When keying radio light turns yellow instead of red..no receive in speaker, headphones,ext speaker but meter is receiving. no transmit
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Galaxy 2547
- Thread starter tom Everhart
- Start date
Check the mic jack board for blobs (shorts)on the solder side. It's happened to me more than once and even on a brand new radio.
The dual-color red/green LED should be green in receive mode, and red when you key the mike.
If the green stays lighted and both it and the red are shining at the same time, you get yellow.
The transmit/receive switching circuit is falling down, and forgetting to turn off the receiver when you key the mike.
The center leg (collector) of transistor Q30 should drop to zero Volts DC, or close to it when you key the mike. Should show about 8 Volts when you release the mike. If it won't drop to zero when you transmit, next question is why. And if it won't come all the way up to 8 Volts or more in receive mode, this could cause receiver trouble.
Q33 is the transmit-side transistor. The center leg (collector) should show close to zero Volts while receiving, and around 8 Volts DC when transmitting.
Q30 depends on Q31 and D70 to function like it should. If Q30 tests okay, Q31 and D70 should get checked next.
73
If the green stays lighted and both it and the red are shining at the same time, you get yellow.
The transmit/receive switching circuit is falling down, and forgetting to turn off the receiver when you key the mike.
The center leg (collector) of transistor Q30 should drop to zero Volts DC, or close to it when you key the mike. Should show about 8 Volts when you release the mike. If it won't drop to zero when you transmit, next question is why. And if it won't come all the way up to 8 Volts or more in receive mode, this could cause receiver trouble.
Q33 is the transmit-side transistor. The center leg (collector) should show close to zero Volts while receiving, and around 8 Volts DC when transmitting.
Q30 depends on Q31 and D70 to function like it should. If Q30 tests okay, Q31 and D70 should get checked next.
73
i check them this weekend..i got a 949 at work ..bringing it home to compare voltages..thanks for reply.
Thanks for the reply, looking for voltage chart. no luck .. i guess i can compare my galaxy 949 for voltage. i can check those parts over weekend. this job thing gets in the way..again thanks for the help Mr Nomadradio.
Q30 is not dropping out .stays on 8 volts..guess i need to replace it and see if it change things.Q33 is working.Q31 is only showing 4 volts on key up center leg
Lets start from the comparator. Pin 7 of the 4558 goes high during RX and low during TX. Verify that first.
That high or low signal sees two diodes, D70 to turn off RX and D71 to turn on TX.
TRANSMIT
With the comparator output low, Q33 can turn on because the control voltage is low enough to forward bias the PNP transistor and the 3-junction KB362 diode package.
At the same time, that low voltage cannot forward bias the zener D70, so Q31 stays off keeping Q30 off too.
RECEIVE
The opposite happens. The comparator goes high, D70 (zener) conducts and turns on Q31, and that pulls down the base of Q30 which in turn brings the collector of Q30 (the RX rail) high.
At the same time, that high level comparator signal is so high that it cannot forward bias all three junctions of D71 (plus the b-e junction of Q33) so Q33 is thus turned off.
My drunken (but this time thought through) assessment is:
I don't think Q30 is the problem, because with 4v at the collector of Q31, Q30 would obviously be driven into conduction keeping the RX light on. Looks to me that Q30 is just fine. If I had to gess, i would say that D70 blew and is leaking current and the 4v at the collector of Q31 is a result of te divider formed by R208 and R210. Long story short, I think all yur transistors are just fine and that you need to look at that 5.1v zener diode!
That high or low signal sees two diodes, D70 to turn off RX and D71 to turn on TX.
TRANSMIT
With the comparator output low, Q33 can turn on because the control voltage is low enough to forward bias the PNP transistor and the 3-junction KB362 diode package.
At the same time, that low voltage cannot forward bias the zener D70, so Q31 stays off keeping Q30 off too.
RECEIVE
The opposite happens. The comparator goes high, D70 (zener) conducts and turns on Q31, and that pulls down the base of Q30 which in turn brings the collector of Q30 (the RX rail) high.
At the same time, that high level comparator signal is so high that it cannot forward bias all three junctions of D71 (plus the b-e junction of Q33) so Q33 is thus turned off.
My drunken (but this time thought through) assessment is:
I don't think Q30 is the problem, because with 4v at the collector of Q31, Q30 would obviously be driven into conduction keeping the RX light on. Looks to me that Q30 is just fine. If I had to gess, i would say that D70 blew and is leaking current and the 4v at the collector of Q31 is a result of te divider formed by R208 and R210. Long story short, I think all yur transistors are just fine and that you need to look at that 5.1v zener diode!
thanks again for all your input, I"ll start looking at diodes when time permits.
As a secondary note, make sure when you've opened the clarifier (that control PCB) the Fixed voltage feed needs to be 8V from the PLL side - not that it matters.
Just saying - any mods that have been done to it, are possibly why the "Yellow" is not True Red - or True Green - because of a mod that was done, has to be undone.
This radio also uses a lot of diodes for "Steering" - so the concept of how the RX TX works dates back to the Galaxy 3600 series boards, this board is no different, just that the part numbers is different. The Circuit concept is the same.
The PLL has a pin this concept works with - Pin 6 of the RCI8719 - when it's high - everything is ok, when it low, is when things go quiet.
This affect the 4558 chips Pin 5,6,7 and 8 side - with Pin 8 having the same power level as the 8Volt Regulator output at Q37. (Pin 8 is the + Power side of the chip - Ground is Pin 4)
Basically the 4558 chips' Pin 6 is held to "mid point" (approx 3~4V ) at a given "load of impedance" (15K / 10K) while Pin 5 is held to float at a higher impedance (100K / 100K) and monitors Pin 7 output (470K) - just enough to make it a "logic 1".
This makes it a "go" to help open the RX/TX Switch, which in reality- is also set up to look at the PLL for "In or Out" of lock using D141 - from the Squelch Amp side of IC1 - when it's in Lock - the state of the squelch operates normally - when the PLL is out of lock D141 conducts power out of the Squelch "balancer" (threshold adjust) forcing the Squelch to engage - quieting the Receiver
When the PLL is out of lock, D60 sends power out of Pin 6 - dropping the voltage on it's pin down to a "logic 0" state. This flips the output of Pin 7 and toggles the NPN and PNP arrangement to twist the lines it powers thru the 8V regulator. This keeps the thing from going beyond RX mode "Green LED"
When you try to TX and the PLL is out of lock - the LED goes out - no RED LED nor is Green - for when the signal that toggles the TX side, is enough to turn off RX first, does so - but Since the PLL Pin 6 is out of lock, Pin 6 of the 4558 is keeping the system shut down. This also keeps the GREEN LED off.
So when the Green LED and RED LED are on - the switching circuit is suspect, but you will need to look at the Voltages at the 4558's 5, 6, 7 and 8 Pins.
You'll need to keep you ducks in a row on this...
So note Pin 6 is high or above 3V when the PLL is in LOCK
Pin 7 is HIGH in RX, forcing PNP to go LOW when in RX - turns off TX lines unless the Zener blew up...
Pin 5 "monitors" Pin 7 - Then you TX, Pin 3 MIC is grounded - so Pin 5 drops - this "inverts" and makes Pin 7 go HIGH - which makes the Zener conduct and turn on the TX side.
So for RX and TX to be on at once - means something is keeping Q30 enabled all the time - it's driven by 2SA945 Q31. Q31 and Q30 invert - so between the two - one isn't.
But too, keep an eye on your frequency counter - Q62 - it looks to see if conditions are stable. Goofy counter, means goofy RX/TX switch can be affected too.
Just saying - any mods that have been done to it, are possibly why the "Yellow" is not True Red - or True Green - because of a mod that was done, has to be undone.
This radio also uses a lot of diodes for "Steering" - so the concept of how the RX TX works dates back to the Galaxy 3600 series boards, this board is no different, just that the part numbers is different. The Circuit concept is the same.
The PLL has a pin this concept works with - Pin 6 of the RCI8719 - when it's high - everything is ok, when it low, is when things go quiet.
This affect the 4558 chips Pin 5,6,7 and 8 side - with Pin 8 having the same power level as the 8Volt Regulator output at Q37. (Pin 8 is the + Power side of the chip - Ground is Pin 4)
Basically the 4558 chips' Pin 6 is held to "mid point" (approx 3~4V ) at a given "load of impedance" (15K / 10K) while Pin 5 is held to float at a higher impedance (100K / 100K) and monitors Pin 7 output (470K) - just enough to make it a "logic 1".
This makes it a "go" to help open the RX/TX Switch, which in reality- is also set up to look at the PLL for "In or Out" of lock using D141 - from the Squelch Amp side of IC1 - when it's in Lock - the state of the squelch operates normally - when the PLL is out of lock D141 conducts power out of the Squelch "balancer" (threshold adjust) forcing the Squelch to engage - quieting the Receiver
When the PLL is out of lock, D60 sends power out of Pin 6 - dropping the voltage on it's pin down to a "logic 0" state. This flips the output of Pin 7 and toggles the NPN and PNP arrangement to twist the lines it powers thru the 8V regulator. This keeps the thing from going beyond RX mode "Green LED"
When you try to TX and the PLL is out of lock - the LED goes out - no RED LED nor is Green - for when the signal that toggles the TX side, is enough to turn off RX first, does so - but Since the PLL Pin 6 is out of lock, Pin 6 of the 4558 is keeping the system shut down. This also keeps the GREEN LED off.
So when the Green LED and RED LED are on - the switching circuit is suspect, but you will need to look at the Voltages at the 4558's 5, 6, 7 and 8 Pins.
You'll need to keep you ducks in a row on this...
So note Pin 6 is high or above 3V when the PLL is in LOCK
Pin 7 is HIGH in RX, forcing PNP to go LOW when in RX - turns off TX lines unless the Zener blew up...
Pin 5 "monitors" Pin 7 - Then you TX, Pin 3 MIC is grounded - so Pin 5 drops - this "inverts" and makes Pin 7 go HIGH - which makes the Zener conduct and turn on the TX side.
So for RX and TX to be on at once - means something is keeping Q30 enabled all the time - it's driven by 2SA945 Q31. Q31 and Q30 invert - so between the two - one isn't.
But too, keep an eye on your frequency counter - Q62 - it looks to see if conditions are stable. Goofy counter, means goofy RX/TX switch can be affected too.
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Figures I got to explain this...
Sounds confusing - yes it is, but in the circuit - the Pin 7 - SINKS current - meaning when I say high - lets power flow into it...letting the transistors' base it has connected to it - turn on.
In this instance Q31 and Q33 both are turned on, but remember NPN inverts - while PNP needs inverted with respect to NPN to operate - inverted.
So with Q31 and Q33 on, and PLL Pin 6 in LOCK - Q32 turns off and this works, which is why I made up the "see-saw" graphic to help understand the forcing RX level versus the Sensitivity TX side would have - in changes to PLL Pin 6 condition.
This is due to the nature of single ended power supplies - the Op-Amp inputs needs a working pull down and pull up network to "lift" the signal detection and it's threshold is fixed, using biasing schemes like this.
So Pin 6 PLL "check" for Go-no go condition - is weighted differently than the MIC Pin 3 detect used on Pin 5. Since Pin 5 is the inverted input - this also looks at Pin 7 condition - with Pin 6 in the balance...
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