philips: Neon bulb specs from Phlips 203U

I'm hoping someone has the specs for the neon bulb that was in this set.  The original socket in mine is missing.  Did the original bulb have threads, bayonet, or did it solder in?  The schematic calls for a 7121D on the 203U and a Z10 on the 208U.

Best regards and thank you,

Donald 

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Hello Donald.

The glow lamp is soldered.

Another thing I noticed about this Philetta 203U - Philips Belgium, the pictures ID= 2738001, 2738002, 2738006 show the model Philetta 203U [no ventilation openings] - Philips Eindhoven.
See the nameplate

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Thank you for the kind reply.  Mine is marked "Holland" and does not have the

vents.  I think only the 208U had them.  Perhaps they had a problem with

heat on the 203's.  I finished the restoration and the radio plays well and is very selective on BC

band.  Now I have to find a socket for the neon bulb.

Donald

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Dear Donald,

All 203U versions are equipped with a neon bulb, as power indicator. They don't have the function as a scale illumination. The same holds for all versions of the 204U.

Only the first 5 versions of the 208U (version /10, /46, /47, /48 and /49) were equipped with neon bulbs. All later versions, including the popular 208U /05, were equipped with scale illumination. This is externally visible, as the hole for the neon bulb indication light at the front of the housing, right above the station scale, is absent with the later 208U versions.

The scale illumination for the late 208U versions was provided by Philips dial lamp 7121 (6 V), only version 208U /08 used a 8095 (19 V).

The neon bulb is a Z10 (part code A1 358 18)  and is nowadays a very rare object. I had a few in stock, but in the meantime I made all bulbs available to collectors. The best way to get hold of a neon bulb Z10 is by acquiring a chassis of a 203U, 204U or early 208U.

The early versions of the 203U and 204U had no ventilation openings. Due to heat problems, ventilation openings were made. Initially the openings were simple holes, in a later stage a series of slots were made.

Kind regards,

Gidi Verheijen

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Only for information.
Thanks to Mr. O. Jung for moving the pictures from Post 2 to the correct model.

WB.

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Hi Donald,

I'm just wondering if you found the neon bulb and what was the voltage rating of it.

Kind regards.

Thank you.

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I ended up using an American neon bulb of similar size and voltage and it worked.  A friend came over and begged to buy the radio and I gave it to him.

Donald

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In general the small neons with two rods strike (light) at about 90V and have then about 60V across them. Both rods light with AC and one with DC. They have a minimum holding current and the supply must be either via a suitable resistance or current limiter otherwise they will shatter with over-current. Thus they have a negative resistance. With suitable low leakage parallel capacitor and large enough resistance the relaxation oscillator will work from a small fraction of 1 Hz (as low as one flash per minute) up to several thousand Hertz.

The wire ended type are commonly available new in two sizes and NOS larger sizes as ex-Soviet stock.

They are still made as they are a more sensible power indicator for AC mains sockets, switches and kettle indicators for 115V or 230V nominal systems than an LED. About 220 k to 470 k Ohms in series for 230V AC. The resistor has about 170V across it when the neon is lit, so I leave it as an exercise to calculate the resistance for 115V AC or DC.

The striking volage is higher in the dark and lower when there is excessive radiation. The on voltage is unaffected. 

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Fun fact: there are screwdrivers on the market with internal neon bulb and resistor (in german "Phasenprüfer"). So if you buy 10 of them in a pack you get 10 neon bulbs (which are wired nowadays) and the mandatory resistor - don't worry the screwdrivers are very cheap made and I wouldn't use them ...

If you buy the 10 bulbs seperately they are more expensive than that - modern times ;-)

Kind regards,

D.Consales

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In 1970s BBC the "neon screwdrivers" were forbidden because you can get a fatal shock if wet and the resistor also might be easily shorted.

I've bought both common sizes of neons online far cheaper than neon screwdrivers, which I've not seen locally for years. Though it's likely you might get a neon screw driver locally and with Maplin gone, that was the last local retail electronics parts.

Ten neons from China might be more expensive than one local "neon screwdriver".

I have a non-contact device to detect live wires from Aldi or Lidl.

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You can still get them on amaz** - 10 pcs at 15€. The bulbs you can get there, too. Also for about 15€ - but only 5 pcs ...

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