[volt-nuts] Neon bulbs for HP 3420B or 419A chopper

[David C. Partridge]

Then an A3C (NE-2U) shouldn't work.  The drive voltage is 125V.

The operating current is 1.5mA (.15V/102R) in the 3420B, so I would expect this to be the A2B (NE-2V) part.

Interestingly the operating current for the 3420A is 2.45mA which you would think might suggest the A3C (NE-2U), but the drive voltage isn't high enough!

Dave 

-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces at febo.com] On Behalf Of Charles Steinmetz
Sent: 17 November 2017 20:53
To: volt-nuts at febo.com
Subject: Re: [volt-nuts] Neon bulbs for HP 3420B or 419A chopper

george wrote:

> Farnell (UK) list NE-2U neon lamps.

Note that the NE-2U is a "high brightness" lamp with a 135vDC (max) strike voltage.  Standard brightness lamps strike at 90vDC (max).  The Farnell site available to me here in the US lists the CML (Chicago Miniature Lamp) A3C, which CML list with NE-2U as the "Old Reference Number."

Farnell do not seem to carry the CML standard brightness lamps with reduced dark effect.  According to the CML datasheet, there are four part numbers with that combination:  A1D, A1D-T, A2B, and A2B-T.  "T" 
indicates tinned leads.  The design current of the A1 parts is 300uA, and of the A2 parts it is 700uA.  Check the schematic and you should be able to calculate the neon operating current of the circuit, and choose
A1 or A2 accordingly.

Dave, perhaps Farnell will special order one of these part numbers for you.  If Farnell can't get you the right part, I believe both Mouser and Digi-Key operate in the UK and both have A1D(-T) and A2B(-T) parts in stock (in the UK, I think).

Cheers,

Charles


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