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2517 no receive meter is stuck at 9s HELP
- Thread starter Justwantdahifiaudio
- Start date
This may be a message from hell, but remember - I'm trying to answer these condensed into one list...
Ok, firstly...
Ok, we kinda addressed this - so I'll stop here and reinterate that there are several events that have to occur for you to be in TX mode. So you may have a flakey transistor in the RX side - which may affect your ability to release the mute feature on the audio chip...
How the 4558 works is...one side Pin 1,2 and 3 handle the Mic amp - it's all it does...
The complex part is how it uses PLL LOCK, TX Mode, and POWER GOOD all at once to turn off RX and turn on TX.
Q 30 and Q33 are PNP
Q32 not on the schematic, but if you can look for X4 and 3 coil cans...
There it is...
Check that part!
Ok means that at least it is in lock, the PLL says ok to transmit and there is enough power from the on-board regulator to hold up and stay stable...else if the power had been too low, it would immediately knock it down...
Check your onboard - Green / Red LED - make sure it's does change when you switch from RX to TX...
Again Q32 is a undocumentated - meaning it's there but not on the schematic - but R211 and R212 feed it...
It holds up the X4 VCO...if anything goes wrong - it's down...
Ok, again -- part of the RX side is to power D75 - but it uses the 8 volts from the REGULATOR - if you're not getting 8 volts - something is wrong.
Q31 drives Q30 to turn on RX (Q32 is involved...)
Q33 turn on power (shunts across from 8V regulator) to power D75 and if Q36 is not on, MUTES Audio.
But if Q32 is bad, you won't get audio anyways...
Ok, firstly...
Ok, we kinda addressed this - so I'll stop here and reinterate that there are several events that have to occur for you to be in TX mode. So you may have a flakey transistor in the RX side - which may affect your ability to release the mute feature on the audio chip...
How the 4558 works is...one side Pin 1,2 and 3 handle the Mic amp - it's all it does...
The complex part is how it uses PLL LOCK, TX Mode, and POWER GOOD all at once to turn off RX and turn on TX.
Q 30 and Q33 are PNP
Q32 not on the schematic, but if you can look for X4 and 3 coil cans...
There it is...
Check that part!
Ok means that at least it is in lock, the PLL says ok to transmit and there is enough power from the on-board regulator to hold up and stay stable...else if the power had been too low, it would immediately knock it down...
Check your onboard - Green / Red LED - make sure it's does change when you switch from RX to TX...
Again Q32 is a undocumentated - meaning it's there but not on the schematic - but R211 and R212 feed it...
It holds up the X4 VCO...if anything goes wrong - it's down...
Ok, again -- part of the RX side is to power D75 - but it uses the 8 volts from the REGULATOR - if you're not getting 8 volts - something is wrong.
Q31 drives Q30 to turn on RX (Q32 is involved...)
Q33 turn on power (shunts across from 8V regulator) to power D75 and if Q36 is not on, MUTES Audio.
But if Q32 is bad, you won't get audio anyways...
4558's normally don't go out, because of what they are.
They CAN fail, because of the parts around them - make them behave erratically and then they sink too much current and fail - but not on their own - the parts around them cause this.
How is the 8 Volt regulator doing?
Pin 4 of the 4558 is Ground, while Pin 8 is the 8 volts.
Here's a trick someone taught me a while ago,
SCOPE pin 8 - or at least put a good quality meter on it - Pin 8 to Pin 4 - just so you can see what the chips being fed. IF it's not being fed well, like it's current starved, either the Regulator supplying this is faulty, or the parts around it, using the 4558 outputs are causing this.
Yes, it doesn't hurt to swap in a spare known good 4558 to remove the possibility - but then - I've seen boards take out the next one, that one, and the other one, after the other two - because the parts they are supposed to operate are sending MORE power than the 8 volt line - or if it was getting 5 volts in power because of another part was pulling down the line that was feeding that 4558, you just zapped the chips input pins and it's shot...start over with another...
They CAN fail, because of the parts around them - make them behave erratically and then they sink too much current and fail - but not on their own - the parts around them cause this.
How is the 8 Volt regulator doing?
Pin 4 of the 4558 is Ground, while Pin 8 is the 8 volts.
Here's a trick someone taught me a while ago,
SCOPE pin 8 - or at least put a good quality meter on it - Pin 8 to Pin 4 - just so you can see what the chips being fed. IF it's not being fed well, like it's current starved, either the Regulator supplying this is faulty, or the parts around it, using the 4558 outputs are causing this.
Yes, it doesn't hurt to swap in a spare known good 4558 to remove the possibility - but then - I've seen boards take out the next one, that one, and the other one, after the other two - because the parts they are supposed to operate are sending MORE power than the 8 volt line - or if it was getting 5 volts in power because of another part was pulling down the line that was feeding that 4558, you just zapped the chips input pins and it's shot...start over with another...
I hope you are doing continuity and voltage checks too...
Q32 being in proximity to the X4 and it's power feeds, yes, you need to check, verify it's getting power
An example of Talkback installed hopefully correctly for you to review.
I do know that there is an 8 votl "rail" that goes along the front of the board - if someone accidentally shorted out that trace to the side panel - it can pop like a fuse...
Q32 being in proximity to the X4 and it's power feeds, yes, you need to check, verify it's getting power
An example of Talkback installed hopefully correctly for you to review.
I do know that there is an 8 votl "rail" that goes along the front of the board - if someone accidentally shorted out that trace to the side panel - it can pop like a fuse...
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This may be mode dependent, AM and FM versus SSB.
R211 and R212 - shown above, tell the story.
It is supposed to turn off Q32 if things aren't right.
Now, to help - Q30 and Q31 that "pair" one, an NPN drives another PNP to shove power into the RX line. IT uses a 5.1 volt Zener to protect it's input from excessive drive level output from the 4558 chip. So it won't toggle on, unless the power is good because it's higher in voltage to turn on, HAS to be there TO TURN ON the NPN thru that Zener.
IF something is keeping the Regulator from producing enough power, the RX side won't kick in even at idle because there is not enough power to pass thru the "zener" to avalanche and turn on the base.
So again - I will say this and although it sounds repetitive - it's for that reason...
Check and do continuity checks on those traces. When you have catastrophic failures like lightning (per their claim) you have several issues if dead traces because the parts that steer and buffer, protected the sensitive stuff, but in doing so, passed the current into the break - and the subsequent short burnt up the trace.
Found a lot of complex issues got solved from blown traces getting fixed because of their (Galaxy's) incessant desire to be cutting edge in multi point routing tap traces, but also in GUTTING edge technology layouts from using such thin trace methods - would have been easier to lessen the loading thru branch versus a trip to grandmas' house thru the woods - too many wolfs in sheep's clothing in there - especially when it comes to echo...
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