GE Orion VCO adjustment / alignment for band changes

What you’ll need: Multimeter, dummy load, Orion programming software OrionVCOs(Programmer for Windows or the older DOS software), radio code files for the radio (used when programming; re-uploaded each time the flash memory fills up).

If you are moving the band split (and this is probably why you are here), you also need the SC or SC4 files.

Full instructions follow this silliness…

Step one: prepare and program a personality set covering all frequencies you plan to use the radio on, TX and RX, add 500kc or so to either side and add additional channels so that there’s *something* at 250 or 500 kHz intervals all the way across the range for testing. The reason for this is that the oscillators are multi segmented. Connect a dummy load. Receiver testing using a signal will not be necessary.

Click for fullsize. The TX VCO is toward the back of the radio; RX VCO is toward the middle, and the test point is the hole closest to the front. I just tucked the other lead from the meter under the springy CPU shield for grounding. Laaaazy.
Click for fullsize. The TX VCO is toward the back of the radio; RX VCO is toward the middle, and the test point is the hole closest to the front. I just tucked the other lead from the meter under the springy CPU shield for grounding. Laaaazy.

The tuning voltage should be 3.5-7.5VDC measured at test point TP201.
TP201 is visible and easily accessible through a hole in the shield (no removal needed). If you’re lucky, multimeter test leads fit right in there such that the hole nicely cradles the plastic shell around the probe end and leaves the probe end sitting right on the nice wide round pad on the board.
TP202 is the modulation voltage test point. Don’t use that one. You’ll chase your tail in circles forever.
The two pots are CV280 for transmit VCO, CV240 for receive VCO.
Now, the crafting of your test file is important. If you study the schematic you will notice that each VCO has THREE additional tuned circuits that can be attached or detatched to it by the CPU. I believe the VCO has four banks (one of the valid states being none of the additional circuits attached). The way I usually do my test file is to put in 250kc steps across the entire range of the radio I want to use.
The synthesizer may lock with the voltage outside of the 3.5-7.5VDC range, but don’t leave it there! Doing so will create a temperature dependent picky son of a @$%*@!!! radio.
As you tune you will notice the voltage will ramp gradually up then drop down suddenly – this is a VCO band switch. I believe you can manually force selection of a certain VCO band in the personality…?
When you land on a frequency where it’s not locking, the radio will flash ERR=0401 NO LOCK and if you’re stuck in a RX no lock, the radio will keep constantly rebooting(??) to try to restore operation. The VCO voltage will jump all over the place in a maddening fashion. First dial in the pot for the VCO until it locks, then worry about getting the voltage in order.

See LBI #38910 for more info (a quick search for LBI 38910 will return it from multiple sites.)

19 comments

  1. We have successfully tuned the TX VCO to lock in Talkaround (simplex – 927.0625). However, we are not able to tune the TX VCO to lock using the repeater offset (902.0625). We find just one pot (the rearmost) to adjust the voltage for TX. Is there a second TX pot for the second TX VCO? If so, where is it located? If there is only one TX pot to adjust and the VCO is locking properly in Talkaround what technique is suggested to get the VCO to lock on the repeater offset frequency?

    We are having the same problem with two Orion’s. One radio has been modified for repeater operation and the other has not.

    The same code plug (personality) has been programmed into these two radios. These are the mobile Orion radios with the attached control heads…not the remote head configuration.

    1. I haven’t played with the 900s yet… did you perform any hardware mods to get it to lock simplex?

      I’ve seen a mod documented that kind of forces the VCO bands to switch around and that allows you to enable/disable it as needed. I think it’s posted on the Yahoo ge-orion group.

  2. I got the 150-174 mod’ed and have the unit locking on the ham bands, however the tx freq isnt transmitting any power out and shows 155.700 instead of 145.700. wonder if you have had this problem?? Rx works fine. Thanks Larry

        1. That’s weird. Do you know the radio’s prior history – whether it was working when removed from service, and was it tested into a dummy load before conversion? I’m wondering if you just got a dud 🙁

          Fortunately, Orion drawers are getting pretty inexpensive and plentiful, especially ones that are wideband only (not switchable).

          I still have moments of feeling mad over toasting a nice 110W VHF, though it did have an old 256K logic board and would have made my plans to dual it with a 512K UHF difficult… Radios is radios… 😉

          1. Well i tried another 150 to 174 Orion. same results sorry to say. Receiver good but TX isoff freq a bunch 20 meg and will sync most of the time without err some power output. Freq is not stable.

          2. Well i tried another 150 to 174 Orion. same results sorry to say. Receiver good but TX is off freq a bunch 20 meg and will sync most of the time without err some power output. Freq is not stable. It is recognized as 136 – 153

  3. Finally got the 150 to 174 to the ham bands….
    It does not require the hardware mod as the notes make you think has to be done and when loading the sc4 file you have to select the 150-174 radio line then put your freqs in with the +6 added to the true freq…IE 145.7000 would be entered as 151.7000 and once you load the per file you can read the radio and it will show the ham freq. the sc4 -6 file will set it up. DO NOT over write your per file as this would be incorrect if you reload it at a later date. I have done three units without any problem..

    1. Yes. Treat the radio as a write-only memory now 😉
      Don’t READ it or the frequencies will all come back wrong. The conversion takes place during the write process.

      Hardware mods are optional – some radios will need them, but I haven’t run into one that needed anything more than the VCO adjustment.

      The only ones I know of where you really have to perform modifications are where you push the low band one up into 6 meters. The LPF roll off point has to be pushed up or the power amplifier just won’t get ‘da watts out.

  4. anyone have the ENC file for the D2BHG3
    trying to go six meters have it working but
    the enc file is corrupt and load everything..
    Thanks Larry

    1. great they all work fantastic, just one caution if I haven’t mentioned it when you read radio the frequency will read correct. Be careful not to overwrite your original file.( the sc4 file setup)

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