Rci 2970 low voltage on pin 9 of ta7222ap

[That_guy_in_wv]

I'll check the cap and Q57 and see what's what and get back with you, thanks handy Andy.

FM is out no carrier and no sound transmitted. Seems only sideband upper and lower is the only tx I'm getting. Am transmits but very low modulation dead heading at around 40% and swings no farther. Wattage in swing is only 5 watts from wherever the carriers set on am also.

 

[That_guy_in_wv]

Which cap would be the audio out at 330uf?

 

[That_guy_in_wv]

I meant the audio out and voltage returns.

 

[Handy Andy]

C240 (330uF) amongst others...


NOTE THEY LEAVE PIN 3 FLOATING!​

 

[That_guy_in_wv]

Thank you Andy, I went ahead and just swapped out both Q56 and Q57 with new c945's I'm looking for a replacement that's high enough voltage for R240 now. I have some here in the pile somewhere.

 

[Handy Andy]

Forgive the "spurts" - (delayed responses)
I'm working on Groceries, Car - Lawn and Animal Husbandry for a small pooch...

It brings it's own Fan Club...​

 

[NZ8N]

The TX audio does not go through the TA7222 audio amplifier. Not for TX. The TA7222 has a mute circuit that "disables" it in TX. Pin 5 and 4 are hard clamped by a diode and 10k resistor, I am at work now, so I can't pull up schematics.

 

[NZ8N]

Check the dual OP amp, 4558.

 

[That_guy_in_wv]

Forgive the "spurts" - (delayed responses)
I'm working on Groceries, Car - Lawn and Animal Husbandry for a small pooch...
View attachment 38033
It brings it's own Fan Club...​

Lol man's gotta stay busy.... nice puppy doggy

 

[That_guy_in_wv]

The TX audio does not go through the TA7222 audio amplifier. Not for TX. The TA7222 has a mute circuit that "disables" it in TX. Pin 5 and 4 are hard clamped by a diode and 10k resistor, I am at work now, so I can't pull up schematics.

It's fine NZ8N I got time to play around with this one some. I appreciate the help alot though, I have things to get done also. I'll be back around this evening to try some more tinkering with it.

 

[That_guy_in_wv]

Checked the 4558 op amp before I left, 3 pins were just 0.3 volts over what the book says but voltage was reading about where they should be on TX-RX and voltage seems right.

 

[NZ8N]

Also, check the AMC/ALC circuit, it might be hard clamping too. There might be just enough audio to bleed through to tickle the side band modes, but not enough to tickle the carrier modes.

I have this exact same 2970 first gen model, have had a lot of them in the past, so I am very familiar with the chassis.

 

[NZ8N]

Desolder the center pin of TR32, this will disable the AMC and ALC circuit, see if you have TX Modulation. This is from the pic of the solder side of the board on http://www.cbtricks.com/radios/rci/rci_2950/graphics/ept295013z_main_pcb_trace_layout.gif
If this restores your TX Moduation, we can debug from here.

 

[That_guy_in_wv]

I'll check when I get home thanks NZ8N, been busy and didn't get back in time last night to do much with it and have been at it all day today lol.

 

[That_guy_in_wv]

Sorry y'all just got time to play around some. I just desoldered tr32 and modulation went from 40% before to around 82% after, but still with d104 and mic gain wide open not very good.