Axial 4,700uF replacement prototype board.

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Axial 4,700uF replacement prototype board.

Postby exxos » Tue Feb 28, 2017 2:44 pm

A mini-project I did today, is to try a solution to replace the generic 4,700uF Axial caps as found in many Atari's from ST to Falcon etc.

The overall size of the board isn't any larger than the existing axial capacitor. While the 4,700uF original probably has a pretty bad ESR figure, my board has a bank of 8x 1,000uF low ESR capacitors which can push 660mA per capacitor (5,280mA total). This is likely a huge overkill, but less capacitors can be used.

I'm not planning on a PCB run of these unless there is enough demand. It is also possible other values can be replaced, like the 2,200uF, or 10uF used in the falcons etc.

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Re: Axial 4,700uF replacement prototype board.

Postby dlfrsilver » Wed Mar 01, 2017 12:43 pm

Interesting, so you mean Chris that the original value is not good enough, or is it something else ?

what this capacitor is doing exactly, and what is its role on the motherboard ?

your idea is in anyway very interesting.
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Re: Axial 4,700uF replacement prototype board.

Postby Maeke » Wed Mar 01, 2017 1:45 pm

the value was good, 20 years ago, but those caps tend to go bad while aging. It's simply the same thing as the psus needing new caps.

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Re: Axial 4,700uF replacement prototype board.

Postby dhedberg » Wed Mar 01, 2017 5:41 pm

exxos wrote:A mini-project I did today, is to try a solution to replace the generic 4,700uF Axial caps as found in many Atari's from ST to Falcon etc.

Actually, the 4700uF 16V radial capacitor in the Panasonic FR series can be used to replace the original axial capacitor without any changes. The distance between the ends of the terminals is about 6 cm and the distance between the holes on my motherboard was about 4.5 cm, so the terminals are long enough to reach thru the holes.
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Re: Axial 4,700uF replacement prototype board.

Postby exxos » Wed Mar 01, 2017 9:56 pm

dlfrsilver wrote:Interesting, so you mean Chris that the original value is not good enough, or is it something else ?


They are 30 years old. All caps are failing these days.

dlfrsilver wrote:what this capacitor is doing exactly, and what is its role on the motherboard ?


It's bulk capacitance for the board.


dhedberg wrote:Actually, the 4700uF 16V radial capacitor in the Panasonic FR series can be used to replace the original axial capacitor without any changes. The distance between the ends of the terminals is about 6 cm and the distance between the holes on my motherboard was about 4.5 cm, so the terminals are long enough to reach thru the holes.


That is what I have been doing, but think the leads were to short to solder directly to the board. I never really liked that idea, but is of course doable. I just thought as I had a free few mins I would try a alternative board layout. The value of the caps is double and the ESR likely better than a single cap. Its not a huge deal, but at least in 30 years time when the capacitance starts to fail, it's still going to be better than the original spec cap.

I think such boards offer an interesting solution as many smaller axial's could be replaced with ceramic SMT versions which will likely never fail, easily done with a little adapter PCB.

I have had a fair bit of interest in this board so far, So seems others like the idea of this type of solution. I likely will get a few made, and if people like them and want other "ranges" of boards then they can be done also in due time. Of course if there isn't much interest in such boards, then no big deal.

One thing I have also noticed is the white background on floppy power up on the desktop isn't dimming anywhere near as much now. Even with my own designed PSU where the regulation is super great, there is still the wires and track length to the motherboard, so it makes sense to replace the cap either way.
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Re: Axial 4,700uF replacement prototype board.

Postby dlfrsilver » Thu Mar 02, 2017 8:52 am

exxos wrote:
dlfrsilver wrote:Interesting, so you mean Chris that the original value is not good enough, or is it something else ?


They are 30 years old. All caps are failing these days.

dlfrsilver wrote:what this capacitor is doing exactly, and what is its role on the motherboard ?


It's bulk capacitance for the board.


dhedberg wrote:Actually, the 4700uF 16V radial capacitor in the Panasonic FR series can be used to replace the original axial capacitor without any changes. The distance between the ends of the terminals is about 6 cm and the distance between the holes on my motherboard was about 4.5 cm, so the terminals are long enough to reach thru the holes.


That is what I have been doing, but think the leads were to short to solder directly to the board. I never really liked that idea, but is of course doable. I just thought as I had a free few mins I would try a alternative board layout. The value of the caps is double and the ESR likely better than a single cap. Its not a huge deal, but at least in 30 years time when the capacitance starts to fail, it's still going to be better than the original spec cap.

I think such boards offer an interesting solution as many smaller axial's could be replaced with ceramic SMT versions which will likely never fail, easily done with a little adapter PCB.

I have had a fair bit of interest in this board so far, So seems others like the idea of this type of solution. I likely will get a few made, and if people like them and want other "ranges" of boards then they can be done also in due time. Of course if there isn't much interest in such boards, then no big deal.

One thing I have also noticed is the white background on floppy power up on the desktop isn't dimming anywhere near as much now. Even with my own designed PSU where the regulation is super great, there is still the wires and track length to the motherboard, so it makes sense to replace the cap either way.


That's a great discovery, this means that this huge capacitor is mostly responsible for the dimming.

I'll look for your price for the little replacement board.
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Re: Axial 4,700uF replacement prototype board.

Postby nukebloodaxe » Thu Mar 02, 2017 8:55 am

I'd be interested in a small quantity of these (let's say 7 at most) to upgrade the machine collection my end. I am especially interested in one-shot replacements using ceramic SMTs where possible, as they will likely outlive the lifetime of the other components on the boards. However, ceramics or electrolytic, it's going to improve the stability of the machines anyway.

Quick question, I tend to buy components in small batches to avoid the customs duties my end, and I can see myself running through your 4MB STFM upgrades this year (the compacted on MMU RAM version.) Do you have any plans to produce more of those?

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Re: Axial 4,700uF replacement prototype board.

Postby Maeke » Thu Mar 02, 2017 9:56 am

nukebloodaxe wrote:I'd be interested in a small quantity of these (let's say 7 at most) to upgrade the machine collection my end. I am especially interested in one-shot replacements using ceramic SMTs where possible, as they will likely outlive the lifetime of the other components on the boards. However, ceramics or electrolytic, it's going to improve the stability of the machines anyway.

Quick question, I tend to buy components in small batches to avoid the customs duties my end, and I can see myself running through your 4MB STFM upgrades this year (the compacted on MMU RAM version.) Do you have any plans to produce more of those?


How many do you need? It would be usefull for him to know.

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Re: Axial 4,700uF replacement prototype board.

Postby exxos » Thu Mar 02, 2017 11:55 am

nukebloodaxe wrote:I'd be interested in a small quantity of these (let's say 7 at most) to upgrade the machine collection my end. I am especially interested in one-shot replacements using ceramic SMTs where possible, as they will likely outlive the lifetime of the other components on the boards. However, ceramics or electrolytic, it's going to improve the stability of the machines anyway.


Ceramics used in the audio stages will give better quality for starters, all the "hiss" comes from electolytics. I know this well as I have designed many amplifiers over the years. Anyone using them in audio paths should be shot. Though price is always a factor.

I don't have time at the moment to work out all the dimensions and voltages needed for the Falcon , theres a few different ones there. Though if anyone has any ideas for the next board then let me know. There are 2,200uF used on some machines for example. Though the 4,700 is used on just about everything, so makes sense to start with something like that value.

I will get some prices on some PCB's, would be cheaper per PCB to get a run of like 200 or something, though if only 20 or less are going to sell, it works out cheaper to do them as a prototype run. But will see what the options are.

Someone suggested adding a couple more pads to give power to upgrades which need more juice, I think thats a great idea, considering the caps total a large value and mA rating, then it would be perfect for a break out power connector.

nukebloodaxe wrote:Quick question, I tend to buy components in small batches to avoid the customs duties my end, and I can see myself running through your 4MB STFM upgrades this year (the compacted on MMU RAM version.) Do you have any plans to produce more of those?


I do indeed yes. I brought some more DRAM a few weeks ago and have about 50 PCB's from the last PCB runs. I am hoping to start building next week, though it depends on free time, and I need to also do the Falcon PSU's which people been waiting for for ages.

A guess is there will be about 10-20 made, though I can confirm there will be more made and in my store at some point , hopefully in the not to distant future.
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Re: Axial 4,700uF replacement prototype board.

Postby spiny » Thu Mar 02, 2017 1:56 pm

if they are around a tenner , then put me down for five :)

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Re: Axial 4,700uF replacement prototype board.

Postby alienkidmj12 » Thu Mar 02, 2017 2:04 pm

ill take 1, where do they connect to ?

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Re: Axial 4,700uF replacement prototype board.

Postby exxos » Thu Mar 02, 2017 2:07 pm

alienkidmj12 wrote:ill take 1, where do they connect to ?


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Re: Axial 4,700uF replacement prototype board.

Postby exxos » Thu Mar 02, 2017 2:09 pm

spiny wrote:if they are around a tenner , then put me down for five :)


If I order 250 caps the price comes right down, though thats like 32 boards.. I guess thats a sensible number to stock up on anyway.

Also depends if people want this as a kit, or assembled ?, as assembling stuff is very time consuming.
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Re: Axial 4,700uF replacement prototype board.

Postby alienkidmj12 » Thu Mar 02, 2017 2:35 pm

i meant where do the other end of those cables goto, they disappear off the right side of the image :)

ignore me, i think those cables are from something behind lol .. im being stupid, everthing looks easy.
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Re: Axial 4,700uF replacement prototype board.

Postby exxos » Thu Mar 02, 2017 2:37 pm

alienkidmj12 wrote:i meant where do the other end of those cables goto, they disappear off the right side of the image :)


That is the PSU connector.. nothing to do with this cap kit..
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Re: Axial 4,700uF replacement prototype board.

Postby spiny » Thu Mar 02, 2017 2:39 pm

alienkidmj12 wrote:i meant where do the other end of those cables goto, they disappear off the right side of the image :)



thats the power lead for the floppy drive, nothing to do with the replacement cap board :)

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Re: Axial 4,700uF replacement prototype board.

Postby nukebloodaxe » Fri Mar 03, 2017 6:08 am

exxos wrote:
spiny wrote:if they are around a tenner , then put me down for five :)


If I order 250 caps the price comes right down, though thats like 32 boards.. I guess thats a sensible number to stock up on anyway.

Also depends if people want this as a kit, or assembled ?, as assembling stuff is very time consuming.


Personally, I can cope with the kit form, it will give me more practice with the soldering iron as well. You could always put up the majority in kit form for sale, and periodically put up assembled versions; the best of both worlds approach.

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Re: Axial 4,700uF replacement prototype board.

Postby nukebloodaxe » Fri Mar 03, 2017 6:18 am

exxos wrote:Ceramics used in the audio stages will give better quality for starters, all the "hiss" comes from electolytics. I know this well as I have designed many amplifiers over the years. Anyone using them in audio paths should be shot. Though price is always a factor.
...
Someone suggested adding a couple more pads to give power to upgrades which need more juice, I think thats a great idea, considering the caps total a large value and mA rating, then it would be perfect for a break out power connector.


Those pads would be a very valuable addition to the design, and I appreciate your expertise in audio; I can hear capacitors "singing" a bit too well, to the point I can listen to my wireless mouse.

exxos wrote:
nukebloodaxe wrote:Quick question, I tend to buy components in small batches to avoid the customs duties my end, and I can see myself running through your 4MB STFM upgrades this year (the compacted on MMU RAM version.) Do you have any plans to produce more of those?


I do indeed yes. I brought some more DRAM a few weeks ago and have about 50 PCB's from the last PCB runs. I am hoping to start building next week, though it depends on free time, and I need to also do the Falcon PSU's which people been waiting for for ages.

A guess is there will be about 10-20 made, though I can confirm there will be more made and in my store at some point , hopefully in the not to distant future.


I'm glad to hear that, but please help the Falcon guys first, I can wait. I'm still a bit amazed that I've come across such a decent person as yourself helping out the community, the only other I personally know is Mario Becroft (we used to meet up at the Tariland club when it was still going.) Which reminds me, I need to sort out lunch with him soon.

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Re: Axial 4,700uF replacement prototype board.

Postby exxos » Fri Mar 03, 2017 10:02 am

nukebloodaxe wrote:Those pads would be a very valuable addition to the design, and I appreciate your expertise in audio; I can hear capacitors "singing" a bit too well, to the point I can listen to my wireless mouse.


RF interference somewhere. I remember years ago when I designed a radio receiver, if I tapped a electrolytic on the board, I could here it in the audio. It was like a "boing" sound which decayed over a few seconds... I guess like tapping a microphone.. That's how sensitive things can be. I've designed a lot of audio gear and electrolytics always give trouble. Large value of ceramics are available in recent years, so no need to keep using electrolytics (there are exceptions such as 1,000's of uF will cost a lot in ceramic form, so cost is still a factor in some cases)

nukebloodaxe wrote:I'm glad to hear that, but please help the Falcon guys first, I can wait. I'm still a bit amazed that I've come across such a decent person as yourself helping out the community, the only other I personally know is Mario Becroft (we used to meet up at the Tariland club when it was still going.) Which reminds me, I need to sort out lunch with him soon.


Ahh Mario Becroft, did he never release his stuff like IDE interface ?

Yeah need to stop getting side tracked on all these little projects... Though sometimes I am just to tired to work on some stuff, so a little project like the caps boards can be done when I am like 90% asleep, so no creation time gets wasted ;)
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Re: Axial 4,700uF replacement prototype board.

Postby dlfrsilver » Fri Mar 03, 2017 11:05 am

Chris, you can tell me the approximative price for this little enhancement ? The price on your site looks very pretty.

If you confirm, i will then buy one each for all my STs and STEs.
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Re: Axial 4,700uF replacement prototype board.

Postby exxos » Fri Mar 03, 2017 11:24 am

dlfrsilver wrote:Chris, you can tell me the approximative price for this little enhancement ? The price on your site looks very pretty.

If you confirm, i will then buy one each for all my STs and STEs.


I am hoping to produce the kits for about £7.
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Re: Axial 4,700uF replacement prototype board.

Postby dlfrsilver » Fri Mar 03, 2017 12:31 pm

Oh now that an awesome price. Ok, tell me when you have some boards done then, i will buy them :)
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Re: Axial 4,700uF replacement prototype board.

Postby exxos » Fri Mar 03, 2017 1:09 pm

dlfrsilver wrote:Oh now that an awesome price. Ok, tell me when you have some boards done then, i will buy them :)


The PCB's are basically on order, likely be a couple of weeks. I guess it depends on how much customs rip me off for import duty more than anything for the price. Can't see it being far out from £7 anyway.
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Re: Axial 4,700uF replacement prototype board.

Postby dlfrsilver » Fri Mar 03, 2017 10:44 pm

Will those be the electrolytic model or the ceramic one ?
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Re: Axial 4,700uF replacement prototype board.

Postby exxos » Fri Mar 03, 2017 10:50 pm

dlfrsilver wrote:Will those be the electrolytic model or the ceramic one ?


Don't get what you mean ? For the falcon there are lots of caps, I haven't looked what options there are for the values yet.
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