My R26 is literally touching my tube socket V21 pin no. 5 on the PC board. That freaked me out because R16 is not touching V11 pin no. 5 on the board.
I noticed this just as I was getting ready to solder the R26 location in question.
I looked at George's website and several of his photos look like the solder on the back of the board is touching at R26 and V21 pin no. 5. But I'm confused, because wouldn't the design require symetry on the other side of the amp (i.e. at R16 V11 pin no. 5)?
Or am I not seeing this right?
Please help! I had a great, calm and methodical process going on--absolutely enjoying this project. And I don't want to go further until I figure it out. I'm wondering if I'm just not understanding the layout or if my printed pc board is off a bit.
Thanks much!
I noticed this just as I was getting ready to solder the R26 location in question.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I looked at George's website and several of his photos look like the solder on the back of the board is touching at R26 and V21 pin no. 5. But I'm confused, because wouldn't the design require symetry on the other side of the amp (i.e. at R16 V11 pin no. 5)?
An externally hosted image should be here but it was not working when we last tested it.
Or am I not seeing this right?
Please help! I had a great, calm and methodical process going on--absolutely enjoying this project. And I don't want to go further until I figure it out. I'm wondering if I'm just not understanding the layout or if my printed pc board is off a bit.
Thanks much!
A close up R26 overlapping v21 pin no. 5.
An externally hosted image should be here but it was not working when we last tested it.
R26 and R16 are low value resistors, 100 ohms, placed in series with the control grid of the power tube, as a precautionary measure for the purpose of suppressing possible parasitic oscillations in the power tube, under unusual operating conditions.
Pin 5 is the control grid of the power tubes.
Other than the remote possibility of some excess heat being physically transferred to the resistor, and possibly compromising its lifespan, I don't see much of a problem with it physically touching the tube socket at pin 5.
Symmetry is pleasing from a builders point of reference, but electrons can't see and it is of no consequence to them in this instance.
I wouldn't worry about it. Just take your time, and enjoy your build. If you have questions, just ask. We all learn that way. Sometimes it may take a bit for somebody to see a question and get back to you on it.
Welcome to the Tubelab forum.
Win W5JAG
Pin 5 is the control grid of the power tubes.
Other than the remote possibility of some excess heat being physically transferred to the resistor, and possibly compromising its lifespan, I don't see much of a problem with it physically touching the tube socket at pin 5.
Symmetry is pleasing from a builders point of reference, but electrons can't see and it is of no consequence to them in this instance.
I wouldn't worry about it. Just take your time, and enjoy your build. If you have questions, just ask. We all learn that way. Sometimes it may take a bit for somebody to see a question and get back to you on it.
Welcome to the Tubelab forum.
Win W5JAG
Mine looks just like yours. This project was my first amp build. The completed amp is on in my studio all day every day and has thousands and thousands of hours on it. I'm currently building one for my son and another for a friend as gifts. It's truly one of the few projects that have given back to me more than I put in. Enjoy.
There is no problem with your board....they are ALL that way.
It's just one of the many things that happen when laying out a PC board. The layout guy (me) considers the spacing of things with respect to thermal, voltage and current perspectives. R24 is connected to pin 6 of the tube, and can stand a lot more heat than it will find beneath the edge of the tube socket, but a poorly installed R26 accidentally touching the lead of R24 will cause bad things to happen to that output tube and probably a few more parts. The two output tubes must have as much space between them as possible, so as with most things in life, PCB layout is all about compromises and balancing them to make things fit.
It's a lot cooler than my usual stack of books!
It's just one of the many things that happen when laying out a PC board. The layout guy (me) considers the spacing of things with respect to thermal, voltage and current perspectives. R24 is connected to pin 6 of the tube, and can stand a lot more heat than it will find beneath the edge of the tube socket, but a poorly installed R26 accidentally touching the lead of R24 will cause bad things to happen to that output tube and probably a few more parts. The two output tubes must have as much space between them as possible, so as with most things in life, PCB layout is all about compromises and balancing them to make things fit.
It's a lot cooler than my usual stack of books!
In the early 80's I worked for Beltone when their hearing aids were designed and built in Chicago, Ill. I was a packaging engineer which at the time meant I was responsible for making all of the components of the hearing aid fit into its enclosure. I started off working on the 'behind-the-ear' hearing aids which had acres of space compared to the 'in-the-ear' hearing aids which were relatively new at the time.
A typical hearing aid had a microphone, a speaker, a volume control and a PCB that contained a IC chip and the amplifier circuit along with potentiometers that were used to adjust the equalization of the sound. Of course there was also the battery.
At the time PCB layout design was done BC (before CAD) on a light table that was about 3 feet by 6 feet in size. The circuits were developed using translucent tape in either 2 or 4 colors depending on how many layers the PCB had.
Imagine taking everything into consideration that George described and once completed reducing the PCB layout to 1/100th the scale it was created in.
Back then the circuit designers thought of themselves as being special. Of course once computer aided design software for PCB circuit became automated I think those guys lost some of their exclusiveness once the software was able to create the circuits.
A typical hearing aid had a microphone, a speaker, a volume control and a PCB that contained a IC chip and the amplifier circuit along with potentiometers that were used to adjust the equalization of the sound. Of course there was also the battery.
At the time PCB layout design was done BC (before CAD) on a light table that was about 3 feet by 6 feet in size. The circuits were developed using translucent tape in either 2 or 4 colors depending on how many layers the PCB had.
Imagine taking everything into consideration that George described and once completed reducing the PCB layout to 1/100th the scale it was created in.
Back then the circuit designers thought of themselves as being special. Of course once computer aided design software for PCB circuit became automated I think those guys lost some of their exclusiveness once the software was able to create the circuits.
I'd like to see the photos of the holder you mentioned. What I did was use 4 4 inch long screws that I could mount to the board in the four corners using two nuts tightened up against washers on either side of the board.
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