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RCI 2995DX no transmit power
- Thread starter Crambone
- Start date
well I did get it working but am having issues with LSB & USB being off frequency. I was in the process of trying to align everything and got stuck at one point in the alignment at the OSC adjustments. Got the AM OSC set to 10.6950 with L18 but I’m having problems reading frequencies in Side Band to adjust L19 &L20. Seems like with no output wattage I can’t get a good reading. Not 100% how to proceed or if the 10.6950 I did get on AM is even correct. Could use some guidance in what equipment is needed and how to sniff the frequency for them?
Plus the fact it’s all boxed up now as I’m in the middle of a move! Uhhhhh
Plus the fact it’s all boxed up now as I’m in the middle of a move! Uhhhhh
Crambone,
signal levels in the IF oscillator circuit can be very low, and it can be hard to get a solid reading on your freq counter there.
get the AM set right just like you already did, and then get out your smartphone.
you need a pretty accurate 1000Hz tone, and you can find one on youtube by searching.
if you have an audio sig gen, or a function generator, those can be used as well.
once you have a good 1000hz tone you can hold a mic up to, set the clarifier at center, and put your freq counter in line with the output of the radio (antenna jack).
DO NOT just put a cable from the antenna jack into the counter. you need attenuation or a sampler. (i feel like you probably already know about this)
now set the radio on channel 20, in USB mode, mic gain up enough to modulate the transmitter.
key the mic, hold it up to your 1000hz tone, and read the frequency displayed on the counter.
on channel 20 in USB mode, you should be reading 27.20600 mhz.
(that's 27.205 plus the 1000hz equals 27.206)
tune the USB IF coil for 27.20600.
now go to LSB and do the same thing, only look for 27.20400.
(27.205 minus 1000hz equals 27.204)
tune the LSB IF coil to get 27.20400.
that should put you pretty darn close.
you haven't centered the offsets in the passband yet, and you kind of need a person transmitting to you on a known on frequency radio (like a new ham radio) to get it dialed in completely.
you might be fine with what you already accomplished, and that's just fine.
leave it there.
if you want to get it better, just tune those IF coils very very slightly when your friend is talking to you in order to get the best voice quality.
you will notice they get more bassy and then eventually really low pitched.
on the other side you will notice they get very tinny sounding, and then high pitched.
tune back and forth slightly for the best quality in each mode.
a good way to tell if you have it balanced right is that USB and LSB should sound the same when you switch back and forth between them.
hope this helps.
LC
Don't know where this went, so I did have the graphic for ya' so I'd thought I'd post again...
I'm more worried you blew some traces from the current surge that happens in "oops" like that...
But since you've got it working...to a point...
How's the Bias thingy going?
I'm more worried you blew some traces from the current surge that happens in "oops" like that...
But since you've got it working...to a point...
How's the Bias thingy going?
I found a popped cap but can’t recall the number. Everything is packed up now and ready for my move. Once I get everything set up I will look through my notes
ok not same person but very similar problem 2995 dxcf replaced power supply now no tx (power out) also now have talkback never did before
Odds are that the linear has suffered failure of the four MOSFET transistors. Probably what clobbered the old power supply.
I need to snap a picture of the 2-wire plug that activates the linear in that radio. Unplug it and this will disable the relay in the linear amplifier. The barefoot radio should show normal transmit power. The factory has changed the wires from one brown and one black to one green and one yellow. But this is a pair of wires in a tiny plug that's just forward of the driver transistor on the main radio circuit board. Unplug it and see if you can get barefoot transmit power.
Do you have a second radio you can put on the same channel to listen for a weak signal coming out of the 2995? If you can't get the wattmeter to respond at all, this would be the next step.
73
I need to snap a picture of the 2-wire plug that activates the linear in that radio. Unplug it and this will disable the relay in the linear amplifier. The barefoot radio should show normal transmit power. The factory has changed the wires from one brown and one black to one green and one yellow. But this is a pair of wires in a tiny plug that's just forward of the driver transistor on the main radio circuit board. Unplug it and see if you can get barefoot transmit power.
Do you have a second radio you can put on the same channel to listen for a weak signal coming out of the 2995? If you can't get the wattmeter to respond at all, this would be the next step.
73
Old Power supply is still good just really noisy
So I got new one
Room full of radios 2 antennas up multiple meters tried that
All MOSFET's (6) have been replaced still no tx but I get TalkBack audio from internal speaker
I keyed up for about 5-7 minutes felt driver and final area started to get a Lil warm but still nothing
This does suggest either the transmitter's RF signal is being interrupted upstream from the parts you changed. Or the power feeding the radio driver and final has been disrupted.
A second radio tuned to the channel this one transmits on will reveal if a transmit signal is being generated at all.
A coax jumper with the far end's barrel backed down off the plug gets you a half-inch long "sniffing" antenna. If you hear anything holding it near the driver transistor while it's keyed, this confirms that the radio produces a weak signal.
And if the radio doesn't generate anything at all you can hear in the second radio, your problem is underneath one or more of the shield covers.
Had one of these radios show up with cracked tuning slugs in enough of the transmit circuits to shut it down. Might have a close look at those for signs of damage.
73
seen this mentioned tried it got nothing ....
but i think i may have found the problem
I did try it with no luck but I think I may have found the problem five-legged I think audio chip might be the culprit
But unable to tell what the numbers are if you have access to knowing the numbers it would be helpful.
Again thankz for your help.
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