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2510 Again
- Thread starter kopcicle
- Start date
Had a boo-boo decades ago with this model. It was powered up with the CPU/Synthesizer tray pivoted up to expose the solder side of the main pcb. But with the two screws for the front slots removed.
Bad idea. The tray flopped down onto the solder side of the main circuit board. The two front screws would have limited the travel, and the metal tray wouldn't have touched the main circuit board's solder pads. But they had been removed.
With the power on. Shorted a few things in that 10.695 oscillator to ground. Blew out all three of the slug-tuned trimmer coils, some diodes and RF chokes.
Bummer. Worked fine once I replaced enough blown stuff.
Haven't made that error since, not even once. But if a brief short to ground has screwed up the switching circuit that selects only one slug-tuned coil at a time, it will prevent you from getting the proper adjustment.
Simple test is to see if each slug makes a difference when you turn it **ONLY** for that mode.Turning the slug in any of the other modes (except for AM/FM/CW overlap) should not change the crystal's frequency by very much.
If it does, you have too many of those slugs active at once. Slugs won't turn far enough like that. Sorting out which switching diode(s) and/or RF chokes are blown would be next.
73
Bad idea. The tray flopped down onto the solder side of the main circuit board. The two front screws would have limited the travel, and the metal tray wouldn't have touched the main circuit board's solder pads. But they had been removed.
With the power on. Shorted a few things in that 10.695 oscillator to ground. Blew out all three of the slug-tuned trimmer coils, some diodes and RF chokes.
Bummer. Worked fine once I replaced enough blown stuff.
Haven't made that error since, not even once. But if a brief short to ground has screwed up the switching circuit that selects only one slug-tuned coil at a time, it will prevent you from getting the proper adjustment.
Simple test is to see if each slug makes a difference when you turn it **ONLY** for that mode.Turning the slug in any of the other modes (except for AM/FM/CW overlap) should not change the crystal's frequency by very much.
If it does, you have too many of those slugs active at once. Slugs won't turn far enough like that. Sorting out which switching diode(s) and/or RF chokes are blown would be next.
73
Nomad You are not the only one that has done that. I left the two front screws in the CPU board tray and flipped it up to check something and burnt a trace. Radio worked after the fix but I was hurt worse than the radio. Pride that is. I will never do that again. I hate learning by my mistakes.
...ever run across a 470uh inductor partially fubar ?
That will be next since I have no shortage of known working examples here
*ever try and find the OEM replacement ? Yes I have a full parts list and description.
Still looking for a replacement knob.
That will be next since I have no shortage of known working examples here
*ever try and find the OEM replacement ? Yes I have a full parts list and description.
Still looking for a replacement knob.
meanwhile back at the PB-111 main board ...
I inserted the replacement audio chip into the radio with the corrupted audio and as is typical for such repairs I didn't fix it. Taking the original out I placed it in the radio with no chip at all and immediately had another working radio. So back to the distorted audio radio and start taking readings with the DC coupled O scope. Then back to the freshly restored radio and promptly short pin one and two ....
Word to the not so wise, one is none, two is some, three is better. The destroyed chip was replaced in just 10 minutes and back to the distorted chassis. I had bought three NTE7000's just in case.
I looked at the schematic and data sheet for a good long while and began a systematic "substitution (shotgun?) repair. The second electrolytic I replaced fixed it Again for those following along at home it was C97.
I'm still having trouble with the standard alignment procedure. Specifically getting the correct frequencies out of the computer board so that adjustment of the TX oscillator falls at reasonable insertion points. Get it right and it sounds great . Miss and the outgoing signal sounds tight and tinny or more noise passes than signal. I suspect a bit of omission in the manual if not outright mistakes. I've been driven back to a calibrated step attenuator and a 10.695 pierce oscillator in order to find the actual filter pass band instead of the published figure. Old schoolers can have a laugh here. The 5U4 shorted and took the transformer with it. I suppose I should eventually join the present century and get a syn/func/gen that has some functionality. One of my obsessive traits at the bench is that when I switch between LSB and USB there can be no difference in received audio tone/passband. Same goes for transmit. I've been reduced to using my phone as an audio generator and an "L"pad in the mic line for attenuation. Use what you have .
Last but not least is the curiously complex but ineffective noise blanker in these radios. So much has been written that sorting fact from static is a challenge. I'll have the advantage of being able to do a back to back to back to back test of the modifications using a different recipe for each example. That detail is for another time .
Still looking for a replacement knob. Anyone have a parts radio laying around? I seem to have run out . The ones I thought were irrevocably dead are now working :-(
...and so it goes
I inserted the replacement audio chip into the radio with the corrupted audio and as is typical for such repairs I didn't fix it. Taking the original out I placed it in the radio with no chip at all and immediately had another working radio. So back to the distorted audio radio and start taking readings with the DC coupled O scope. Then back to the freshly restored radio and promptly short pin one and two ....
Word to the not so wise, one is none, two is some, three is better. The destroyed chip was replaced in just 10 minutes and back to the distorted chassis. I had bought three NTE7000's just in case.
I looked at the schematic and data sheet for a good long while and began a systematic "substitution (shotgun?) repair. The second electrolytic I replaced fixed it Again for those following along at home it was C97.
I'm still having trouble with the standard alignment procedure. Specifically getting the correct frequencies out of the computer board so that adjustment of the TX oscillator falls at reasonable insertion points. Get it right and it sounds great . Miss and the outgoing signal sounds tight and tinny or more noise passes than signal. I suspect a bit of omission in the manual if not outright mistakes. I've been driven back to a calibrated step attenuator and a 10.695 pierce oscillator in order to find the actual filter pass band instead of the published figure. Old schoolers can have a laugh here. The 5U4 shorted and took the transformer with it. I suppose I should eventually join the present century and get a syn/func/gen that has some functionality. One of my obsessive traits at the bench is that when I switch between LSB and USB there can be no difference in received audio tone/passband. Same goes for transmit. I've been reduced to using my phone as an audio generator and an "L"pad in the mic line for attenuation. Use what you have .
Last but not least is the curiously complex but ineffective noise blanker in these radios. So much has been written that sorting fact from static is a challenge. I'll have the advantage of being able to do a back to back to back to back test of the modifications using a different recipe for each example. That detail is for another time .
Still looking for a replacement knob. Anyone have a parts radio laying around? I seem to have run out . The ones I thought were irrevocably dead are now working :-(
...and so it goes
You're having the luck I get at times.
Take a part out - sub it in another radio and the subbed radio now works!
Still doesn't fix the original bur I've got a basement full of magically fixed radios from borrowed lifelines of others.
SIGH - Sorry, no, I don't have any here either. Care to make a hold and just "create" one?
:+> Andy <+:
Take a part out - sub it in another radio and the subbed radio now works!
Still doesn't fix the original bur I've got a basement full of magically fixed radios from borrowed lifelines of others.
SIGH - Sorry, no, I don't have any here either. Care to make a hold and just "create" one?
:+> Andy <+: