Ok got a few of these radios trying to get one working, story to this radio there was an outdoor PA speaker and the speaker was hit by lightning, PA Jack is removed.. originally had nothing at all no Rf power and no receive. I have replaced q51 q55 Q37, powered it up and was stuck in transmit with good power and mic would work when keyed so I replaced q33 and now have working Tx and good audio with good power. Meter is stuck at 9s units and roger beep makes a funny flicking noise when turned on doesn’t matter if the mic is keyed.. I have pulled q39 q31 q42 and tested all ok. Thanks for all your help (handy Andy) just trying to get one these guys going
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2517 no receive meter is stuck at 9s HELP
- Thread starter Justwantdahifiaudio
- Start date
At times a bias will get thru to VR9...
Else other problems may include...
AGC / S/RF Meter AMP - all located by IC1 - Quad Op amp...
D11 and D12 act like a doubler to raise enough voltage to make AGC work - Pins 5 (input) and Pin 6 (Offset / Comparator) are set up with feedback to make the S/RF meter sensitive yet linear - drives S/RF meter thru Vr1 or Vr2 depending on mode selected.
AGC is "tickled" to START to operate by a R55 270K (RX Voltage) and R50 680 ohm (S/RF Meter) - with a diode resistor piggyback to act as a trigger for activity (Diode) and provide some linear scale (Resistor) of function.
When you start to see voltages on the S/RF meter - it usually indicates board work and a bad cap or three - of the electrolytic variety. Although if power was applied and you had to replace finals - then suspect the Network output caps like C199 and C200 to have welded their plates together.(shorted)
Something else I noticed when the squelch is turned all the way up the meter drops but no sound out of the speaker... I do see the meter move when signal generator is flipped very weak but I see about 2s units
When SSB is no audio - there may be problems with the "Mode selector" it uses a set of diodes to "Steer current" to make the conversion process work. IF one or more of those steering didoes are blown - the de-conversion of SSB thru the process of heterodyne can't be completed - it needs an IF signal from the VCO to mix with the PLL's selected channel IF frequency to "decode" the information by mixing the two signals - you get audio from it.
It could also be from the age of these radios - if it's beyond 2007 (See PLL Chips' date code for an idea) then these Galaxy radios were a lot like Mr. Phelps Tape Recorder reel-to-reel - "This message will self-destruct in 5 Seconds" well after about ten years, these caps start to fail and give you goofy problems.
So you have some work on your hands...
But Wife calls - so I must answer - I will review the posts and any notes you find tomorrow.
Good luck and Good Night.
It could also be from the age of these radios - if it's beyond 2007 (See PLL Chips' date code for an idea) then these Galaxy radios were a lot like Mr. Phelps Tape Recorder reel-to-reel - "This message will self-destruct in 5 Seconds" well after about ten years, these caps start to fail and give you goofy problems.
So you have some work on your hands...
But Wife calls - so I must answer - I will review the posts and any notes you find tomorrow.
Good luck and Good Night.
Lightning damage.
A trip down the rabbit hole. Normal patterns of component failure go out the window.
You didn't say, but for the moment I'm assuming that the frequency display shows the channel frequency that it should. If NOT, that means the PLL is not locked onto the channel frequency. This will shut down transmit and receive.
Next I'd make sure the center pin of Q37 (collector) has between 9 and 10 Volts DC on it.
Next, establish that the transmit/receive switching circuit is shutting down the transmit voltage in receive mode. Collector (center pin) of Q33 should be less than 0.4 Volt in receive. Should to to 8 Volts or more while transmitting.
Center pin of Q30 should show around 8 Volts or so while receiving, and this should drop to 0.4 or less while transmitting.
There is literally no limit to the number of screwball failures a lightning strike can cause. Starting with the power supply is what we do.
73
A trip down the rabbit hole. Normal patterns of component failure go out the window.
You didn't say, but for the moment I'm assuming that the frequency display shows the channel frequency that it should. If NOT, that means the PLL is not locked onto the channel frequency. This will shut down transmit and receive.
Next I'd make sure the center pin of Q37 (collector) has between 9 and 10 Volts DC on it.
Next, establish that the transmit/receive switching circuit is shutting down the transmit voltage in receive mode. Collector (center pin) of Q33 should be less than 0.4 Volt in receive. Should to to 8 Volts or more while transmitting.
Center pin of Q30 should show around 8 Volts or so while receiving, and this should drop to 0.4 or less while transmitting.
There is literally no limit to the number of screwball failures a lightning strike can cause. Starting with the power supply is what we do.
73
Ok I have 1.5 volt on my collector on q33 I did replace this transistor and it stared transmitting.. I’ve been testing transistors since the post I’ve found q55 q51 q33 all bad... I think something is funny with q33 Base should be 8 V, collector 0 V, emitter 8 volts, I have 1.5 on my collector in rx?
The radio does transmit and make good power on am no rx audio and meter stuck at 9 s units, ssb works and meter works on ssb but no rx audio
Ok this morning I pulled diodes and found d77 bad... replaced now everything seems to work except rx audio? Meter is working talk back does not work, don’t know if that has something to do with the rx audio.. but transmit audio is good and rf power is good! Dang I’m so close
I can’t find much info on testing tda2003 5 pin audio chip? I did the ole finger test nothing no buzzing or humming? I do have voltage at one pin on the chip. And do have tx audio
Ok, time to see if the TDA even works...
The almighty "talkback" feature plays with the "Mute" pin on the audio line.
Had to grab this from another Galaxy chassis but this gives you an idea of how they treat the TDA2003 and throw straight DC to the comparator / offset / inverted pin (2) by overwhelming the audio presence with straight DC. This basically puts the chip in a switch mode.
Since I've got this schematic here. I wanted to point out the "Number values" - it's a pinout for a Stereo jack to fit a stereo plug like the headphones people used to use - note the lines of "up" contacts use two simple 1 watt resistors while the upper "V" contact is the touch/engage switch so that when you push in that headphone into the plug, it disconnects the speaker ground.
Why this comes up is if you are having problems with audio - look for "strange" rework of audio output paths like this. You said the PA jack was missing - here's a good example of how they wire one set of speakers to run internal or thru headphones or external. Either way you look at it, each time they add in an extra set of contacts - so does the multiplier effect of the amount of fun the tech will have to be dealing with sorting out issues.
Ok, to know you have TX audio helps me - you now have Mic audio and that path it uses to get to the AM Regulator is functional. But that is TX - RX is another beast...
It has several "stages" one is the PA side and is it's own Audio AMP shared with Talkback - Q42. The other is the RX side, which pipes thru and piggys with - another amp stage used for Talkback (Q42).
Q16 works SSB, AM, FM modes - RX amp "detects" audio from the AM/FM and SSB side and routes it down to here - the "Talkback" taps from the TX Mic Audio side and injects it into the TDA2003 but "mutes" the RX side - AND D75 is conducting as well as Q36 is off - and in the above graphic, R216 is the power feed "buffer" resistor sending power to mute Pin 2
Squelch - that's Q44...in the above graphic.
When you TX (NO TALKBACK), the RX side mutes, Q36 turns off and D75 applies DC bias to turn off Pin 2 using what R216 supplies - quenching audio from working Pin2 at the TDA2003.
Then you have Talkback -
Q43 then turns on, Turning on Q36 - leaving D75 low (empty of power) - Q43 powers the Talkback/PA Mic amp Q42 and its "tap" from the Mic amp line gets amplified and sent to Pin 1 of the TDA2003.
When you are using Talkback, and the Radio is in TX mode, D75 is low, no power to it, because Q36 is on thru Q43, so it is pulling power sent by R216 thru it, into ground, keeping the line low and to keep Pin 2 ACTIVE with audio. When you switch over to RX, the Talkback amp Q42 quits working - and allows Q16 to send RX audio and Q44 (Squelch) can work that RX line - which gets sent to the Audio chip (Pin 1)
That mess is in the above graphic, in your work.
The TDA chip may be blown, but to test it? All I can do is provide a PDF datasheet - but has no way to tell you how to test it...since you have no buzz, have you tried PA? If that is out of the question - then the brute force method of continuity checks and part verification may be the only means to check - step - by - step
The almighty "talkback" feature plays with the "Mute" pin on the audio line.
Had to grab this from another Galaxy chassis but this gives you an idea of how they treat the TDA2003 and throw straight DC to the comparator / offset / inverted pin (2) by overwhelming the audio presence with straight DC. This basically puts the chip in a switch mode.
Since I've got this schematic here. I wanted to point out the "Number values" - it's a pinout for a Stereo jack to fit a stereo plug like the headphones people used to use - note the lines of "up" contacts use two simple 1 watt resistors while the upper "V" contact is the touch/engage switch so that when you push in that headphone into the plug, it disconnects the speaker ground.
Why this comes up is if you are having problems with audio - look for "strange" rework of audio output paths like this. You said the PA jack was missing - here's a good example of how they wire one set of speakers to run internal or thru headphones or external. Either way you look at it, each time they add in an extra set of contacts - so does the multiplier effect of the amount of fun the tech will have to be dealing with sorting out issues.
Ok, to know you have TX audio helps me - you now have Mic audio and that path it uses to get to the AM Regulator is functional. But that is TX - RX is another beast...
It has several "stages" one is the PA side and is it's own Audio AMP shared with Talkback - Q42. The other is the RX side, which pipes thru and piggys with - another amp stage used for Talkback (Q42).
Q16 works SSB, AM, FM modes - RX amp "detects" audio from the AM/FM and SSB side and routes it down to here - the "Talkback" taps from the TX Mic Audio side and injects it into the TDA2003 but "mutes" the RX side - AND D75 is conducting as well as Q36 is off - and in the above graphic, R216 is the power feed "buffer" resistor sending power to mute Pin 2
Squelch - that's Q44...in the above graphic.
When you TX (NO TALKBACK), the RX side mutes, Q36 turns off and D75 applies DC bias to turn off Pin 2 using what R216 supplies - quenching audio from working Pin2 at the TDA2003.
Then you have Talkback -
Q43 then turns on, Turning on Q36 - leaving D75 low (empty of power) - Q43 powers the Talkback/PA Mic amp Q42 and its "tap" from the Mic amp line gets amplified and sent to Pin 1 of the TDA2003.
When you are using Talkback, and the Radio is in TX mode, D75 is low, no power to it, because Q36 is on thru Q43, so it is pulling power sent by R216 thru it, into ground, keeping the line low and to keep Pin 2 ACTIVE with audio. When you switch over to RX, the Talkback amp Q42 quits working - and allows Q16 to send RX audio and Q44 (Squelch) can work that RX line - which gets sent to the Audio chip (Pin 1)
That mess is in the above graphic, in your work.
The TDA chip may be blown, but to test it? All I can do is provide a PDF datasheet - but has no way to tell you how to test it...since you have no buzz, have you tried PA? If that is out of the question - then the brute force method of continuity checks and part verification may be the only means to check - step - by - step
I will get busy in the morning, I’m sure I can make something work for the pa jack for a test.. I’m going to recheck voltages in the morning on those transistors.. thanks again for your time
Ok got some free time this morning, I tested voltages on q36 have 5 volts at base and q42 base 4.7v ,collector 4.1v, emitter 4.2v, these two don’t seem right pulled transistors and tested good. Also tested Voltages q43 q44 q16 all tested good, as for the pa jack I tryed but don’t think I have pa.