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Astro Spectra problems

Posted: Tue Jan 21, 2020 1:51 pm
by PETNRDX
Pretty familiar with Spectra and plenty of other Moto radios. Very Familiar.
Not so much with the Astro Spectra specifically.
Does the Astro low power use the same programming cable as the analog Spectra?
Model is T99DX+089W_ASTRO with an ID of D04KKF9PW5AN.
Setup is Astro Spectra R05.03 that has worked on a consolette, with REAL RIB and home made DB 15 cable that I have used for decades.
Also, have two radios, a UHF analog Spectra, and the above mentioned Astro, and get NO RX audio out of either.
Not one tiny bit.
I am painfully aware of the electrolytics, so will change those.
But, if the previous owner had fried the audio PA (likely) is there an fairly easy way to check that audio IC?

Re: Astro Spectra problems

Posted: Wed Jan 22, 2020 6:16 pm
by jackhackett
The first thing to do is just visually inspect the audio IC, often when they are blown they will have vented either on the top or from around the pins.

If it looks okay, you can check the DC voltage on the speaker outputs. With no audio they should be around half the supply voltage. If I recall correctly the radio has to be unmuted, so inject an on frequency signal with proper PL/DPL but no audio modulation and measure the DC voltage from each speaker lead to ground with no speaker attached. Both leads should measure the same, around 6 to 7 volts.

If you get no voltage on the speaker outputs check the mute signal at the IC, you'll have to look at a schematic to see which pin it is, and be careful with your probe to not short between pins. You should see the voltage change when the squelch opens and closes, I think it goes from 0V to 12V but it's been a while since I've worked on one so I don't remember for sure. I have had several Spectras that had a transistor in the squelch circuit go bad so that the radio would never unmute.

Re: Astro Spectra problems

Posted: Thu Jan 23, 2020 11:46 am
by PETNRDX
thanks for reply and suggestions.
As expected, previous owner fried the IC.
Then did a crappy job trying to replace it.
I have the radio working now.
Sometimes doesn't accept programming, but works after several tries.
Good enuf for now.
Thanks again.

Re: Astro Spectra problems

Posted: Sat Jan 25, 2020 6:17 pm
by FireCpt809
Yes the Astro Spectra uses the same cable as the mid power analog spectra