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Mirage/Galaxy 88 noggin scratcher....

350GA

Member
Oct 14, 2018
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Good afternoon everyone!

So I've got an 88 on the bench that has me absolutely stumped.

All of the solder joint problems have been addressed, and everything was working flawlessly up until a few minutes ago when things took a dump.

It is constantly displaying 15.195 on the frequency counter, with no RX/TX in any mode, period. No static, nothing. I've went over the board and checked for more possible bad solder joints, but all seems well under board flex and whatnot.

I'm thinking the PLL is *possibly* dead, but wanted to get some input from you guys before it wasted any time testing a ton of parts.

Any input is appreciated! Thanks!
 
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That ~15MHz signal is a "Tone of death"

Might not be anything more than a blown power trace to the PLL, so locate and probe to see if PLL pin 1 has power.

If it does GREAT! If not, locate L15 and that 33 ohm resistor - see if they've failed.

Now - the next spot that can kill a radio is the power supply rail at the EDGE of the radio - also prone to failure due to power surges from accidental (not saying or pointing) shorts placed across this trace can pop it like a fuse BEFORE the Regulator will even see it.

upload_2020-12-23_19-16-20.png
 
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Thanks for the reply Andy! I checked everything you said, and I have 3.2v on pin #1, and the resistor/inductor look and test good at 33 ohms. Any other ideas?
 
Has C90 been changed recently - this cap is a 16V one - but if this board is old, change it for safety.

Right along with C101 and C102...

IF you've done a recent recap - the power trace to the PLL needs to be looked at. You should get about 7.5 to as low as 6 volts on a normal day to the Pin 1 of the PLL when it's working - it's drawdown of the current - and C90 takes and bears a lot of the work in handing power delivery to the PLL.
 
These older Galaxy-esqe radio are NOTOIOUS for bad solder joints.
Might as well resign yourself to reworking as many as you can.
Then, come back the next day and finish off the other half.
But I would do as Handy Andy suggested - first.
 
Hopefully this radio isn't old enough to have the cut traces/jumper wire hookup that powers the PLL. They added a 8-Volt zener to pin 1 and a 100 ohm resistor to feed it across a cut in the original foil trace.

Can't remember which pc board version that was. Probably the "-011" board. Problem we had was they didn't cut the foil trace completely and the zener would run hot as Hades, discoloring its surroundings.

Gotta get 8 Volts to pin 1, or it just won't play well with the other parts.

73
 
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giphy.gif

So...
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Whether you have Kittens or whatever...
... You can have your Cake and Eat it too!​

Congratulations
Glad to know it's working!
!
 
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