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Thread: XTS2500 Fail 001 Error

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    Default XTS2500 Fail 001 Error

    Oddly, I experienced a Fail 001 error last Friday. At the time, I was scanning a scanlist that contained rx-only channels. The error occured after keying the radio (which produced the standard error tone since I was on rx-only channels). I moved around zones and channels as an experiment, and intermittently got the error on receive.

    After heavy use of the radio since then, there hasn't been a single Fail 001 error. Could this have been a glitch that has resolved itself? The radio was at the depot last November (for something else) and the board was replaced. I would hate to spend another $400 at the depot.
    Last edited by Number 6; May 20, 2012 at 03:52 PM. Reason: Tired eyes - can't spell. :)


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    Fail 001 is the syth out of lock. It looks like keying the radio messed up the sythesisor. Its prpbably a microprocessor usage thing rather than a hardware failure.

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    Thank you I'm hoping this was an isolated instance and the radio doesn't have to go to the depot again. At first I thought that the problem might have been related to recasing the radio, but a complete new housing wouldn't affect the synthesizer.

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    You also might try cooling and/or heating the radio to see if you can aggravate the failure. VCO lock ranges are usually quite temperature-sensitive. This will tell you if you have a VCO on the edge of unlock. I have a 380-470 (R Split) XTS5000 and it gives an error once in a while scanning some of the 476-478 systems, which are out-of-band for that radio, technically.

    If you find that you are "on the edge" as I described, you might be able to muck with the VCO crossover values (I assume the newer A25 stuff has this like the older Astro Sabers/XTS3000's). This is the frequency where the VCO re-uses the tuning voltages to tune over about half the operable tuning range. The entire band has to be tuned in two sweeps of the varactor voltage (usually 3-18 volts) since they don't get enough tuning range out of one "sweep" of the voltage range, they use a signal (called "PIN shift") that makes the VCO sweep the lower or upper half of it's tuning range. Anyway the "Crossover Value" determines at what frequency it resets back to 3V and starts over for the other half, and playing with that value might give you just a bit more range in one half of the tuning or the other.

    The values were different for Astro Saber vs. XTS3000, even though their RF decks are quite similar. I would try tweaking them up or down 500 kHz - 1 MHz or so to see if that has any effect. If it does, try moving them a smaller amount and see if it still fixes the problem. If none of that helps, then the VCO is just defective or unstable and there may be no fixing it with tweaking, unless you have an Excimer laser and can re-trim the VCO substrates

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    Hi guys. I have two radostantsii XTS2500 which will generate an error FAIL 001, but it does not always happen.
    In short it works, then no. How do I solve this problem.
    You change the capacitance in the synthesizer?

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    Like I said, unless you have a high-powered Excimer laser, you aren't going to be able to modify the VCO ranges through hardware changes. Look in the tuner software and see if there's a VCO crossover value as I described above, and if not, or that doesn't seem to affect it your VCO may just be bad or unstable. Since the 2500 is a single board radio, that means if it's bad, the whole thing is junk. As a LAST resort, you might try re-baking or reflowing the solder in and around the VCO area, maybe the chip there has insufficient solder.

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    Thank you for your reply. I'll try to warm the VCO

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    Quote Originally Posted by Alpha View Post
    ~ Look in the tuner software and see if there's a VCO crossover value as I described above ~
    The only things adjustable in the Tuner software (for ASTRO25 radios) seem to be Reference Oscillator, Power & Deviation adjustments? Is there a "Depot" level tuning software that would allow access to a VCO crossover adjustment?

    Fail 001 is quite a common occurrence here in Australia due to our UHFCB frequency allocation being right on the edge of a Q-split radio's capabilities, I don't mind losing a few MHz from the bottom end but that last 1MHz at the top is a real PITA!
    Last edited by Bigfella237; Jun 13, 2012 at 09:52 PM. Reason: not re-reading the damn post before clicking send!
    Andrew

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    I wasn't aware they eliminated the crossover value adjustment in the newer tuning software. I am more used to the older Astro Saber/XTS3000 stuff where that adjustment was present; sometimes it helped, sometimes it didn't. That's too bad, there probably is such a value in the tuning partition, but apparently it's no longer user-editable.

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    Ive just extended the range of a few Q split ASTRO spectra's by a couple of MHz by modifying the resistive divider that feeds the negative VCO steering line. All the was needed was to bend the VCO line down a volt or two, and this increased the frange from 437Mhz to over 440Mhz.

    The VCO Steering lines control the VCO frequency lock range, not the laser cur preselector strip. The laser cut strip is simply a front end filter to remove out of band interference and intermod/images. This can, and has been easily be trimmed with a hobby knife to increase the freq, or with a soldering iron, or conductive pen to decrease the range.

    Althought they don't apply to the XTS2500, the details on the mods have been published here -> http://www.radcomms.net/Spectra.html

    I'm looking at the XTS2500 detailed service manual now, and it appears that the VCO design is completely different so although these mods work for the ASTRO Spectra, they dont apply to any of the newer stuff... Sigh...

    EDIT - Mods, can you please split this out into a new thread? I just realised that everything here is relevant to the legacy ASTRO gear and not the XTS2500 in question in this thread. Apologies for the off topic post.

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    Quote Originally Posted by MattSR View Post
    The VCO Steering lines control the VCO frequency lock range, not the laser cur preselector strip. The laser cut strip is simply a front end filter to remove out of band interference and intermod/images. This can, and has been easily be trimmed with a hobby knife to increase the freq, or with a soldering iron, or conductive pen to decrease the range.
    This is not quite correct, I think you're confusing the RF front-end preselector with the VCO substrate microstripline. I have worked on and modified several hundred VCO's for Spectras and Astro Spectras in my time, and I'm also a hardware RF design engineer so I know how these circuits work. The laser-cut stripline on the VCO is indeed a frequency-determining component of an oscillator. There is an RF preselector in an entirely different part of the radio that is a front-end that is also laser-cut, but that has nothing to do with the VCO.

    An oscillator consists of a resonant tank circuit with feedback, and the stripline is the inductor in that tank circuit. The capacitor part of the tank is provided by the mutual capacitance of the stripline over the ground plane under the substrate, and is further loaded with some physical caps and a varactor diode that acts like a variable capacitor in the tank circuit. So, you can modify the frequency of the VCO by either changing the capacitance or the inductance. The inductance change will be done by adding or taking away from the length of the stripline. Changing the capacitance is done by either adding a physical cap to the circuit, or varying the varactor steering voltage. The latter is how the microprocessor in the radio tunes the VCO. Another varactor causes the frequency of the oscillator to pull up and down in response to a modulating voltage (FM!). The output of the oscillator is sampled and sent to a synthesizer circult which keeps it on-frequency and calculates and generates the steering voltage required for a given frequency output.

    So, anyway, the point of this whole dissertation is that you can either muck with the stripline or you can play with the steering line voltages to effect a change in operating range. Whatever you do you are usually only going to get about 6-8 maybe 10 MHz of difference before you would wind up having to change more components to get the desired changes. I usually do the stripline mod when taking 450 VCO's down to 438 or lower, simply adding a bit to the stripline is all it takes. VHF R2 to R1 mod is more difficult and requires changing several caps as well as lengthening the stripline a bit. For 900 Mhz ham conversion, playing with the steering voltage is easier than modifying the VCO oscillator tank circuit.

    The VCO in the 2500 is basically similar in that it's also a VCO tank oscillator that's controlled by fixed inductors and voltage-variable varactor capacitors, however the inductors are smaller and more highly integrated. You can still change them, or modify capacitor values, or use your method of changing the steering voltage to effect the same type of changes, but things are much smaller of course but the same ideas should still apply.

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    Quote Originally Posted by Alpha View Post
    This is not quite correct, I think you're confusing the RF front-end preselector with the VCO substrate microstripline. I have worked on and modified several hundred VCO's for Spectras and Astro Spectras in my time, and I'm also a hardware RF design engineer so I know how these circuits work. The laser-cut stripline on the VCO is indeed a frequency-determining component of an oscillator. There is an RF preselector in an entirely different part of the radio that is a front-end that is also laser-cut, but that has nothing to do with the VCO.
    Hi Alpha,

    Ahh ok - understood - I always treated the VCO itself as a black box - I didn't realise there was a laser trimmed microstripline in there as well, and thats what you were referring to. I was only aware of the preselector strip, as I had always treated the VCO internals on these radios as a "black box". The tank circuit always amazes me - it seems to pop up everywhere from radios, to magnetic loop HF antennas, to tesla coils.. but anyway I digress. I guess the "Q factor" of that VCO tank circuit always has a finite limit as to how far you can push it before physical modifications are required.

    I consider myself quite well versed in software radio concepts, and digital communications, and even though I hold an advanced (same as extra) class HAM license, analog RF world is something I'm a n00b at, so thanks for taking the time to explain in more detail, it's great having people around that explain and share the secrets of RF hardware design..

    ...and apologies for the "Cowthief" moment

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    Hehe, no sweat. RF is to most people PFM (Pure F*'n Magic), even people with good knowledge of basic electronics and digital circuits. Don't feel bad, I think microwaves are PFM, still things get really crazy above 2 GHz.

    As you point out, resonant circuits (tanks) are integral parts of oscillators, filters, duplexers, antennas, nearly everything RF-related, so understanding them helps quite a bit. A lot of the information is in the DSM theory of operations sections of the manuals, but it always helps to have a plain-english explanation of how things work

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    Alpha

    One thing I have toyed arround with in the past to get a larger tuning range is to mess with the Q of the VCO. Back in the earlier days of sythesized radios I would parallel a second varactor diode across the main tuning one. Then retune the inductor to bring the range back. I havent tried this with a spectra mainly because the adjustment to the inductor strip may be too great to keep the vco locked or stable. What do you think?

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    When going from UHF 450 to 438, just lengthening the stripline about 1/4-1/8" is about enough to bring the low end of the lock down from 442 to about 436 or 438. That seems to be perfect for converting US R2 to Euro/Canadian R2 VCO's.

    For VHF R2 to R1 conversion, I convert the entire VCO from R2 to R1. It involves adding a cap at the base of the stripline, changing one about halfway down the stripline, and possibly lenghening the stripline just a bit, again maybe 1/8-1/4" or so. There's also two resistors that have different values in one corner of the VCO that change the steering line voltage just a bit too, so the VHF VCO requires changes to all three parameters, inductance, capacitance and a steering voltage change as well.

    The VHF VCO is really squirrely in that it can get "holes" in the lock range where it's fine from 136 to about 145.200 then it loses lock up to about 146.000 or so, then it's fine again from 146 to the end of it's range. What's happening is it's running out of lock at the end of the 1st half of the steering range then after the "PIN" shift it runs through the varactor voltage again starting at 146 to the end of it's range. When this happens, the stripline needs to be extended just a bit to fill in the missing range at the end of the 1st varactor sweep. I ususally do the capactior and resistor mods first, then test it to see if the "holes" exist, sometimes it's fine as-is. If the "holes" in the lock are detected, then I do the stripline mod. and that fixes it. I have a "test" codeplug I use for VCO tuning that has transmits every 100 kHz from 136-150 MHz to see if there are any holes in the lock ranges.

    For the 900 MHz ham conversions, I have invented a very cool mod circuit that I will publish shortly, but it's based on a mod I saw at either Batlabs or RR. The original mod is a resistor mod to the steering line, and that is fine for modifying the RX range but it also changes the TX range, which is undesirable. What I did was design a 2 transistor switch circuit that essentially removes the mod on TX, so the steering line voltage is unchanged for transmit. When in RX mode, the mod is applied and it brings down the RX range from about 926 to about 910 or so.

    So far these mods have worked well for most of the range changes that I have done. The only one I haven't really researched is taking a Q Split VCO up to something useful like instead of 403-430 taking it to 438-470, but that seems to be too great a change for just a simple inductor mod, it requires changing an R1 to an R2 design, and a lot of stuff has to change to make that happen, not just retuning the inductor.

    The overall goal is not to change the Q of the resonant circuit but rather the center frequency. Changing the Q would make the VCO lock over a shorter range if you make the Q sharper, and you can't make it much more dull or flat than it already is (i.e. wider). You want to keep the 50-70 MHz range of operation, you just want to move the center up or down in frequency.

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    Quote Originally Posted by Alpha View Post
    ~ The only one I haven't really researched is taking a Q Split VCO up to something useful like instead of 403-430 taking it to 438-470 ~
    When I mentioned "Q-split" previously I was referring to ASTRO25 radios' Q-split (380-470) which will already go out to around 478 MHz but not reliably, sorry for any confusion.
    Andrew

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    Ok on the Q. I had thought that the range was maxed out. its better than having to mess arround with multiple PIN ranges.

    an exellent idea on the 900 LOL im surprised no one thought of it before. The obvious is often overlooked.