Another hacked up dx-2547

[Hawkeye351]

Got another Galaxy DX - 2547 on the desk today. Ehhhh, should I say hacked up 2547, lol.

Issues:
SSB xmit garbled.
RF power control non functional.
Extra channel switch broken.

Evaluation:

Q39 limiter (up front, near mic amp) was gutted out. Wrong limiter to remove on a SSB radio. This would explain the garbled SSB transmit. Reinstalled Q39 with a new one.

The plug on the wires coming from the RF Power control to the board was coming unsoldered on the bottom of the board. Resoldered plug terminals back to board.

Extra channel switch is of the old CB/PA, NB/ANL, etc...switch types. It had come apart. Replaced with another switch.

Fixed all the above with no issues, realigned entire radio, reset driver/final bias', reset carrier levels, readjusted frequency counter (someone messed with it previously), tuned it out.

AM - RF Power adjusts from 1w all the way down, to 4w all the way up.
AM swing - 25w PEP, 18w peak, 14w average.
SSB - 25w PEP, 18w peak.

Locals say it's extremely loud, but yet still crystal clear.

These single final rigs seem to always be louder and drive amps better than dual finals. Hmmm....

 

[whiteastro]

Got another Galaxy DX - 2547 on the desk today. Ehhhh, should I say hacked up 2547, lol.

Issues:
SSB xmit garbled.
RF power control non functional.
Extra channel switch broken.

Evaluation:

Q39 limiter (up front, near mic amp) was gutted out. Wrong limiter to remove on a SSB radio. This would explain the garbled SSB transmit. Reinstalled Q39 with a new one.

The plug on the wires coming from the RF Power control to the board was coming unsoldered on the bottom of the board. Resoldered plug terminals back to board.

Extra channel switch is of the old CB/PA, NB/ANL, etc...switch types. It had come apart. Replaced with another switch.

Fixed all the above with no issues, realigned entire radio, reset driver/final bias', reset carrier levels, readjusted frequency counter (someone messed with it previously), tuned it out.

AM - RF Power adjusts from 1w all the way down, to 4w all the way up.
AM swing - 25w PEP, 18w peak, 14w average.
SSB - 25w PEP, 18w peak.

Locals say it's extremely loud, but yet still crystal clear.

These single final rigs seem to always be louder and drive amps better than dual finals. Hmmm....

I'm glad to hear you got it straightened out and to hear the Flowers you gave it. I have one of those radios I bought new from Bob's CB Shop and is unmolested except he unlocked the clarifier when I bought it new. Seeing it is new I think I'd like to get some Mods done to the receive and add extra channels because it is likely to last me as long as I'm going to be around at my age. End of my Rant !

Good luck with yours !

 

[Hawkeye351]

I'm glad to hear you got it straightened out and to hear the Flowers you gave it. I have one of those radios I bought new from Bob's CB Shop and is unmolested except he unlocked the clarifier when I bought it new. Seeing it is new I think I'd like to get some Mods done to the receive and add extra channels because it is likely to last me as long as I'm going to be around at my age. End of my Rant !

Good luck with yours !

I don't use any receive mods. A complete alignment is all that's needed to help with receive, most vital adjustments are the VCO voltage, VCO buffer(s), PLL offset oscillators and the carrier offset oscillators. After adjusting those, the receive usually turns out a lot better than before. Pay close attention when adjusting the VCO buffer(s), this is where the audio sensitivity for both receive and transmit comes into play. Usually you max the buffer(s) out for maximum sensitivity. After this adjustment, the receiver sensitivity picks up a lot better, even on weak signals. For the transmit side of the buffer(s) it will make your mic audio so sensitive that even a whisper will drive the watts up to maximum swing, every syllable/word/vowel will drive the wattage to the maximum swing with no drop backs on certain words/syllables, etc...
Both the oscillator adjustments will bring all carrier frequencies in focus and create the proper frequencies from the synthesizer circuit.

Nomad, shockwave, Andy, etc...can explain it better than I can.

You can do it, just have confidence in yourself, patience and the right equipment. And if you have questions, then these guys on this site are the best place to get the answers and help from.

 

[doffo]

Got another Galaxy DX - 2547 on the desk today. Ehhhh, should I say hacked up 2547, lol.

Issues:
SSB xmit garbled.
RF power control non functional.
Extra channel switch broken.

Evaluation:

Q39 limiter (up front, near mic amp) was gutted out. Wrong limiter to remove on a SSB radio. This would explain the garbled SSB transmit. Reinstalled Q39 with a new one.

The plug on the wires coming from the RF Power control to the board was coming unsoldered on the bottom of the board. Resoldered plug terminals back to board.

Extra channel switch is of the old CB/PA, NB/ANL, etc...switch types. It had come apart. Replaced with another switch.

Fixed all the above with no issues, realigned entire radio, reset driver/final bias', reset carrier levels, readjusted frequency counter (someone messed with it previously), tuned it out.

AM - RF Power adjusts from 1w all the way down, to 4w all the way up.
AM swing - 25w PEP, 18w peak, 14w average.
SSB - 25w PEP, 18w peak.

Locals say it's extremely loud, but yet still crystal clear.

These single final rigs seem to always be louder and drive amps better than dual finals. Hmmm....

You do awesome fixing radios. And here I am just turning down the ALC on my radios to about 10ish watts so I feel like im trying to save my generic RM Italy 203P from going up in smoke.

Have had that thing since 2012 and still just as good as it was when I bought it.

 

[whiteastro]

I don't use any receive mods. A complete alignment is all that's needed to help with receive, most vital adjustments are the VCO voltage, VCO buffer(s), PLL offset oscillators and the carrier offset oscillators. After adjusting those, the receive usually turns out a lot better than before. Pay close attention when adjusting the VCO buffer(s), this is where the audio sensitivity for both receive and transmit comes into play. Usually you max the buffer(s) out for maximum sensitivity. After this adjustment, the receiver sensitivity picks up a lot better, even on weak signals. For the transmit side of the buffer(s) it will make your mic audio so sensitive that even a whisper will drive the watts up to maximum swing, every syllable/word/vowel will drive the wattage to the maximum swing with no drop backs on certain words/syllables, etc...
Both the oscillator adjustments will bring all carrier frequencies in focus and create the proper frequencies from the synthesizer circuit.

Nomad, shockwave, Andy, etc...can explain it better than I can.

You can do it, just have confidence in yourself, patience and the right equipment. And if you have questions, then these guys on this site are the best place to get the answers and help from.

Thanks for the info and I think I will print it out so I can discuss it with who ever I choose to do it because I don't have the proper training or equipment to take on such a project. I'm just a Old Mechanic who enjoys working on my bucket list. ( Talk a Little Skip ) My thoughts were those ShotKey diodes and a VFO with maybe FM added. But some claim changing those Diodes don't help. Now's the time to gather all the info before I make my mistakes. LOL

Thanks PS My alignment seems OK !

 

[SuperLid]

Thanks for the info and I think I will print it out so I can discuss it with who ever I choose to do it because I don't have the proper training or equipment to take on such a project. I'm just a Old Mechanic who enjoys working on my bucket list. ( Talk a Little Skip ) My thoughts were those ShotKey diodes and a VFO with maybe FM added. But some claim changing those Diodes don't help. Now's the time to gather all the info before I make my mistakes. LOL

Thanks PS My alignment seems OK !

I find that germanium diodes work better and usually install them, when they are not there.

 

[whiteastro]

I find that germanium diodes work better and usually install them, when they are not there.

I've read before what your saying about the germanium diodes and was keeping that in my mind also. Just wondering how those diodes coupled with Hawkeye 351 fix would end up working together. Be nice if it had my Cobra 2000 receive or better. Yeah Yeah I know ( I want My Cake & Eat it Too ) LOL

 

[nomadradio]

I remember a guy on the old CB Tricks forum who asked about a radio with weak receive. Naturally he got several suggestions that included the alignment procedure.

His response was that this advice must be a conspiracy amongst all these tech types, to get people to bring their repairs to a shop.

Don't remember if he figured out that alignment is a diagnostic tool that can tell you where to look for a failure. Or can just fix the problem in some cases.

Good job!

73

 

[nomadradio]

turning down the ALC on my radios

Back in the 70s I stayed away from peak-reading meters. Couldn't afford a trustworthy 'active' peak meter. Just used my trusty Bird 43, a meter that is totally stingy about "swing". A 'scope was all I needed for peak readings. A little arithmetic shows you what the peak power really is. No rocket science, just a square-law comparison on your calculator.

SIdeband operators would express disappointment with average-reading wattmeter readings on their radios, and turn up the ALC. And then they would listen to it and bring it to me.

I would key the radio into the dummy load, and modulate the radio with the ALC turned way too high. The Bird meter would show 12 or 15 Watts and the 'scope revealed a flattened waveform. I would turn the ALC down until it reached a threshold point where the average meter reading plummeted to about half what it showed before. Looked like it dove off a cliff. But now the 'scope would reveal an actual voice waveform, with nice spiky peaks and a MUCH smoother sound. The customer could see that the 'scope showed those peaks still reaching the same level they did when it was flat topping.

I was amused by the customer's reaction when he saw the meter reading drop in half. I would get a look like I had shot his dog until he HEARD the difference.

73

 

[doffo]

Back in the 70s I stayed away from peak-reading meters. Couldn't afford a trustworthy 'active' peak meter. Just used my trusty Bird 43, a meter that is totally stingy about "swing". A 'scope was all I needed for peak readings. A little arithmetic shows you what the peak power really is. No rocket science, just a square-law comparison on your calculator.

SIdeband operators would express disappointment with average-reading wattmeter readings on their radios, and turn up the ALC. And then they would listen to it and bring it to me.

I would key the radio into the dummy load, and modulate the radio with the ALC turned way too high. The Bird meter would show 12 or 15 Watts and the 'scope revealed a flattened waveform. I would turn the ALC down until it reached a threshold point where the average meter reading plummeted to about half what it showed before. Looked like it dove off a cliff. But now the 'scope would reveal an actual voice waveform, with nice spiky peaks and a MUCH smoother sound. The customer could see that the 'scope showed those peaks still reaching the same level they did when it was flat topping.

I was amused by the customer's reaction when he saw the meter reading drop in half. I would get a look like I had shot his dog until he HEARD the difference.

73

That is good to know. For sure I would need a better meter to at least get a better idea. But I suppose as long as I turned it down and not up, it shouldn't cause too much trouble.

 

[Shadetree Mechanic]

Before I got a scope, I would adjust my modulation by listening to my transmit audio. I use a second radio with no antenna and headphones as a station monitor. While talking into the microphone in a normal voice, I slowly turn up the modulation until it starts to sound raspy, then turn it back down a little. When I got a scope, I could also see what the sound was like, and there is a point where you can tell it's starting to look bad, but still sounds good. I also use this for setting microphone level, and do a quick check every time I power up, just to make sure nothing changed.