1306 and 1307 replacements plus....

[Lkaskel]

Hey Gang,
It's been a while. Sometimes your job doesn't realize that you have a hobby!!

I have a Robyn 520 on the bench that had no transmit. I checked C179 and it was bad so I replaced it with a 25 volt version. The radio now transmits about 1/4 watt. The good thing, it transmits. The bad thing, probably need a final and possibly a driver. As the 1306 and 1307's are almost unavailable what are you using in replacement for them? This radio will be set back to stock 4/12 watts so I am not worried about needing to drive the heck out of it. I have read on here that the 2166 and the 1969's may work. If that is the case what bias would you set them to?

On a side note I did buy 5-1306's and 5-1307's from a US E Bay seller. I did question them about the fake parts thing and they assured me that they were real. Well, that was not the case. The writing on them was bad and I even tested them in my personal President Washington (1st edition) and none of them worked. Of course. Oh well. On to a different solution with your help.

Thanks as always!!!!

 

[Robb]

Simply replace the 1306 with a 2sc2166 and replace the 1307 with a 2sc1969.
Drop-in replacements, genuine parts can be had at RF Parts . . .

 

[Lkaskel]

Simply replace the 1306 with a 2sc2166 and replace the 1307 with a 2sc1969.
Drop-in replacements, genuine parts can be had at RF Parts . . .

Thanks Robb!!!
Based on my findings with the radio now putting out 1/4 watt would you agree that it sounds like the driver/final?

 

[Robb]

Take each driver/final out and test them with a meter - to be sure.

 

[Lkaskel]

Take each driver/final out and test them with a meter - to be sure.

They both test (continuity) fine and I have a parts tester and they came up as an NPN transistor.

 

[Lkaskel]

They both test (continuity) fine and I have a parts tester and they came up as an NPN transistor.

Maybe voltage regulator?

 

[Robb]

Never worked on a Robyn before.
You need a schematic to trace things out.

 

[nomadradio]

How weak is it on sideband?

73

 

[ExitThirteen]

The radio may simply need a TX alignment, don't rule out the driver and final being bad until you have performed a proper TX alignment first. If you have done an alignment and it still only puts out about 1/4W or so, then you could take a look at the driver and/or final being at fault.


~Cheers~

 

[nomadradio]

Always possible that the transmitter alignment was sabotaged by someone before you first saw the radio.

73

 

[Lkaskel]

Always possible that the transmitter alignment was sabotaged by someone before you first saw the radio.

73

Hey Men,
I can't tell you how thankful I am for your input when I have questions like this!!! Here is a somewhat detailed update.

I really got caught up in the question of "do I have fake transistors or not". I have the Lou Franklin book Understanding and Repairing CB's so I did a deep dive into his explanation of transistors and the transmitter troubleshooting section. I also have the Sams for the 520 (plus many other 858 PLL radios). I used some basic testing of voltages at the transistors during TX. The base for the driver and final were between .68vdc and .74vdc which is right in line with what the schematic says. There is no detail in the schematic for the emitter but based on transistor logic it should be about .6vdc - .75vdc less than the base which they both were. The collector is supposed to be 4.70vdc. I checked that detail against the President Madison schematic and it was the same detail. The reading was 9.7vdc on both the driver and final. I was not able to understand what would cause the reading to be double. During receive the reading on the collector's is 13vdc which makes sense. As my next logical step I pulled the final and was going to replace it with a 1969 that I purchased a few months ago and I now know that the 1307's I purchased are fake. The 1st thing I did was to put the transistor in my component tester and guess what? It came up as a PNP not an NPN. I took my last 1969 and it was a PNP as well. If I were to be honest, I turned of my soldering iron, my de-soldering machine, the meter and scope and just went and sat in my family room for a while feeling as dejected as I have in a long while. How is it possible that every power transistor that I have purchased is fake? It's because there are that many out there. It almost makes me want to give up but I enjoy the good side of this too much. Last night I ordered new 2166's and 1969's from RF Parts ($100) and I found some 1307's from Barkett Electronics ($55). I feel like I can trust these sources so we shall see when they arrive next week. Any thoughts on the voltage readings?

I have read through many of the post from you 3 men and I know that at times you need to take a break and get your head clear. I need to learn that more and more. For the last 6 months I have had a few radios that I have worked on with transmit issues that have stumped me including a Saturn Turbo that is still here. I think that one possibility has been that I have bad replacement parts. Thanks again for your wisdom and kindness! It's the one thing that keeps me in the hobby. I realize that my knowledge is well below many but my desire is strong.

All the best men!!!!

 

[nomadradio]

RF transistors will fool some fancy computerized transistor testers. My theory is that the RF transistor begins to oscillate when the tester applies base current.

Since most newer transistor testers use a fairly low voltage, a NPN transistor will sorta function backwards. The computerized testers are too smart for themselves. An oscillating NPN transistor screws up the computer's NPN test, so it tries PNP. Unless the test-circuit voltage is higher than roughly 6 Volts, it will (sorta) work well enough to fool the tester. In a 4-Volt circuit, a NPN transistor will amplify with reverse polarity applied to it. Just not very well. And once you exceed that six-Volt limit, this won't work at all.

Just my theory, after trying several of the Chinabay component testers.

73

 

[guitar_199]

Nomad, here is a question though.....

If you try to just match transistor characteristics with another number....lets say you consider breakdown voltages, hfes, any frequency dependent limits.... I mean if you do your best to match those numbers..... is there any chance that the transistor you find will work for the original? Or is there more to it than that?

I just know that one of the issues I have is....I pick up one of my radios, see what final or driver is in it....and all I kind find is that they have been obsolete for 20 years!!!!!! So NOW what do you do???

Thanks for any tips....

Bob

RF transistors will fool some fancy computerized transistor testers. My theory is that the RF transistor begins to oscillate when the tester applies base current.

Since most newer transistor testers use a fairly low voltage, a NPN transistor will sorta function backwards. The computerized testers are too smart for themselves. An oscillating NPN transistor screws up the computer's NPN test, so it tries PNP. Unless the test-circuit voltage is higher than roughly 6 Volts, it will (sorta) work well enough to fool the tester. In a 4-Volt circuit, a NPN transistor will amplify with reverse polarity applied to it. Just not very well. And once you exceed that six-Volt limit, this won't work at all.

Just my theory, after trying several of the Chinabay component testers.

73

 

[nomadradio]

For years the japanese-printed specification books were my best guide. What a transistor does is still just numbers.

The publisher, "CQ" of Japan who printed the spec books also printed a substitution book. Each page had a table with a column for each major japanese transistor brand. The jap "2S" number you wanted to substitute was in the far-left column. Across the row for that part number if a particular brand did not make a competing part that matched it, that spot would be blank.

Transistors used for mass-market products like stereo receivers would have a substitute type number in each column. More-obscure applications like "CB final or driver" would only be made by a handful of brands. 40 years ago Sanyo made some CB final transistors. So did Sony. Not any more.

There were more brands competing for that business 40 years ago than there are now.

The sub book was my start point. The part that had specs with the closest match would generally work as a replacement.

The other side of this coin was whether or not a part was listed at one of our regular suppliers. If they had it, just buying the original part made sense. If not, it was time to check if any of the sub-book numbers were listed for sale.

We had a TV-Parts shop here in town who did a sort of "reverse" cross-reference to the 'catalog' plastic-baggie parts from RCA SK, Sylvania ECG or NTE. Dennis would buy original-type number transistors and diodes and sell them for half or less the price of the remarked parts in a printed plastic heat-seal bag.

His place closed 15 years ago.

73

 

[Lkaskel]

I can tell you what I did for my specific challenge. Last Saturday I purchased 1969's and 2166's from RF Parts and some 1307's and 1306's from Barkett Electronics. I decided to pay what the market charges for "real" parts and the reduced price E-Bay charges for what I now know is fake parts. So far I have replaced the driver and final in a Galaxy Saturn Turbo and it now works great!!! I have been working on this radio on and off for 6 months or more. I have purchased transistors for it from E-Bay (different sellers) a few times and as it turns out every E-Bay part was fake. The RF Parts transistors worked the 1st time. I have asked countless questions regarding how to further troubleshoot the radio because what I was doing was not working and in the end the parts were fake. It is soo frustrating to work so hard on something only to find out you have been had but in the end I won. No more E-Bay transistors for me. I hope to work on the Robyn 520 this weekend and I bet it will transmit with the correct parts the 1st time.

Thanks again for all of you who have helped me throughout the year.