TX 125 AMP

[Steve Hurst]

any way to tell what these resisters circled in red were? the bands have burnt off. It is a tx125 amp and I can't seem to find a diagram on google

 

[Tallman]

This looks like one for the master of repair the "Nomad"!

 

[Steve Hurst]

I have looked all day using google. I don't even find this TX125 amp listed. It has no other name on it.
This is the the view from the top. Front has 3 switches and a knob witch gives you low,med,high and max

 

[Tallman]

any way to tell what these resisters circled in red were? the bands have burnt off. It is a tx125 amp and I can't seem to find a diagram on google

If the color bands are burnt you can't tell what they were. Need more pictures of the amp.
Does the amp put out power, any leds lit? Does the radio receive and work?

 

[Steve Hurst]

It works yes. Transmits on all settings but max. Shows about 80 watts. Receive amp light comes on but the receive goes down when on. When you use the max amp setting it seems to oscillate till you turn it off max. Used it once to get a report and it was heard and had improved signal. What more pic can I give?

 

[Tallman]

It works yes. Transmits on all settings but max. Shows about 80 watts. Receive amp light comes on but the receive goes down when on. When you use the max amp setting it seems to oscillate till you turn it off max. Used it once to get a report and it was heard and had improved signal. What more pic can I give?

The front and rear panel, sides, back. More on the circuit board.

 

[nomadradio]

This one is a real oddball. I have seen circuits in the Motorola handbooks, labeled as "test" circuits that use open coils and capacitors like this for matching impedances.

But every example of a two-transistor push-pull circuit that comes to mind uses broadband ferrite transformers.

This one does not.

Is there a name, or any kind of logo on the front panel. My records don't seem to contain a "TX-125" of any kind.

The two burned resistors reveal no hints about what they do. The one on the right-rear has a first numeral of "1", the brown band that's not burned. Leaves two more color bands to guess.

The one on the left started with the digits "47". The yellow first band is followed by a barely-visible trace of a violet band. But the third one is long gone. Can't see just what it does in the circuit, so could it be a zero point 47 ohm? or a four point seven? or forty seven? Or a 470? No hints from where it's connected that I see to narrow this down.

73

 

[Tallman]

It works yes. Transmits on all settings but max. Shows about 80 watts. Receive amp light comes on but the receive goes down when on. When you use the max amp setting it seems to oscillate till you turn it off max. Used it once to get a report and it was heard and had improved signal. What more pic can I give?

I'm guessing here, but I think those small resistors are in the receiving boost circuits. Those receive boost circuits don't really help because they amplify noise with along your desired signal. Not selective at all. Get me more pictures of the circuit board so I can look for a trimmer cap in the RF power circuits.

 

[Robb]

Looks like at least one resistor is in line with the relay; the other may be too . . .

 

[Steve Hurst]

the right side resistor goes one way to the TP you see next to the relay, the other way it runs up and hooks to the blue resistors (I had to fix this because it was burnt) then goes further up and through the board and hooks to the amp power switch. the one on the left goes across the the coil in front of relays and hooks to the right relay. in the other direction goes through the board and hooks the round transistor and the coil to the right of it

 

[Steve Hurst]

I know the pre amp is not important but if you could have a guess I would be happy. In case I sell it. Not that I will. Thanks for the help

 

[Steve Hurst]

This one is a real oddball. I have seen circuits in the Motorola handbooks, labeled as "test" circuits that use open coils and capacitors like this for matching impedances.

But every example of a two-transistor push-pull circuit that comes to mind uses broadband ferrite transformers.

This one does not.

Is there a name, or any kind of logo on the front panel. My records don't seem to contain a "TX-125" of any kind.

The two burned resistors reveal no hints about what they do. The one on the right-rear has a first numeral of "1", the brown band that's not burned. Leaves two more color bands to guess.

The one on the left started with the digits "47". The yellow first band is followed by a barely-visible trace of a violet band. But the third one is long gone. Can't see just what it does in the circuit, so could it be a zero point 47 ohm? or a four point seven? or forty seven? Or a 470? No hints from where it's connected that I see to narrow this down.

73

I posted a better pic and more info.

 

[Steve Hurst]

Well i am trashing it, well it will be used for parts the good ones at least. Thanks every one for the replies and help

 

[Tallman]

Well i am trashing it, well it will be used for parts the good ones at least. Thanks every one for the replies and help

If the amp works keep it and use it. The receive boost is useless.

 

[Steve Hurst]

It is not worth using. SSB doesn't work I found that out last night when I tried to use it. I don't want anything that is hooked to it to have trouble. It is ok I got a cobra 148 gtl in the deal and it works after a little work. I just need my freak counter so I can line it up and use it.