I marked pin 1 and pin 10 on this pic. This is the direction I've been measuring. Am I confusing the ends?
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Another 2517 low receive issue
- Thread starter Hawkeye351
- Start date
That looks like the right order. Are you measuring with the negative on the chassis or the board ground?
The picure contradicts what was written in post 45 though. In the post you said pin 10 is closest to the 8v regulator and pin 1 closest to the passthrough regulator, in the picture, it looks like you labeled the pin closest to the 8v regulator as pin1 and the pin closest to the passthrough as pin 10. The picture is the correct way.
yeah your picture is correct but everything you posted sounds like you lifted pin 10 off the board instead of pin 1.
also, the chip should be installed with the label facing the chassis wall.
any chance it got put in backwards?
LC
also, the chip should be installed with the label facing the chassis wall.
any chance it got put in backwards?
LC
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Yea, I did lift pin 10. Pin 10 according to the schematic goes through C175 before the speaker if I'm reading the schematic correctly.
Pin 10 lifted:
Pin 10 pad shows 0v
Pin 10 lead (lifted) shows 10v
All other pins still show the same as with pin 10 lead soldered.
Shouldn't pin 10 lead (when lifted) be slightly less than pin 1? If the lifted pin 10 lead shows 10v, then wouldn't that mean the 7222 isn't amplifying?
Pin 10 pad shows 0v
Pin 10 lead (lifted) shows 10v
All other pins still show the same as with pin 10 lead soldered.
Shouldn't pin 10 lead (when lifted) be slightly less than pin 1? If the lifted pin 10 lead shows 10v, then wouldn't that mean the 7222 isn't amplifying?
10 volts does seem a bit low.
here are the correct voltages for the audio chip:
LC
here are the correct voltages for the audio chip:
LC
looks like you got about one diode drop there too. I am convinced that IC is toast.
Backwards. Pin 1 is towards the front of the radio, closest to the MB3756. The voltage on the real pin 10, nearest the rear panel, is coming out of the chip pin onto the foil pad. The pad should show zero with the pin lifted.
Yeah, pin 10 reads a little low, but color me skeptical.
A 'scope is the only way I learned to make sense of missing or messed-up audio signals. A meter only tells you in an indirect way what's going on. Your meter suggests the 7222 is okay.
Maybe. But seeing the audio on both sides of that output capacitor C179 would settle that question.
73
Yeah, pin 10 reads a little low, but color me skeptical.
A 'scope is the only way I learned to make sense of missing or messed-up audio signals. A meter only tells you in an indirect way what's going on. Your meter suggests the 7222 is okay.
Maybe. But seeing the audio on both sides of that output capacitor C179 would settle that question.
73
Replaced the audio IC (7222) with a known working one.
Still low volume, not as low as it was. Now, I have to turn it up just a little over halfway instead of almost wide open. No more strange issues or sounds when cranking volume wide open, but still low.
Voltages now (in correct order this time, lol...) Volume all the way down, RF gain all the way up.
Pin 1 - 14.12
Pin 2 - 6.76
Pin 3 - 0
Pin 4 - 0
Pin 5 - 1.15
Pin 6 - 1.16
Pin 7 - 0
Pin 8 - 0
Pin 9 - 6.98
Pin 10 - 13.38
Volume halfway up, RF gain still wide open.
1 - 14.12
2 - 6.76
3 - 0
4 - 0
5 - 1.15
6 - 1.15
7 - 0
8 - 0
9 - 6.97
10 - 13.38
Looks about right doesn't it?
Only change I made when replacing those few electrolytic caps, was I had no 330uf left so I used a 470uf instead. C179 was originally a 330uf, i used a 470uf instead. Would this cause the volume to be a little low?
I normally run these radios with volume up around 10 o'clock position to hear everyone comfortably. With the bad IC I was having to crank volume up to 3 o'clock position to comfortably hear others, now with this other IC I only have to crank the volume up to 12 o'clock to hear others comfortably. Almost there.
Any suggestions guys/gals?
By the way, thank you for hanging in there with my slow butt, lol...
Still low volume, not as low as it was. Now, I have to turn it up just a little over halfway instead of almost wide open. No more strange issues or sounds when cranking volume wide open, but still low.
Voltages now (in correct order this time, lol...) Volume all the way down, RF gain all the way up.
Pin 1 - 14.12
Pin 2 - 6.76
Pin 3 - 0
Pin 4 - 0
Pin 5 - 1.15
Pin 6 - 1.16
Pin 7 - 0
Pin 8 - 0
Pin 9 - 6.98
Pin 10 - 13.38
Volume halfway up, RF gain still wide open.
1 - 14.12
2 - 6.76
3 - 0
4 - 0
5 - 1.15
6 - 1.15
7 - 0
8 - 0
9 - 6.97
10 - 13.38
Looks about right doesn't it?
Only change I made when replacing those few electrolytic caps, was I had no 330uf left so I used a 470uf instead. C179 was originally a 330uf, i used a 470uf instead. Would this cause the volume to be a little low?
I normally run these radios with volume up around 10 o'clock position to hear everyone comfortably. With the bad IC I was having to crank volume up to 3 o'clock position to comfortably hear others, now with this other IC I only have to crank the volume up to 12 o'clock to hear others comfortably. Almost there.
Any suggestions guys/gals?
By the way, thank you for hanging in there with my slow butt, lol...
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By the way, I checked pin 4 after installing this working IC by doing the screwdriver shaft trick and there is a loud ruckus sound when I do that now.