Pass DIY F5 Amp Build

M

MrBoat

Audioholic Samurai
This is the second one. The first one I built I never really got time to build a proper chassis for. My buddy has it powering his Klipsch RF-7 speakers. I was given a rather large box of matched P & N channel JFETS that are supposedly quite good, albeit NLA. At any rate, the man that has gifted me the use of them also kicks whatever other associated parts I might need if he has them in stock. Only stipulation being, he does not want me to sell or give away the parts. If I ever quit being interested in electronics, he will have them back. I do welding for him, occasionally over the last 25 years to now.

Also, I don't want just another Euro styled, or Chinese type universal chassis. Definitely don't want another black, blue LED amp either. Thinking a hand built aluminum chassis with wood trim. While I am waiting for the rest of the components for the power supply, I have time to think about it. Meanwhile, I have the board stuffed except for the MOSFETS. Will get to drilling and threading the heat sinks this weekend. That's the only thing I am really reliant on is factory made heat sinks. I have thought about making my own, or perhaps even liquid cooled, for having the tooling and experience to make those, I suppose. Maybe something unique will occur to me in the future. There are other amps I want to build, as well.

Here's the boards for each channel. Some time was also spent reading the tiny printed values of those Dale resistors and testing them beforehand.


The heat sinks, which roughly measure 12" x 6.5" x 1.5" are without any holes for the boards. I think when I got these, diyaudio store was out of this particular size so I ordered elsewhere. Diyaudio's sinks has their proprietary, universal mounting scheme.


Here is the PSU board awaiting parts. I thought I had bought them already, but I was mistaken. I am just going for the +/-25V supply for the 25 watt version of the F5. I have higher sensitivity speakers that perform even with 3-4 watts. I may build the 50watt (F5 Turbo) at a later date.


 
M

MrBoat

Audioholic Samurai
Plugging along. Got the heat sinks drilled and tapped. I don't drill all the way through, and since most hardware stores in this overgrown cow town rarely have bottom taps on the shelf, I just buy two regular ones and dress the starter off of one of them. Otherwise, the holes are always on the verge of not having enough threads. I like to leave the bottom most threads just a bit incomplete, so that the screws cut that final half turn and really locks them in good.

It's Important to keep all the swarf cleared from the holes when dealing with such small, fine threads in aluminum or they can be washed out easy by the debris. As far as oil in this case, less is more, and something like olive oil is just sticky enough to hold the swarf into the flutes of the tap. Of course you want to back it out and clean the tap frequently. I used the circuit board, taped to the heat sink to mark the holes with the drill bit first.


I actually drilled the 4 standoff holes first, and then screwed the board with the MOSFETS in place to mark those last two holes last. It's nice when all the screws will start without a wrench.


Here, I was using the board fastened with the standoffs in place to mark the the MOSFETS with a drill bit, before removing the works to drill and tap those. I didn't even bother with the drill press.


Everything lines up. Now all I have to do is solder the leads to the MOSFETS in place. I have the thermal insulators in place. I have the mica/paste system as well but maybe try this way for a change. Either way, success. There is still a thermistor that gets mounted Next to the MOSFETS, and they get bent over until they touch that metal washer on the FET.


Power supply parts won't be here until the end of the week. In the mean time, I will make some of the chassis sub frame parts at work this week, like the rails that mount to the heat sink. Going to use some wood on it somehow.

Also have a tube pre/headphone amp kit to build at some point.
 
M

MrBoat

Audioholic Samurai
Upside-down in the pics just to show the power transistors. I set it up just to start imagining the chassis.

 
M

MrBoat

Audioholic Samurai
Since this section is also about "tips and techniques," I must add what has been a huge improvement to my DIY existence. I was struggling, to the point of my eyes watering, to read the resistors and the values in both schematic, and on boards. This visor, that comes with 5 different magnification strength lenses, really helps, and in a more panoramic sense as well. I was trying to use a jewelers loupe, and the trying to search with such a narrow window was as fatiguing as the vision conditions themselves. By the end of one soldering session, tears would be flowing from my eyes. I have had one cataract procedure and will have another, at some point.

Now I can see at a much more comfortable working distance from my face. Also, the PCB board holder is a luxury as well. Sure makes the task less arduous. The little LED headlamp is adjustable by just sliding it forward from it's hold, or is detachable.


 
slipperybidness

slipperybidness

Audioholic Warlord
Since this section is also about "tips and techniques," I must add what has been a huge improvement to my DIY existence. I was struggling, to the point of my eyes watering, to read the resistors and the values in both schematic, and on boards. This visor, that comes with 5 different magnification strength lenses, really helps, and in a more panoramic sense as well. I was trying to use a jewelers loupe, and the trying to search with such a narrow window was as fatiguing as the vision conditions themselves. By the end of one soldering session, tears would be flowing from my eyes. I have had one cataract procedure and will have another, at some point.

Now I can see at a much more comfortable working distance from my face. Also, the PCB board holder is a luxury as well. Sure makes the task less arduous. The little LED headlamp is adjustable by just sliding it forward from it's hold, or is detachable.


As you know, good tools and the right tools make all the difference!

A combo lamp/magnifier on an articulated arm is another must-have item for this type of work. I have done many gaming controller modifications for XBOX 360 and XBONE, and gutted NES carts and NES/SNES controllers to install RPi and game emulation into them. Especially the xbox stuff with SMDs, it takes a magnifier, tweezers, and a steady hand, as SMDs were not really designed for manual work. I have installed mod chips in XBOX controllers, and moved buttons to triggers on the back instead of the front.

Note that I will manually read a resistor, but I also ALWAYS give it a quick double-check with an Ohm-meter to confirm. Kind of like the old "measure twice, cut once" advice. I do that for my caps and inductors too, it's a quick sanity check, and be sure the new parts are actually in spec.
 
slipperybidness

slipperybidness

Audioholic Warlord
@MrBoat
The DIY scene doesn't get a lot of traffic on this site, but I thought you may be interested to see a bit of my work over the years.


 
M

MrBoat

Audioholic Samurai
As you know, good tools and the right tools make all the difference!

A combo lamp/magnifier on an articulated arm is another must-have item for this type of work. I have done many gaming controller modifications for XBOX 360 and XBONE, and gutted NES carts and NES/SNES controllers to install RPi and game emulation into them. Especially the xbox stuff with SMDs, it takes a magnifier, tweezers, and a steady hand, as SMDs were not really designed for manual work. I have installed mod chips in XBOX controllers, and moved buttons to triggers on the back instead of the front.

Note that I will manually read a resistor, but I also ALWAYS give it a quick double-check with an Ohm-meter to confirm. Kind of like the old "measure twice, cut once" advice. I do that for my caps and inductors too, it's a quick sanity check, and be sure the new parts are actually in spec.
I do indeed check the components, and then write the value on the tabs, and if it's a single component, will even go as far as to write on a piece of masking tape and stick it to it. Tells me the value, and reminds me that I did check it already if I am to put the project down for awhile.

I agree with you. I would not want to 2nd guess the components if something went wrong. Mostly though, the strain was from trying to orient the numeric values on the little vishay resistors on the visible side when bending the legs to fit the thru-holes and orienting the bands a certain way on other, non-polar resistors. Huge difference with the new tools.

I do need to get one of those articulated 3rd hand tools. Thank you for reminding me.
 
M

MrBoat

Audioholic Samurai
@MrBoat
The DIY scene doesn't get a lot of traffic on this site, but I thought you may be interested to see a bit of my work over the years.


Will check this out when I get home this evening.
 
M

MrBoat

Audioholic Samurai
More progress, with the power supply rectifier/filter now completed. Now it's onto the chassis. Have some aluminum being delivered with our other metals order at work. Will probably arrive Monday.

The little diagonal cutters bottom right pretty much suck, in spite of good reviews. The blades have nicks on the cutting edge and all these haver cut is component leads and copper wire. I have a pair of Sandvik (Lindstrom) cutters that are at least 30 years old and although somewhat dull by now, there are no nicks on the cutting edges. Ordered another that is made in Germany. Will see if it is better.

 
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Alex2507

Alex2507

Audioholic Slumlord
A combo lamp/magnifier on an articulated arm is another must-have item for this type of work.
I've got a cheesy one that the socket and switch are super glued together in the ON position (only for the last week or so). It's time for a new one that lacks the external springs which have an audible resonance that's sort of bugged me for years. It's hard to see what the build quality is like on these things from pics so I thought I'd ask for a recommendation.

This one lacks the springs and seems to have a lot in common with similar lamps closer to double the price. I figured somebody on the forum must be a lamp/magnifier expert. :)

Edit: Another one
 
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M

MrBoat

Audioholic Samurai
I've got a cheesy one that the socket and switch are super glued together in the ON position (only for the last week or so). It's time for a new one that lacks the external springs which have an audible resonance that's sort of bugged me for years. It's hard to see what the build quality is like on these things from pics so I thought I'd ask for a recommendation.

This one lacks the springs and seems to have a lot in common with similar lamps closer to double the price. I figured somebody on the forum must be a lamp/magnifier expert. :)

Edit: Another one
The visor I posted earlier is better than the magnifier lamp, IMO. It makes for a wider working window at a comfortable distance without having to keep things in one place so much. It could use a bit stronger light but then, brighter light might reflect off of a shiny circuit board and instead be a handicap. So far, strong overhead light with a color towards daylight (4000k) and all is visible.
 
slipperybidness

slipperybidness

Audioholic Warlord
More progress, with the power supply rectifier/filter now completed. Now it's onto the chassis. Have some aluminum being delivered with our other metals order at work. Will probably arrive Monday.

The little diagonal cutters bottom right pretty much suck, in spite of good reviews. The blades have nicks on the cutting edge and all these haver cut is component leads and copper wire. I have a pair of Sandvik (Lindstrom) cutters that are at least 30 years old and although somewhat dull by now, there are no nicks on the cutting edges. Ordered another that is made in Germany. Will see if it is better.

Yeah, let me know it you find very good flush cutters. I have gone through several of those over the years. Once they start getting worn with normal use, they get demoted to softer plastic snipping only.
 
slipperybidness

slipperybidness

Audioholic Warlord
I've got a cheesy one that the socket and switch are super glued together in the ON position (only for the last week or so). It's time for a new one that lacks the external springs which have an audible resonance that's sort of bugged me for years. It's hard to see what the build quality is like on these things from pics so I thought I'd ask for a recommendation.

This one lacks the springs and seems to have a lot in common with similar lamps closer to double the price. I figured somebody on the forum must be a lamp/magnifier expert. :)

Edit: Another one
Mine looks very similar to the last one you listed. It has been in service for many years.

 
slipperybidness

slipperybidness

Audioholic Warlord
The visor I posted earlier is better than the magnifier lamp, IMO. It makes for a wider working window at a comfortable distance without having to keep things in one place so much. It could use a bit stronger light but then, brighter light might reflect off of a shiny circuit board and instead be a handicap. So far, strong overhead light with a color towards daylight (4000k) and all is visible.
I personally tend to prefer the magnifier lamp myself, I do have and use both. But, I find that I use the lamp much more. A lot of it likely has to do with the brighter light, but then I may be working on even smaller parts too, where the lamp may show its advantage.
 
M

MrBoat

Audioholic Samurai
Yeah, let me know it you find very good flush cutters. I have gone through several of those over the years. Once they start getting worn with normal use, they get demoted to softer plastic snipping only.
I ponied up for the Knipex, and also ordered another pair of the Lindstrom. Also have these that are almost as old as the Lindstrom. These were given to me by a solder tech that were basically from the company's bulk jobber supply house. No daylight through the cutting edges but I cannot make out any brand on them, or even a place of origin. These are my all purpose utility nips that have stayed on my computer desk, or any other place I have kept a regular seat since. The Lindstrom were just slightly more precise than these.

The tiny coil spring has been gone for years. I used these for lure making, and just about anything else to do with wire.



I will say, out of the box, the Knipex are quite sharp and the cutting edges match up perfectly. Will see how long they last. These were 3X the cost of the well, amazon reviewed C.H.P brand.
 
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M

MrBoat

Audioholic Samurai
Homemade current limiter that gets some use occasionally, for these types of things, or for plugging in old electronics that have been idle for some time. It works rather well.

 
M

MrBoat

Audioholic Samurai
Onto the framing. Built a tray for rigidity. Top framing will be easier. Still need to ventilate it and add hardware holes. The two risers for the power supply board will further stiffen the tray.



Here it is, all welded up.


An idea of the arrangement. This saves space, even though, I plan on going beyond the heat sinks with the facade,etc. Still need to add standoffs to the tops of the risers.


ETA: Just noticed the PSU board is in backwards with regard to the transformer.
 
M

MrBoat

Audioholic Samurai
Finished the risers and vented the bottom tray. The feet of the risers will be vented thru as well. Not trying to be fancy with the anodized polished aluminum, but is what I had, cut out from a section of 1" x 4" box tubing. Still cool, even though it will rarely be seen.





 
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