i wrote this out a few years ago on another forum, and i dont have time tonight to proofread it, but i will post it here, and re-read it tomorrow evening to make sure it is right.
this is from the factory service manual for the 2000GTL, but it should work with the 148gtl, the new grant, the new madison, and the tramD300 among others.if your radio has an MB8719 or MB8734 chip in it and a dual conversion receiver, then this alignment procedure should work for you.
for any other radio, you will have to find the specific service info for that radio. DO NOT USE THE NUMBERS IN THIS ALIGNMENT TO ALIGN OTHER RADIOS. YOU WILL SEVERELY DAMAGE THE RADIO!
when looking for sevice info, the internet is your best friend. you can often find the manuals on the auction site for a fair price.
if the radio is older than say, 10 years, then you should be able to find a SAMS PHOTOFACT for your radio. these were made by the Howard W. sams company. they are no longer made but you can find them around if you look. YOU MUST HAVE THE SERVICE INFO FOR THE RADIO YOU WISH TO ALIGN. DO NOT ATTEMPT THE ALIGNMENT WITHOUT THE SERVICE INFO AND THE TEST EQUIPMENT!
here we go:
1. input of frequency counter to TP13 (test point 13) IC1 pin 8.
radio on ch.19 am. clarifier in center pos. NB and ANL off.
check for 10.240mhz.
this means that you will hook the alligator clip rom the shield (-) or the freq. counter and clip it to PC ground. i like to use the tuning cans as they are all grounded. just clip right to the can, or if there is a wire soldered to it, clip to that. make sure the place you clip to is true ground. (connected to the big foil trace) and also make sure you dont use the metal case of the radio or "chassis ground" this is not the same as the PC board ground and will not work.
now take the probe from the freq. counter and touch the tip to pin 8 of IC 1. look at the freq. counter, it should read 10.240mhz. (if you get no reading and the radio seems to work correctly, then you have either hooked something up wrong or your freq. counter is set wrong or doesnt work.
2. input of RF voltmeter to TP10
radio on ch. 19am. clarifier centered.
adjust L21 for maximum RF out.
this means that you will clip the negative lead of your RF probe to where you had the freq. counter hooked to and the positive tip will go to TP10 (location found in service manual)
adjust the can SLOWLY for the maximum voltage. you will notice the volts rise to a point and then start to fall again, go back and forth until you find the peak point and leave the can set there.
3. input of DC voltmeter to TP9
radio set on ch. 40am
adjust L19 for 3.20 volts. check channel 1 for 2.45 volts.
this means set up the same way as before except dont use the RFprobe and set the can for 3.2 volts and leave it there.
4.input of RF probe to TP1.
radio set on ch.19am
adjust L20 for maximum voltage. (you may have to use the mV setting on the voltmeter for this one.
this is done the same way as in step 2.
5. input of freq. counter to TP1.
radio at ch.1 am
adjust L23 for 34.7650mhz + or - 20hz (try to get it exact)
6.input of freq.counter to TP1
radio at ch.1 USB
adjust L59 for 34.7665mhz.
7. input of freq. counter to TP1
radio at ch.1 LSB
adjust L22 for 34.7635mhz.
8. input of freq. counter to TP10
radio at ch.1am
check for .790mhz
9.input of freq. counter to TP3
radio at ch.19USB
adjust CT2 for 7.8015mhz
10. input of freq. counter to TP3
radio at ch.19LSB
adjust L30 for 7.798mhz
11.input of freq. counter to TP14 (IC3 pin 7)
radio at ch.19 AM TRANSMIT (key mic with no modulation)
adjust L31 for 7.800mhz.
12. input of freq. counter to TP15 (FET 1 gate1)
radio at ch.19am
check for 7.345mhz.
13.input of freq counter to antenna input (so-239)
radio at ch.1 AM TRANSMIT
adjust VR5 for 26.965mhz.
thats it for the PLL section.
so here is the reciever alignment procedure.
for this you will be using your signal generator.
make sure you have a .01uf cap in series with the positive test lead.
to set the s-meter and the squelch; you will need a voltmeter that measures microvolts. i do not have one of these, and therefore, i cannot do an accurate adjustment on these two pots.
this is where the bench radio comes in handy.
the bench radio i have has an analog meter on it, and after performing a tune up on a radio, i will find a local with a steady carrier, and match the radio im tuning to the S-meter on the bench set.
same with the squelch. (you wont need to adjust this ever, unless someone has turned the pot by mistake, and then, its not the most critical adjustment on the radio)
for this radio, the squelch range is VR3, the AM s meter is VR1, and the SSB meter is VR2.
YES, i realize that this is not entirely accurate, and i do not claim it to be. if you want it completely perfect, you will have to take it to a tech with a higher quality signal generator.
you could buy a better one yourself, but i dont feel the need for it, and can always find something else to buy with that ammount of money.(more radios!)
here we go:
FOR ALL RECEIVER ADJUSTMENTS: RF GAIN MAX. CLARIFIER AT CENTER, SQUELCH AT MINIMUM, NB OFF, ANL OFF, TONE MAXIMUM CLOCKWISE.
1. output of signal generator to TP16 (TR15 emitter)
7.8mhz
radio at ch.19USB
adjust L14,12,10,9,8,7 in that order for maximum s meter reading.
so, set your sig gen at 7.8mhz, clip the negative lead to PC ground, and the positive lead to TP16.
adjust the output of the sig gen so that the S meter on the radio reads about S-3. (no more)
slowly turn the coils, starting at L14 and working down. you will notice that they cause the S meter to move up or down as they are turned. turn the coils SLOWLY until you find the peak reading. leave the coil in that position and move on to the next.
2.output of sig. gen. to TP15 (FET 1 gate 1)
455khz.
radio at ch.19AM
adjust L15,13,3 for max. s-meter reading.
same as last step.
3.output of sig. gen. to antenna input
27.185mhz.
radio at ch.19AM
adjust L6,5,4 for max. s-meter reading. readjust L7,8,9,10 for max. in that order.
i also adjust L1,and L2 at this time. these are the NB coils, and should be adjusted using an oscilloscope and very high quality signal generator.
at this point, its up to you whether or not to mess with them. if you are doing a tune up on a radio that you know the history of, then there is no need to adjust them. if, however, you happen to be working on a garage sale special that you want to get working; then adjust them for max. s-meter reading using the set up from the previous step. this is how i do it on my radios, and my ear cant tell the difference.
and finally, the transmitter alignment.
you should use a dummy load for these tests, if you dont, you will be causing malicious interference, and generally being a jerk. and your results wont be as accurate. dont do it!
hook up a wattmeter between the radio and the dummy load.
radio should be on ch.19
1.radio at ch.19 AM
key the mic, and say "aaahhhhh" in a steady natural voice tone. using a two tone generator here can be very helpful. there are numerous designs around on the net, and they are simple to build. i use one. do not tune the coils for max. deadkey, as this will weaken the modulation to a great extent, sometimes making the output power actually DECREASE when you are speaking. (downward modulation)
while speaking into the mic, adjust L47,48,46,45, and L38 in that order for max. peak (modulated) power. on one or more of these coils, you will notice that there is a waxy substance covering the opening. carefully pick this away, and then, right before you make your adjustment, put your soldering iron on the ferrite core for just two seconds. be careful not to melt the plastic threads on the edges. this will allow the core to turn easily. if you dont do this, you can break the core, and then you'll have to scrounge another one from a different radio which may or may not work as well. be careful, dont turn anything fast, and never force anything.
2.ch.19USB mike gain at minimum.
adjust VR4 for 0 watts. (no carrier)
3. ch.19USB mike gain at minimum.
insert DC ammeter at TP8. (driver bias)
this means that you need your DC volmeter set to milliamps on a scale that can read 200ma (milliamps).
this hook up is not the same as voltage testing! when you test for current, you hook the voltmeter in series with the lead under test.
so, pull the wire off of TP8, and clip the negative lead to the end. touch the positive lead to TP8. key the mic and adjust VR9 for 30ma.
reconnect the wire to TP8.
4. ch.19USB mike gain at minimum
pull wire off of TP7 and clip negative lead of voltmeter to it.
touch positive lead to TP7.
key the mic and adjust VR8 for 60ma.
reconnect the wire to TP7.
VR11 is your SSB power out. set it wherever you want it. if you are running an amp after the radio, you should set it for no more than 15 watts.
i set mine at 12 watts.
VR7 is the mod control in the 148 chassis. in the 2000 chassis its VR12.
i just set this at max and use the front panel mic again to adjust the modulation. (you wont have to run the mike gain all the way up anymore)
VR10 is the AM carrier power. this is where people blow up their radios. they say, "wow! how cool! the manufacturer put in an easy adjustment for more power out!" dont be fooled! most radios cant handle the increased wattage for very long when this is turned up.
if you are running an amp; set this control for 2-3 watts and NO MORE! otherwise you will sound very quiet coming out of your amp, and you may just smoke it!
if you are running barefoot, then set it for about 5 watts. this is safe, and no one can tell the difference between 5 and 8 watts anyway. your radio will last for a very long time if you keep this control under control. if you get the power bug, you will be buying transistors that are getting more expensive every day.
finally, adjust VR6 so that the S meter on the radio agrees with the wattmeter.
well, thats pretty much it, except for the 50 flaming posts ive got coming my way for condoning such cheap and dirty tricks.
make no bones about it. this is not as accurate as sending your radio to a good tech shop, but if you wanted to do that, you wouldnt have read this far would you!
good luck, and please feel free to point out any mistakes or bad advice that you see. all quesitons are good questions.
i will correct any mistakes tomorrow, gotta go for now.
LC
