HELP PLEASE? 2N3904NPN RFout trans of 3 stg fm trns brng hot

[NGNEER23]

Hello,
I have recently built a 3 stg. fm transmitter from a copper clad board using the toner-transfer method. Once I got everything soldered in and verified my work I plugged in the 9v source and noticed that the RF out transistor was getting so hot that I couldn't touch the top of the plastic without burning myself; thought the plastic was going to melt. No other component is hot that way; the pre amp and oscillator Ts aren't hot nor are any resistors or caps. I bought a 3 pk of magnetic wire for the coil and there were 3 ones, 2 colored and 1 copper color and I know you have to scrape enamel off but[color=#0000BF] I assumed[/color] that on the [color=#0000BF]copper colored one[/color], which is the one I used [color=#0000BF]for the 5Turn/3mm coil, didn't have enamel[/color]. Thought that was the problem so I made new coil and scraped the ends and replaced it and the rf out trans. hoping that would help, but it didn't. Here are the schematic, board layout and some pics of completed circuit. I am very grateful and appreciative of any help you can give me. Thank you so much. If you want to see the video( you can ff through a lot to get to pertinent parts) [url]http://www.youtube.com/watch?feature=player_detailpage&v=ft7-bxCA0y4[/url] of the one I built, I would appreciate it cause I think it might help. I built this one with the toner-transfer trace method where as this guy built his with pieces of one-sided board and glued on 9V rail and 5(5mm^2 pieces) as a crude but effective brd and soldered the varcap on with positive on the 9V rail but on a 3V 3stg he build with a manufactured board he soldered it like I did with flat part facing down ??? BTW, power trace is roughly 40 mil, trace around varcap, cap, and coil to oscillator trans net is roughly 30 and the rest is 25 mil. Thank you again for any help. Don't know if it works because my frequency counter hasn't arrived yet but put on hold when I felt that trans. 2N3904 NPN transistors throughout.

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Schematic done in Eagle Cad

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Board in Eagle Cad with suggested traces using rat's nest and some minor changes

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Traces with board oriented like schematic

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Component side. Unsure about polarity placement of varcap.

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[pebe]

Your bottom two pics are the same so I assume the PCB layout in the centre one is as viewed from under the board.

I assume you are using the 2N3904. If so, you have the emitter and collector connections of the transistors reversed.

[NGNEER23]

Actually, I flipped the picture of the bottom so y'all could see it like it was on top. The pic posted of the bottom has been rotated 180 and flipped 90. Here's what the bottom really looks like. I double checked the 2N3904s and looking at the flat side, its EBC. There's a B????? that is a NPN that's, from flat side, CBE and I made sure I got it right. I probably shouldn't have flipped the pic of the bottom. Again here it is from the top turned horizontally from right to left:

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That should help you guys see it correctly now. I don't know why i flipped the back in the first place. What should I do knowing that everything is in correctly? That transistor is hot as all get out. Got my thermocouple out and it went from 78 to 160 and climbing as it sat with the 9V connected. I don't know if I should have run a trace differently or what. The way it looks is that it's possible the electrons are flowing over that 27K res to the base or maybe the inductor is wrong somehow(polarity?) and it's jumping to the collector straight away or bypassing the inductor and going to the emitter???

Help please. Thanks again in advance!!!

[pebe]

Yes, my fault. I didn't scroll down far enough to see the bottom photo. If I hand then I would have seen that you had flipped the other two.

There are three possible faults.
1) C7 is short circuit.
2) R6 is the wrong value (too low).
3) T3 is itself faulty.

I suggest you remove C7 and R6 and see if T3 still gets hot.
If T3 is then OK, replace C7 and R6 one at a time until T3 again gets hot.

[NGNEER23]

Thank you so much, Pebe. I greatly appreciate the suggestions. Will try as soon as I can and let ya know what happened. I suspect I need to make another board with a heavier toner lay because at fed ex kinkos, the gent put it on normal and I read that you need it on heavy. Maybe too thin of traces? IDK. Can't hurt to try.

The value of R7 is 2k7, so what might you suggest as a better value. That's what the bloke in the video used and his was fine. They even have a store where they sell em. ??? Who knows. Thanks so much again. Cheers

[pebe]

There is no R7 so I suppose you mean R6. Its value should be 27K. That is what is in the circuit and also the man in the video referred to the value when he said when he said he had put it in the wrong place.

If it looks like that transistor may be faulty (and it wouldn't surprise me if it got that hot) then replace both R6 and C7 with new ones in case they caused it.

The size of the tracks on your board should be quite OK. None of them are taking much current.