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Another 139XLR power supply problem.

I disconnected TR401 I removed TR301. I hooked 13.8V to green wire that would have went to the emitter of TR401. Radio powered up. D302 WAS SHOWING .5VA AND 6VC. Pads of TR302 6VC, E.2V B0.
I Thought RT301 will adjust base voltage of TR302. I can not get more than 6 now. I am doing this without the radio plugged in. So what am I doing wrong. I am loosing my confidence lol.
 
I suggested removing TR302, not TR301. Leave TR301 in there. Was that a typo?

I would also remove fuse F402 during this adventure. There is no need to power the radio while diagnosing power supply issues :) If something goes wrong, you could end up with more melted wires and I do not want to take that blame.

RT301 does adjust the base voltage of TR302, but it requires TR 301 in place to do so. Please go back to post #74 and very carefully do exactly as written in the order that it is written in. I am not trying to be rude, but I cannot make sense of the situation if steps are skipped or misread. If your statement about removing TR301 was a typo, and in fact you removed TR302 and still had those readings with TR301 in place, then that tells me something about TR301 and D302, but I won't say it until I know for sure you have removed TR302.
 
OMG I am getting brain dead. No I removed TR302 we have talked about that transistor so much I just removed it. Oh boy. I may go back to this tomorrow when I am fresh. I am putting a new TR301 in this time. Also when I was looking threw old parts I saw the last hack that worked on this radio had 2SC7105YC in TR301 spot.
 
Low_Boy said:
OMG I am getting brain dead. No I removed TR302 we have talked about that transistor so much I just removed it. Oh boy. I may go back to this tomorrow when I am fresh. I am putting a new TR301 in this time. Also when I was looking threw old parts I saw the last hack that worked on this radio had 2SC7105YC in TR301 spot.
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With how common 945's are, why put anything else in there? I have a parts galaxy FULL of them lol. Ill even mail you one or two if you need one.
 
Low_Boy said:
I stick with them until they work. You will see the final episode. That is if the people helping me stick with me. LOL
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I'm not going anywhere, this is my version of fun!

You should see all the failures in my shed :) Circuits I tried making from scratch that simply didn't work... (partial credit to amazon and ebay for fake parts). I remember when kids toys went from mechanical to electronic, and none of them survived my childhood, lol! Don't let failure deter you, there will be A LOT of that (and cussing) in this hobby. Countless evenings wasted, countless bottles of rum, countless soldering iron burns (my first was at age 7)... You will probably have about two dozen broken radios doomed to be parts sources (which will turn out to be a good thing) before confidence becomes the thing that pushes you forward...
 
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OK This radio is making me crazy. Yesterday I did remove TR401 and TR302. So there was a typo. So looking back. I corrected my errors.

I disconnected TR401 I removed TR302. I hooked 13.8V to green wire that would have went to the emitter of TR401. Radio powered up. D302 WAS SHOWING .5V Anode AND 6V Cathode. Pads of TR302 Collector 6V, Emitter.2V Base 0V.
I Thought RT301 will adjust base voltage of TR302. I can not get more than 6 now. I am doing this without the radio plugged in. So what am I doing wrong. I am loosing my confidence lol.

Unfortunately this morning while still asleep I put a new TR302 back in I removed TR301 like I was not supposed to do. Anyway Even the wrong way I still can not get more than 6 volts on the base of TR302 adjusting RT301 in any direction.
All these components are numbered too much alike.
 
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This process still requires the power supply in the radio to be on and outputting 25v (just make sure F402 fuse is removed.

The reason you were only getting 6v is because, with the power supply not running, it is taking voltage from the divider at RT301, passing it through the base-collector junction, to the base pad of TR302. This is what I would expect with the 25v supply off.

Start over, this time we will take one little step at a time. TR401, TR302, and Fuse F402 removed. Power supply on, but for right now, don't connect the 13v to the green wire (that's part of the next step, be patient). Tell me what voltage you have at the cathode of D302.
 
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There is a sentence I do not understand. If I do not put voltage to the green wire. I will not get voltage to TR302. Also I really do not want to remove TR302 and risk messing up the pads.
 
I can only give advice if the advice is followed. It seems like every suggestion I've made has been deviated from in some way - I'm kinda at a loss here. The pads should be fine unless you are using way too hot of an iron.. Do you have solder wick to remove solder before removing parts? If not, grab the cheapest scrap 50Ω coax you have, separate the braid and flatten it, warm it with your lighter, and rub a small amount of flux on it. Use that to suck the solder from the pads so when you go to put the part back in, the hole is clear and the pad isn't pushed on by the lead being inserted.. If you do that and keep the temperature within 50° of the solder's melting point, you should not damage pads.
 
The reason for not applying voltage to the green wire in this step is to simply look at the diode with nothing drawing power through R304. Thats why you need the 25v supply on and no feedback voltage on the green wire. I was interested in taking this one step at a time because when several steps are done at once it is difficult to say for sure what is working and what is not. With the amount of trouble you have had, it seems like the logical way to approach this. Once we know D302 is working, then we can give it the feedback voltage and assess TR301. And only after we know that is working would we go on to TR302 and so on.
 

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