Record Out on Cobra 1000 GTL (Transmit audio too loud)

[shadow]

Hi guys, i've got a bit of a problem here and I was wondering if someone can help me out...

So I've decided to use this Cobra 1000 GTL as a base station which means that I'll also be using it for my Videogates. The good news is that it has a 'Record' output which lets you record receive and transmit audio. The bad news is that the levels are way off. The transmitted audio is way too loud. Does anyone know of a way to bring down the transmit audio on the 'Record' out? Unfortunately, I don't know enough about electronics to find this out on my own with the schematic diagram, but I'm assuming that there must be a way to do this...

[Please login or register to view this link]

[ external image ]

[Night Crawler]

To lower the Transmit Only find R60 a 47k fixed resistor lift one side of it from the board install a 50k trimmer pot in series with the center leg of the pot going to the empty hole on the board and one of the legs on the side going to the end of resistor lifted from the board.
Adjust for the level needed if it doesn't lower it enough use a 100k trimmer pot.

[Nagant]

I figured Night Crawler would have a solution for you.

That is a really nice 1000 you have. They are much less common than the 2000 for sure. Fewer of them were made and for not many years at all. I've noticed prices have risen on the 1000's this year judging by what I've seen some bring on eBay.

[knuckle1947]

Sorry I can't help you with your problem, but wanted to say that IS a nice 1000 ya' got there ...

[TheCBDoctor]

Hi guys, i've got a bit of a problem here and I was wondering if someone can help me out...

So I've decided to use this Cobra 1000 GTL as a base station which means that I'll also be using it for my Videogates. The good news is that it has a 'Record' output which lets you record receive and transmit audio. The bad news is that the levels are way off. The transmitted audio is way too loud. Does anyone know of a way to bring down the transmit audio on the 'Record' out? Unfortunately, I don't know enough about electronics to find this out on my own with the schematic diagram, but I'm assuming that there must be a way to do this...

[Please login or register to view this link]

[ external image ]

Hi shadow,

That is one sweet Cobra 1000 GTL. Your question was already answered so I won't add anything to it. I just wanted to let you know that you will not find very many, if any, in that shape. Take care of it for me.

[Please login or register to view this link] Photos and info on the 1000 GTL

If you wouldn't mind I would like to put that photo on my educational website. If you would can you send that photo to me directly at thecbdoctor@gmail.com I am a sponsor so you would not be breaking any rules.

Thanks in advance,

[shadow]

To lower the Transmit Only find R60 a 47k fixed resistor lift one side of it from the board install a 50k trimmer pot in series with the center leg of the pot going to the empty hole on the board and one of the legs on the side going to the end of resistor lifted from the board.
Adjust for the level needed if it doesn't lower it enough use a 100k trimmer pot.

Night Crawler, you are awesome! Thank you! I'm gonna go pick up the trimmer pots and get this done. I do have to ask, did you know about this previously, or did you just look over the schematic and figure it out on the fly?

If you wouldn't mind I would like to put that photo on my educational website. If you would can you send that photo to me directly at thecbdoctor@gmail.com

Would you like the full resolution original?

Thanks to everyone for the compliments. I got this radio just recently and I haven't had a chance to clean it yet. After I get it where I want it, I'll clean it up and post more pictures.

[knuckle1947]

I'm sorry Shadow, but I see very little that needs to be cleaned ....

[Night Crawler]

I do have to ask, did you know about this previously, or did you just look over the schematic and figure it out on the fly?

Just by looking at the schematic I worked for motorola as an electronic service technician a number of years before I retired.

[shadow]

Just by looking at the schematic I worked for motorola as an electronic service technician a number of years before I retired.

That's pretty awesome.

I've added about .5 mega ohms and it's still a bit loud. I'll have to see if I can get my hands on a 1 Mohm trimmer unless you have a better idea. Thanks again for the help!

[Night Crawler]

I've added about .5 mega ohms and it's still a bit loud. I'll have to see if I can get my hands on a 1 Mohm trimmer unless you have a better idea. Thanks again for the help!

Add a fixed resistor in series with the pot you'll have to experiment with the value start with a 100k and work your way up in value until you get a good range on the pot.

[shadow]

That's what i've done, but I ran out of resistors. I used 5 100k resistors, the original 47k, and the 100k pot and it is still a little loud, but it's getting there.

[Night Crawler]

Here's something else to try instead of using all those resistors in series with the pot.

Refer to Figure 1 you can leave out the fixed resistor marked R or add it if you like your option.
[Please login or register to view this link]

What that fixed resistor R does is make the pot an audio taper so when it adjusts the volume it has a smooth control over the increase or decrease in the audio gain instead of going quickly from one extreme to the other.


1.Remove the 100k resistors that are in series with the pot.

2.Set the pot up with the center leg going to the hole left from the 47k resistor lifted from the board and one of the legs on the side of the pot going to the end of the 47k resistor that was lifted.

3.Connect the remaining open leg on the pot to a ground point on the circuit board