A16 FAN

[braincell]

I hooked up my A16 after many years and wow it is noisy. It's loud and uneven. I should replace it. What size fan is this? I will be using this for mixing as I now have three very nice stereo hardware effects. I normally use the Echo Gina for recording. It has 2 XLR inputs. I heard you can remove the fan of the A16 and mount it upside down without the case. I am a little reluctant to do this. I don't want a lot of dust to get in there. Maybe I should do that.

[astroman]

you can safely remove the fan if you use an original Thinkpad 16V PSU.
Those IBM PSUs were really high quality, it will auto-shut itself off if you switch off the A16, no need to unplug
It doesn't have (AC) leakage over the output DC, as many other PSUs show.
Point is that the internal regulation of the A16 probably hasn't got much to regulate, so it keeps cool.
Try it, there are tons of these PSUs on ebay for a few bucks...
But it has to be an original IBM, 'compatible' units will not work and may even fry the A16
(I've seen it myself with a supermarket switching PSU, the A16 became hot as hell, but survived...)

cheers, Tom

[braincell]

Sounds like good advice. What does the original one look like? I'm afraid I might get the wrong one and fry it! I see a lot of PSUs on ebay but all are cheap copies and they don't even say the brand name. I wonder what is the highest quality fan I could get?

[astroman]

that's the proper one - you may find a cheaper supplier, but it's worth the amount.
iirc a fan is not very effective, as the regulator's heat dissipation sits under the main circuit board, away from airflow.
I'd choose a radial type as used on graphic cards to shovel air to the outside and run it on 5V
but it's not necessary, the box becomes handwarm only.

cheers, Tom

[borg]

My 13 year old A8 has been working for almost 10 years without a fan... It was making a lot of noise, so I removed it (not that easy, though).
In the beginning I checked regularly if the unit was running hot, but that didn't happen.
Last week it had been on for more than 24 hours, no problem.

I don't know about an A16, if it draws more power...

[jhulk]

the only things that get really hot are negative

and positive power regulators

i take it the psu supply for the a16 is a ac supply

and there is a power diode to retify the ac to dc then power regulators and ripple caps for the regulated supply

you can fit passive heat sinks

or replace the fan with the same type but a silent one if you get a fan controller

you can slow them down they will still give enough air for cooling but run slower for no noise same type of thing for the zalman silent flower coolers

there cheap of off ebay a couple of quid for each

[astroman]

sorry jhulk, but this special case is about a different kind of beast...

the regular PSU is an 18V 3A DC type, of course a transformer plus rectifier as to be expected.
BUT what follows as regulation inside the A16 is so strange that even educated folks shook their head.
It's NOT the usual 7805 plus 7815/7915 design

I have no idea why, but with the afformentioned IBM PSU the regulation doesn't seem to kick in at all
(hence no heat)
while an 18V 'chinese' switching PSU makes it go totally out of control

there is nothing to modify for improved airflow, as the heat spreader sits below the circuit board
it hasn't even contact with the space in whicht the fan is running...
probably the reason why borg's unit still lives

it's most likely a design flaw by accident: someone mirrorred the parts in the CAD software...

cheers, Tom

[Immanuel]

So Tom, are you saying that it is worthwhile to swap the original 18v PSU for the 16v IBM PSU - even though, there will be a voltage loss?

[astroman]

there is no voltage loss: opamps usually run at 15V bipolar
the original PSU is rated 18V but delivers way more, which is non-critical as the difference is simply transformed into heat
(dunno how the drop is calculated exactly, but it depends on load)
if the designer was slightly generous in estimating what opamps and converters will draw there may be some stuff to burn
and that's what the unit is doing...

btw I've replaced mine as some channels showed intermediate spikes of noise, not really audible, but on the meters.
It's not easy to work on that circuit board, solder is very(!) solid on it.
I happened to get a couple of Korg converters from the 880 Soundlink series, which feature the same chips as the A16
(but technical manuals with circuit diagrams are available, so some modding may apply)

cheers, Tom

[jhulk]

most opamps work from -18/+18 volt rails max but can go as low as -5/+5

the higher the voltage usually the less the noise floor

optimal working voltages for opamps is -15/+15

but there are a lot of single voltage opamps that work at a lower voltages

18v dc 16vdc the only thing thats going to happen there is less heat

but you would need a higher ampage for the same wattage range

due to there being less voltage

if the psu is rated for 1000w

and you use a less voltage psu you would need the psu to still give out the 1000w

as if it gave the same amp reading of say 2amp

then the lower voltage 16v x2amps will give you 32 watts

but the 18v x2 amps will give you 36watts

meaning the 16v psu will work harder than the 18v version

so if you do use the 16v version make sure the output wattage is the same as the 18v version

so say its a 2amp on the 18v version giving 36watts you would need to devide the 36watts by 16v to get the correct ampage for the correct wattage required

which would be 2.25 amps

so that both provide the correct power rating as if not then heat problems will happen

[astroman]

a bit long winding... what's the point ?
I have suggested (and linked) a powersupply which is speced for 72 Watt
(and of course I measured the opamp and converter rails before connecting it)
it's a top notch device and worked flawlessly, there is no if, when, or maybe
I had the PSU from a Thinkpad and I bought a 2nd one for the A16, which worked equally well...
the original A16 PSU (external+internal) is a piece of crap.
originally I wanted to get rid of it alltogether and thought it would be an easy trick to replace it
but then I couldn't even figure out the logic behind it :p
(which I've heard from some other folks, too)

cheers, Tom

[jhulk]

thats fine then

you have worked it all out for him

im a keyboard repair tech and was just putting caution to the wind

as you cant just use any old psu

but as seeing you have tested a psu with the same rating and found it works great

then you have provided a good working substitute for others to use

but from a view point from some one who does not know

its good to know all information

as if they did something wrong on your say so

it would be you that would get the blame even if they do it wrong or use a different device on your suggestions

as this is a diy solution so use at your discretion as im not accountable if it goes wrong statement

[astroman]

yeah, that's why I always emphasize it has to be THAT IBM model and only that.

I wouldn't have expected the overheating with a noname switching PSU (18V), unless someone hadn't phoned me about it.
His original PSU was broken, he picked up the noname at the electronics department and the box ran nuts.
I verified his statement with a similiar device that's used for TFT monitors.
Exactly the same result.
As he was in urgent need because of a project I sent him my original PSU
(I wanted to replace it anyway, but at that point in time didn't know it's details yet)

the IBM Thinkpad PSU was just a 'let's see what this will do...'
after checking the internals... without a clue how to replace that kind of regulation.
didn't expect it to perform that well.

soundwise I'm a big fan of the old A16, so I try to support them as good as possible...

cheers, Tom

[braincell]

Astro:

Could you post a photo of your psu?

By the way I had a problem recording bass direct with my A16 but I think that was computer related as I had other issues which seem to be resolved with my new computer. Don't know why but this is true or it could be some improvement in Scope 5. Since you said it sounds so fine, I can't wait to try it again! I only wish it had some XLR inputs.

Are we in agreement that it is safe to remove the fan with the current psu and it would be fine? Why is it so difficult to remove the fan? I had hoped it was a clip-on but now you say it is soldered. That is bad since it is so small and cheap. Small fans spin faster and are more prone to failure. I know it's going to die because the sound is not steady.

[astroman]

here's the front and back of the 2nd one I bought, there are lot's of different part number for the same device
this one is from the Lenovo time obviously
you might as well use the 3.6 A version which came with the Thinkpad

but my memory betrayed me... sorry, for dissing, but airflow isn't that bad in the A16
it's not cool that the regulation is in the basement to heat the chips from below, but there's roughly an inch for airflow from left to right

iirc the on/off switch is on the top cover with rather short wiring, not sure if you can open it fully without cutting the wires
but probably enough to cut the wires of the fan
I wouldn't suggest to run the unit without a fan in a rackmount.
best option would be to put it on a large metal plate, as the heat spreaders are mounted to the bottom of the A16 case

actually you don't need to open it, if you mount a fan to the outside and let it blow into the A16's lower half.
(depends on where the unit sits)

cheers, Tom

[astroman]

... By the way I had a problem recording bass direct with my A16 but I think that was computer related as I had other issues which seem to be resolved with my new computer. Don't know why but this is true or it could be some improvement in Scope 5. Since you said it sounds so fine, I can't wait to try it again! ...

with a passive bass you should use an impedance matching device, either a preamp or a transformer (DI)
an active bass is ok to be directly connected

I said that I like the sound a lot, but it's far from what most people would consider 'a great tone' today
it's a bit grainy, not hifi at all, highs slightly rolled off... but it's a cool sound, it's fat ...

cheers, Tom

[braincell]

I'll have to check it out again. If anyone wants to buy it let me know. The Echo Gina does not require a box for bass.

[astroman]

it probably has an input with instrument impedance, called hi-z (usually 500K - 1MOhm)
the A16 has 20 KOhm impedance if you plugin an asymetric source, which is an inconvenient load for a passive PU
it will deliver sound, but slightly harsh
(for a rockbass sound supposed to end in an Ampeg emulation not that much of a problem)

cheers, Tom

[braincell]

At least my Scope cards are still good!

[jksuperstar]

I was just looking for a 2nd/backup supply for my A16 ultra.

Astroman, just to be clear, you just plugged a T42 power supply into an un-modified A16 ultra? The plug fit ok, and you didn't modify the internal part of the supply in the A16?

I like the T42 option, since those supplies are cheap ($15US), even if they are a bit bulky for portable use. At least they aren't wall warts (hate them, since I use a rack mounted power filter, and that means the space next to power filter needs to be shallow and inaccessible due to the wall warts hanging over them, or just left empty).