RCI 2950 No transmit indicator

[MrJace]

1st gen 2950 (appears someone did change to the blue led for display).

Radio will power up, and I hear the static floor. I do not believe I am receiving or transmitting. When I key the mic, the TX does not come on the lcd display. The frequency knob on the left above the mic plug also does not work. There is continuity from the knob so it is making internal contact.

I was told Q37 and Q40 was for the receive and transmit so I changed those, but I seen it may be something else. I have 12 volts in and 8 volts out on the voltage regulators, and 2 volts to 6 volts on the green voltage regulator depending on what rf power is set at.

Do I have a CPU problem, or is it a transistor problem?

If I can get it working, I'll be needing a button panel.

 

[sp5it]

In newer versions of 2950 there was a transistor keying CPU when you press PTT on the microphone. Check it.
In older radios PTT from mic socket was wired directly to CPU and any mess in mic plug was destroying CPU.
Mike

 

[MrJace]

In newer versions of 2950 there was a transistor keying CPU when you press PTT on the microphone. Check it.
In older radios PTT from mic socket was wired directly to CPU and any mess in mic plug was destroying CPU.
Mike

It's the older version pre 1995 I believe. Has the battery spot on the board, with the multi board cpu design instead of the single board they changed to after 95.

 

[sp5it]

So ground processor leg corresponding for TX
If nothing happens CPU is defective.
Mike

 

[MrJace]

Grounding pin 2 cuts sound, but the tx indicator on the lcd is still a no go. I'm thinking this would make a parts radio at this point, the cpu boards are scarce.

 

[NZ8N]

I have had a good number of 1st gen 2950's and 2970's (have one in my storage now).
I noticed when operating in split frequency, and the Roger Beep was on, it would beep on the RX frequency.
I rerouted the PTT line from the Mic plug, to the dual op amp like in a Galaxy (etc...) then run the TX line on the CPU to that, (been a long time since I looked) I think that I used a C945 to buffer/invert the RX +8v to the Base, and the Collector to the TX input on the CPU. Now the beep is on the TX frequency.
This also had the benefit to not blow the CPU up.

 

[MrJace]

I have had a good number of 1st gen 2950's and 2970's (have one in my storage now).
I noticed when operating in split frequency, and the Roger Beep was on, it would beep on the RX frequency.
I rerouted the PTT line from the Mic plug, to the dual op amp like in a Galaxy (etc...) then run the TX line on the CPU to that, (been a long time since I looked) I think that I used a C945 to buffer/invert the RX +8v to the Base, and the Collector to the TX input on the CPU. Now the beep is on the TX frequency.
This also had the benefit to not blow the CPU up.

It seems right now that the CPU is already messed up, so that is something I would have to look at doing with a good CPU board after it's operational again.

My main pcb is part# EPT295013Z which was usually found on the 2nd gen radio. I have the battery so it's definitely the 1st gen.