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Pres. Grant Export V-Power....
- Thread starter 15minigrass
- Start date
if that grant export has the MB8719 chip in it, and i think it does; your
AM power control is VR11.
it is a 5 K pot.
just find a 5K linear taper pot to mount somewhere on the chassis, remove the VR, and run wires from the PC board to the new external pot.
if the power goes down when you turn it up, switch the two end wires.
VR5 is your modulation control.
good luck,
LC
AM power control is VR11.
it is a 5 K pot.
just find a 5K linear taper pot to mount somewhere on the chassis, remove the VR, and run wires from the PC board to the new external pot.
if the power goes down when you turn it up, switch the two end wires.
VR5 is your modulation control.
good luck,
LC
if the radio is a grant export pc999 board then vr11 is the driver bias preset which is something you don't want to be messing with. if it is a pc999 grant export then vr13 is am carrier power preset.
doing it loose cannons way isn't the best way to do it but its the way most people do it,the reason its not the best is if you remove the am carrier preset and replace it with a potentiometer you have nothing to stop the carrier going beyond the stage of harmonics and premature meltdown of the dual 2sc1969 rf final transistors,not a wise move as they are exceptionally difficult to source now and becoming very pricey.
nearly every export radio i've ever seen with it modded that way ends up with burnt out rf final transistor/s.with all due respect too loose cannon its a suicidal way of doing it,and i mean no offense by that loose cannon as most people read how to do it off the net.please don't take it the wrong way.
the best method is to copy the way ranger rci do it on the ept 3600 chassis with variable rf power,i'll explain why after i tell you how its done.as that particular part of he circuit is very similar in all export chassis that clone the pb010 uniden board.
you would take a wire from the vr13 wiper end of r279 (5.6k) or from the wiper of vr 13 itself,run it via the wiper of a 20k potentiometer added to the radio and out one of the sides,(if the pot works in reverse change the side) then through a 3k variable resistor or a fixed resistor too circuit ground. the reason this way is better is that with vr13 still on the board you can set maximum power within the linear region of the final transistor/s,and minimise harmonics/burnout,the 3k or fixed resistor sets the minimum power level and the 20k pot allows adjustment between the min/max preset levels,ensuring you can't go above the linear region.
ssb power is already variable by using the mike gain control as in all ssb radios with variable mike gain.
all the chassis below use this method,as do all ranger chassis with variable power with ept3600 boards,the only thing that changes is the value of the added potentiometer and the variable range setting preset,the circuits are all identical,i would imaging the best value would be for whatever range you want the variable power to cover.trial and error will find the best arrangement for you.
http://www.cbtricks.com/radios/galaxy/dx11b/graphics/dx11b_sch.pdf
http://www.cbtricks.com/radios/galaxy_other/ssb_base/graphics/galaxy_ssb_sch.pdf
http://www.cbtricks.com/radios/galaxy/dx44v/graphics/dx44v_sch_main.pdf
doing it loose cannons way isn't the best way to do it but its the way most people do it,the reason its not the best is if you remove the am carrier preset and replace it with a potentiometer you have nothing to stop the carrier going beyond the stage of harmonics and premature meltdown of the dual 2sc1969 rf final transistors,not a wise move as they are exceptionally difficult to source now and becoming very pricey.
nearly every export radio i've ever seen with it modded that way ends up with burnt out rf final transistor/s.with all due respect too loose cannon its a suicidal way of doing it,and i mean no offense by that loose cannon as most people read how to do it off the net.please don't take it the wrong way.
the best method is to copy the way ranger rci do it on the ept 3600 chassis with variable rf power,i'll explain why after i tell you how its done.as that particular part of he circuit is very similar in all export chassis that clone the pb010 uniden board.
you would take a wire from the vr13 wiper end of r279 (5.6k) or from the wiper of vr 13 itself,run it via the wiper of a 20k potentiometer added to the radio and out one of the sides,(if the pot works in reverse change the side) then through a 3k variable resistor or a fixed resistor too circuit ground. the reason this way is better is that with vr13 still on the board you can set maximum power within the linear region of the final transistor/s,and minimise harmonics/burnout,the 3k or fixed resistor sets the minimum power level and the 20k pot allows adjustment between the min/max preset levels,ensuring you can't go above the linear region.
ssb power is already variable by using the mike gain control as in all ssb radios with variable mike gain.
all the chassis below use this method,as do all ranger chassis with variable power with ept3600 boards,the only thing that changes is the value of the added potentiometer and the variable range setting preset,the circuits are all identical,i would imaging the best value would be for whatever range you want the variable power to cover.trial and error will find the best arrangement for you.
http://www.cbtricks.com/radios/galaxy/dx11b/graphics/dx11b_sch.pdf
http://www.cbtricks.com/radios/galaxy_other/ssb_base/graphics/galaxy_ssb_sch.pdf
http://www.cbtricks.com/radios/galaxy/dx44v/graphics/dx44v_sch_main.pdf
A swing mod and turning down the carrier a bit - may be what you are looking for. I'm guessing that you want to set this radio up to run a linear amp. Putting a swing kit when you turn down the AM carrier will keep the modulation swinging strongly into the amp.
But take this route with some caution, as you must match the output of the radio to whatever input requirements are for the linear you have. If it is a low-drive linear; then a swing mod with the AM carrier turned down to 1/2-1 1/2 watts will keep that linear running cool and clean. If it is a high drive amp; then the radio may have enough - if it is dual final radio. But even then, you will want to make sure that you don't overdrive the input! Hope you have an accurate meter to use when doing this.
But take this route with some caution, as you must match the output of the radio to whatever input requirements are for the linear you have. If it is a low-drive linear; then a swing mod with the AM carrier turned down to 1/2-1 1/2 watts will keep that linear running cool and clean. If it is a high drive amp; then the radio may have enough - if it is dual final radio. But even then, you will want to make sure that you don't overdrive the input! Hope you have an accurate meter to use when doing this.
no offense taken whatsoever jazzsinger.
i have only done this to a few of my own radios back in the day, and i guess they never burnt out on me because i never turned them all the way up or all the way down.
i havent done it in years because i have no use for a variable deadkey.
back in the day (we're talking about 1988 when i was 14) i never had a linear, so i thought being able to adjust my carrier was the coolest.
ah the things we learn. LOL
so, if i understand what you are saying; this is sort of similar to doing a clarifier mod in that you dont want to be able to go all the way up to the supply voltage or all the way down to ground?
makes sense to me. thanks for the lesson.
oh, and 15minigrass, sorry i mislead you; i definitely should have posted that my info came from a schematic and not from personal experience.
LC
i have only done this to a few of my own radios back in the day, and i guess they never burnt out on me because i never turned them all the way up or all the way down.
i havent done it in years because i have no use for a variable deadkey.
back in the day (we're talking about 1988 when i was 14) i never had a linear, so i thought being able to adjust my carrier was the coolest.
ah the things we learn. LOL
so, if i understand what you are saying; this is sort of similar to doing a clarifier mod in that you dont want to be able to go all the way up to the supply voltage or all the way down to ground?
makes sense to me. thanks for the lesson.
oh, and 15minigrass, sorry i mislead you; i definitely should have posted that my info came from a schematic and not from personal experience.
LC