Millenium 4-20 (Maplin Electronics)

[leesonic]

Ooops. Meant to add one more thing to my message above.

I've found what looks like a suitable transformer for the Millenium amp, it's here :

http://www.edcorusa.com/products/tra...xpp/index.html

The CXPP50-MS-6.6K has a 6.6k primary, but it's screen voltage is 40%, not 43% of the original Maplin transformers, plus it's rated at 50w as well. Would this be a suitable replacement? It has 4, 8 and 16 ohm taps for the output.

[Mike H]

I'd forgotten how to get the quick reply to work! Doh...

Yes should be alright.

40% versus 43% taps wouldn't make any difference I don't think.

Re Maplin in Yorkshire, the mail order warehouse had already been up there since about 1992. So not sure about the speed of post difference

[pre65]

Originally Posted by Mike H

Re Maplin in Yorkshire, the mail order warehouse had already been up there since about 1992. So not sure about the speed of post difference

I never noticed much difference (if any !) when they moved.

[Mike H]

FYI U54 has same size and shape glass bottle as GZ37. Or at least mine does

Nearest electrical equivalent is probably 5U4, tho depends whether you like its directly heated cathode or not

[Mike H]

Hello Philip!

[pre65]

Originally Posted by Mike H

Hello Philip!

Hello Mike.

[pre65]

Originally Posted by Mike H

FYI U54 has same size and shape glass bottle as GZ37. Or at least mine does

Nearest electrical equivalent is probably 5U4, tho depends whether you like its directly heated cathode or not

My personal taste is for some sort of "slow start", so for me an indirectly headed rectum frier (ie GZ34/37) would be preferable.

Or (as i have done before) a means of separately switching a directly heated one after allowing for a 10 sec (or so) delay.

[Mike H]

Quite so, also, my thermistor in series with rectifier heater supply idea. Still works!

[pre65]

Well,i think the thermistor is more about controlling surge on switch on !

My preference is for 6D22s damper diodes,either as a pair for full wave rectification or as part of a bridge (hybrid bridge).That way you get a 30 sec delay before full ht.

I think hybrid bridges,with either two vacuum diodes,or a GZ34/37 are a good idea when the transformer size dictates a bridge,but you need/want slow start up.

[Mike H]

Originally Posted by pre65

Well,i think the thermistor is more about controlling surge on switch on !

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