1050 Power Supplies

[seastalker]

I've enjoyed this thread on A8 computer PSUs here: https://atariage.com/forums/topic/95416-power-supplies/

 

For the 1050 Floppy Drive, what is a good reliable (not frying-out) power supply IF one were to go original vs a new custom one?

 

In my current stash, I have one with just the Atari logo and name on the top with the bottom microscopic Model # 14310 (or 14319?) Power 4481J (maybe date code) = 9 VAC / 15.3 VA.

 

I also have one with the name and logo bigger and additional line "A Warner Communications Company" (Part Number C017945) Outputting 9V AC 31 VA

 

I don't know the suggested VA from the manual .PDF. Maybe this is a case of tomato tomato (you READ that... maybe I should write Toe-MAY-Toe / Toe MA Toe)

 

[Nezgar]

9VAC / 15.3VA is enough for a 400/800/1200XL, 850, 830, 1010 but not enough for a 1050 or 810.

 

9VAC / 31VA is ample for a 1050 or 810.

 

The Atari AC supplies are good and reliable, you don't have to fear them frying anything. Just don't use the underrated supply on the disk drives.

[seastalker]

Thanks Nezgar! Sometimes I buy collections and forget which PSU goes to what. I put my 15.3VA with my 400 and my 31VA for my 1050 with another 31VA spare. Now what to do with my two 1.5 amp 'The Ingot" PSUs...

[Nezgar]

Perfect pairings Of course, the 31VA supplies will also work just fine on the other stuff too.

 

Best course of action for the ingots is to trash them BUT - snip off the cord with the DIN connector at the brick, and save it for future attachment to a modern trustworthy 5V 2A+ supply. ... and might as well keep the AC cord end too, there's a chance you might ever need it for something there... Needed one recently for a flakey 1702 monitor that turned out to be just a frayed AC cord that only worked when contorted certain ways...

[+DrVenkman]

Thanks Nezgar! Sometimes I buy collections and forget which PSU goes to what. I put my 15.3VA with my 400 and my 31VA for my 1050 with another 31VA spare. Now what to do with my two 1.5 amp 'The Ingot" PSUs...

 

I've got five or six of 'em. You know what to do - cut off the DIN ends and solder them to modern reliable +5VDC 2.5A power supplies.

[Nezgar]

[seastalker]

Just circumcised two bricks at both ends. I wouldn't feel right selling time bombs to Atari friends for a couple of dollars. Got to keep them Atari machines in good health. I solder, but if anyone is interested in my cut-offs to make modern day reliable jobbies, just pm me.

[_The Doctor__]

Nice to know about the cords, wonder what shipping could or would be. I rejoice every time an ingot gets chopped up and leaves this earth!

The real fun of the ingot can be had on the business end of a sledge hammer! You never know how the epoxy will crack and what goodies might become exposed destroyed or turned to dust! It's fun, it's ingot whacking day! Everyone celebrate!

Edited September 5, 2018 by _The Doctor__

[xrbrevin]

for 1050 power see this thread:

http://atariage.com/forums/topic/282454-atari-dd-1050-repair-tips-and-psu/?hl=%2Batari+%2Bdd+%2B1050+%2Brepair+%2Btips+%2Band+%2Bpsu&do=findComment&comment=4102956

 

any PSU that outputs 9 volts AC at 1.3 amps is sufficient

[1050]

Don't you mean instead 3.1 Amps?

[xrbrevin]

the research on the linked thread concluded that 1.3 amps is sufficient. there are links to other threads from there that provide more research info. one on an atari sector forum provides idle, read and write max amp draw figures

 

i dont fully understand the "VA" measurement of the Atari device AC output but many aftermarket AC power supplies dont use that format, they just list an "a" number instead.

i thought the info from the thread may be of use in case people on here were found aftermarket PSUs that just list the "a" number - so they can make an informed decision.

anyone know how to explain "31VA"?... is it old terminology?

[_The Doctor__]

https://www.rapidtables.com/convert/electric/va-to-amp.html

 

http://www.powerstream.com/VA-Watts.htm

 

depending on ball park figure....

 

31/9=3.444 repeating

 

however I did not take the root mean squared value in the formula, in any event 3.1 A to 3.4 A is just fine. This provides enough power for inductive kick as a drive powers up completely with perhaps a dragging disk already loaded in the drive(or the off chance you left cardboard in the spindle producing locked rotor), it handles sustained work loads across many hours of head grinding disk spindle rotating fun. It ensures enough stored energy in the core of the transformer without cooking the windings/coils over time as energy is dissipated to heat both in the drive with perhaps with locked stepper and spindles or a stubborn dragging disk as well as the heat given off in the transformer block itself.

So the power block won't be so hot as to be a great way for making eggs or bacon and won't burn down your house.

Edited September 6, 2018 by _The Doctor__

[manterola]

31VA=9V x 3.45A

[+tf_hh]

i dont fully understand the "VA" measurement of the Atari device AC output but many aftermarket AC power supplies dont use that format, they just list an "a" number instead.

i thought the info from the thread may be of use in case people on here were found aftermarket PSUs that just list the "a" number - so they can make an informed decision.

anyone know how to explain "31VA"?... is it old terminology?

 

No, in the days were power supplies have an efficiency factor below 75% and less, it was common to declare the max. power in VA (Volt-Amps). The simple reason: This value is higher than the real power in Watt. So it´s a typical marketing / advertisement thing... today it´s more common to use Watt instead of VA.

 

Take a look here. This whitepaper explains in english the differences between Watt and Volt-Amps (VA).

[_The Doctor__]

yep the ole peak vs rms scam of years gone by.... why that's a 1000 watt speaker boi! Hey wait, yes-siree you betcha peak for an instand before the voice coils smoke

I think someone mentioned root mean squared...(RMS) in an ealier post...

Hey I got this killer amplifier kicking out a zillion watts per channel... look at the massive current rating! It weighs a few ounces, hot as all get out and produces nothing but wow flutter clipping and drop outs... if only the buyer new it was not RMS and only peak rated and what ohms.

LOL ah what fun.

Edited September 6, 2018 by _The Doctor__

[Nezgar]

With the drives only needing 1.3A, I guess it means the original 31VA supplies should be able to decently handle 2 drives, even more so with my 3rd-part 3.4A one.

 

IE I've used a 5.5x2.5mm splitter like this before, and it does work: https://www.ebay.com/itm/322951654092/

Usually only really with 1 drive actually on at a time, but now I shouldn't have to worry too much about 'overloading' the supply if both drives happen to be operating.

 

Although if its efficiency is only 75%, real available power may only be 2.4A-2.5A, so could still be pretty close.

[Gunstar]

For two years now I have been using the 1027's 9.5V 31VA PSU with one of my 1050's without issue. Of course the 1027 PSU's plug is too large for the 1050, so I had to splice in a proper size barrel plug. It's all pretty relative, as all my 9V 31VA Atari uneversal PSU's actually rate 10.4V on my multimeter, the 1027 PSU registers around 11-11.5V, IIRC, on my multimeter. The Atari peripherals where made to handle power variances that are surprisingly substantial, IMHO.

[Nezgar]

Atari gave those voltage regulators a big job in their AC computers and peripherals, and beefy heatsinks.... Oh the warmth.

[_The Doctor__]

unloaded transformers always read higher than what they are actually putting out.... once resistance is met the the magnetic field settles down to it's actual intensity and you should see it's closer to the 9.1VAC the droids were looking for...

[Level42]

With the drives only needing 1.3A, I guess it means the original 31VA supplies should be able to decently handle 2 drives, even more so with my 3rd-part 3.4A one.

 

IE I've used a 5.5x2.5mm splitter like this before, and it does work: https://www.ebay.com/itm/322951654092/

Usually only really with 1 drive actually on at a time, but now I shouldn't have to worry too much about 'overloading' the supply if both drives happen to be operating.

 

Although if its efficiency is only 75%, real available power may only be 2.4A-2.5A, so could still be pretty close.

What gives you the idea that a 1050 or 1027 PSU has an efficiency of 75% ?

 

They are only transformers and transformers have an efficiency of about 98-99%.

 

I guess you misunderstood tf_hhs post about old (linear) power supplies BITD, but the efficiency figure he mentioned is about power supplies that include a linear way of AC to DC conversion and regulating DC.

 

With the 1050 (and 400 and 800) this part of the PSU is inside the device. So in your example, the transformer is rated at 3.4A and it should actually be very well capable of supplying that AC current.

 

The loss in effiecny is done inside the 1050.

Edited September 9, 2018 by Level42

[Level42]

Atari gave those voltage regulators a big job in their AC computers and peripherals, and beefy heatsinks.... Oh the warmth.

No idea where this feeling comes from ?

 

Ataris designers actually practiced something that was very common in those days.

An external transformer and AC/DC conversion and regulation inside the device.

 

If you check the 1050 schematic for its ac dc conversion and voltage regulation section you will see they used the 7805 for the 5v. 7805s accept anything between 7V and 25V, so supplying it with (rougly) 10V DC Input is simply just fine.

 

For the 12V they needed a higher input voltage of course so they used a simple doubler circuit which makes about 20V as an input for the7812. The input voltage of this is specced between 14,5 and 30V.

 

They also provided a pretty big heat sink and put it well in the back end of the 1050. It also doesnt become that hot. People think that when they feel something is hotter than their hand then that it is bad for electronics but electronics are usually fine with higher then body temperatures. The designers also provided for pretty damn large electrolytic capacitors for good filtering of AC. Those caps are the parts most influenced by heat though.

 

Remember they designed for devices that expected to work for a year or 5......its amazing enough that most still work fine after 35....

 

So...IMHO, they did a good job. You have to realise in the late 70s, early 80s the 78XX regulators were pretty new, reliable, SAFE, and cheap. Switching power supplies were expensive and tstill had some issue then....not the least high frequency interference and possible lethal voltages when one of the many parts needed for a switching PSU died.

Edited September 9, 2018 by Level42

[Nezgar]

IE I've used a 5.5x2.5mm splitter like this before, and it does work: https://www.ebay.com/itm/322951654092/

Usually only really with 1 drive actually on at a time, but now I shouldn't have to worry too much about 'overloading' the supply if both drives happen to be operating.

So... I finally actually tried this silly splitter cable with two drives connected at once... and all weirdness happened. If either drive is switched on, the other drive will also turn on (even if the power switch is off!) .. Only happens when there is also an SIO cable connection between the two drives.

 

So definitely a ground loop going on there, and I hereby revoke the above recommendation, except as a source of 2.5x5.5mm barrel connectors to hack off

[_The Doctor__]

You are lucky nothing is damaged. No melty SIO cable line!

Edited October 28, 2018 by _The Doctor__

[retrotechshop]

For those still looking, I found this power adapter one that looks like it should work: https://www.acdcpowershack.com/products/ac-ac-power-supply-9v-ac-3330ma-2-1-x-5-5mm?variant=44704878982

[retrotechshop]

Update: The connector that game with the adapter was too small for the socket so I soldered a compatible connector on it and I can report the drive is powered up and working