Batboard

jry

yet another weak point on the COM-120 series.

lots of different stuff fails ...assume you are talking about the first LO generate.

PM me if you want it repaired . note repairing just the module is possible by itself but the calibration may be impacted.

jry

the monitor beeps on the C/D versions and not on the A/B version .

PM me if you want it repaired and updated

PS Always check the processor board battery and replace every few years ( better early than late ) since they can leak and damage ( read total unit ) the PCB.

jry

com-120c uses the same display setup as well.

Usually RTV the connectors as well to hold them in place.

jry

you need to have a U43 with those options enabled as well.
That EEPROM is model specific at the very least ( R2600A/B is different than the R26XXC/D) and in theory has some HW specific calibration data so make sure you keep a copy of your original one.

jry

actually on the very early R2600's there were two different ASIC's ...one with the tracking gen option and one without. Later they went to a single ASIC ...late B's and C version always had the tracking gen ASIC. You can run the 1.07 firmware on the A/B version but regardless of what options it show...

jry

latest was actually 7.X that would work in the R2600C ...primarily for the R2670A to support the narrow band SmartNet trunking feature though

jry

There are adjustments on the video card. You can try to adjust. On the B version you may want to make sure you clean the CRT and anode cap and cable along with the side of the chassis near the anode cap. If it doesn't have an insulator on that part of the chassis I usually use some clear packing tap...

jry

There are adjustments on the video card. You can try to adjust. On the B version you may want to make sure you clean the CRT and anode cap and cable along with the side of the chassis near the anode cap. If it doesn't have an insulator on that part of the chassis I usually use some clear packing tap...

jry

I would pull the cellular ...you may want to install the jumpers on the backplane to bypass but not sure it's always needed without looking at the SM Usually the cellular option is installed in either the A12 or A13 slot and in the case of a 2010D you should have a blank/jumper board installed as we...

jry

so there are internal filters that have to be aligned on the R26XX series. I always align and test these on units and replace the processor battery as SOP They become very apparent in the track gen mode and especially as the width increases. Part of what you are also seeing is the R26XXC/D stitching...

jry

the actual one is a four pin ...only two are really used ...1and 2 are A+ and 4 is A- ....or something like that.

PM me if you want it exchanged

jry

standard four pin circular connector ....top pin is A+ bottom is ground /chassis...takes around 7 amps depending on the DC voltage used ...higher DC lower amps. Measure resistance across the hot and neutral on the AC connector with good fuses. Should be around 200 ohm IIRC. verify the AC operating r...

jry

12v is the minimum to run the dc-dc converter. you have to ground the on off control as well as providing DC power usually a 6 ohm load would work on both to start with. I would just repair what you have unless the PCB is severely damaged. In that case you be able to substitute a single IC type regu...

jry

so I have repaired more of these than I can count. You really need a professional de-soldering tool to work on these. Without one chances are you will damage the PCB. The DC-DC section is likely where your problem is and usually they need to be re-capped regardless of the tops of the capacitors. Usu...

jry

so I would look at the outputs of the LO's .... the R26XX uses a number of these even on just the monitor side. It may be that one of them is having a hard time locking. Look at the service manual ...you will need an SA that covers up to 2 or 3 Ghz for the higher frequency ones. You can look at the ...

jry

one other thought is that after you check the power supply and bias resistors to pull the PCB's, clean the edge connectors with 99% alcohol and re-seat.

jry

The TXCO typically just runs off of one of the lower voltage rails like +12V. All that says is that the oven has come up to temperature.

If that light is not on than the frequency will be inaccurate and drifting as it comes on temp which is where the frequency was adjusted in the reference.

jry

I have swapped the batteries without pulling the processor but I have done over a hundred of these units over the years .

You may want to pull the card ...remember it goes on the non component side when you re-install.

Yes the NVRAM clear is under the SPF and System Functions

jry

on all of the R26XX series I always start by doing a NVRAM reset which forces a full calibration.

The R26XX is heavily software driven and dependent on values calculated in the calibration routine,

After that compare to your known good unit

jry

power supply caps for one . check the PS voltages and noise ...anything that old you usually have issues there. Also a lot of the CRT biases tend to drift due to the old carbon resistors aging and changing value. Usually these resistors will increase with age as the carbon used to create the value l...

jry

yes but there may be a firmware compatibility issue. The latest displays required the firmware above a certain level ...there was an SRN and Motorola did provide the firmware update for awhile. Someone may know the minimum or provide the SRN with the info. Worst case is try it and if you need the la...

jry

that Onan part number is the same as Motorola 0184906T04

Usually the Onan is better though

jry

he is probably referring to one of the other OEM's that supplied that part/module to Motorola. It's common to outsource the power supply modules to multiple vendors in lots of equipment and Motorola did this all the time in later products. In the good old days they designed and built them in house b...

jry

should be a ton on EBay.
They are selling 800 mhz chassis cheap right now

jry

that part would cover the 500, 1200 and 1500 as well. Believe the 1100 typically used a different form factor but this version may fit inside as well depending on the exact vintage.

jry

low loop is bad. 1200 series has two loops ...high and low. High loop is the 2Mhz ( 1.3 to 2.3 Ghz IIRC ) granularity part. Low loop covers the under 2Mhz part of the frequency synthesis. there are some alignments on the low loop and the crystal used as part of the loop has been known to drift out o...

jry

doubt there is much or any difference ....have not looked at the datasheet though

jry

you may have to run the module outside the unit. Input a signal mid band at 100% modulation or there about and adjust the bias to get the same modulation and minimal distortion. At least that's roughly what I did on the 1900's output module. I used the typical 8902A with the power sensor but an 8901...

jry

Well it sounds like your baseband card may have issues if the temp is off. Look at and the diagnostics and see what is failing. If both of those showing as unlocked than you may not have made it through the initialization of the unit. Either that or one of the reference signals is gone ...check the ...

jry

"just to be clear the output device is NOT and MMIC but a discrete device GaAs HFET that needs to have the bias adjusted as part of the replacement. The output needs to be biased in the linear range in order to correctly pass AM as well as the other complex digital waveforms used in the cell ph...

jry

may actually be a discrete device.

You may want to reverse engineer the schematic around it and you may find there is a bias adjustment.

I think it may be the same device as used in the IFR 1900 output.

The bias adjust was for AM mode to get it in the middle of it's operating range.

jry

not sure from your post what vintage MotoTrbo you are on but I would make sure your firmware is updated. On the initial radios Motorola apparently intentionally degraded the audio quality so that P25 /higher tier radio sales would have an advantage ( not my discovery ...Mars was the one who looked i...

jry

I would replace both Q19 and Q20 on that board

jry

I glanced at the schematic ...pin 1 on the 16 pin is the horizontal / sweep which sounds like its OK Pin 3 is the vertical drive and does have an offset from the input transistor bias ....look at the schematic. Set the 1Khz tone level so you get the signal level indicated on the schematic for pin 3 ...

jry

understand that that a CRT horizontal and vertical deflection is really just a DC coupled amplifier that has a relatively high impedance and high voltage output. Just couple a 1khz since wave back into the scope in from the tone out jack and use another scope to trace the signal. You may want to set...

jry

re-cap the power supply. I would replace the two large caps on the AC supply and all of the caps in the DC - DC converter You can try to run off of DC and see if it does better but I would still re-cap regardless. I would not replace the Tantalum ones ...they do fail but when they go it's usually a ...

jry

have done more than I can remember and other than doing the mistakes I previously noted they all eventually worked fine. Not sure it's possible to get the display connector on wrong but maybe that's another possibility. You can try to get into the RS-232 port as well but never had a firmware update ...

jry

this is pretty straight forward. You may want to get someone to assist since the manual and access are pretty straightforward. if the horizontal position doesn't work than it may be the connection between the scope module driver board and the scope amplifier board ...16 pin dip ribbon on the top fro...

jry

there is no blanking program. You have something wrong ...see below. There are a number of vintages to the 1200 processor card ( at least three IIRC ) so not all firmware works in all boards. Not sure if you have a multi ROM or single rom setup Normally what you are seeing is due to 1. wrong firmwar...

jry

easier to inspect the boards and see exactly what you need
usually end up using SMD Aluminum CAPS
100uf 6v 47uF 16V 10uf 16v 1uf 16V ( maybe 50V ) IIRC
Mostly the 47uF and 10uf.
Usually the non polarized are OK so it's typically the 47uF and 10uF polarized

jry

There are a number of boards in the COM-120 that need to be recapped. The deviation test loops the 1khz audio through the GEN back to the RX so anything in that loop can cause the failure ...not really a pure Deviation Meter test ...more of a system modulation test. I would start at the front panel ...

jry

looks interesting ...the display resolution conversion has been the core issue with a substitute display.

I would start a separate thread on the project.

jry

just to be clear the output device is NOT and MMIC but a discrete device GaAs HFET that needs to have the bias adjusted as part of the replacement. The output needs to be biased in the linear range in order to correctly pass AM as well as the other complex digital waveforms used in the cell phone te...

jry

numerous threads on this ...you have to use the higher end GBS-8219 version .

The cheaper version will work with the HP 892X and SA's with a video out but needs an add on sync separator

jry

power supply control ( inside power supply ) is bad ...it controls the power to the main supplies as well as the fan.
Buried in there and a real PITA to access and repair.

PS I never found a schematic

jry

someone adjusted an I-button to max number of refresh flashes. ( I have a good idea how it was done ...not really important any more since APX finally has this included ) Just for firmware updates on older version radios ...P25 and older. Most vendors do not charger for this ....I think Motorola was...

jry

1600's leverage some of the same engineering but for the most part did not have the amount capacitor failures as the COM-120. Not sure which test is failing on the 1600 but usually there are HW failures and alignments to correct the issues. The 1600 is bigger and heavier but usually more reliable th...

jry

usually loose the options as well ...battery on the RTC is dying

jry

firmware issue possibly ...need to update.
May be your baseband card as well.

jry

As before both fans are hardwired directly to a 12VDC supply and will come on with unit powered on. You have a broken fan with a seized bearing that loosens with higher temp and allows the fan to spin. Replace both. There is no circuitry in the COM-120 power supply that switches fans on based on tem...

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