Millenium 4-20 (Maplin Electronics)

[pre65]

Originally Posted by Mike H

At the risk of appearing to argue, no it doesn't (well additionally), it actually delays the HT for between 60 - 90 seconds. Depending on local ambient temperature

Velly inkerestink !

Can you link to the type you use pleeeeeeeeeeeeeze ?

[Mike H]

Yes sorry Phil didn't mean to seem snooty or anything sho nuff it's a RS part No. 216-1422, "Type S237 NTC thermistor, 2.5ohm 170deg C", may also be described as "NTC inrush limiter"

On this page:
http://uk.rs-online.com/web/search/s...duct&R=2161422

Basically what happens is when I turn on the amp, nothing happens for at least a minute then the rectifier cathodes begin to glow, then the front panel lamp lights up. The front panel lamp is a neon powered off the HT

The rect tube is a U54 (2 Amps, I think), but should do up to GZ37 (3 Amps).

Here's the gizmo in situ:




Edit ~ forgot to mention thermistor is in series with the rectifier's heater supply.

[pre65]

Originally Posted by Mike H

Edit ~ forgot to mention thermistor is in series with the rectifier's heater supply.

I have a similar item in my KT66 set power supply,and I thought at mains voltage it got hot and worked quite quickly.

If you are using it in a 5V supply that might be why it takes longer to get going.

Neat trick,and so inexpensive !

[Mike H]

Well even on mains they assume 90 seconds, suppose depends on what the load is or maybe how they're testing it. Anyway as it is it certainly depends on heat up time which as you say the power isn't that much from 5V

[John Caswell]

Pre 65 wrote:
"If you are using it in a 5V supply that might be why it takes longer to get going".

No, it is a current sensitive device not a voltage sensitive one.

John - Dr John

[Mike H]

Yes that's my understanding too. It has a 'cold' resistance and a 'hot' resistance. Think in Phil's example though if it's on the mains side the cold resistance is very small compared to that of the mains load. That'd be why it just has the much more immediate surge limiter effect, which is of course what its function would be in that case.

[pre65]

I found the packet for my one,it was Rapid 26-3326 (now discontinued) and was called a 4R/8A inrush limiter.

So it's probably different to your one.

I prefer to use Rapid, so this seems to be their version

http://www.rapidonline.com/productin...miter#techspec

[Mike H]

Yes I would like to use Rapid, if they sell what I want! Or what they used to. First one I used (it's in me phono pre-amp) was from Rapid as well, might have been 26-7606 (going by the spec) but I notice that is DIS as well. If it is that one it's been DIS for some time. Also seems 26-7610 is going to go as well as it's on 'special offer'

[Mike H]

The Mk II version prototype is finished, here it is 'in action':

Input valves are EF37A and EF36 (the latter as cathodyne type phase splitter). Sounds very nice indeed actually, the wasp's ankles












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[Mike H]

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