Batboard

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...

jry

there are a number of boards on the COM-120 subject to cap failures ...the baseband card just has a lot more of them than the others. i goes beyond just replacing caps ... you often have to remove and clean components ( op amps , resistors and capacitors ) and clean the PCB. If you wait too long you...

jry

The fans run directly off of a 12VDC supply and should always be on when the unit is on, If one if not coming up right away its because the bearings are shot ...replace both. There is a thermal switch which will cause the fans to stay on until the unit cools off ...its switches the fans to the 12VDC...

jry

same as the 1600 ( more or less ) ...10 Mhz oscillator mounted on rear panel....1900 has a bracket around it

jry

4.6V is not enough to run the processor. You have to consider there is more of a drop getting to the actual components.

Chances are a tantalum cap is starting short loading the supply.

Usually that supply is set to just under 5.2 on the analog ...the digital will be a little above 5 volts

jry

have never seen a service manual or schematic on the Minitor V series but suspect you cannot band change that way. The IF and other functions on the LB main board are probably not compatible. The UHF and VHF may be compatible but you would have to try it to be sure ...I think I did that once Short a...

jry

have never seen a service manual or schematic on the Minitor V series but suspect you cannot band change that way. The IF and other functions on the LB main board are probably not compatible. The UHF and VHF may be compatible but you would have to try it to be sure ...I think I did that once Short a...

jry

this is why I bought a bunch of the new APX6k (top works on the 7K as well ) frames with the top on our favorite auction site while they were cheap. Still some out there but the price has tripled ....still cheaper than the depot for just a volume. A lot of the early APX's are coming off the extended...

jry

really surprised that they do not use fibre for this out of the box. Nothing new here ...just standard networking stuff for decades. Not really all that expensive in most cases. The usual rule on fibre is you never run just one pair in that situation ...there is often breakage during the install so ...

jry

you know I would run optical ( Multi Mode FIbre should work if the distance is not too long OM4 a plus)...not sure they have an SFP port instead of copper ethernet ports( RJ45) but this would have a number of advantages. 1. should fix your noise issue 2. more reliable especially outside over distanc...

jry

I would have thought the power supply would be the same.

IIRC differences ( there is a thread on this if you search the board ) were mostly around a minor change in the receiver

jry

you could try and use an external 10Mhz reference. That many loops unlocked points to a reference issue I would look at the reference signal on one of the failing loops and make sure it matches the level and freq in the service manual on repeater builders. If the external reference doesn't resolve t...

jry

the last place you want to check SINAD is at full volume.

Just about guaranteed to have distortion on the audio so the SINAD will be off as well.

Usually mid to lower audio levels provide the lowest distortion in the audio amp and a more accurate SINAD measurement.

jry

that is how it is supposed to work. The RF inputs are just for "tuned" measurements. Believe the manual is on repeater builders so I would look through the operations section of the R2001A manual. Do not think there was a separate OM for the A version. The D version of the R2001 is almost ...

jry

not really. proc chip has to be switched IIRC

W9 can be switched by changing firmware.

not sure about w3 ...never tried.

jry

do not mean to hijack the thread but the DCS is under the signalling options .
not as easy to configure on the 892X series but it works.
I usually have to play around with the settings to get the decode going

jry

for the current price of an 700/800 XTL why bother ?

jry

do not believe you can.

The beep is to warn you that the TX is in the clear.

jry

do not believe you can.

The beep is to warn you that the TX is in the clear.

jry

so W9 is remote only and W7 was dash or remote.

I f you have a dash W7 than a W series TIB and a spectra series remote cable are needed along with the 9000 head and Astro firmware installed.

Most of the later 9000 series heads can be used on Astro and XTL5000's with a firmware update

jry

head change in CPS ...NBD

jry

it has to be programmed

jry

the cap near the LM412 failed.

The cap failures need more than just replacement you often have to pull and clean the surrounding components as well.

There are a number of boards in the COM-120 that can have cap issues.

jry

the cap near the LM412 failed.

The cap failures need more than just replacement you often have to pull and clean the surrounding components as well.

There are a number of boards in the COM-120 that can have cap issues.

jry

On the COM-120B I would NEVER put that amount of power directly into any service monitor. Always us a high power external attenuator. Those are cheap and easy to replace. The power termination repair on any service monitor is extremely expensive and often the parts are NLA. Did you verify that power...

jry

PM sent

jry

given the cost of the batteries vs. scrapping the unit due to a corroded processor board every ten years would be the maximum I would go. three to five years would really be more in line . Most of these will not leak in that time frame and usually fail firsts forcing a re-calibration every power on ...

jry

so upgrading these units can be done but its non-trivial and not just software in most cases. So much of it depends on where you are starting from since there are a number of hardware,updates and software changes that need to happen depending on the desired configurations. P25 was not originally par...

jry

they used a low impedance microphone ( amplified ) just like the standard two way version. Used an odd ball connector on the CB's but the microphone and connector were consistent internally across the generation of Motorola CB's ...MOCAT and later System 500. The SAM's manual has the schematic and a...

jry

Look at the TS4317 service manual on the repeater builders site. the amp schematic is there at the end

jry

PM me if you want it repaired.

jry

It sounds like a keyboard or keyboard interface ( processor board ) The first beep is good. ( boot ROM self test OK ) The next three says it thinks you have the F1 button pressed . It may be looping after that. The beep sequences are not all that well documented in any one place. There are some fail...

jry

sounds like the temp sense is OK. See if you can calibrate the DVM. You can get close enough using some known power levels from another signal gen and radios on the power meter. Not really calibrated to spec but will get you operational. Sounds like you have still have major issues on the baseband c...

jry

I would look internally then on the RF I/O wattmeter module. Measure the resistance at the input attenuator output. ( PCB side as opposed to the N connector ) That should be lower ...around 25-30 ohms IIRC. If you get something else CAREFULLY lift the tab from the PCB and that should measure 50 ohms...

jry

you can just measure at the N connector ...should see 50 ohms.

sometimes its the connection but more often the attenuator is blown/failed.

jry

I would pick one of the issues or self test failures to work on . Verify the functional blocks of the unit separately like the Distortion Meter ,DVM , SIgnal Gen, audio gen and Monitor/modulation. Go through the calibration process and see what doesn't calibrate. The Distortion SINAD self tests loop...

jry

chances are the IC is bad. You often get fractures of the internal IC especially in the use case you have inside the reference with the temp changes over the 30+ years . You should see a pretty solid 10Mhz coming into the first buffer in the 7404 on pin 11 since that should be TTL levels. You can tr...

jry

for the cost of 10Mhz OCXO's on Ebay I would just go for a replacement ...less than $20. You can tear into what you have but given the age the material may disintegrate as you try to disassemble and try to repair. Just get a replacement module and mount in the box. You may have to drill another hole...

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