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2950 Old school TX Off only from 26.980 to 27.460

cavhooah

Member
Aug 10, 2011
8
0
11
Yep, pretty dang weird and Ive never seen anything like it.

Right on target for TX/RX from 24.000 to 26.980...... then after 26.980....and all the way to 27.460 my TX is WAY off freq. My RX is on target through those frequencies, but transmit is around 27.36-27.44 no matter what frequency my readout says. TX magically snaps back on target after 27.460 and RX is always on target even when my TX is off.

This one really has me scratching my head here, Im at a loss.


Anyone ever seen anything like this ?

The readio is actually a Eagle 5000, wich is a copper labeled RCI2990/ Galaxy saturn turbo, with the 100 watt amp built in.

If some are wondering, its the same board used in ALOT of RCI/Galaxy/Mirage radios (EPT295013Z)
 

Gee, sounds like it is avoiding the CB band.
Maybe, per chance, possible that the unlocking dongle is missing from the radios?
It's a little circuit board that plugs into the radio and unlocks it for 11m use . . .
 
I know right ?

Ive never seen anything like it. Im flattopping on my scope in that area also. I tried moving the jumper (Ive owned a blue zillion 2950/2970 clones and such) to no avail.

Im going to run through the alignment procedures shortly (gonna be a late night) and see where that gets me, perhaps Im getting some kind of oscillation ? Feel free to comment and offer advice, Im hoping its something simple.
 
I know right ?

Ive never seen anything like it. Im flattopping on my scope in that area also. I tried moving the jumper (Ive owned a blue zillion 2950/2970 clones and such) to no avail.

Im going to run through the alignment procedures shortly (gonna be a late night) and see where that gets me, perhaps Im getting some kind of oscillation ? Feel free to comment and offer advice, Im hoping its something simple.

i'd be checking the individual oscillators with a counter to see which one is free running/self oscillating, help you narrow it down to one area.


does it only do it on one mode or all modes?
 
All modes, and the frequency span thats infected slightly changes as the radio is left on. The radio has sat for years out in a garage, my good freind passed away and I just found out. Id always wanted the radio, and his brother gave me a screaming deal for it. Its kinda sentimental, so Im in it for the long haul.
 
This is a pretty odd way for a radio to behave. Are you totally sure that it's behaving correctly on receive on these frequencies. More than once I have seen a PLL that was "barely" stable, but locked in properly on receive, and would act wrong only on transmit. The small amount of stray RF from the power stages would not disturb a PLL that has a strong lock on the frequency. And a PLL that is barely locked in would act up when you key the mike.

But the PLL in this radio is more than a little odd, even when it's working perfectly. There are some tuned circuits in this PLL that will prompt it to do squirrelly stuff if someone has turned the slugs, usually while watching the wattmeter, whistling into the mike.

I would start with the 5-Volt regulator that runs the PLL section. Looking for noise spikes would reveal an open electrolytic. Noise on the 5-Volt supply causes unpredictable behavior in most PLLs, and this one is no exception. And if the voltage is off by more than 10%, that's a bad sign. The 5-Volt PLL supply should show up on the scope as a steady DC line, clean as the proverbial driven snow.

This radio has the "in-between" display/controller board. RCI replaced the original two-board computer/display (with the battery) in 1995. Upgraded to a single board with no lithium coin cell, and an electrolytic cap to retain memory channels. They told us it was good for a week before it would run down. Your mileage may vary.

After 1999 they went to a different main pc board, the "6950" series, with a new display/controller. THOSE radios require the dongle, but yours does not.

Have a look at the main tuning voltage at jumper J13. The factory alignment says to set L17 for 2.2 VDC at 28.0 MHz. L17 is the main VCO that feeds out to the receiver mixer and transmit mixer.

It also says to read DC voltage at pin 3 of IC7. Much easier to scrape the brown plastic from the long end of R200 and clip your probe there. L21 should be set for 1.2VDC there. When this one is set wrong, the radio tends to do odd stuff.

L24 and L25 are the weirdest part of the PLL alignment. Factory book says to adjust for "best waveform", without being specific. What they are trying to tell you is tune for least jitter. Trouble is, if you turn them too far, you get an out-of-lock PLL with stable but wrong waveform on the 'scope.

Watching the main VCO tuning voltage at J13 while tweaking L24 and L25 will reveal when you have gone over the edge with either of these two slugs.

Still have a strong suspicion you'll find an open electrolytic among several that are sprinkled around the PLL section, decoupling different circuits from the 5-Volt supply.

Or a tuning slug that's a half-turn off.

73
 
Thanks Nomad !

Now that you mention it, there were a few crispy traces over by the 5 volt regs. Ill be digging into it as soon as I get off the puter' here.

Ill post results !
 
Im glad to see him too shockwave....lol.

Measured the emitter of IC4 (5vdc reg) reading 5.093 VDC.

Ive noticed, RX 26.0-27.0 TX on freq.
RX 27.06 starts TX on 27.323 and TX slowly falls back in line as I move up in freq untill 27.420 when TX/RX match back up.

Moving past 27.420 to 27.920 TX/RX match up........ I take it all back. Its fluctuating in the jacked up freqs as I move the radio up and down freq.

It jumps to 28Mhz when its jacked up.


5 volt reg is reading a solid 5.093 even when the radio is trransmitting off freq.


This is a REALLY clean radio, and my buddy never used it as it was his deceased fathers rig. All parties who have owned the rig have passed on now, so I cant ask them if they had any issues before with it.


My scope is just an inline wawasee meter/freqcounter/scope combo without an probe input for the scope. My old heathkit gave up the ghost a year ago, so its all I got for now.


On the flip side, using my Kenwood 450S on a dummy load as a reference, recieve is on track and only TX is effected.
 
well L24 and L25 were the culprits here.... working fine now. But another issue arrive after I put the cases back on.... I now have talkback through the speaker (wich I dont want) and Q40 has SMOKE eminating from it...lol.

Any ideas on this one fellas ? Ive looked for pinched wires from the cases and have found none..... might take the faceplate back off and look behind it.
 
"On air" LED wire was grounded to the chassis, replaced Q40 and fixed the short to ground and all is well.

2600, your the man bro, glad I rustled you up via PM on grumpys. Thank you for your expertese in the hobby, I hope you realize what an asset you are to folks around these forums.....not to mention your awesome DX-300 work and stellar Browning fabrications.

For those who dont know (Im sure they will be new to this hobby if they dont) "2600" can be found on just about EVERY forum out there offering sound advice and amazing talent through his works.... you are truly a oracle of knowledge and wisdom for the home tinkerer and your kind is a rare bird indeed.

To many people now days either lack the knowledge or care to help others in need, and you sir, stand alone with your pro-bono (sp?) work for these communities.


God bless you, till me meet again.

Cav
 
Their is no way this is an Olds School RCI 2950 they did not cover 12 meters at all. People made them do it but the amount of work that had to be done was insane and even then no guarantee it would do it with out looking up the PLL the old school models had about 26-32Mhz coverage. I had a 2950 with battery on board and a reset button. I did every mod you can imagine to it that was worth while....A bad cap or faulty voltage regulator would make that that radio do some really odd things. Freq. shift's, PLL lock up, freq. drift, squealing, etc......In 90% of the cases it was a bad cap or voltage regulator these radio's do not tolerate dirty power or power flucations well at all. I think in the 12 years or so I owned it I never had a bad resistor or diode and the only transistors that routinely failed where for voltage regulation. I had a lot of cap failures around the 10 year mark.

I would start with the main voltage regulator first these fail often, then I would check caps feeding the PLL .......it goes with out saying this is more then likely a voltage and noise issue feeding the PLL!!!
 
Hey bro, thanks for the tech advice.....but It was rectified with an alignment of TX/RX and PLL circuits...specifically L24 and L25.

And also....yes this IS an old school 2950... Re-read the original post and youll see it actually is a "Eagle 5000" using the 295013Z board. Also, if your saying the old ones were hard to convert to 24Mhz, I dont remember that.. There have been a few articles talking about reaching 15 meters being intensive to reach, butThe older rigs, as stated above also, required nothing more than moving a jumper for 26-32Mhz... Only the newer "DX" series requires a "dongle" pluged in to reach 12-and 10...and even then, IIRC only the "blue dot" American specified units require that chip.

If I had every 2950 variant Ive ever owned (Mirage, RCI, galaxy..ect using this board) Id be sitting upon thousands of dollars worth of radios....just in this stlye board alone mind you.

There are a few posts on here where I actually have done board transplants and other misc projects with this board, one specifically was "de-modding" a 295013Z for a transplant in a Saturn Turbo radio...wich is FAR more complex than it may at first seem. My account here at the time was a name "Mudduck". Check it out.



Any who, If you want good solid accurate info, get ahold of "NomadRadio/2600".

really its pretty easy to tell good techs from BS techs if you have half a clue about transceiver technology.... and If youd rather not spend the time learning, ship your crap to Nomad/2600 and get it done right.


Im pretty sure this rig was sold around the early to mid 90's as a relabeled 2990....Although I been around this hobby for 20+ years (still new compared to some) it "Do" quallify as old school...considering there have been no less than 4-5 model revisions therafter.


Ive owned no less than 10 of the first edition 2950's. And all were great rigs and extremely easy to modify.... 15 meters on the other hand, is a whole other topic.
 
I have seen mods that will make the DX model run as low as 20 MHz But I have never gotten that deep into the radio, 24 to 32 is enough for what I do with it.
The radio must have the module connected to RX/TX from 32.000 - 24.000 MHz.

Open radio on the speaker side.

Face the back of the radio towards you so the front panel is away from you.

Looking where the module is plugged in on the back side of the front panel there will be 2 sets of pins right above the module plug in.

Connect the 2 right pins together.

Reassemble the radio and turn radio on.

The radio should start at 21.000MHz.




How to get LOWER than 21.000MHz ! (on DX versions)


Here is the procedure to cover 18-36MHz though the functional limits of the radio, usually from 20.000MHz to 30.000MHz (functional meaning TX with measurable wattage and on frequency).
You need the expansion module installed and the two pins jumpered to cover 21 to 29.699MHz (as shown above), if your radio covers 24 to 32MHz this will work too but with a different range.

Next you manipulate the SPLIT feature.

We start with a reference frequency in CB mode...let's use CH 1 (26.965).

To get to 20.000MHz, program the split function by pressing [PROG] then [SPLIT], move the curser with the [SHIFT] key and program in 6.965....Now press [ENTER], press [SPLIT] until you see "-split" in the display.

Next press [MAN] to get to the CB band mode and move to CH1...press the mic-key and you hear a "buzz" from the radio (this step is neccesary).

Release the key and press the [MAN] button and BINGO!---you now have 20.000MHz in the display (you might even hear WWV in Ft. Collins CO, there).

To transmit, just press [SPLIT] until the "split" is off of the display and you're good to go!

(Caveat: you can't move from the jumped-to frequency without defaulting to 21.000MHz and you can't save the frequency to a memory).

Using this math trick, you can jump ANYWHERE from 18.6251MHz to 36.1049MHz (yes, you can go up using the "+split" function).

Enjoy!............THE INSPECTOR


There are old RCI's with the red displays, (three generations of these to be exact).

Version 1 has the onboard battery for the memory and has to switch from CB band to frequencies by using the LOCK button.

The second generation unit will have the battery eliminated, and still has the large capacitor right in the way of the bracket knob mounting hole on the right side, problem there is someone gets aftermarket knobs and they are too long and bend the cap over till it shorts out or breaks the solder loose on the board. This radio is also where they began using the MAN button to change from CB mode to frequency mode.

The third generation they fixed a few of the interior flaws, such as the large capacitor problem.

Then the modifiable 2950dx, and the "Blue Dot" 2950dx which is the non modifiable version.

Easiest way of identification on these is the green display and they actually say 2950DX right on them.

The DX is also modifiable to seven megs, play around with the jumper settings, you will be amazed what this radio appears to be able to do. I have yet to put a 40 meter capable antenna on this unit to see if it actually works there or not, I do know that it keys there and seems to pick up static there too.


Have a good day and hear from you later.
Larry

----------------------------------------------------

Here is the Mod Info Larry sent me, remember what he said,it is not for the poor solderer, unless you want ot ruin your radio.

RCI 2900 DX Series (Blue Dot Version) , First Generation DX

Modification of “blue dot” unit is possible with “E-Chip” sold separately. Unfortunately, color-coding is not possible, as these chips never seem to come with the same color wires on them, so I have given them numbers instead. These instructions are in the simplest of laymen's terms possible so anyone can do them with a steady hand and a good soldering iron.

Turn off power and remove power leads
Remove top and bottom covers, knobs, and faceplate
Remove the 4 screws holding the CPU board to the chassis
Flip radio over so solder side of main board is facing you and back of radio is toward you
Fold CPU board down carefully so it looks somewhat like Image 1
Now, on the right side of the CPU chip count up 5 legs from the bottom, you will know you have the right one as there is no trace going to this leg
If “E-Chip” comes with wires and plug, remove plug and leave wires as long as possible, strip 1/8” of wire ends and tin. If “E-Chip” comes with plug only, unsolder plug and add 3 wires in its place.
With solder side of “E-Chip” facing you as in Image 2 , connection #3 solders to the 5 th leg previously identified in step 6 (This is the most dangerous part, be careful!)
Now, flip the radio over so you can see the same side of the CPU board, still from the back as in Image 1 , but now it will be upside down
Solder connection #2 of the “E-Chip” to the negative side of the 220 capacitor as shown in Image 1
Connection #1 on the “E-Chip” gets soldered in place as in Image 3
Put radio back together, hook up power, and turn it on. Unit is expanded to 24.0000 to 32.0000 mhz
Remove “Blue Dot” from back of radio!

See images Below.
I have done the "Math trick from Inspector" just to see if the radio will go there, Mine will, but I have not attempted to operate the radio down there, experimental only, proceed at your own risk.
;)
The Inspector used to be a member here many years ago.
The E Chip Mod came from The Quack Shack.




73
Jeff
 

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