Teaberry Five by Five looking for correct schematic

[Kage]

Hi all, I have this radio and it's similar to other Teaberry radios of that era but the schematic on cbtricks is not correct. The manual and service manual are right but the schematic they linked is for a different radio.
The one I have is a 4 pin mic, uses a 2SC756 for the final RF amp.
Curious if it's possible to get a bit more power out of this since it's a 70s radio and manufactured to put out 3.2 watts carrier. The RF power transistor should be able to provide a bit more w/o taking a golden screwdriver to the traps and other nonsense. Wondering if the B(base) of the transistor has a low value resistor to ground to limit RF output or something obvious that can be modified to get her up to a full 4 watts without downward swing to cancel out the loss of power in my 100' of old RG 8/u coax out to the tower.
I suppose this is pulling hairs considering how little of a difference there is in RF power output between the 3.2 and 4 watts considering few would notice on their S-meter, but simply wondering, and I can't find the actual schematic online anywhere.
Also would love to get the receive to pull out well beyond 27.255. With the VFO I can get it to cover well out to channel 40, but beyond that the receive sensitivity drops off fast when taking it to freeband frequencies. Wondering if adjusting the IF coil section could help with this but I'd need the schematic to see what I am doing.
Thanks.

[Kage]

BTW the picture they use is correct..
www.cbtricks.com/radios/teaberry/five_by_five/graphics/teaberry_five_by_five.jpg
Only the schematic is wrong

[Kage]

After tracing out the RF output section by eye onto paper I found that the buffer PA transistor had a air coil slug that could easily be adjusted to get the TX section out to 27.700 but that's about the limit before the TX begs for mercy. Removing the slug wasn't the answer as it introduced harmonics but right below the maximum the transmit stage could handle the TX out to there with respectable power. Any frequency beyond that point introduces spurs and harmonics with reduced power, so the limit of the Five by Five radio is from 26.515 to 27.700 TX. With the VFO it covers this well w/o harmonics that are problematic. Receive is a bit wider covering 26.300 to 28.100 w/o much of any change. It's possible to receive up to 28.900 as I've found but birds exist up there and the RF gain drops bad.
Changing that slug also increased output power across the entire band while still maintaining full stock modulation besides on the skirts of the range which I wouldn't use for TX anyways.
Looking at what I jotted down it seems it's simply a HPF stage on the output of the buffer amp transistor before the final RF stage so that makes sense.
I'll post more info about the mod eventually, but it's sickingly golden screwdriver, but I really did check the scope and final output and for harmonic/spur issues. It only increases TX out to 4.0-4.2 watts and expands the TX high frequency range, that's it. The 50MHz trap coils are still doing their job and it's still clean output. Nice to know some 23ch radios can still do what 40ch radios can with a little mod like this. It's still transmitting with headroom so 100% modulation is no issue.
I like this radio a lot, it's simple and easily modifiable. Going to buy a Albrecht 6110 or as it's called for US "Anytone Smart CB". I've been really wanting one of those because they seem capable out of the box for range and frequency capability.
I really miss my SSB rigs I had in the past, but getting back into this hobby, and AT THE WRONG TIME given the low solar cycle, but even right now as I type this there is lots of Mexican skip so maybe there is a window of hope?

[Sandbagger]

Sept 27, 2017 13:26:24 GMT -5 Kage said:

After tracing out the RF output section by eye onto paper I found that the buffer PA transistor had a air coil slug that could easily be adjusted to get the TX section out to 27.700 but that's about the limit before the TX begs for mercy. Removing the slug wasn't the answer as it introduced harmonics but right below the maximum the transmit stage could handle the TX out to there with respectable power. Any frequency beyond that point introduces spurs and harmonics with reduced power, so the limit of the Five by Five radio is from 26.515 to 27.700 TX. With the VFO it covers this well w/o harmonics that are problematic. Receive is a bit wider covering 26.300 to 28.100 w/o much of any change. It's possible to receive up to 28.900 as I've found but birds exist up there and the RF gain drops bad.
Changing that slug also increased output power across the entire band while still maintaining full stock modulation besides on the skirts of the range which I wouldn't use for TX anyways.
Looking at what I jotted down it seems it's simply a HPF stage on the output of the buffer amp transistor before the final RF stage so that makes sense.
I'll post more info about the mod eventually, but it's sickingly golden screwdriver, but I really did check the scope and final output and for harmonic/spur issues. It only increases TX out to 4.0-4.2 watts and expands the TX high frequency range, that's it. The 50MHz trap coils are still doing their job and it's still clean output. Nice to know some 23ch radios can still do what 40ch radios can with a little mod like this. It's still transmitting with headroom so 100% modulation is no issue.
I like this radio a lot, it's simple and easily modifiable. Going to buy a Albrecht 6110 or as it's called for US "Anytone Smart CB". I've been really wanting one of those because they seem capable out of the box for range and frequency capability.
I really miss my SSB rigs I had in the past, but getting back into this hobby, and AT THE WRONG TIME given the low solar cycle, but even right now as I type this there is lots of Mexican skip so maybe there is a window of hope?

Hopefully you have a decent group of locals that you can converse with. I much prefer a good steady local group to hit or miss skip talking anyway.

Most of the older 23 channel rigs had limited bandwidth, since they only needed to cover 300 Khz.

[Kage]

Sept 28, 2017 15:07:44 GMT -5 Sandbagger said:

Most of the older 23 channel rigs had limited bandwidth, since they only needed to cover 300 Khz.

Yeah made my first decent contact the other night to someone around 8 1/2 miles from my town running barefoot into an EFHW dipole mounted up 20'. Took me by surprise considering they were giving me around S6 off their mobile and said my signal is big and booming
Then there's other people who I swear buy the smallest magmounts and I wonder why I can barely talk to them under a mile away until they tell me what they are using.
I still prefer skip since it's fun to see how far I can cast that signal and don't have to worry about the occasional unsavory local types that pop in and out to stir up trouble.
Anyways, still curious to find a schematic eventually for this radio but maybe that's a pipe dream at this point.

[Sandbagger]

Sept 30, 2017 17:46:25 GMT -5 Kage said:

Sept 28, 2017 15:07:44 GMT -5 Sandbagger said:

Most of the older 23 channel rigs had limited bandwidth, since they only needed to cover 300 Khz.

Yeah made my first decent contact the other night to someone around 8 1/2 miles from my town running barefoot into an EFHW dipole mounted up 20'. Took me by surprise considering they were giving me around S6 off their mobile and said my signal is big and booming
Then there's other people who I swear buy the smallest magmounts and I wonder why I can barely talk to them under a mile away until they tell me what they are using.
I still prefer skip since it's fun to see how far I can cast that signal and don't have to worry about the occasional unsavory local types that pop in and out to stir up trouble.
Anyways, still curious to find a schematic eventually for this radio but maybe that's a pipe dream at this point.

Ask and you shall receive:

www.cbtricks.com/radios/teaberry/five_by_five/index.htm

Edit: I just reread this thread and see that the CB tricks schematic is not the same as your radio. Somehow I missed that post along with your desire to up the power out of the 2SC756 final. That was a very common part, used in many (especially Uniden-made) AM radios back then. It's certainly very possible to get up to and over 4 watts of carrier out of them. The problem is with the modulator circuit. Those modulators sometimes barely made enough audio power to properly drive a 3 watt carrier without flat topping. Trying to modulate a 4 watt carrier without distortion (or even with enough power) might take a bit of modification to the modulator. And for less than 1 watt worth of gain, as you correctly pointed out, it won't be noticed on the S-Meter. I'm of the school that say's back the radio's power down, and go for max modulation, and then drive a small amplifier to get the required signal gain.

[cbrown]

Sept 30, 2017 20:16:10 GMT -5 Sandbagger said:

I'm of the school that say's back the radio's power down, and go for max modulation, and then drive a small amplifier to get the required signal gain.

Exactly this. No need to try and get every last watt out of a rig when there are plenty of amplifiers out there. I do recommend using a Class B or better (AB or A).

[Kage]

Thanks for the replies. Yeah like I said the cbtricks website is incorrect in its schematic.
I'm not worried about getting more carrier out now. It was an issue when I got it and I had the idea in my head that the little bump in RF out meant something realistically but even then I knew it was a fruitless effort trying to get more out w/o stressing the RF output device.
Reality is the modulator in this radio should be fully capable of some serious modulation given it's push pull with two modulator transistors and recently I replaced the original modulation transformer in it with one out of an old scrapped Johnson 123. Yes I know it's a sad swap as the Jonnson was worth more but it was already in my part bin from years ago.
The new tranny allows a hell of a lot more modulation and RF output with a ton of headroom. Johnson really didn't joke around.
Also after sweeping the audio in to the mic I noticed a large improvement in bandwidth in audio for TX.
Neat little upgrade, not sure how many here have ever tried swapping modulation transformers but it can make a dramatic difference. This radio can now sweep a huge range of audio coming close to HIFI that some ops want w/o the need to go to series modulation.
Eventually I will post some pics and circuits of my franken CB lol.