take a look at the early 2950 service manual. it has voltage charts that should help you out checking your radio.
http://www.cbtricks.com/radios/rci/rci_2950/index.htm
http://www.cbtricks.com/radios/rci/rci_2950/index.htm
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RCI-2985DX voltage schematics
- Thread starter islander
- Start date
I have downloaded pretty much every 2950/2970 schematic I could find. My checks so far
show that PLL1 will adjust, PLL 2 will adjust but the voltage changes on its own. 10.100 oscillator is ok. VCO 1 should be 38.6950 but reads 35.225 and will not adjust. No output at TP5 ifor usb.am or lsb. oscillators. I will post the info from the pll mc145162 tomorrow.
Thanks.
did you look at this voltage chart?
http://www.cbtricks.com/radios/rci/rci_2970/rci2970_trvolt_chart.htm
http://www.cbtricks.com/radios/rci/rci_2970/rci2970_trvolt_chart.htm
Yes, I spent a fair amount of time looking at the voltages mainly the oscillators and mixers but the transistors being used are different. Some oscillators are ICs. I found a schematic for the RCI 5054 which uses the same mc146162 pll but it too has no voltage chart.
At any rate the problem appears to be VCO 1. According to pll alignment instructions, vco1 should be the frequency displayed 28.000 plus the 10.695 to get 38.695. However TP 3 reads 35.225. Subtract the 10.695 and you get 24.530. That is 3.470 below the frequency displayed. My plan now is to hunt down whatever is supposed to generate the 10.695 and the 28.000 and check the active and passive components. Hopefully I can figure out why vco1 is not working properly.
Lots of shields to remove before I can get at the pll transistors. Maybe too much heat to do it in one go. I attached the schematic for RCI5054 so any one wants to help can take a look at it.
haven't read through the whole thread but these radios are notorious for having badly manufactured tuning coils. also some of the tuning coils have a small capacitor internal to them that can go bad.
If you notice any cans around the pll area that either dont show a peak, or show a peak with the ferrite slug flush with the top of the can, then you probably have a bad tuning coil and need to replace it.
best of luck.
LC
If you notice any cans around the pll area that either dont show a peak, or show a peak with the ferrite slug flush with the top of the can, then you probably have a bad tuning coil and need to replace it.
best of luck.
LC
Thanks for the intervention. You are probably spot on. The oscillators are off specs and won't adjust properly. The mixers and other devices are ok . I have removed the shields am down to checking the passive components, so I will give the coils a good look. I need to check with the radio powered down so grid dip meter or something to see the resonating range. thanks for the suggestion.
Resurrecting an 8 year old thread. I just had a 2950DX on the bench that had the same symptoms. I removed the PLL IC, and checked both VCO's by applying a low voltage to each VCO, and both were working correctly. I traced it down to corrupted data coming out of the microprocessor. The data is not communicating with the RX Phase Detector. Also there should be 10.100 MHz at TP16 which there was not. But the 10.100 MHz oscillator was also working correctly. The radio made it way to the parts bin, as the CPU boards are un-obtainium.
Are the inputs and outputs for those CPU's written down anywhere? If we can't get the original parts maybe we can emulate them.
That would not work in this particular radio.
That would require firmware from RCI, which I doubt you could get. Plus you would need a programmer/hardware for the HD4074818 microprocessor.
It would have to be approached as black box reverse engineering project. The same way Mark Rutherford (Mark19960 on YouTube) approached the Uniden 980SSB replacement control board he designed and briefly sold. But it is doable. Whether or not the result would fit inside the 2950DX case is a different problem.
I've replaced the MCU in a SBE Console V and a Sidebander VI. While those are admittedly not nearly as complex as the 2950DX, the principal is the same. Except with those I was starting with a dead radio. I did not have access to SBE's source code in either case, and did not use the same processors, yet ended up with a working radio both times.
Bought a digital 'scope a few years back with the ambition of reverse-engineering the data stream from a 2950 CPU to the PLL. The post-1995 processors get assasinated by runaway power supply regulators putting 23 Volts on it, or they just die for no apparent reason. The long-discontinued DX2527 was a barefoot 2950 base radio that seemed to have a high death rate for the CPU.
Had one customer who had the D104 on his 2527 on the desk too close to his wireline phone. Lightning struck a utility pole and an arc visibly jumped from the phone to the D104. Instant brain death for that radio.
Never did complete the reverse-engineering process. Just figured that if I were to mimic the data stream with a replacement that it would control the Sony PLL chip okay. Was gonna use 7-segment LEDs for the display, and small LEDs with shadow-mask legends for ANL, NB, SWR etc.
Found that smaller projects produce income a lot sooner.
73
Had one customer who had the D104 on his 2527 on the desk too close to his wireline phone. Lightning struck a utility pole and an arc visibly jumped from the phone to the D104. Instant brain death for that radio.
Never did complete the reverse-engineering process. Just figured that if I were to mimic the data stream with a replacement that it would control the Sony PLL chip okay. Was gonna use 7-segment LEDs for the display, and small LEDs with shadow-mask legends for ANL, NB, SWR etc.
Found that smaller projects produce income a lot sooner.
73