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142 gtl alignment help
- Thread starter kaos513
- Start date
Greetings!
Ayiee, if I read your photos' meter correctly - or meters' photo selfie - I see 31mA - and looks like it went well.
How does it sound though?
Regards!
:+> Andy <+:
(I don't want to be premature but I think Congratulations are in order...)
Ayiee, if I read your photos' meter correctly - or meters' photo selfie - I see 31mA - and looks like it went well.
How does it sound though?
Regards!
:+> Andy <+:
(I don't want to be premature but I think Congratulations are in order...)
FantastiK!
Ok, tell me all the long winded posts I made were all wrong and all you needed to do was refill the Hamster with more RF Oil and off she went...
Regards!
:+> Andy <+:
Ok, tell me all the long winded posts I made were all wrong and all you needed to do was refill the Hamster with more RF Oil and off she went...
Regards!
:+> Andy <+:
well the only way was to ground black grabber and got my reading dont know if that was the correct way but worked.
I think in this context it is meant to be a "GROUND GRABBER" an equipment probe that is black, "I thinks me is right?"
Greetings!
Thinking a Back Grabber - as in those little thingies by the whatchamacallit that hold up the backside of the board - by the thingamabob do-dads...
There are mounting tabs if the form of Soldering lugs pressed onto or riveted to the aluminum case panels - these are for insulated chassis mounting RF grounding. They keep the radios' own Foil Board Ground isolated from the external earth to prevent a ground loop from forming that can damage the radio and potentially the operator using it.
And Very Important thingies too! for they prevent a ground loop current a path to so you aren't throwing bias back into a live ground Chassis ground versus Foil return only to have it haunt you later.
If you look at the schematic and then the foil side of these boards - they have live grounds - meaning the power supply supplies 13.8V DC and it's own ground - but the case (shield chassis) it's in, is oftentimes at the mercy of the apparent ground present at the case...
Review those Positive and Negative ground chats - for this fits the scenario.
If Foil potential doesn't match Chassis grounds' own - a return path forms amongst those little thingy's - those soldering tabs that hold the rear board - they can provide a path to equalize current and potentials from external sources. You don't always want that - can be lethal...potentials can rise to levels that can possibly electrocute the operator. Because the case is connected to the Antennas' Shield at the radios SO-239 connector - and we may not have the antenna properly mounted or the ground for it at the mounting location is not reliable - means that if the antenna has an electrical problem - it can transfer that back to the radio.
Many people reheat the solder back there and re-seat and reset the connections of that steel lug to the aluminum back panel "rivet" nub - works for a little while until oxides reform and you do it all over again.
Each reheat cycle shortens the lifespan of the connection - simply due to the heat causes fatigue and oxides - the flux will attempt to suspend and keep this "dirt" within itself - but do it too many times and the flux becomes like a carbon trail and affects both the board and panel and even the PCB board components and leaves residue as a carbon trail.
Note that later models of Galaxy use BOLTED lugs to Panel. Mostly for support but also to provide a low-impedance (low potential problem path) to earth and case ground - which is also Chassis ground and Foil BOARD ground (those screws to hold the board in the case are a good example of this reasoning...)
Meanwhile, Cobra and Uniden in some of their Cheapie radios (687 / 787) are simply Negative Ground Only so the Foil, Board and Power supply Grounds are all the same...(like the Galaxys' above)
Other Unidens, like the PC66/68 and 76/78 series use Positive of Negative ground which means the case is not always at EARTH ground. The case "floats at whatever the coax shield potential is and only provides an RF return path (it's insulated form DC but allows AC to pass) so the NEGATIVE wire has to either go to a good ground (return path) or you solder a braid from the FOIL board ground (Transformer Power Choke Core is good for this) to the CASE and then when the radio is bolted in and coax hooked up - Ground is provided thru the case or via the shield of the coax braid if you're in a Negative Ground Ignition vehicle or have access to earth ground thru grounding rods and/or locations and equipment made to for it.
Sounds involved but it isn't - just have to keep your grounding points clean.
If you want to use the case as a single point ground - it has to be BONDED or some call it, Strapped - to ground.
I only mentioned it in an earlier post, but if my hunch is right - the above applies as the best explanation I can give to help explain what is going on back there
Regards!
:+> Andy <+:
Thinking a Back Grabber - as in those little thingies by the whatchamacallit that hold up the backside of the board - by the thingamabob do-dads...
There are mounting tabs if the form of Soldering lugs pressed onto or riveted to the aluminum case panels - these are for insulated chassis mounting RF grounding. They keep the radios' own Foil Board Ground isolated from the external earth to prevent a ground loop from forming that can damage the radio and potentially the operator using it.
If you look at the schematic and then the foil side of these boards - they have live grounds - meaning the power supply supplies 13.8V DC and it's own ground - but the case (shield chassis) it's in, is oftentimes at the mercy of the apparent ground present at the case...
Review those Positive and Negative ground chats - for this fits the scenario.
If Foil potential doesn't match Chassis grounds' own - a return path forms amongst those little thingy's - those soldering tabs that hold the rear board - they can provide a path to equalize current and potentials from external sources. You don't always want that - can be lethal...potentials can rise to levels that can possibly electrocute the operator. Because the case is connected to the Antennas' Shield at the radios SO-239 connector - and we may not have the antenna properly mounted or the ground for it at the mounting location is not reliable - means that if the antenna has an electrical problem - it can transfer that back to the radio.
Many people reheat the solder back there and re-seat and reset the connections of that steel lug to the aluminum back panel "rivet" nub - works for a little while until oxides reform and you do it all over again.
Each reheat cycle shortens the lifespan of the connection - simply due to the heat causes fatigue and oxides - the flux will attempt to suspend and keep this "dirt" within itself - but do it too many times and the flux becomes like a carbon trail and affects both the board and panel and even the PCB board components and leaves residue as a carbon trail.
Note that later models of Galaxy use BOLTED lugs to Panel. Mostly for support but also to provide a low-impedance (low potential problem path) to earth and case ground - which is also Chassis ground and Foil BOARD ground (those screws to hold the board in the case are a good example of this reasoning...)
Meanwhile, Cobra and Uniden in some of their Cheapie radios (687 / 787) are simply Negative Ground Only so the Foil, Board and Power supply Grounds are all the same...(like the Galaxys' above)
Other Unidens, like the PC66/68 and 76/78 series use Positive of Negative ground which means the case is not always at EARTH ground. The case "floats at whatever the coax shield potential is and only provides an RF return path (it's insulated form DC but allows AC to pass) so the NEGATIVE wire has to either go to a good ground (return path) or you solder a braid from the FOIL board ground (Transformer Power Choke Core is good for this) to the CASE and then when the radio is bolted in and coax hooked up - Ground is provided thru the case or via the shield of the coax braid if you're in a Negative Ground Ignition vehicle or have access to earth ground thru grounding rods and/or locations and equipment made to for it.
Sounds involved but it isn't - just have to keep your grounding points clean.
If you want to use the case as a single point ground - it has to be BONDED or some call it, Strapped - to ground.
I only mentioned it in an earlier post, but if my hunch is right - the above applies as the best explanation I can give to help explain what is going on back there
Regards!
:+> Andy <+:
OR he measured at the wrong grounding point - but I saw the metr with a pretty heavy amerage in one of his earlier shots - so I only hope he measured from Foil Ground not panel ground...see above...
What I am trying to get at is what was exactly the fix. Was it a resistor over the bias diode? A lot of people follow these threads to learn things so they like to know the fix.
Those are a nice thing to have for the Test Points - springload too.
Holds on tight - have some from Braden that "screwed onto" your test leads with those sping clippy things - holds it in place and keeps the "Capacitive coupling" effects of the human body away - making the test more hands free.
Kaos and Nomad were discussing a possible fault to ground - so - once fixed - good to see it was working and that nothing else got in the way.
I've had radios that don't always recover completely after a single simple fix. Had some like I wrote above, older chassis and their ages/corrosion and brittleness add a complexity you need to work thru to accomplish getting it working right.
Sometimes, after all the effort - it's hard to fight back the urge to "yell back to the customer" about their carelessness - which in some instances, is not their fault - you just get attached to the object as if you were fixing it for a member of the family not just another customer.
Browning did up some ads like that...
Again! Congratulations!
:+> Andy <+:
Holds on tight - have some from Braden that "screwed onto" your test leads with those sping clippy things - holds it in place and keeps the "Capacitive coupling" effects of the human body away - making the test more hands free.
Kaos and Nomad were discussing a possible fault to ground - so - once fixed - good to see it was working and that nothing else got in the way.
I've had radios that don't always recover completely after a single simple fix. Had some like I wrote above, older chassis and their ages/corrosion and brittleness add a complexity you need to work thru to accomplish getting it working right.
Sometimes, after all the effort - it's hard to fight back the urge to "yell back to the customer" about their carelessness - which in some instances, is not their fault - you just get attached to the object as if you were fixing it for a member of the family not just another customer.
Browning did up some ads like that...
Again! Congratulations!
:+> Andy <+:
- No one is chatting at the moment.
