R-2001C Service Monitor Help needed

[KI4M]

Guys tonight while using my R-2001C monitor I experienced a problem. It was on for about 3 hours working just fine then it stopped working above 160.6999 MHz all together. Below is what happens...

Using an external transceiver a signal is generated at 160.7000 MHz on FM wide into a dummy load. Signal is around 5W into dummy load and dummy load is about 2 feet away from service monitor. Service monitor is tuned to 160.6999MHz and spectrum analyzer shows the signal as it should being centered just a bit higher than center of scope. Well when you take and change the RX frequency of the service monitor to 160.7000 MHz the spectrum analyzer goes completely blank. Does not show any signal at all. To verify that it is still working retune service monitor to 160.6999MHz again and instantly a signal appears on the scope again slightly off center like it should be. So basically from every test that I can perform the monitor works great below 160.6999 MHz but anything above that it is totally 100% dead. I have looked for any loose connections, etc but alas cant find any. I have scratched my head and what little hair I have already has been pulled out. I have checked for loose boards etc but nothing can be found...

Can anyone point me in the right direction as I need this thing working asap!

Shane KI4M

[George]

Take the cover off and look at the modules inside.

See that big one that has four captive screws on it? Yea, that one.

Take the screws loose, pull it out and clean the contacts on the bottom.

If that doesn't fix it, you need a set of extender boards and get an education on the drug induced fantasy that drives that VCO arrangement. There is more mixing going on and things happening than in a Penn State dorm room.

What you have found is a switch point between mixes and likely one of the injections is loosing lock. I have heard of cases where just touching a pot inside of that A5 module will restore it to service. On the other hand, you may have a screwed up A5 and you get the golden once of a lifetime opportunity to fix it.

If this proves to be the case, beg for mercy on the altar of DJP and maybe he can help you with it.

There, I am asleep and I have pointed you in the way of enlightenment. Good luck and may the A11 module be with you.

George

[jackhackett]

If that doesn't fix it, you need a set of extender boards and get an education on the drug induced fantasy that drives that VCO arrangement. There is more mixing going on and things happening than in a Penn State dorm room.

Thanks, I had a mouth full of coffee when I read that.

[KI4M]

I will check the boards listed above. I also spoke with a gentleman off the board who also said it could be one of the chokes in the bottom of the chassis. He said there are some grey chokes that supply filtered voltage on the bottom of the main board and that supplies each module.
He said if the unit is set on something other than the feet the cover will push up on the chokes and crack them. That then kills the supply to that section of the monitor...

He said there is not a lot of clearance in the bottom of the case between the board and the case. I had the monitor sitting on an uneven surface and he said he has seen that cause a choke to be cracked. I had the front propped up with a book with a little pressure on the bottom of the case just behind the feet. I will advise what I find... I sure hope the chokes are commonly available if that is the case here...

[George]

While I won't rule out broken inductors for feeding power to the module and I think I know of what you speak, I find it a little hard to believe UNLESS you are getting intermittent operation across all or most of your ranges.

Now, and I will defer to the wisdom of DJP, but I don't believe the VCO has seperate power feeds for each VCO loop. You are hitting a loop end and the next frequency to make a change just isn't there to keep everything running. This isn't some magic VCO from hell with a range from DC to light to get you some output. Rather it's a combination of things and VCO loops that result in what you want. It's not unlike a government spending bill or a sausage press. A lot of crap goes in for something that should be good on the receiving end.

I have seen one instance of a pot that was not on the print for the A5...and this was on a B model and I don't know if this was carried over to the C model...and praise be to M if it was not...but there was a pot...a pot...not some pot or maybe it was some pot in the A5 and I want to say it was on the left side that all it needed was a touch...just one touch and the locking problem was solved. It was just lonely for the touch of my alignment tool.

The problem never reoccurred. Oh...and it probably helped that I sold that monitor for a D model and my 2600 a year later.

Anyway, you may be correct about the coils but I wanted to point out the idea of the loops because...and here is an idea...try it on another C model if you have one...I don't know if the A5 is the same for a C verses B model, but try one that works and watch your spectrum analyzer. Scan slowly up to your 160 MHz channel and see if the display moves slowly and smoothly and when it gets to your magic number, see if it SNAPS and then stabilizes again while still stepping up slowly. You will know it when you see it. My B model used to do that.

Good luck and remember to ALWAYS be in power monitor if you insist upon using your A11 as a dummy load...and yes, those loads are a pain in the ass to change.

George

[DJP126]

George is correct, you,re A5 module (VCO) is losing lock and you have found the point of switching. The part that George has wrong is

beg for mercy on the altar of DJP and maybe he can help you with it.

I don't have the equipment to service the analyzer properly. Best bet is calling the service depot ( or what ever trusted service lab someone else might recommend).

[KI4M]

Turns out it was what the guy off list said it was. I went home at lunch and took a look. The inductor/choke was broken loose on one end. I simply resoldered the broken lead and we now have full operation again.

I will post some photos on my photobucket account later this week or early next week so anyone in the future will have something to reference off of. I will link them in a post here...

I appreciate everyone's help and suggestions.

Shane KI4M

[drop_dead_fred]

While we're on the subject...

I was gifted with a R 2001C with the provision that if I decided to upgrade or
not use it anymore that I return it to the former owners son. Well, I'm good
with that. The unit is in good shape, with all items and a cordura slipcase
replete with the legendary Batwing logo (it doubles as a bra for my VW Beetle).
The only thing missing is anything printed- like manuals. Does Motorola continue
to archive this information, or, if not; whither shalt I go to find such?

Thanks, Happy Holidays and 73 de KE5LIB!!!

drop_dead _fred

[KI4M]

I was fortunate that my unit came with a user manual for a R-2001D. They are very similar in operation and the manuals will work nicely for both. There is someone on fleabay that sales CD ROM versions of the manuals but man are they pricey. If I had some way to copy my manual I would but I do not have access to a good copy machine. If you can't find a source of a manual let me know and I can see what a local printer would charge to do a copy for you..