Batboard

Wowbagger I am back on the Com120B Generator with the modulated hum. PS volts & waveform look like this is not the issue. However on the top of the Generator there is a Lock/Unlock LED with no light. The same is true on the Synthesizer module. I don't know if this is Red/Green or just Green or ...

the COM-120's GEN give a good clean square wave, the signal gen used is also good as I have two other 120's that do not do this. Not every screen capture looked like this, some look normal, some look half power, then you have the above that is a mix of the two. the low level part of the above is no...

OK, what do you get if you use the COM-120's generator to make a square wave? Are you sure your signal generator isn't the issue?

I'm curious - why did you use an inverter, rather than just using the DC input on the 1600?

Wowbagger I saw on one of the other post you have done that you stated the 1600,1900 and com120c used the same tft lcd display, my question, can the display board and screen from a 1600 be used to replace a screen in a 120b? COM-120 C is the operative word here. The 1900 (not the 1600) and the COM-...

My suggestion would be: 1) Issue the following commands from RS-232 *idn? *opt? and record them somewhere. Also record what IF filters you have on the receiver. Then, *when* your battery dies, you can replace the Dallas part with the equivalent plain RTC chip and wire a battery onto it, and once you...

I am sorry for the PM as I was just wanting the option codes for the options the unit already has and did not think I should post that in the open as that would fill this with *IDN? posts, if Cobham Customer Service can and will do this, I will contact them. I did not think that they supported the ...

Can you give a better description of how you are making this measurement? Ideally, either post a screen shot from the unit, or give step by step instructions on what you are trying to do?

OK, I am willing do to that within the bounds of reason. 1) anybody want this WILL follow these instructions. Ignore them, I ignore you. Remember, I am doing this as a favor. 2) You WILL provide me with the output from the following 2 commands, issued to the unit over RS-232 or GPIB. *IDN? *OPT? Tha...

That's odd, because the power switch on the front controls the DC/DC sections that are common between battery, DC, and AC operation. In theory, swapping out the AC/DC brick shouldn't impact that part of the system.

Well, it's worth plugging in a battery (either to the internal connections or to the DC in) and seeing if the off button works for that.

Actually, it's just a signal to the power supply - the PSU is supposed to shut down when it sees that signal. Since that shutdown works for both the DC and the AC inputs, I'd guess that you just forgot to connect the line from the front panel to the power supply.

Could you have capacitor plague on the gen board, or the PSU?

I've posted some info over the the Aeroflex questions thread.

OK, since the COM-120 series is no longer sold or supported by Cobham, I will reveal a few useful items to help people out. I hope I don't come to regret this.... How to reset the serial number (e.g. in case of RTC battery fail). You will need a serial terminal connected to the unit, with the correc...

It could be that an IRQ conflict is causing problems. I don't have ready access to a 2975 to look up what the IRQ mappings are, but if you could get the IRQ map from the BIOS, I can see if I can dredge up the information.

You need to have the serial # set before the options numbers will take - otherwise the serial # embedded into the options won't match the unit's, and it won't be accepted. Since the 120 is now well and truly out of support, give me a bit to verify my memory, and I'll give you the commands to reset t...

The speaker problem may be that the wire that goes from the speaker on the left side of the unit to the speaker on the right side of the unit has become pinched between chassis and case and is shorting (that happened to mine). Take the case off and look at the bottom of the unit - you may want to pu...

My guess is that the hard drive parameters in the BIOS are wonky. I really came to regret the decision to use VxWorks as the OS, as it really was limited. One problem is that the initial boot loader has to use the drive geometry the BIOS reports, which is LBA, but VxWorks uses the actual drive geome...

Gosh, with such a pleasantly written and politely phrased message, I am so motivated to spend my personal time answering your question, knowing that with the detailed description of the behavior of your unit I can identify the problem and that you will be gladdened by my response. Every time you pre...

The COM-120B can also do a TX frequency search (it's under the Spectrum Analyzer screen). It also supports automation - there are applications for it that will automate testing a radio across multiple TX and RX frequencies. One key feature to look for is a tracking generator (if the unit has a spect...

Are you sure that's a spring, and not a helicoil (http://www.stanleyengineeredfastening.c ... /heli-coil) , used to repair a tapped hole that has had its threads stripped out?

OK, it turns out I had the information here. First of all: if you DON'T have the 486 board, DO NOT FOLLOW THESE INSTRUCTIONS. You WILL BRICK your unit totally, and there's nothing I can do to help you. AGAIN: if you don't have a 486 board - if you have the old 80188 based board, DO NOT FOLLOW THESE ...

When you say "type 1 CPU", do you mean the old 80188 CPU boards? If so, then the files you have are not going to do you any good, as they are for the 80486 board. If you have a 486 board, then I can walk you through the reload process. Let me pull some information together at work, and I'l...

No, I'm not looking to use Cadweld in the building - the rods are outside, with ground wires exiting the building to the rods.

The site has a ground network, and our rods are connected to that ground network. We are bonding the building electrical, antenna entries, and equipment both internally and to the rods.

It's as much a chance to learn something new as anything else. Granted, it's unlikely to help my day job; but it is fun when I run into somebody who thinks that I cannot possibly understand all the intricacies of radio because I do SDR.

I have a repeater site that I'm trying to bring up to best practices. The electrician and I both agree we need more grounds, and to bond them together. However, the electrician is thinking like an electrician - grounds are for safety, they carry at most amps of current if there is a system fault. I ...

1: Make sure your hood is well bonded to the frame - I'd install a separate ground strap from the hood to the frame just to be sure. You want the hood acting as a ground plane and a shield, not an antenna. 2: Get some snap on ferrite cores, and put them on your injector wires and ignition wires. 3: ...

One thing to check is what audio filters are being applied to the measurement. Normally, the specified test conditions for SINAD in FM voice work are that a C-Weighted filter should be applied to the audio before measuring the SINAD. If your set up is not applying that filter, but is instead applyin...

If the unit stays up on DC, then I would check the 300v capacitor across the Vicor power module in the power supply - maybe it has gotten old.

Check and see if he has the optional amplifier on the gen port. My guess is that there is a fault in that amp, and when switching to the Gen port, the level is above -13dBm, the amp is switched on, and blows the fuse.

The distortion being dashed out worries me - you should be seeing a value there. Check that your squelch is wide open, but if it is, then you have an issue on the baseband tray, and that issue likely is a failing cap - it may not yet be leaking, but it is not at all well.

It *it* indicating it's off frequency during self test, or are you testing it against an external reference? If the former, you may have capacitor plague - it should never see itself as off frequency against its own generator. If the latter, then the TXCO just needs to be calibrated. The others soun...

No, the options are NOT stored on the front panel, only the calibration settings (upon reflection, I wish I had stored a copy of the options structure on the front panel, and in the flash file system, but oh well).

The RTC module has a built in battery, which has probably died. That kills the options storage, so the unit forgets it's serial number and installed options. It's tricky to replace, as the modules aren't being built anymore - I've heard of people carefully cutting the top off and replacing the batte...

Best bet: check the board for bad caps.

Hmph. I'm trying to remember how the differences between scope, zero span, and normal analyzer differ on the state machine that drives the sweep, and what would cause that behavior. If you go to the diagnostics page, are any of the loops showing unlocked when it stops?

It sounds like system controller issues - that's what drives the analyzer sweep. Does the scope work? If you set the analyzer to zero span does it work? If you change the span on the analyzer does it start sweeping?

I don't think you blew the output for a couple of reasons: 1) most HT style outputs don't hit high enough voltage to damage themselves if unloaded. 2) Most modern transmitters (i.e. not tube amps) that could generate such voltages will have fold-back circuits to prevent that. 3) If you'd blown the o...

Now, upon power up, the fan runs and I hear a pattern of two beeps. A single beep followed by two beeps, pattern repeating. The monitor CRT does not come up. It sounds like the main firmware is not loading - it may be your EPROM board (or flash board, if the unit is new enough) has been corrupted.

That's good advice. I thought I'd be able to just pull my copy of the service manual and get the information - and I was surprised that I didn't have schematics. Unfortunately, all that existed were the engineering drawings, and those have long ago been moved to the salt mines (literally: we have st...

When i powered it up the display was upside down and there were horizontal lines all through it. I turned it off and much later turned it back on after plugging it back in to MY UPS power and it was working fine. Perhaps a power supply issue? Sounds like the actual LCD panel got a glitch when you s...

Yes, because Microsoft still supports Windows 95, you can still use your AMPS cell phone, you can still get your Zenith 26" CRT TV aligned by Zenith, etc. The COM-120B came out a long time ago. Is it really fair to expect it to be serviced in perpetuity? And if you do have such an expectation, ...

At this time, your posts require approval to be viewed - you have to wait until a queue moderator (like me) approves them. That usually happens fairly quickly. Eventually, when you've posted enough that it's proven you aren't a spammer, your posts will go through automatically.

The 3900 has a lot more computing power under the hood than the 8800 - as such there are a lot of measurements the 8800 takes more time to make than the 3900. There are quite a few more tests the 3900 can perform due to having more power, it can handle simultaneous multi-channel protocols, it can ha...

Wowbagger, I'm just curious if IFR/AEROFLEX/COBHAM here in the USA can repair all the analyzers that Cobham sells now, including the LTE test sets? Or, is there a list of analyzers/test sets that are set here for the USA and the others go overseas to England? I have a client that has an Aeroflex 71...

ESR and heat range I wouldn't get excited over - what you put in will likely be as good if not better than what is there now.

Keep to about 10V for things like the baseband tray (unless what is there is already rated for more than 10V).

The pop is because the system is powering up the amp when it unsquelches, and powering it down when squelched - so you are seeing the DC component of the audio line go from 0V to 6V. There's no way you can prevent the pop with just a capacitor. See if you can get a audio PA transformer - I know Drat...

Could you use an audio transformer to isolate the radio side of things?

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