had a guy give me one of these to align for him, and i could not find service info for it ANYWHERE!
there are some freq mods for it online, but very little else.
some say its like the albrecht 485, and while they are close; the info online is still not of much help.
so, with only a similar schematic to go by, i had to come up with an alignment procedure from scratch.
so here it is for all the future searchers; the alignment/tune up of the radio shack trc485.
i can pretty much GUARANTEE that you will not find this info anywhere else on the net.
that being said, if anyone does have an actual service manual for this specific chassis, i would really appreciate any additions to this procedure.
i have done the alignment, and this does work:
1. set radio to channel 20, AM mode, clarifier centered.
unsolder and remove the bias board. (PC board near driver and final like in the galaxy style chassis)
2. hook freq counter up to TP3. (its a wire jumper near T9) adjust T10 for 16.5100mhz.
3. switch to USB mode and check for 16.5125mhz. slightly tweak T10 if its a bit off.
4. switch to LSB mode and check for 16.5075mhz. T10 is the adjustment for all three modes, so once you get AM and USB in, LSB should be good also.
5. switch to AM mode and key the microphone. check for 16.5100mhz.
if its off, adjust RV3 for 16.5100mhz. check USB TX mode for 16.5125mhz, and LSB TX mode for 16.5075mhz. again, RV3 adjusts all modes, so once one is in, all should be good.
6. connect freq counter to TP2. (wire jumper near T11, 12, and 13)
in AM mode, adjust T11 for 10.6950mhz.
in USB mode, adjust T12 for 10.6925mhz.
in LSB mode, adjust T13 for 10.6975mhz.
(there is no typo here. that is the way they should be)
7. to align the receiver, set signal generator for 27.205mhz, and in AM mode, adjust T1, T2, T3, T4, and T5 for max signal. (only use signal of S3 or less) check channels 1 and 40 for even receive gain. if its off, use T2 and T3 to even it out.
8. switch to either LSB or USB mode, and adjust T6, and T7 for max.
9. to align the transmitter, first set the driver and final bias.
set radio to either USB or LSB mode. set multimeter to read milliamps.
connect positive lead to TP5, and negative lead to TP6 (driver bias).
key microphone and adjust RV9 for 50mA.
move negative lead to TP7 (final bias), key microphone and adjust RV8 for 100mA.
replace bias board.
10. set radio to either USB or LSB mode, channel 20, and using a 1khz tone or steady "ahhh" sound into the mic, adjust T17, T16, T15, and L8 for max modulated wattage.
11. set radio to AM mode and key mic with no modulation. adjust RV10 (AM POWER) for desired deadkey. (4 watts max)
12. adjust RV5 for 100% modulation. (or turn it all the way up if you so desire LOL)
13. set radio to either LSB or USB mode, key mic with tone or modulation, and adjust RV6 (ALC) for 10-12 watts PEP. (this chassis has poor voltage regulation, and while the wattage can be turned up higher, it causes the lights to dim, and i left it at about 10 watts PEP.)
14. RV1-S meter.
RV2-squelch threshold.
RV7-RF/TX meter.
well, thats about it. yes, there are a couple of PLL adjustments i left out, but they are best not messed with unless you have a scope and know what you are doing with it. they are T18, and T9, and can be set with a scope, but i dont have the data as to what levels to set them at.
they may just need to be peaked, but i cant be sure.
i sure hope this helps someone in the future from having to go through what i went through trying to find info on this radio.
its a neat little unit, and actually uses a 2SC2166 driver and 2SC1969 final!
good luck,
LC
