RCI issues

[nomadradio]

There are a lot of "This worked for my buddy's radio" tips out there.

If you track down the trouble to a particular circuit, this kind of method might work.

But removing a part that's perfectly good and installing a replacement just to see what happens introduces a chance for adding a problem the radio didn't have before. The wrong part, or turning it the wrong way, or a tiny sliver of solder that bridges across two adjacent foil pads can create a new problem you didn't have before. It's just a risk, but even a pro will cause this sort of 'oops" from time to time.

Somebody (else) really needs to write up a troubleshooting chart for the PLL in that radio. Just pointing out where you can check for an unlocked PLL would be valuable.

Just changing parts to "see what happens" is called the shotgun approach. If you're really careful you won't create new problems when you find out the part you changed doesn't fix the fault.

I still don't know how to fix this PLL without a decent 'scope.

Or troubleshoot it without one.

73

 

[711]

I agree with you Nomad. I was lost for an answer at the time and came across a post by Bill Eitner mentioning the cap. I had gone through full alignment and everything lined up perfectly. Then I'd get the same symptom. no TX or RX until I turned it off then back on. I don't know if the cap aged or was close to the limits of taking it out of Lock. I could also adjust the VCO and bring it back into lock but I couldn't leave the covers off and keep twisting the VCO every time I turned the radio off and it lose its Lock. Its up to the OP to use it or not.

The solution to the first problem is somewhat
involved, but I'll give it to you anyway. You can
decide for yourself if you want to tackle it or not.
1. Find C-107. It's located just to the left
of L-17. It might be buried in wax. It's a .001uf
ceramic disc capacitor. You need to change it to a
100pf NPO type ceramic disc capacitor.
2. Readjust the VCO. Set the radio 28.000 MHZ,
in the FM mode. Attach the positive lead of a digital
voltmeter to J-13, (located between L-46 and L-11), and
the negative lead to any convenient board ground. With
the radio on and set to receive, adjust L-17 to get a
reading of 1.9 VDC on the meter.
This procedure usually solves the first problem
mentioned. On newer versions of the 2950 this change is
already made. As for it not coming back at all, I can
only suggest resetting the CPU. If that doesn't work,
it'll need to go to Ranger for more extensive repair.
If resetting the CPU brings it back, perform the mod
I just outlined, and it should be alright.
Good luck...BILL

 

[Handy Andy]

But, depending on the type of CPU "card" used - referring to the display only or the one with all the buttons and controls attached as a "unit" to the card - there are several things that can cause it to reboot or freeze.

Deals with the power regulation and boot process.

The CPU uses a clock and it has to start running in order to cycle thru the boot process.

It uses several "steps" to accomplish it.

It also uses several regulators and storage caps with diode matrix to supply power to specific pins on the CPU so it can power down and not corrupt itself so it has to reboot fresh each time - it's done so it can remember the last settings - like a Sleep mode versus Hibernate. One mode is a short term where power is kept as a feed to keep it alive, current settings and the other is where the power is pulled and the CPU relies on the storage caps to feed it and so it stores it in Non-Volatile memory. IT can only store so much, there are functions within the radio itself that are controlled externally - so they are "lost" when power is lost. Like ANL NB and other non-physical settings LCR as well as Beep.

So it helps to pay attention to what you lose as the radio ages.

IN what you're posting - it looks more like some of the power feeds used to keep it alive as well as the power down process - those caps that hold a charge long enough for the CPU to tuck itself to bed, are losing their ability to store charge.

These caps are not easy to find anymore - they are a unique profile and have a large area to store power in in Farads - but are hard to find because of the design, size and working voltage and it's profile.

I've had to go to computer reclamation stores to find older laptops to glean off caps to help keep my Mirage 2950 still active - it pretty much did the same thing yours is doing - losing memory. Powers up, but works for a little while correctly then has an "Old Timer" moment and you're toast and unable to get back to the roundtable.

IF the radio is a older board style then it means a re-cap is needed but these are expensive to replace and I am not sure if there are too many parts for these boards still left. There may be hope in using older NOS stock from a computer parts supplier that caters to the older Motherboard industry - which is going to be a booming business now that more and more offices are finding out that the tower and desktop workstations are no longer supported.

So you may have to take apart the radio - layer by layer and locate the CPU card and hope the regulators the caps were charged by - didn't fry up when the caps dried out and shorted out the power feed - killing the SMD regulators in the process.

 

[743SEPA]

Thanx for all the replies and help. Sold radio,end of problem. replaced with President Lincoln II. More features and smaller. It was nice while it lasted.

 

[Robb]

But, depending on the type of CPU "card" used - referring to the display only or the one with all the buttons and controls attached as a "unit" to the card - there are several things that can cause it to reboot or freeze.

Deals with the power regulation and boot process.

The CPU uses a clock and it has to start running in order to cycle thru the boot process.

It uses several "steps" to accomplish it.

It also uses several regulators and storage caps with diode matrix to supply power to specific pins on the CPU so it can power down and not corrupt itself so it has to reboot fresh each time - it's done so it can remember the last settings - like a Sleep mode versus Hibernate. One mode is a short term where power is kept as a feed to keep it alive, current settings and the other is where the power is pulled and the CPU relies on the storage caps to feed it and so it stores it in Non-Volatile memory. IT can only store so much, there are functions within the radio itself that are controlled externally - so they are "lost" when power is lost. Like ANL NB and other non-physical settings LCR as well as Beep.

So it helps to pay attention to what you lose as the radio ages.

IN what you're posting - it looks more like some of the power feeds used to keep it alive as well as the power down process - those caps that hold a charge long enough for the CPU to tuck itself to bed, are losing their ability to store charge.

These caps are not easy to find anymore - they are a unique profile and have a large area to store power in in Farads - but are hard to find because of the design, size and working voltage and it's profile.

I've had to go to computer reclamation stores to find older laptops to glean off caps to help keep my Mirage 2950 still active - it pretty much did the same thing yours is doing - losing memory. Powers up, but works for a little while correctly then has an "Old Timer" moment and you're toast and unable to get back to the roundtable.

IF the radio is a older board style then it means a re-cap is needed but these are expensive to replace and I am not sure if there are too many parts for these boards still left. There may be hope in using older NOS stock from a computer parts supplier that caters to the older Motherboard industry - which is going to be a booming business now that more and more offices are finding out that the tower and desktop workstations are no longer supported.

So you may have to take apart the radio - layer by layer and locate the CPU card and hope the regulators the caps were charged by - didn't fry up when the caps dried out and shorted out the power feed - killing the SMD regulators in the process.

I am guessing that you are talking about a supercap that holds memory? Would it be possible to use a coin battery and clip to make it still work?

 

[Handy Andy]

Most of the time the NVRAM that's is in these things just turns into "Volatile RAM" when the CPU goes to sleep. There are a series of slowstep processes the radio goes thru. As the main 12V drains off that is a signal from the power system the CPU uses as a "sense" to use the 5V power to "Keep Alive" and eventually the Farad Caps that "hold" up the data lines are supposed to take over and keep it going. So yes, a Lithium would work

The problems don't go away - it lies in the externals though too - the CPU, if not burnt in with a "ROM" to load from - the address lines sit at "zero" - waiting for instruction. That's where Ranger and Midland/ALAN radio took and installed a layer or an extra step that President and Uniden wound up doing too.


They use Microcontrollers - a simple serial data out chip that takes the CPU clock and starts feeding the CPU a series of instructions on how to step thru the process, then the CPU LOADs from that controller - it's abilities and hierarchy structure - which chips are in the supporting role, that sort of thing and takes off. So the CPU doesn't need to look at it's own code - it can retrieve the data to operate from a microcontroller.

It's in (effort of) keeping the CPU from having to look for code - that makes the reset and old timers moments occur - that is from the poor power feed structure the thing has nowadays. The caps that help provide the very cushion the CPU needs to refer back on itself thru it's own "scratchpad" memory fail quickly. To fix that - you'd have to install diodes to act like valves nearly everywhere. In the old TTL days they did it as a set of matrices to make sure the CPU had data kept in it and ROM kept it's own data from corrupting using the valves as one way "outs" for data to prevent re-writes. (DIP switches too - to force address loads from a specific pinout "set" as an address)

Look back at an HR2510 and the CPU chip - the 4 resistors used that you "clipped" (Shhh - don't tell anyone we talked about this ok?) were address default pulldowns to make the CPU step PAST a set of instructions that were the PLL datastream and the Display controllers programmable display counters for (ulp!) - 11 and 12 meters. The PLL in a HR2510 doesn't use BCD - it uses serial data from the controller to make the IF the radio needs to work - the Display gets data from the same controller on what to show.

So, to keep the newer Rangers alive you need to keep 12V on all the time. (And even then as you can see that is no guarantee) Else the CPU is going to "bomb" and bounce to a microcontroller to look for instructions. This way, the CPU doesn't need ROM, the Microcontroller can be programmed for one-shot "forever to be this way" program. The CPU uses it then for all the current data it thinks is ROM - so the controller allows the company to quickly program the radio for EU, Asia or US frequency allocations and allowances. Its' all there - the CPU is just a very fast switch and calculator ALU - the controller is what makes or breaks the radios' nowadays...welcome to Chinas' way of doing things. Only thing is, these microcontrollers are cheap - read crappy cheap - easily spoiled and corrupted cheap. So any effort the CPU tries to execute these days requires intervention from the Microcontroller - if the controller is bad, so is the rest of the radio - period. Poor battery or bad regulation - once the controller got spiked from a pulse or hit from EMP or a cosmic ray event - its' corrupt and the radio becomes toast - until you can load another microcontroller code and install a new chip to replace the old one...