What figures are critical. Matching AC/AC 16v adaptor

[thomo57]

l'm trying to find a matching a wall step down transformer to a Thorens TD 147.
This particular turntable is missing its adaptor.
I have tried one off a Thorens TD318 that l have and it run beautifully so next step is to buy one.
I'm no electrician so I'm asking for some advice.

The one that l found closest to it on the bay is slightly different to the Thorens one l tried so my question is if the ebay one can be used.

The Thorens
Input 240 volt, 50hz
Output 16 volt / 160 mA, 2.6va

Ebay one
Input 230/240 50hz
Output 16volt 2.5 a,(24 volt 2500ma)

 

[wmgwizard]

Input voltage/frequency must match

Output voltage must match

Output current should meet or exceed requirement IE: item requires 1a input 1a + is acceptable, .8a is not

 

[lini]

Output current should meet or exceed requirement (...)

Actually that's not quite correct or respectively a bit simplified. Overdimensioning in terms of current capability can be problematic in case of conventional (= transformer-based) AC/AC and unregulated AC/DC power supplies - due to the nominal voltage referring to the nominal current capability, while the actual output voltage can be a good bit higher, if the current demand is lower than the nominal current capability. And it can also be problematic in case of switched-mode AC/DC power supplies, quite a few of which will behave rather oddly, if the powered device doesn't draw enough current.

Greetings from Munich!

Manfred / lini

 

[toxcrusadr]

Assuming the above is true - and I don't doubt it - your proposed unit has about 15x more current capability than required. If you already have this unit, you could try it out, and monitor voltage in use. If it's high, or noisy (or ? ), you could try one with lower output. Or figure a way to 'waste' some of the output.

 

[thomo57]

It will run fine on a little less than 16 volts, and polarity doesn't matter, so a lot of older power supplies can be pressed into service. Try a thrift store.

Long ago I used to run a TD160 on 9 V AC, if memory serves. It would still spin up on its own, just took a little longer. Once it's spinning, lower voltage actually means lower motor vibrations. Some more advanced power supplies (e.g. Linn Axis) intentionally ramp down the voltage after start-up.

Is this a viable option from an AK post last year

 

[45rpmspinner]

As long as the hertz and voltage [which can in fact vary] are correct, the available current doesn't matter.
The motor will only ever draw the current it needs under load anyway.
Honestly, if the input mattered that much, I would think Thorens would've provided a regulated power supply originally.

 

[WaynerN]

Wait a minute. The OP says the wall wart is AC to AC, so he has to be concerned about the sine wave which I believe in Australia is 50 hertz. His Ebay model has more current then required, but his motor is more then likely a synchronous, which is dependent on line frequency (50 Hz), so there really should be no problem, as the Ebay one is a higher ampacity.

 

[lini]

Honestly, if the input mattered that much, I would think Thorens would've provided a regulated power supply originally.

Not necessarily. Because a manufacturer will of course choose an unproblematic model as stock power supply for his product. And if a user swaps that for a different model, that's his own risk - an understandable postition, but of course not really helpful, if original replacements aren't available anymore...

Anyway, let's go into detail: Buffer cap for the electronics after the rectifier is a 25 V type - so effective input voltage shouldn't exceed (25 V + ca. 1.4 V (= rectifier loss)) / 2^0.5, which is ca. 18.67 V, and that at a current of ca. 17 mA (= stopped state current demand according to the service manual).

For example, the popular Triad WAU16-400 (16 V/400 mA nominal) has a specified idle Voltage of a 18.6 V - and hence will most likely unproblematic. But if they offered an even weaker one with for example 300 mA, the idle voltage would be even higher and might not drop enough at a current demand of 17 mA.

I'd still call the TD147 not all too problematic in that regard, though. Whereas a more problematic case would for example be the TD280II: Service manual says "powered from a low voltage AC source between 16 and 19 Volt" - but the buffer cap after the rectifier is again just a 25 V type, so that the effective input voltage again shouldn't exceed ca. 18.67 V, although in this case at a not quite as low current demand of ca. 38 mA. So from the service manual text a user might think that for example an 18 V/500 mA power supply should still be ok, while I'd rather deem that somewhat problematic already.

Greetings from Munich!

Manfred / lini

 

[thomo57]

Anyone of these suitable.
I've gotten lost in the technical conversation and still lost for what l need.
I had a mini stroke last year and figures bamboozle me
Not that l was any good at maths and figures to begin with

Any of the ones in the images suitable

 

[lini]

t57: The first one would most probably be ok, but I'd deem that likely to have a UK power plug. The others don't qualify at all.

Hmmm, let's see... Ok, found the Ebay auction for the first one: First and third picture show the output plug - which to me looks like it's most probably a 5/2.1 mm variant, but one with just a short barrel length of 9 mm. So this plug might not be a good fit, so that I'd suggest to swap that - ideally for the original plug type (this one: https://roka-berlin.de/produkte/stromversorgungs-steckverbinder/fremdspannungsstecker/#content-area[/URL] - over here in Germany available from various electronics vendors like Voelkner or Buerklin, but I've no idea where you could get that in NZ...). Provided that power supply would be of any use for you at all, that is - 'cause from the first picture it would indeed look like that model sports a UK mains plug.

If you could use a model with UK plug, however, another alternative would be this IdealPower model (77DB-10-15M), offered by Farnell: https://uk.farnell.com/ideal-power/77db-10-15m/power-supply-ac-ac-11-5w-15v-0/dp/2368009 Whereas the Stontronics model S2234ST, I formerly used to suggest as a replacement to user in the UK, unfortunately doesn't seem to be available anymore.

Greetings from Munich!

Manfred / lini