make a copy or scan from your manual for me.Of course i will pay for it.Would be great, Ben

author: Jarek
author_rank: Regular Contributor
timestamp: August 22, 2023, 08:34:34 am
content: HiI have the same problem with YIG.If anyone has a schematic diagram of the Marconi 2390 help me please .

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: August 22, 2023, 04:36:25 pm
content: maybe try on groups.ioThere was a discussion about the 2390 but I do not remember who has a manual. The 2390 was apparently put together by assembling different manufacturers partshttps://groups.io/g/Marconi-Test-Instruments/search?p=created%2C0%2C%2C1%2C2%2C0%2C0&q=2390

author: Jarek
author_rank: Regular Contributor
timestamp: August 22, 2023, 08:50:51 pm
content: Quote from: Wallace Gasiewicz on August 22, 2023, 04:36:25 pmThank you for the link .They are also looking for a service manual there.2390 is good equipment, it's a pity to let it stand broken on the shelf.

author: George Edmonds
author_rank: Frequent Contributor
timestamp: August 22, 2023, 10:35:54 pm
content: HiAs far as I have been able to discover the Marconi 2390 was not a Marconi Instruments product, it has its origin in a collaboration between Aeroflex (American) and NEX1 (South Korea) . For a time Marconi Instruments factored the unit. The last true Marconi designed spectrum analyzer is the 2386.Eventually, via a number of takeovers, all of the players assets were acquired by Viavi Solutions who finally ceased using all of the company names is 2021.G Edmonds

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: August 23, 2023, 03:33:00 am
content: I have two 2398 spectrum analyzers. There should be a square wave on the 10MHz output unless you set the SA to use an external reference. I think this option is in the CONFIG menu.It probably isn't the 10MHz reference though. I physically unplugged the 10MHz reference and the YIG CAL still passed. The problem is most likely in the RF module.In any case one of my 2398s has recently started to give the YIG CAL error. I suspect a bad solder joint, as it was working a week ago. I will take my module apart, debug it, and post pictures here.

author: George Edmonds
author_rank: Frequent Contributor
timestamp: August 23, 2023, 05:08:19 am
content: HiJust to make it absolutely clear, the Marconi 2390 and the Marconi 2398, both factored products, are NOT the same instrument, in fact they were not even designed or made by the same manufacturer.G Edmonds

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: August 23, 2023, 06:36:14 am
content: Fair enough, but the principle of operation for the YIG self test might be similar.On my spectrum analyzer, after failing the YIG test everything except for the frequency still works. The frequency is off by about 50 MHz when I feed in a 1 GHz signal. I don't know if it is the same on your analyzer or not.There is an RF switch at the input which switches between the N connector on the front panel and a calibration signal (which is at -30dBm I believe). The RF switch is broken on my device I think, since the input of the switch has a DC voltage of -5V when the switch is on (which definitely shouldn't happen). If your spectrum analyzer works mostly but has a frequency error and fails YIG calibration, I would look for the calibration signal / RF switch. Of course, since the devices are different there is no guarantee that calibration is done in the same way (perhaps yours has a sampler or prescaler to measure the frequency).

author: George Edmonds
author_rank: Frequent Contributor
timestamp: August 23, 2023, 12:54:42 pm
content: HIlook at this,https://www.eevblog.com/forum/repair/aeroflex-ifr-2398-calibration-repair-help/msg4652008/#msg4652008G Edmonds

author: Jarek
author_rank: Regular Contributor
timestamp: August 24, 2023, 08:17:58 pm
content: Thank you for your posts.I checked my YIG today, it works (at a current of about 140mA on the coil, tune starts).I have a DAC error as in the photo. Where should I look for the cause?

author: Jarek
author_rank: Regular Contributor
timestamp: August 26, 2023, 09:23:20 am
content: Does anyone know what the voltage should be on that purple wire?Does anyone have a picture of the wire connections, I don't know if I have them well connected.

author: Jarek
author_rank: Regular Contributor
timestamp: August 27, 2023, 08:51:04 pm
content: Problem solved .The voltage on this purple wire is now about 35V (previously it was 0V)The reason was a damaged thantal capacitor see photo.The analyzer is working.

author: Jarek
author_rank: Regular Contributor
timestamp: August 28, 2023, 06:56:27 pm
content: The analyzer works, but the amplitude of the signals is too low by about 10 dBm for low frequencies up to 1000MHz and about 5 dBm for frequencies above 3GHz.The input attenuator is good.Does anyone know what component is marked in the picture?It looks like a attenuator ?I already know it's a 3dB attenuator.

author: Jarek
author_rank: Regular Contributor
timestamp: August 29, 2023, 08:47:49 pm
content: The attenuator was damaged, for now I soldered a simple attenuator. The signal level is correct.Now the problem is where can you buy an attenuator?

author: EggertEnjoyer123
author_rank: Frequent Contributor
timestamp: August 30, 2023, 06:16:46 am
content: The circuit board construction looks like it's for the low GHz range. Your attenuator should work fine if that's the case.If you want an actual attenuator you can buy them off Mouser:https://www.mouser.com/datasheet/2/1030/PAT_3_2b-2936572.pdfhttps://www.mouser.com/datasheet/2/392/n_catalog_partition16_en-2487399.pdfIt might be difficult to find one with the exact package but you should be able to bodge one in

author: Jarek
author_rank: Regular Contributor
timestamp: August 31, 2023, 05:54:00 pm
content: Thank you EggertEnjoyer123.You are right it is a board probably up to 3 GHz.

author: divane
author_rank: Newbie
timestamp: February 16, 2024, 05:59:16 pm
content: Hello,I've got a Marconi 2390 22Ghz spectrum analyser with a YIG fault.As Jarek's posts I can confirm that there is +35VDC present on the purple cable.Does anyone has a service manual for this device or could you help identify which of them enclosed metal boards hosts the YIG?