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Nelson Pass DIY F-5 take 4

If I had it to do over again, I'd likely go with the HEXFREDs as well, just when I ordered the power supply board, the diode boards came with it. I was using the DIYAudio group buy thread for most of my info and figured I should do as they were doing in Rome. I'm sure if you post over on Peters group buy he can explain his selections. My guess is he would fully support the use of the HEXFRED devices as well. His power supply board/diode boards arent built for the F-5 particularly, but are as Peter calls them, a "Universal Power Supply" board, intended for many different projects. He built them, so I figured he knew what he was doing and bought the same parts, there really isnt any dark secret meaning or anything. I saw info, bought the suggested parts, nothing more. I definately believe there is a sonic difference between standard rectifier diodes and FREDS, or other such high brow diodes. As to whether there is any sonic differences between various high brow devices, I doubt it seriously, unless one particular brand was just crappy, I think the difference would not be noticeable.

russellc
 
golana said:
The word I might use would be "discrete". With the ability to use various distributors components. There is a time and place for everything, and if I missed on this one. Oops.
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I think you are right about the time and place thing. The boards Peter supplies are a universal board, not specific to F-5. While doable, this wire thing just caused a glitch is all. Really I think the HEXFREDS would be preferable assembly wise here, and If I had them, they would go in. But, Alas I only have these, and they are dam fine, I'm just having to make adjustments in order to implement them.:sigh:

Russellc
 
Newest development!

Well today I got a new helper! He was walking down the highway and the wife picked him up. Hard to believe someone would have dumped him.
Some times I'm embarrassed to be a Human being. I think it was Mark Twain who said "Humans are the only animal that blushes, or has any need to" or something like that. To what ever sorry bag of poo did this, THANKS! We love him! Typical male, he's going for the remote...

Russellc
 

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specialidiot said:
Good for you Russell!
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Hey, this drilling and tapping isnt so bad! Unfortunately I broke the bit after the third hole. Is the material the heatsinks are made of a lot harder than the stuff ( I believe 6061 aluminum ) I used for the panels? It took forever to drill the first two holes. Plenty of oil, careful drilling, killed the rechargeable battery after two! The only other variable is the bit itself. It came in a two piece set, bit and matching tap for 10-32. Its a funny gold color, doesnt appear to be very high quality. It wasnt hot when it broke either. Off to home depot or ace to find another. Anyone know what size bit goes with the 10-32 tap set?

Russellc
 
Funny gold color = Cobalt alloy, not a bad choice for aluminum but brittle. You need to make sure that, if you are drilling without a press, the drill is held straight and plumb to the work. Take it slow and clean the hole of filings as you drill and tap.
 
westend said:
Funny gold color = Cobalt alloy, not a bad choice for aluminum but brittle. You need to make sure that, if you are drilling without a press, the drill is held straight and plumb to the work. Take it slow and clean the hole of filings as you drill and tap.
Click to expand...

Yes, will do. Do you happen to know what size bit goes with the 10-32 tap?
The bit broke close to the drill, leaving a long piece of it. When clamped in the drill, it was obvious it isnt true any more, but wobbles while turning, so must get new. I think I'll pick up more than one! That's why I wondered if the bit was a standard size, I could just buy a bunch of bits. Unfortunately, I dont have a bit doctor.:sigh:

Russellc
 
Found it. Looks like 10-32 is equal to 5/32's, or a #21 bit. I need to get the 4-40 tap and bit anyway.

Russellc
 
It was a bad bit I guess, I've drilled and tapped three holes faster than just drilling the first hole!

Russellc
 
Glad to hear that you didn't break off that drill bit inside the heatsink. You would have had a most interesting afternoon! :D:D
 
1MOR said:
Glad to hear that you didn't break off that drill bit inside the heatsink. You would have had a most interesting afternoon! :D:D
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Fortunately, it came out. It was very poor quality. The tapp seems to work fine. Oh well. If it had broken off flush, I dont know. I'm sure there are machinist's tricks to deal with that. Otherwise, it would likely just have been sealed up behind the angle piece for its entire life.

I now have the entire box assembled, with the exception of the angle pieces that connect the bottom to the heat sinks. Looking around the amp, everything fits well, but there are a few places where some adjustment is needed, usually by hogging out the through holes in the angle pieces to allow a little adjustment of the panel before clamping down.

I figure I may as well wait until everything else is in place before drilling for them. I'd like to have the basic amp done, minus the aforesaid angle pieces (and I'll be leaving the lid off as it isnt ventilated yet) so maybe it may be playing for Twangfest. After that, dissemble to anodize or powdercoat if I decide to do that. Then the final angle pieces and ventilated top added/adjusted. I have a long weekend off, I'm trying to finish.
Thank heavens the B-1 box of Westends looks easier to assemble!

Once the B-1 is built, focus will go back to finishing the speaker measurement rig....I figure if I say that out loud, the Pearl 2 boards will become available!

Russellc
 
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Glad to hear you have the drill bit thing sorted out.
If you're bringing the amp to Twangfest and you want some protection over the top, you could place a nut or washers between the top plate and the angle pieces the top mounts to, attach the top through those nuts with your 10/32 fasteners. If the top ends up having a 1/4" gap between the bottom of the top plate and the chassis, you'll have a 15 sq. in. vent on the top of the amp.

FWIW, I took some temp measurements, recently. All of these were taken in an ambient 75 f constant with a cheap Harbor Freight pocket infrared device. I've checked this device against other temp gauges and it is fairly accurate. All temps after an hour of power with a plywood board sealing the interior.
Output MOSFETS-136.56, 136.89, 136.1, 136.9 Between the fins, exterior 84.3 Heat sink surface, interior, between the MOSFETs 93 Air temp inside case 88 Again, these temps were taken immediately after sealing the interior space for an hour. I wanted to see the potential for overheating by sealing the top. Surprisingly, no big run ups in temp were seen. I haven't "shot" temps with the top off since I saw what I needed to see, the all-aluminum case and the M&M heat sinks are able to dissipate all the heat the amp can produce.

BTW, I think I'm going to ship your B1 in the assembled state so you can easily see the manner of the fasteners. We should exchange some PM's about how many, what size, and location of your through holes. There aren't many so I can drill and chamfer them before sending.
 
westend said:
Glad to hear you have the drill bit thing sorted out.
If you're bringing the amp to Twangfest and you want some protection over the top, you could place a nut or washers between the top plate and the angle pieces the top mounts to, attach the top through those nuts with your 10/32 fasteners. If the top ends up having a 1/4" gap between the bottom of the top plate and the chassis, you'll have a 15 sq. in. vent on the top of the amp.

FWIW, I took some temp measurements, recently. All of these were taken in an ambient 75 f constant with a cheap Harbor Freight pocket infrared device. I've checked this device against other temp gauges and it is fairly accurate. All temps after an hour of power with a plywood board sealing the interior.
Output MOSFETS-136.56, 136.89, 136.1, 136.9 Between the fins, exterior 84.3 Heat sink surface, interior, between the MOSFETs 93 Air temp inside case 88 Again, these temps were taken immediately after sealing the interior space for an hour. I wanted to see the potential for overheating by sealing the top. Surprisingly, no big run ups in temp were seen. I haven't "shot" temps with the top off since I saw what I needed to see, the all-aluminum case and the M&M heat sinks are able to dissipate all the heat the amp can produce.

BTW, I think I'm going to ship your B1 in the assembled state so you can easily see the manner of the fasteners. We should exchange some PM's about how many, what size, and location of your through holes. There aren't many so I can drill and chamfer them before sending.
Click to expand...

All that news is great! I had a feeling these slightly larger sinks you guys used would pay off.:thmbsp: The Idea about protection is valid. Now that I've got the process down, it isnt going to take that much more time to drill a few more. Mind keeps wandering to B-1 Power supply ideas, got to stay focused on F-5!:D

Russellc
 
And for anyone else wondering about this drilling and tapping the first time,
its quite doable. Also, hand drilling works just fine. The tapping is really the easiest part of the process, and it concerned me the most. It did take a little nerve to drill into the heatsink for the first time! After threading the first hole, I was horrified to find a screw from my 10-32 bag wasnt quite large enough! No worry, one slightly smaller screw got mixed up in the bag, all the tapped holes have worked perfectly. Now I'm not so nervous about drilling the holes for the face plate.

The drilling and tapping process has been well covered in the other 4 or 5 F-5 builds so I wont replicate that here, just a word to those like me with little metal working experience, this is no problem. I worried way to much about it.

Russellc
 
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specialidiot said:
update?
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After a brief delay waiting for some items to be delivered from Ebay purchases, I am ready to resume. I was racing for Twangfest, and to that end I was cutting corners and using more and more parts figuring "I'll change that out afterwards" until I just decided to slow down and build it right the first time.

The entire box is now built, heatsinks drilled and tapped with the exception of the 2 holes to hold the output devices, which are going to be done this evening. All 16 holes are drilled for the diode sets, I just need to grease the backs and tighten the screws.

The barrier strip is mounted and wired, the ebay purchase is teflon insulated hookup wire to go between the barrier strip and the diodes, and from the diodes to the power supply cards, which are all mounted on stand offs.

The binding posts and RCA are mounted, RCAs to board is a run of Cardas wire I had left over from making interconnects. Its shielded and should work nicely. Cardas is always tricky to solder, I just dialed the heat up a little and the enamel flowed off and the solder flowed smoothly on.

Its getting very close. Just heard from Westend, the B-1 box is on the way,
I should have a PASS amplification system soon. Now for that Pearl II, hopefully that board will materialize soon!

Another thing, I think I've said this already in other posts, but for this amp, using the HEXFREDS like you did is the far simpler way to go. I may have eliminated the barrier strip, would have required a fraction of the holes, and NO assembly! Next Time.....

Russellc
 
Still out here, should be mounting the outputs/amp boards tonight. Final wiring/grounding before fire up. Dam its hot out in the garage! Thanks goodness for beer!:D:beer:

russellc
 
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