R2001C problems - help gratefully received

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icttutor
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R2001C problems - help gratefully received

Post by icttutor »

Recently acquired a Motorola R2001c Service Monitor from a well known auction site in the UK. Sold as not-working, so I didn't expect too much.
The unit powers up, Imagethe crt display works (photo attached), but none of the up/down keys work. Occasionally it emits a continuous beep which I think means there is a fault, but it doesn't always do this. Also, sometimes when switched from stand-by to on it will sometimes switch on one or more of the red leds (but this doesn't always happen). Again, sometimes it will provide what appears to be a modulated signal which can be squelched and the volume changed as I would expect. I guess the main thing that I can't seem to work out is that the front panel keys seem to work at all. Looking at the manual, it says 'swap main processor board A9' not much help I'm afraid. I have taken the main processor board out and had a look at it. I can't see anything obvious, but there are 4 EPROMS as well as a Motorola Processor on there so perhaps there is a problem with that?
Anyhow - I'd be grateful if someone could give me some ideas as to whether it is the A9 board that is the problem, or if it is something totally different.
If it is the A9 board, is there any chance at all that I could source a replacement - I'm in the UK so that will probably be more or less impossible.
Be a shame for it not to work.
Really grateful for any advice as to how to sort this out.
Thanks.
jry
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Re: R2001C problems - help gratefully received

Post by 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 loosens. Often a good idea to check the resistor values in the high voltage circuits

the keyboard may be a different issue.

service manual and scope ...have fun
icttutor
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Re: R2001C problems - help gratefully received

Post by icttutor »

Many thanks for this. Just a question - would the OXCO Ready light come on even if the PSU is misbehaving?
Will certainly start to look at the relvant voltages and the CRT resistors. I do (fortunately) have a service manual that I downlaoded from the great website Repeaterbuilder - seems like a very valuable source of documentation for lots of the old Motorola sets.
Thanks again. I hope that I can begin to make progress with this in time.
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fineshot1
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Re: R2001C problems - help gratefully received

Post by fineshot1 »

The oven ready light does not mean the TCXO will be accurate.
That would be one of the first things to check, checking the accuracy
of the tcxo should be on your check list.
NOTE: Should be 10Mhz exactly
fineshot1
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icttutor
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Re: R2001C problems - help gratefully received

Post by icttutor »

Many thanks for your help. I will certainly check this out.
jry
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Re: R2001C problems - help gratefully received

Post by 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
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Re: R2001C problems - help gratefully received

Post by 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.
DJP126
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Re: R2001C problems - help gratefully received

Post by DJP126 »

First, the oscillator module contains its own 9 volt supply to the oscillator. As soon as the unit is connected to a power source, voltage is applied to the oscillator.

Second, your problems seem to be intermittent. If so, I suspect that the connectors from the front panel flex circuits to the mother board could be dirty. CAREFULLY remove and clean. These circuits become very brittle with age and are NO LONGER AVAILABLE.

I worked for Motorola's Test Equipment Service Center for 20+ years, very seldom did we have problems on the processor board.
Dave
icttutor
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Re: R2001C problems - help gratefully received

Post by icttutor »

Many thanks for all these comments. I really appreciate the expertise and wealth of knowledge here. It's particularly reassuring to discover that processor board problems are rare.
Thanks again. I will certainly try all these options in due course. This looks like a long journey, but I am very glad I have some guidance from experts.
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kcbooboo
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Re: R2001C problems - help gratefully received

Post by kcbooboo »

One of the LEDs in the column to the right of the power switch should also be lit up. It's possible that one function has been selected with the up/dn arrows below, and that particular LED is bad and is therefore not lighting up. In fact, one LED in EACH column should be lit up; there is no "All LEDs Off" position on any of those modes.

The unit will emit a rather obnoxious beep if the input deviation (noise in this case) exceeds a preset limit, which can be set on one of the screens, if you can read it. If you squelch the receiver, this should not happen.

As was said above, the "Oven Ready" LED lights up when the oven heater current goes down because the oven has heated up sufficiently. This should happen within 3-5 minutes of plugging the unit in.

Bob M.
icttutor
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Re: R2001C problems - help gratefully received

Post by icttutor »

Hi Bob,
The photograph above I realise doesn't show lights in the first led column working, but intermittently the lights on all the led columns do come on. I can't cycle through them to check that all leds are working, and there is certainly an intermittent fault here. However, knowing that there should be some light on in each column is certainy useful, thanks.
In terms of sound, mostly what I get is static. Nothing I seem to turn (such as the rf scan) seems to make any noticeable difference. The squelch and volume do work, but seem to be about the only things (other than the main switch and the focus and intensity controls for the CRT) on the front panel that do.
I am hopeful that as I do some more work on this and uncover more detail about the faults, it might be easier for the fantastic colleagues from this forum to provide more advice.
I am grateful for your reponse and suggestions.
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kcbooboo
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Re: R2001C problems - help gratefully received

Post by kcbooboo »

I have an R2001B, which is almost identical to the C. You can fold the front panel out about 45 degrees after disconnecting the CRT shield and a few other screws around the perimeter. Check that all the cable connectors are fully seated, especially the flat cables going to the LED/switchpad boards. I've had the LED/switchpad boards out of mine; just be careful you don't hit any of the actual buttons with the boards removed as nothing holds them in once the boards have been removed. Of course you can take them out and clean things too as long as you get them back where they belong. I think the toggle switches along the top right are on a separate board that may have to come out first.

Usually the unit powers up with the topmost LEDs in each column lit up and those functions selected. The squelch control should open and close the squelch. When it's closed, the red LED to its right should extinguish. There should be no noise emitted from the speaker at that point. The only sound should be from the fan on the rear panel.

I couldn't tell if your display was very blurry or the photo was. If the focus and intensity controls are working properly and your CRT is good, the display should be clear, in-focus, and very readable. The screen in your photo looks like one that shows a spectrum, modulation (noise), or the IF signal. Most of the other screens are text-only, all selected by the leftmost column of LEDs.

Take things one at a time. Get the front panel switches working first so you can navigate.

Bob M.
icttutor
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Re: R2001C problems - help gratefully received

Post by icttutor »

Thanks again Bob,

I did take the front panel off today and did a check to see that everything was connected. I also cleaned with Isopropyl alcohol the main connectors (blue) with the flexible brown circuit connecting leads (not a very good description I'm afraid). I was quite hopeful that this would brong some kind of response from the front panel buttons and leds, but still no joy! Drat!

I can confirm that the squelch and led next to it works as you described.

The CRT display is not blurred - there is no discernable text - there is the modulated spectrum you describe and then a row of something above, but it is unintelligible. As I can't select any of the options, then I have no way of knowing what is displayed in the other functions of the machine.

I am sure you are right - get the switch gear working first - I think I will have to have another look at this and perhaps clean the switches and check all the cables again.

Let's see what happens once i've done that.

Best wishes and thanks,

Martyn
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Re: R2001C problems - help gratefully received

Post by icttutor »

I've done a bit more playing.

I have undone the front panel section and subsequently taken off the led/switchpad board that is connecteed inside the front panel. Despite warnings from Bob, I did manage to get all the small buttons everywhere - that was fun trying to find them all afterwards.

I'm still making no progress here. None of the micro-switches works and the leds still come on randomly and very intern=mitently when the unit is switched on at the mains. In the absence of any other ideas, I have decided to start by repoacing the ribbon cables that link the switchboard to the main unit. These are 16way cables and from what I can see, the onse in my unit are a bit flaky in their seating. Not sure what difference this will make, but it looks to me as if the micro-switches on the front panel are connected via these cables rather than the large brownish connectirs below which seem to be only associated with the pots and other controls below the leds etc. At worst, I suppose this will eliminate these form the list of issues to be considered.

In another playtime, I did try connecting a scope as display as suggested on the repeater builder website to see if I could display anything sensible. It involves taking some signals from the R2001 scope display board - I didn't get anything sensible, so it looks like I have plenty to sort out, once I can get something working from the front panel as Bob suggests.

Definitely a long-haul this one!

Martyn
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