On Monday, October 9, 2017 at 9:13:34 AM UTC-5, John Robertson wrote:
On 2017/10/09 4:29 AM, @yahoo.com wrote:
I should clarify a few things.

-I already purchased new bulbs. The old ones worked but were very dim.

I suspect you have Rapid Start bulbs that are self starting. What is the
code number of the bulbs you used?


It's item# 147940 from Lowe's, and the specs say they are not rapid start.


-The ballasts each measure about 30 ohms. I have not yet put an inductance meter on them but my guess is they are good.

A quick ballast test is to power up the fixture then read the ballast
side against the other side of the line - should be around 130VAC. If it
show 115 (or whatever your AC source is) then the ballast is bad.


-I connected the bulbs using jumper wires to eliminate bad connections in the sockets. No change.

-If I install only one bulb with everything wired as it originally was, that one always starts. If I remove it and install the other bulb in the other bulb socket pair, that one also always starts. With both in circuit, I've never seen them both start, only one does.

Try grounding the metal frame of the fixture. Or if grounded (someone
would have added that, wouldn't have been there originally), remove the
ground


Interesting. It does have the original cord but I've considered putting a grounded cord on there because I started wondering about the safety of this thing should something internally touch the enclosure. For what it's worth, is does the same even with the innards laying out on a table.


-With both bulbs in circuit one specific bulb tends to start, but randomly the other does instead.

-If I separate out each bulb-ballast circuit so they look like completely independent fixtures and start each manually by temporarily shorting the one bulb pin at each end, each starts and runs no problem. So that's why I believe both ballasts are good.

True.


The part of the original circuit I'm having trouble dealing with is how the bulbs are permanently connected at the same end as the ballast connection. It seems one bulb could steal the start pulse from both ballasts, hence the reason for the issue. But then again this was designed this way and supposedly would work?

The bulbs are only connected to the non-ballast line side when the
button is pressed. Otherwise the interconnections can't conduct current
as they are on the same side of the line for each bulb.


I was most concerned about the ballast side of the bulbs where they essentially connect together through the heater/filament even when start isn't pressed. That seems like not such a good design and maybe why the problem is occurring.


I have a DPDT relay on the way to isolate each starting switch and that will fix it, but did these desk lamps ever intend to work correctly? Seems odd..

Why not use a DPDT push button switch? While I don't think it will
change anything it can be wired to isolate the two bulbs from each other
more easily than fitting a relay in there.


That's what I first looked at, but the relay was much cheaper and most importantly, keeps the outward appearance the same. There's also plenty of room inside this thing.



It is odd, I agree, that both bulbs won't light if everything is as
described. They should. You do press and hold the button until the ends
of the tubes glow for a second, right?


Oh yeah. I pressed and held it, and both ends of both bulbs begin glowing white. When I release it, one lights, and the other has this very dim flicker that decays within a few seconds. The interesting thing is one end of one bulb randomly flickers while holding start. Now whether that's the one that doesn't start, I didn't think to observe until now.

John :-#)#

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