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L37 RCI-2995DXCF How tune?
- Thread starter ALANFede
- Start date
If you're following the service manual's instructions and using an oscilloscope which is the easiest way to see the peak at the Base of Q64 (TP17).
Have you tried to detune L38 first, then tuning L37 and watching the scope for its peak output? Then going back to retune L38 for its peak output. It may take a few tries before you're happy, but you"ll get the hang of it.
73
Have you tried to detune L38 first, then tuning L37 and watching the scope for its peak output? Then going back to retune L38 for its peak output. It may take a few tries before you're happy, but you"ll get the hang of it.
73
We set the radio to sideband, (either, doesn't matter) and set mike gain for about 2 Watts with a steady 1 kHz tone in the mike. Holding the power this low makes the peak a lot easier to see.
73
73
Thank you for the valuable suggestions, unfortunately the manual I'm using is very lacking on how to perform the alignment steps specifically. I'm also having difficulty with the noise blanker, which I can't get to the required voltage on the TP1.
Is it possible to find a complete and detailed service manual?! Thank you all.
Is it possible to find a complete and detailed service manual?! Thank you all.
For some advice...
Be careful with this.
You do this with the AMP side off, disable it - verify that you have enough power and the current is stable under your testing conditions.
L37 is the TX side of L17 - the IF from the VCO.
So you'll need to verify TP3 is properly peaked - not just by looking for maximum - but maximum without flattopping which, in this chassis, it is easily capable to do.
Once you overpeak, then L37 or anything further down - is moot - won't work.
Best to detune / retune TP3 and ensure your P-2-P values are not flat-topping on your scope image. AT L17!
Then retune L37 - for you'll find L17 then will "buffer" between RX and TX side better.
In the tuning manual from cbtricks - the L17 is peaked using RX AM mode
Note the use of the amp in Strong Brackets " [ ] "
Do the low power first - then worry, or indulge yourself - with the amp on...
Be careful with this.
You do this with the AMP side off, disable it - verify that you have enough power and the current is stable under your testing conditions.
L37 is the TX side of L17 - the IF from the VCO.
So you'll need to verify TP3 is properly peaked - not just by looking for maximum - but maximum without flattopping which, in this chassis, it is easily capable to do.
Once you overpeak, then L37 or anything further down - is moot - won't work.
Best to detune / retune TP3 and ensure your P-2-P values are not flat-topping on your scope image. AT L17!
Then retune L37 - for you'll find L17 then will "buffer" between RX and TX side better.
In the tuning manual from cbtricks - the L17 is peaked using RX AM mode
Note the use of the amp in Strong Brackets " [ ] "
Do the low power first - then worry, or indulge yourself - with the amp on...
I'll second this procedure.
it absolutely makes the peaks easier to see, especially with the widebanded coils used in these multiband radios.
one thing to note about the alignment instructions found in service manuals is that they were written by a technician for a technician.
there are a lot of assumptions made about the ability and experience level of the person expected to be able to make it all work.
LC