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Fixed level audio output from MaxTrac 100

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HbgNRHS
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Joined: Fri Nov 16, 2018 11:44 am

Fixed level audio output from MaxTrac 100

Postby HbgNRHS » Fri Nov 16, 2018 12:03 pm

Hello all,

I am new to this forum and new to MaxTracs. I've done a message search and didn't really come up with an answer so I thought I'd post a new thread.

I have a MaxTrac 100 that has been programmed for "receive-only" in order to use it for an Internet radio stream. The radio has the 5 pin accessory connector which only has an "Ext Spkr" output. My question is whether there is a jumper setting or modification I can make that will provide a fixed-level audio output; one that is independent of the volume control setting.

Also, is there a jumper or modification that will allow the speaker volume level to go all the way to zero? Currently, turning the volume control all the way down does not completely mute the radio.

On both of the above, I'm handy with a soldering iron if physical modifications are necessary. I can't imagine I'm the first to want to do something like this so I thought I'd post here to avoid re-inventing the wheel. Any insight you guys can provide would be appreciated.

Thanks in advance and 73,
Dan Rapak
WA3ATV

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arlojanis
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Re: Fixed level audio output from MaxTrac 100

Postby arlojanis » Fri Nov 16, 2018 2:08 pm

There is a 10 ohm resistor in the low side of volume control. It is R9001, the only resistor on the volume control board. Jumper across the resistor. Volume will go all the way down.
"The world runs on radio."

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arlojanis
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Joined: Mon Jan 28, 2002 4:00 pm

Re: Fixed level audio output from MaxTrac 100

Postby arlojanis » Fri Nov 16, 2018 2:14 pm

Top of volume control (audio in lug) might be good place to try for receive audio.
"The world runs on radio."

PETNRDX
Posts: 818
Joined: Sun Nov 25, 2001 4:00 pm
What radios do you own?: Too many

Re: Fixed level audio output from MaxTrac 100

Postby PETNRDX » Mon Nov 19, 2018 2:09 pm

Got to the Batwing Laboratories site, into the model specific section, Maxtrac sub-section, then click on the highlighted "mic connector" link in about the second paragraph.
Should take you to a little GIF file that shows a drawing of the mic connector.
One of the pins of the mic connector is "handset audio".
Handset audio is a fixed level for use with a "telephone style" handset (mic and earpiece) instead of a plain old microphone.
I think it is pin 8 for handset audio, and pin 4 for ground. Go look.
Much easier to plug into the mic socket than any other method.
And jumper that resistor on the mic plug/vol pot board and that will drop audio to almost nothing.
Steve K.

HbgNRHS
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Re: Fixed level audio output from MaxTrac 100

Postby HbgNRHS » Thu Aug 08, 2019 7:49 am

Guys,

Life caused this project to be put on the back burner. Just getting cranking on this now.
Please accept my belated thank you to both of you for replying to my question!
VERY much appreciated!

Dan Rapak
WA3ATV

PETNRDX
Posts: 818
Joined: Sun Nov 25, 2001 4:00 pm
What radios do you own?: Too many

Re: Fixed level audio output from MaxTrac 100

Postby PETNRDX » Fri Aug 09, 2019 8:06 am

No worries.
I have life get in my way all of the time.
Steve K.

Jim202
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Re: Fixed level audio output from MaxTrac 100

Postby Jim202 » Fri Aug 09, 2019 11:47 am

You might have a look at pin 11 on the accessory connector. Most of Motorola radios have a fixed level RX audio output that doesn't vary with the volume control. But this radio is so old, I can't be sure.

The other point to consider is that most of the audio pins on the Motorola radios have a DC bias voltage on them. So you might have to cap couple the pin with something like a 1.0 uf. cap to block the DC voltage.

Jim

HbgNRHS
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Re: Fixed level audio output from MaxTrac 100

Postby HbgNRHS » Sat Aug 10, 2019 10:43 am

Thanks Jim! The accessory connector was the first place I looked, but this particular vintage only has the five pin connector so I struck out there. Looks like tapping the mic/handset connector will be the way to go. Thanks for the heads-up regarding the DC bias. I wasn't aware of that.

Dan

Karl NVW
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Joined: Wed Sep 03, 2003 7:13 am

Re: Fixed level audio output from MaxTrac 100

Postby Karl NVW » Sat Aug 10, 2019 5:56 pm

Remember to use the pin labeling for the 8-pin mic jack as shown in the manual. Israel did is backwards from everyone one else in the world, but that's what they used and printed in the manuals. Put a 680 ohm resistor in series with the handset audio high on pin 8.
Karl - WA8NVW AFA5VB
SHARES + NCS


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