I got hold of another 2990, and boy...there's been some fingers in this radio! I've been trying to find a service manual to properly do a full alignment, an am wondering what mobile would have the same chassis?
Thanks,
Dave
Thanks,
Dave
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RCI-2990 Service manual?
- Thread starter Tweek
- Start date
I have the 2990 playing and looking good. Been listening to 38lsb in the workshop today, worked a couple of locals and 004 in Barbados.
Don't know what the story on this beast was, but it amazes me to see a radio like this with parts missing, stuff clipped all over the place, things broken, etc. Couldn't have all happened at one time, but was far from working.
Had a power supply problem to start with. After that was resolved, I started working through it... It had a hairline crack in the receive i.f. path that took forever to find.
Everything that could be turned, had been turned. It wouldn't transmit carrier on am or fm. Found someone had clipped out a transistor that offsets the balanced modulator in am / fm and mutes mic audio to it. Replaced that..
Then found a bunch of wires cut in the cw circuit, it was trying to transmit all the time in cw mode...because someone had swapped polarities on the cw keying circuit at the cw jack.
The receiver wouldn't detect AM, found two glass diodes cut. I think someone was maybe looking for a mod limiter, and made a mess.
Then found the mic gain control didn't work, wires had been zip tied to the frame rails so tightly it had cut through those.
The rf gain control didn't work because the connector on the chassis was busted off the board, traces and all
.
I did a few updates to it, got rid of that stupid audio mute when you spin the channel selector knob fast. Replaced the modulation limiter and set it up right. Modified the clarifier, and the tx now tracks the rx.
I repainted the cover, cleaned the face, and reassembled. The paint was worn off the front panel at the mode switch. I had to install a stick-on white background for black lettering, gotta get some white lettering and change that. Does anyone make a front panel overlay?
Dave
Don't know what the story on this beast was, but it amazes me to see a radio like this with parts missing, stuff clipped all over the place, things broken, etc. Couldn't have all happened at one time, but was far from working.
Had a power supply problem to start with. After that was resolved, I started working through it... It had a hairline crack in the receive i.f. path that took forever to find.
Everything that could be turned, had been turned. It wouldn't transmit carrier on am or fm. Found someone had clipped out a transistor that offsets the balanced modulator in am / fm and mutes mic audio to it. Replaced that..
Then found a bunch of wires cut in the cw circuit, it was trying to transmit all the time in cw mode...because someone had swapped polarities on the cw keying circuit at the cw jack.
The receiver wouldn't detect AM, found two glass diodes cut. I think someone was maybe looking for a mod limiter, and made a mess.
Then found the mic gain control didn't work, wires had been zip tied to the frame rails so tightly it had cut through those.
The rf gain control didn't work because the connector on the chassis was busted off the board, traces and all
.I did a few updates to it, got rid of that stupid audio mute when you spin the channel selector knob fast. Replaced the modulation limiter and set it up right. Modified the clarifier, and the tx now tracks the rx.
I repainted the cover, cleaned the face, and reassembled. The paint was worn off the front panel at the mode switch. I had to install a stick-on white background for black lettering, gotta get some white lettering and change that. Does anyone make a front panel overlay?
Dave
Attachments
Haven't seen one for that radio.
Best favor you can do for it is to unload the original power transformer/rectifier/filter/regulator from the thing. A 300-Watt switchmode "brick" power supply will run the radio just fine, and protect it from runaway unregulated 24 Volts. The factory power supply is famous for popping the computer board when this happens. And that board is made from unobtanium.
Second-biggest favor is adding a 4-Amp fuse to the power wire feeding the radio circuit board.
Most people wouldn't run a mobile radio from a 25-Amp power supply without a fuse. But that's what the factory delivered.
73
Thanks for the tips, I'll go ahead and add the fuse. I may have a switcher from a computer, need to see if it's voltage is adjustable.
Haven't seen one for that radio.
Best favor you can do for it is to unload the original power transformer/rectifier/filter/regulator from the thing. A 300-Watt switchmode "brick" power supply will run the radio just fine, and protect it from runaway unregulated 24 Volts. The factory power supply is famous for popping the computer board when this happens. And that board is made from unobtanium.
Second-biggest favor is adding a 4-Amp fuse to the power wire feeding the radio circuit board.
Most people wouldn't run a mobile radio from a 25-Amp power supply without a fuse. But that's what the factory delivered.
73
Best advice on the net.
I have seen 3 of these radios turned scrap by suicide, they go poof and once the CPU is cooked it is done.
73
Jeff
Thanks, I bookmarked your link. This radio is the older 2990, not the dx. I'll see if I can find pics to compare and see if the faceplate layout is the same.
Know this post is old but anyone know what ohm's the channel encoder is in the rci 2990
It contains two switch contacts. Close to zero ohms when the contact points touch, open circuit when they don't.
It's a "momentary" quadrature encoder. No continuity through it until you click it. One of the two contacts closes before the other. The computer can tell which direction you turned it by which one or the other of the two contacts closes first.
The contacts have a tendency to "bounce", that is the contacts are springy and will make/break multiple times when clicked. The computer is supposed to sort this out, but doesn't do it all that well. Even a new radio will jump multiple channels with one click, or change frequencies the wrong way if turned too quickly.
Takes an oscilloscope, power source and resistor to test it. A meter alone just can't.
73
It's a "momentary" quadrature encoder. No continuity through it until you click it. One of the two contacts closes before the other. The computer can tell which direction you turned it by which one or the other of the two contacts closes first.
The contacts have a tendency to "bounce", that is the contacts are springy and will make/break multiple times when clicked. The computer is supposed to sort this out, but doesn't do it all that well. Even a new radio will jump multiple channels with one click, or change frequencies the wrong way if turned too quickly.
Takes an oscilloscope, power source and resistor to test it. A meter alone just can't.
73
Got a replacement got lucky that part is good to.go now I got.a problem with receive when I touch the board at R145 receive is normal when I leave off it dies out and the same if I touch the top of the resistors it will pick up I got this a few months back at a sale