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IFR-1600 with no RF gen output below 0.317 mV

This forum exists for the purposes for discussing service monitors (This includes but is not limited to Motorola, HP, Aeroflex, GD, etc). Additional topics allowed include test procedures, interpretation of test results, where to find information about specific tests, antenna VSWR, return loss testing, duplexer and filter alignment, etc.

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DuplexerRepair
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IFR-1600 with no RF gen output below 0.317 mV

Postby DuplexerRepair » Fri May 12, 2017 7:29 am

Perhaps this has been seen and discussed before, but I am not finding mention of it. My IFR-1600S has decided that the RF generator does not want to put out any signal if you turn it below 0.317 mV using the Duplexer Port for output, or below 0.142 mV when using the T/R port for output. It's the same regardless of what frequency the unit is set for. It *seems* to be okay in the Analyzer (generator/tracking) mode, but I'm having this problem when using the RF GEN function and DUPLEX function. If you start below either of those respective voltage levels and start turning up the output, it's like it JUMPS TO LIFE at that given level and works great from there up.

Anyone seen and resolved this before? Or have any clue as to what might be happening or where to look?

Thanks in advance for any feedback or suggestions.

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Wowbagger
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Re: IFR-1600 with no RF gen output below 0.317 mV

Postby Wowbagger » Fri May 12, 2017 12:10 pm

It sounds like the step attenuator has a bad relay in it, and when it kicks that stage of attenuation in, you get an open circuit.
This is my opinion, not Aeroflex's.

I WILL NOT give you proprietary information. I make too much money to jeopardize my job.

I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.

DuplexerRepair
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Re: IFR-1600 with no RF gen output below 0.317 mV

Postby DuplexerRepair » Sat May 13, 2017 5:35 am

Are you referring to the "prorgrammable attenuator" that's located on the underside of the unit?

jry
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Re: IFR-1600 with no RF gen output below 0.317 mV

Postby jry » Sat May 13, 2017 8:12 am

chances are one of the pads is open. Not really repairable if that is the case.

Normally the dbm levels are easier to work with since the unit is a 0 to -127dbm 1dbm step attenuator

Good news for you is the part is still available ( bad news is a new one is very expensive )

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Re: IFR-1600 with no RF gen output below 0.317 mV

Postby DuplexerRepair » Sat May 13, 2017 8:27 am

JRY and Wowbagger, thanks much for your input/feedback. I had already suspected the attenuator was the issue (pretty logical in such equipment.) Your replies gave me the motivation to probe into the machine deeper. The control voltages are all there, and I went through the switching levels on each one for the full range of the machine and the 32 db pad is the only one which kicks in at precisely the level settings mentioned and it stays switched in all the way to the analyzer's minimum output, or switched out all the way to max output I carefully removed the metalized label, the metal cover, and the inner metal rf foil and probed the pins at the the 32 db relay contacts and confirmed that when it switches in all RF flow through the attenuator goes to nothing. I'm not 100% certain whether the pad or relay contacts are open or perhaps the pad is actually shorted, but logic leads me to suspect that the pad or relay contact has burned open and the IFR senses the high SWR/impedance at a previous/generator stage and shuts down the RF completely as an auto-protect mechanism. Now... off to shop around for a replacement. BTW... you're right about new ones being pricey... to the tune of a bit over $400. Ouch!

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Re: IFR-1600 with no RF gen output below 0.317 mV

Postby DuplexerRepair » Sat May 13, 2017 8:36 am

PS: I do SMD work here in my lab, so you can bet that after I secure a replacement and get the machine going again I'll be putting this failed one under the video microscope and making an attempt at repairing it. I love a good challenge... I just don't love having to spend precious time working on the equipment I use to work on OTHER PEOPLES' equipment. Being one of (if not by chance the ONLY) shop in the country dedicated to duplexer repairs and overhauls, this 1600 is the heart of my workbench. It has served me well and has held to within 1 Hz of WWV since the day I purchased it used. Knocking on my wooden head... I hope to get at least a few more years out of it. The folks that took over Aeroflex lines now have a well-rehearsed reply of "We quit supporting that equipment" which is what I've received in response to any inquiries about parts, etc. on this thing lately. Nonetheless, they (IFR/Aeroflex) have a history of building excellent equipment and I'll never have reason to regret having purchased this machine.

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Re: IFR-1600 with no RF gen output below 0.317 mV

Postby DuplexerRepair » Sat May 13, 2017 11:34 am

Update: just ordered a used, exact replacement. Has a 30-day return policy, which makes me more comfortable with going with a used one. Not to mention it's going to cost about 1/6th the price of a new one.

GlennD
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Re: IFR-1600 with no RF gen output below 0.317 mV

Postby GlennD » Fri May 19, 2017 2:11 pm

The military service manual on repeater builder has steps to isolate the problem. It sounds like you found it but the manual is nice to have

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Re: IFR-1600 with no RF gen output below 0.317 mV

Postby DuplexerRepair » Sat May 20, 2017 4:04 am

I finished repairing it yesterday. Had to install a replacement step attenuator cell module. Wound up costing me $70 to repair it using a used programmable attenuator module. I had to desolder and install the logic/driver board (which didn't come with the attenuator cell module, but my board was okay. That wasn't a problem since I have a decent vacuum desoldering station. If anyone is interested in seeing photos and a more detailed description of the repair, go to Facebook and search for "DuplexerRepair" in the FB search box. There is an album on that page showing what I had to do in order to repair it. The IFR-1600 is working perfectly now, so I can get back to working on all the radios and duplexers which have been coming in lately.

Just on a related note, one of the well known manufacturers of mobile/compact duplexers stopped doing any tuning or repair work on their own duplexers several months back. When they found out that I'd diagnosed a factory defect in a set which they'd manufactured and sold over a decade ago (i.e., "it had never worked properly or to specs since the day it was manufactured due to a misformed loop inside one of the six cavities") they started referring all of their tuning and repair requests to me. No complaints here. It keeps the electricity on and the water running (nice things to have most days.) 8)

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d119
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Re: IFR-1600 with no RF gen output below 0.317 mV

Postby d119 » Sun May 21, 2017 3:28 pm

Do that many duplexers actually fail? Whats the story there?

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Re: IFR-1600 with no RF gen output below 0.317 mV

Postby DuplexerRepair » Mon May 22, 2017 4:17 am

They do indeed fail, especially the ones which use ceramic encased precision trimmer capacitors. Those capacitors don't tolerate excessive heat or arcing at all, both of which can happen when SWR levels are high, during lightning strikes, when high levels of RF from adjacent transmitting antennas get coupled into an RF system, when the filter/cavity is grossly mistuned, etc. In addition, the electromechanical components inside duplexer and filter cavities will naturally oxidize over time (as all metals will do) which causes changes in resonance and tuning, along with problems such as RF arcing which can literally fuse or "weld" fingerstock contacts to the tuning plungers. It's a time-consuming and labor intensive process to perform a full overhaul/refurbishing job on the things, but it's what I specialize in. For some reason I got hooked on doing so years ago. It's actually very gratifying to test a filter, cavity, or set of duplexer cavities, give them an overhaul, and then see the increases in performance after the work is done -- which can be quite dramatic.

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d119
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Re: IFR-1600 with no RF gen output below 0.317 mV

Postby d119 » Mon May 22, 2017 5:41 am

I understand your feeling entirely. I get quite the personal satisfaction out of tuning cavity filters and watching them come up to spec properly. Same with receiver front ends and what not.

I may want to speak with you about re-doing some cable harnesses on a couple of duplexers for amateur VHF service. Interested?


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Re: IFR-1600 with no RF gen output below 0.317 mV

Postby DuplexerRepair » Tue May 23, 2017 3:56 am

d119, thanks for the info. Unfortunately, that cell enclosure won't work for a few reasons. First the connectors to the driver/logic board are not correct for the IFR-1600. Second, the one in the eBay listing is a 64.5 dB (max) attenuator, whereas the IFR uses an arrangement of cells which total 127 dB max. It's also important to note that according to what I was advised of recently by the folks at Weinschel, there are other electrical specifications WITHIN the 9682-1 attenuator cell housing which were custom built for -- and proprietary to -- IFR/Aeroflex. I was hoping to find out that one of their current models in particular (3200T-1) would be a compatible replacement for the 9682-1. the 3200T-1 is a 127 dB assembly with the same value cells in the same order and exactly the same physical dimensions (feed-thru capacitor pin spacing, etc.) as the 9682 used by IFR, so I was hoping that attaching the logic/driver board from the IFR-1600 to the 3200T-1 attenuator assembly would work. But according to Weinschel it actually isn't due to reasons of the before mentioned INTERNAL electrical specs being different. I'm still considering acquiring one and a failed 9682-1 with a good logic board but bad attenuator cell(s) and trying it.

Regarding the work you need done, I really don't want to go into that here, as I do want to adhere to the rules of the forum(s) on this site. If you want to discuss those matters, you can contact me via telephone or email. Contact info is available on the DuplexerRepair(dot)com website. Otherwise, we'll stick to technical discussions within this forum and perhaps we'll steer other topics to the correct topic areas on the site if/where such exists.

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d119
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Re: IFR-1600 with no RF gen output below 0.317 mV

Postby d119 » Thu May 25, 2017 8:44 am

Sounds good!


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