Hey Guys,
I'm working on what I believe is a cybernet board: PTBM146AOX with a LC7131 PLL. This radio started my interest in trying to repair radios a year ago. Bought off ebay as untested of course
Unfortunately I didn't have the soldering skills at the time and made a lot of beginner mistakes working on it fixing dry solder joints and replacing a few caps, wrecked a few tracks, bridged the odd thing etc.
At the time I didn't have the schematic either which really added to the confusion. It was a humbling experience and I put the radio away and spent a month training myself on circuit board soldering techniques etc and bought solder sucker etc. I've picked my game up and always understand the board electrically (whats connected to what) as as well as taking pics before working on it. Theirs no guessing (cringe....) anymore.
This board seems a bit rare , but not special, and no-one is talking about them on the net.
NOTE: Right now I'm focusing on getting the RX back 100% before worrying about the TX side (both driver and final tested fine out of circuit early on before I stuffed up the RX)
Original state: Received in AM and SSB with low volume but with warm up volume would reach normal levels and occasionally fading in/out once warm. Radio was on frequency. No TX output but switched between RX/TX fine.
Current state:
The radio had full volume on AM RX but very low volume on SSB. I believe this was due to my early stuffs up. ie I had lost ssb volume.
After re soldering some areas yesterday I've worked on using the schematic I lost AM all together (no volume, and now no RX light AM mode) but now have SSB receive at a higher volume but still not as loud as it should be, ie volume is at maximum for what I would call half volume. The SSB receieve is better (higher volume) after I found some dry solder joints under a metal plate solder side of board that I think was the back of the VCO block circuit but those dry solder joints werent part of the original work) as well as fixing a lifted track on Q16 (previous owner had glued track back on) Was listening to channel 35 DX skip yesterday while checking voltages - its on frequency.
btw, I believe the mode selector switch is working fine and that its something I've done.
I have a few questions:
- if the RX light is out on AM, does that mean the PLL is out of lock on AM?
- Should I have R75, R78, R141 and J20 tied together?. What is J20? (see attached pic) I can't find R141 or J20 on the schematic thats at the end of the user manual I've attached. I had accidently bridged the earth of C106 thats nearby to the above resistor grouping. Maybe there was a knock on effect upstream/downstream and I damaged something?
I have few more questions/pics/areas of concern but I'm keen to work through the above first. Schematic is at end of user manaual attached. I wish it was of better quality but is the only version on the internet I can find.
Any help/direction is appreciated.
Regards,
Rob
I'm working on what I believe is a cybernet board: PTBM146AOX with a LC7131 PLL. This radio started my interest in trying to repair radios a year ago. Bought off ebay as untested of course
Unfortunately I didn't have the soldering skills at the time and made a lot of beginner mistakes working on it fixing dry solder joints and replacing a few caps, wrecked a few tracks, bridged the odd thing etc.At the time I didn't have the schematic either which really added to the confusion. It was a humbling experience and I put the radio away and spent a month training myself on circuit board soldering techniques etc and bought solder sucker etc. I've picked my game up and always understand the board electrically (whats connected to what) as as well as taking pics before working on it. Theirs no guessing (cringe....) anymore.
This board seems a bit rare , but not special, and no-one is talking about them on the net.
NOTE: Right now I'm focusing on getting the RX back 100% before worrying about the TX side (both driver and final tested fine out of circuit early on before I stuffed up the RX)
Original state: Received in AM and SSB with low volume but with warm up volume would reach normal levels and occasionally fading in/out once warm. Radio was on frequency. No TX output but switched between RX/TX fine.
Current state:
The radio had full volume on AM RX but very low volume on SSB. I believe this was due to my early stuffs up. ie I had lost ssb volume.
After re soldering some areas yesterday I've worked on using the schematic I lost AM all together (no volume, and now no RX light AM mode) but now have SSB receive at a higher volume but still not as loud as it should be, ie volume is at maximum for what I would call half volume. The SSB receieve is better (higher volume) after I found some dry solder joints under a metal plate solder side of board that I think was the back of the VCO block circuit but those dry solder joints werent part of the original work) as well as fixing a lifted track on Q16 (previous owner had glued track back on) Was listening to channel 35 DX skip yesterday while checking voltages - its on frequency.
btw, I believe the mode selector switch is working fine and that its something I've done.
I have a few questions:
- if the RX light is out on AM, does that mean the PLL is out of lock on AM?
- Should I have R75, R78, R141 and J20 tied together?. What is J20? (see attached pic) I can't find R141 or J20 on the schematic thats at the end of the user manual I've attached. I had accidently bridged the earth of C106 thats nearby to the above resistor grouping. Maybe there was a knock on effect upstream/downstream and I damaged something?
I have few more questions/pics/areas of concern but I'm keen to work through the above first. Schematic is at end of user manaual attached. I wish it was of better quality but is the only version on the internet I can find.
Any help/direction is appreciated.
Regards,
Rob
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