Presiden Jackson stuck on transmit

[alyxlyon]

Hi!

I have a problem with my PJ

Model - President Jackson (A-F band version black faced)
PCB - PB-042AE
PLL - Don't know (Kinda new to this stuff) I think its MC145106 maybe

Radio is stuck on transmit.
It has been modified with following mods: hxxp://www.radiomods.co.nz/presidentjacksonmods.html

It also has a modification that reduces AUX-output lvl so that it is better suited for packet radio. (just ceramic cap and 2 resistors)

Tryed so far:

I removed the modifications, still transmitting.
I removed the W26 (yellow wire) going into the small PCB infront of the radio, it stopped transmitting. Schema says its TX-FREQ, what confuses me is that its attached with roger beep.

Some other stuff to go with:

When I go to low band A and set channel to 40 and switch between roger on / off following happends -->

ON - transmit and receive leds flicker and signal meter jumps up and down like crazy

OFF - both leds are lit and receive flickers a bit. Signal meter steady at max (this also happends on all other bands).

I'm pretty much clueless about that can cause this, but from symptoms I assume either transistor or capacitor failures. Help a bit please, I'de hate to throw this thing into the garbage bin

Person who has modified this CB refuses to take blame and doesn't want to "fix" it, and he said it should last a life time with these mods.

PS. I can provide photos of the mods if needed.

[Rick]

Try removing TR33, if this cures the problem then replace with a new transistor.

[alyxlyon]

Try removing TR33, if this cures the problem then replace with a new transistor.

Yeah, was reading about that, was going to measure the voltages (found a thread in here that you have replied to), but then I came accross a problem with schematics and the PCB, PCB has typo error in it . theres 2 TR11's in the board, now I have a question, close to TR33 is the TR31? On my board theres text that says TR11 in it, but at schematics theres R202 linking TR31's pins so I assume thats TR31 since there is TR11 at the back end of the PCB.

Going to remove 33 now to see if it helps.

EDIT: Nope, didn't start to listen, when I turn it on RX led doesn't lit, when I change channel it lits up tho. When I go above band C it turns off and signal jumps to max. Going to take those measurements now that CB doesn't send anymore.

EDIT 2: Not much help on the voltage measure, removed tr31-33 and going to local radio repairer for possible replacements. It's funny that the values on the transistors are totally different from what it says in the schematics of Jackson. I had 2SC2785, 2SC2001 and B1035

[alyxlyon]

Ok, I have replaced TR31-34 and both 25v 1000uf caps, also D66 and resistors seem to be ok. It still doesn't work. Now I hear electrical fuzz, transmit doesn't work at all.

When I transmit with other CB I hear the sound extremely faintly from PJ speaker and theres an extra sound that sounds like bzz bzz bzz ... (I can't describle it haha), when I put more output power to transmitter I'm transmitting with, receiving stops completely on PJ and receive led goes off. Also when I go to USB / LSB green led stops burning. And same thing happends on bands E-F.

Edit: Buzzing sound was because transistor TR32 was facing wrong way, again board images didn't match with part orientation --- wonder why... Anyway, PJ now listens on all bands and modes, but transmit doesn't work at all. TR33 voltage values Emitter 8.52v Base 0 Collector 3.62v, why is collector voltage so low?

Voltage regulator seems to be ok, considering I only have max power output of 13.28v on my PSU TR501 values are E 13.28v B 12.28v and C around 8.25V

If you need I can measure voltages from TR31 and 33, tho TR33 doesn't get the needed power to collector while I press transmit.

I'm clueless now...

[Rick]

I do not understand what the fault is, in you first post, the radio was stuck in TX.

If you had followed what I told you to do it would be easy to find the fault, there is no point in just changing components because you think they are faulty.

What is the voltage on the collector, base, and emitter of TR31, TR32, and TR33 in TX? and RX?

What is the PJ?

[alyxlyon]

Ok, maybe I should've posted the voltage values in the first place.

So here they are (with original TR32 and TR34 and replaced TR31 and 33, since it stopped transmitting constantly after I put the new transistors in).

TR31 E RX 7,48 TX 0,02 - C RX 8,50 TX 7,47 - B RX 6,84 TX -0,04
TR32 E RX 0 TX 0 - C RX 7,48 TX 0,03 - B RX 0,03 TX 0,79
TR33 E RX 3,37 TX 0 - C RX 0 TX 0 - B RX 8,48 TX 8,48
TR34 E RX 1,03 TX 1,03 - C RX 12,57 TX 12,62 - B RX 1,66 TX 1,66

TR501 B RX 12,56 TX 12,61 - C RX 8,46 TX 8,48 - E RX 13,28 TX 13,32
Took TR501 values just in case. As you can see, something is really messed up in there. Values aren't what they are supposed to be I quess.

And once again, when I try to transmit, green led turns off and red doesn't turn on. And that buzzing sound I keep hearing ... well it reminds me of faulty capacitor, I quess the sound is like constant spikes caused by cap charging and decharging endlessly. Accures only when receiving.

PS: what I mean with PJ is simply President Jackson --- just beeing lazy to type it all the time.

So all previous symptoms are there, only thing that has changed after new TR31 and 33 is that it doesn't try to send and receive at the same time anymore, meaning red light isn't on after power has been set on, tho now it doesn't lit at all.

Confirm that I have the right transistor locations from the picture

http://personal.inet.fi/clan/tca/TR31-34_locations.jpg

[Rick]

From the voltage you have given, it looks like TR33 is in the wrong way round and is most likely short base to emitter.

What is the number of the transistor you have used?

The transistor I you is a BC640, looking from the front is Emitter Collector Base.

[alyxlyon]

TR33 is now 2SB892 replacing 2SB1035 (original transistor that was in the radio), according to ECA transistor book 892 is simular to the 1035 and pin polarity is PNP, also pin order is suppose to be E-C-B

Is B892 facing right way when its on a same position as in the picture of previous post. (That picture has been taken before I have done anything, I always take a picture just to be sure). In that picture 2SB1035 text faces inside radio and half circle outside.

I'll try to turn that later on. Don't have much time today.

[Rick]

The easy way to find if TR33 is correctly installed is to first remove it, switch the radio on, and with your DVM check the solder pads where you remove TR33 from the one with about 8 volts is the Emitter.

You may have a short on the collector side on TR33 but this is not a common problem.

[alyxlyon]

Emitter voltage is 8,50 +-0,1v and I checked transistor and it seems to be right. Measured wrong. So Emitter and base values are around. Now, what drops Base down to 3.37v?

And the sound I hear when tr33 is installed sounds like capacitor charging, high pitch sound with increasing pitch, just like camera's flashlight charge sounds. Tho in this case it comes from the speaker. The sound occures only after I've either shorted out tr33 with ground while radio is off or when I switch to PA and back to radio mode. Few seconds after radio has been set on the pitch noise starts. During these few seconds radio doesn't transmit and noise sounds totally normal, but when high pitch sound starts the transmitter led starts flashing.

I'm trying to rule out the transistors, since I have a feeling they aren't the fault here, that 3,37 volts constantly isn't right.

[Rick]

If you are sure that TR33 is ok and fitted in the correct way round, try unsoldering one end of D41 and D71 to see if the problem goes away.
Let us know how you get on.

[alyxlyon]

Yes, I'm pretty sure TR33 is ok, found D71 but where is D41 located? Nvm, found it.

[alyxlyon]

No change, only high pitch sound is now constant steady and really loud, both transmit and receive leds are glowing a bit. Red glows a bit more than green.

I reinserted the original transistors and the sound is precicely the same as begin with. When I put roger beep on both leds starts to flash rapitly and high pitch noise steady noise changes into endless series of short beeps.

[Rick]

D41 is near the 10.695 osc.
If you remove TR33, is the RX ok?
What is the voltage at Pins 6, 7, and 8 of IC4 in RX? and TX?

[alyxlyon]

Heres IC4 values (RX is without TR33 on board, since when it's installed the CB is stuck at transmit)

______TX___RX__
pin 6 4,68v 4,00v
pin 7 4,30v 1,92v
pin 8 7,82v 8,25v

[Rick]

Solder TR33 back in place.
Unsolder one end of D49, it should now be in the RX only mode.
If the RX is ok now it looks like IC4 has failed.