Seeking Realistic trc452 advanced audio tweaks

[Uncle Ronnie 336]

So now I know why I could not find c350, in this radio it was marked off as c261.

 

[Uncle Ronnie 336]

So I think we have another issue involved in which some of the Caps are misnumbered or labeled different at the factory for this model. But more so than that yet another problem has cropped up in which I do not have any transmit or meter movement so I'm looking for a solder bridge again lol.

 

[Uncle Ronnie 336]

I have not found a solder bridge and I have no transmit. I do have an idea for what to put in place of the c350 electrolytic. I am thinking a .056 ceramic disc cap in series with a 10-15 ohm resistor. I don't know whether I should leave the .01 cap tacked in underneath or not

 

[Handy Andy]

The bigger culprit is the Electrolytic cap - they tend to "go inductive" - some types will induce some instability and not work well.

The 0.01uF (103) and the 0.039uF (393) are listed - since you're seeing different - not sure if this radios even stock. Sounds like work has been done to it before.

Radio Shack, although not directly responsible for the manufacturer of the radio - is the one responsible for selling and servicing it (back then) so for them to put something way different or mislabel it as something else - is not.

 

[Uncle Ronnie 336]

I have a bigger problem now in which it it is not transmitting at all. It seems to be somewhere connected to the PTT switching controls.

 

[Handy Andy]

Have you gone to the link I provided back in Post #7?

Then you know the radio is similar to Cobra 25 or 29 series...uses the CB/PA switch (three pole) to work TX toggle and route speaker audio to correct jack.

To power a section - like TX - it leaves power applied all the time to the Driver and Final - like the 25/29.

But when you key, the Mic jack Pin 3 "grounds" and turns on the Pre-driver TR215 - to send a signal and turn on the Driver and Final. IT completes the circuit from Supply to Ground thru Pin 3 of the Mic.

 

[Uncle Ronnie 336]

I did hit up that link. CBtricks is usually the initial go-to. I will be poking around that transistor in a little bit.

 

[Uncle Ronnie 336]

I'll be honest, I'm pretty stumped

 

[Uncle Ronnie 336]

Ok so I held a communications receiver antenna up to the radio itself to see if there's a signal and there is. So now I have to figure out whether the driver or final is blown. I might have made this audio so hot that I popped the 2166.

 

[Uncle Ronnie 336]

So I changed the final and it appears I still get signal from the driver but I just do not have any transmit at all

 

[Handy Andy]

Replace the cap, try again, this may explain the phenomenon - that Cap acts like a tank circuit storing energy - like or similar to, the Miller Effect

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• It is a feedback method of generating a recirculating current to "sustain" an effect, but limit the Gain the stage is able to process from this effect.

So, put the cap back in and see if it recovers. This is where your problem is - as far as getting more out of it...

This is your physical limit...

 

[Uncle Ronnie 336]

Are you talking about c350?

 

[Uncle Ronnie 336]

I put the last things back to where they were before I lost transmit but I still do not have transmit. I really am stumped on this one. All I know is there is too much into this radio to just put it in the bin. It's had more use on my bench than it has in the last 15 years at least

 

[Handy Andy]

Yes, C350, but that 2028 2029 paring - well, looks like the other half - the Driver - may have failed.

 

[Uncle Ronnie 336]

I just put another driver in and I still have nothing. The 2166 that I had in there had an hfe gain reading of 82 and when it came out it was at 54 so I'm guessing I cooked something there mildly.