Folsom's great little 7297 Chip Amp

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Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #580 on: 12 Sep 2016, 03:37 am »
Nice to hear Brad, are you working on some buffers from Keantoken? I think he's going to have some regulated ones shortly too. I sure like mine.

BRN

Re: Folsom's great little 7297 Chip Amp
« Reply #581 on: 12 Sep 2016, 04:35 am »
Jeremy,

I have the first run boards that do not include the regulation. I purchased the RJM X-reg to supply the regulated power. I have all the parts but still need a chassis. Also, I have not had the time to put it together. In addition everything sounds so good with the 10k passive I put together I have not felt the need for the buffer. The reason I wanted the buffer was to match the new phono kit I just got, so I want to put that together first and see how it sounds with the passive first.

I jumped on the buffer based on your recommendation, so can't wait to try it.

Brad

KR500

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Re: Folsom's great little 7297 Chip Amp
« Reply #582 on: 13 Sep 2016, 05:07 pm »
I mounted the heat sink on the inside of the chassis with the fins butting up against the rear wall interior .
My question is;  by drilling 3/32nd" holes on the back and bottom of the chassis located between each fin of the heat sink ..... is that  adequate ventilation or should I enlarge them or make more of them. don't want to perforate more than I need to
thanks

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #583 on: 13 Sep 2016, 05:19 pm »
Really you want holes on the top and bottom for convection to occur. On the bottom and side won't do too much.

KR500

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Re: Folsom's great little 7297 Chip Amp
« Reply #584 on: 13 Sep 2016, 07:03 pm »
Thanks Folsom !
I will drill in the top also

shadowlight

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Re: Folsom's great little 7297 Chip Amp
« Reply #585 on: 13 Sep 2016, 08:06 pm »
Anyone have a recommendation for IEC connector with fuse builtin.  Need something to use with antipole.

lacro

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Re: Folsom's great little 7297 Chip Amp
« Reply #586 on: 14 Sep 2016, 01:17 pm »
Thanks Folsom !
I will drill in the top also

If you want to drill nice evenly spaced ventilation holes in your case, here is a method I developed that works very well.

http://www.audiocircle.com/index.php?topic=142008.msg1514790#msg1514790

S Clark

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Re: Folsom's great little 7297 Chip Amp
« Reply #587 on: 14 Sep 2016, 02:15 pm »
Anyone have a recommendation for IEC connector with fuse builtin.  Need something to use with antipole.
Apex Jr. has one cheap that should work.  Scroll to mid page...
http://www.apexjr.com/FuseHolders.htm

indosmokejon

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Re: Folsom's great little 7297 Chip Amp
« Reply #588 on: 14 Sep 2016, 04:27 pm »
Hello, my name is Jon, brand new to this forum.  I found my way here from searching for Folsom's 7297 chip amp after seeing it referred to somewhere else on the web.  Are these boards still available for purchase?  I would love to give this a try.  I don't own a single chip amp but I am definitely intrigued after reading quite a bit of this thread as well as others regarding Folsom's work. 

KR500

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Re: Folsom's great little 7297 Chip Amp
« Reply #589 on: 15 Sep 2016, 11:00 pm »
Thanks for the link on how to drill evenly spaced holes. I'll probably add those to the top .
To start I drilled 5/32nd holes between each heat sink fin on the bottom and top of the chassis and also a row on the top of the chassis back.
Putting rubber washers on the transformer mounting screws and a thin layer of rubber on the bottom of the unit allowed me to test fit the chassis top on with no issues.
I was wondering if having the large caps on the Antipole where they are so close to touching the chassis bottom is a potential issue/problem ? The Antipole just fits on the partition height wise or I would have raised it . When I got the NABU surplus case I grabbed a sheet of amplifier isolation rubber for a buck so I could add that if needed.
I soldered the chip to the PCB after lining it up on a flat surface with the heat sink but now I wonder if my wood workbench top wasn't perfectly flat as the chip in the case only matches up to the sink on the top third. The chip isn't perfectly perpendicular to the sink surface or I drilled and tapped the mounting hole at a slight angle.
Might have to desolder and raise the sink with a sheet of something so the mounting screw for the chip lines up properly.







Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #590 on: 15 Sep 2016, 11:19 pm »
The Antipole's caps are fine.

The heatsink to chip really is the hardest part of building this amp... which isn't very hard compared to lining up a dozen transistors!

indosmokejon

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Re: Folsom's great little 7297 Chip Amp
« Reply #591 on: 16 Sep 2016, 05:36 am »
Hey Folsom, is this project still available for purchase?  I would love to give it a try.

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #592 on: 16 Sep 2016, 05:37 am »
Yes, I've emailed and personal messaged you.

indosmokejon

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Re: Folsom's great little 7297 Chip Amp
« Reply #593 on: 16 Sep 2016, 09:15 am »
Ok. Sorry about that. I am obviously new here and I am not quite up to speed on the site. I will search for that. Thanks!

lacro

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Re: Folsom's great little 7297 Chip Amp
« Reply #594 on: 16 Sep 2016, 01:56 pm »
Thanks for the link on how to drill evenly spaced holes. I'll probably add those to the top .
To start I drilled 5/32nd holes between each heat sink fin on the bottom and top of the chassis and also a row on the top of the chassis back.
Putting rubber washers on the transformer mounting screws and a thin layer of rubber on the bottom of the unit allowed me to test fit the chassis top on with no issues.
I was wondering if having the large caps on the Antipole where they are so close to touching the chassis bottom is a potential issue/problem ? The Antipole just fits on the partition height wise or I would have raised it . When I got the NABU surplus case I grabbed a sheet of amplifier isolation rubber for a buck so I could add that if needed.
I soldered the chip to the PCB after lining it up on a flat surface with the heat sink but now I wonder if my wood workbench top wasn't perfectly flat as the chip in the case only matches up to the sink on the top third. The chip isn't perfectly perpendicular to the sink surface or I drilled and tapped the mounting hole at a slight angle.
Might have to desolder and raise the sink with a sheet of something so the mounting screw for the chip lines up properly.

It looks like there is a gap between the HS and the PCB which would indicate the chip is tipped outward at the top.
You can try bending the chip slightly back in vertical alignment. However, the hole you drilled and tapped in the Heat Sink (HS) may also be out of alignment or drilled at an angle as you mentioned. This could pull the chip outward at the top.

I would take the board and HS out of the chassis, and set it on a known flat surface such as glass or a piece of MDF. Use a combination square to check if the chip is perpendicular to the board. If it's not, try bending it into alignment then check that the the tapped hole is perfectly centered. If the hole is off, flip the HS over, and drill/tap a new hole.

A good way to make a perfect tapped hole is use a drill dress to drill the hole, and use the drill press to tap the hole by inserting the tap in the drill press chuck, and turning the chuck by hand, not under power. This keeps the tapped hole perpendicular.

If bending the chip perpendicular with the board creates a gap between the chip and the heat sink when the HS is pressed tightly to the board, it would indicate that the chip was installed with the straight legs set deeper than the bent legs during soldering. This would make the top of the chip contact the HS, but not the bottom of the chip. The solution would be de-soldering the straight legs only of the chip, and lifting it into perpendicular alignment.

Something else to consider is anchoring the HS to the chassis. The reason being, the heat sink is a little top heavy, and could tip, and bend the chip possibly damaging it if the chassis was carried on its side. With my latest build I am going to drill/tap the thick section of the HS, and screw it directly to the bottom of the chassis.
« Last Edit: 16 Sep 2016, 03:05 pm by lacro »

KR500

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Re: Folsom's great little 7297 Chip Amp
« Reply #595 on: 16 Sep 2016, 06:03 pm »
Thanks for your post and suggestions Lacro , the one about using the tap by hand mounted in the drill press is a good one , the Heat sink is mounted to the chassis base with three #4 bolts and butts right up to the rear plate . I hate to desolder the chip but may have to , shimming the heat sink to make it perpindicular to the chip seems like not the answer

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #596 on: 16 Sep 2016, 06:09 pm »
This is why I only solder the chip in two places at the far ends on the top. It's easy to just hit their solder point and get the chip to adjust. Then do the rest when you're sure.

If there was an easier chip mounting process I'd be all about it. There was another version of the chip but it was lower wattage and discontinued.

KR500

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Re: Folsom's great little 7297 Chip Amp
« Reply #597 on: 16 Sep 2016, 08:53 pm »
Yep Folsom , I definitely should have waited after soldering the first 2 legs on the chip per your instruction sheet . I never thought of tapping with my drill press turning by hand , that would have made the non perpindicular issue go away. Going off the path just a small amount on the heat sink mounting hole made it a problem.

lacro

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Re: Folsom's great little 7297 Chip Amp
« Reply #598 on: 16 Sep 2016, 10:23 pm »
I never thought of tapping with my drill press turning by hand , that would have made the non perpindicular issue go away. Going off the path just a small amount on the heat sink mounting hole made it a problem.

Using the method with the tiny m3 or 4-40 screws requires a bit of finesse. Keeping constant downward pressure on the DP quill with the hand crank requires a gentle, but firm touch. It might be better to have an assistant so your not fighting the quill return spring at the same time your turning the chuck. When tapping these tiny fine threads, I like to tap the first 3-5 threads, and release the tap from the chuck. Then finish tapping with a tap handle.

Folsom

Re: Folsom's great little 7297 Chip Amp
« Reply #599 on: 20 Sep 2016, 06:43 pm »
I'm down to 6 amp boards, and around 20 Antipoles. One gentleman has a claim to 5 amp boards if he claims them soon, but otherwise, I guess... form a line :lol:

If I reprint I don't know when at this point, because they won't pay for themselves anytime too soon.