UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Other Vintage Household Electrical or Electromechanical Items

Notices

Other Vintage Household Electrical or Electromechanical Items For discussions about other vintage (over 25 years old) electrical and electromechanical household items. See the sticky thread for details.

Reply
 
Thread Tools
Old 18th Jan 2024, 8:29 pm   #1
Tinker1966
Triode
 
Join Date: Nov 2014
Location: Leominster, Herefordshire, UK.
Posts: 25
Default Christmas light problems - help please !!!

Hi - I know it’s not the right season but ….. I have a love of vintage lights not so much Father Christmas etc just strings of old bulbs dotted around the house.

I have a string of 1960’s 20v bulbs which I under run by having 16 bulbs on and they are much admired and are no trouble.

So I have slowly been collecting early milk glass bulbs to do something similar with. I have 16 various 16v bulbs and have made a string of 18 so as to under run them as before however I am 2 bulbs short so I put in a couple of 20v bulbs thinking they would just be a bit dimmer ….. what actually happens is every time I try the lights, one of the 20v bulbs blows.

I am at a loss now and don’t want to keep wasting bulbs …. Is it the voltage rating ? Different wattage ?

Help please !!!
Attached Thumbnails
Click image for larger version

Name:	IMG_1915.jpg
Views:	119
Size:	108.4 KB
ID:	291230   Click image for larger version

Name:	IMG_1917.jpg
Views:	117
Size:	72.5 KB
ID:	291231  

Last edited by Tinker1966; 18th Jan 2024 at 8:36 pm.
Tinker1966 is offline   Reply With Quote
Old 18th Jan 2024, 8:43 pm   #2
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
Default Re: Christmas light problems - help please !!!

They probably have a much lower current rating than the rest of the string. This will cause them to be overvoltage and one of them will fail.

A power diode (1N4007 or similar) in series with the string is usually a better way of preserving bulb life, though it may cause visible flicker. Sensitivity to this varies between individuals.
paulsherwin is online now   Reply With Quote
Old 18th Jan 2024, 9:38 pm   #3
Tinker1966
Triode
 
Join Date: Nov 2014
Location: Leominster, Herefordshire, UK.
Posts: 25
Default Re: Christmas light problems - help please !!!

Quote:
Originally Posted by paulsherwin View Post
They probably have a much lower current rating than the rest of the string. This will cause them to be overvoltage and one of them will fail.

A power diode (1N4007 or similar) in series with the string is usually a better way of preserving bulb life, though it may cause visible flicker. Sensitivity to this varies between individuals.
Thank you for the explanation Paul - that makes sense !
I know most of the more modern bulbs tend to be 3w and that some of the earlier ones are 7w as some of them are stamped with both voltage and wattage.

I have just found some plain bulbs rated at 7w and added them in and hey presto nothing is blowing ! However now, once they’ve been on for a minute or so they all flash in unison - I am now beyond confused ……
Tinker1966 is offline   Reply With Quote
Old 18th Jan 2024, 9:43 pm   #4
Cobaltblue
Moderator
 
Cobaltblue's Avatar
 
Join Date: Dec 2010
Location: Exeter, Devon and Poole, Dorset UK.
Posts: 6,824
Default Re: Christmas light problems - help please !!!

Quote:
Originally Posted by Tinker1966 View Post

I have just found some plain bulbs rated at 7w and added them in and hey presto nothing is blowing ! However now, once they’ve been on for a minute or so they all flash in unison - I am now beyond confused ……
They did flashing bulbs you used one in a string you havent found a flashing bulb have you?
They have a Bi metallic strip near the filament.

Perhaps a picture of the inside of the bulb will confirm?

Cheers

Mike T
__________________
Invisible airwaves crackle with life or at least they used to
Mike T BVWS member.
www.cossor.co.uk
Cobaltblue is online now   Reply With Quote
Old 18th Jan 2024, 11:44 pm   #5
emeritus
Dekatron
 
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 5,316
Default Re: Christmas light problems - help please !!!

After I had extended a string of twelve 20V 3W bulbs to 16 and had no spares when one blew, I used a 12V bulb of the same current rating until I was able to get some 20V replacements.

If you have a string of higher current bulbs and replace one by a lower current bulb, the higher current bulbs behave like a constant current source that attempts to force the higher current through the lower current bulb, causing the voltage across it to rise to a high value in excess of its voltage rating and making it blow.

Conversely, when replacing a bulb in a low current string by a high current one, the constant current provided by the string will result in a low voltage appearing across the replacement, making it glow dimly.
emeritus is offline   Reply With Quote
Old 19th Jan 2024, 2:44 pm   #6
Tinker1966
Triode
 
Join Date: Nov 2014
Location: Leominster, Herefordshire, UK.
Posts: 25
Default Re: Christmas light problems - help please !!!

Quote:
Originally Posted by emeritus View Post
After I had extended a string of twelve 20V 3W bulbs to 16 and had no spares when one blew, I used a 12V bulb of the same current rating until I was able to get some 20V replacements.

If you have a string of higher current bulbs and replace one by a lower current bulb, the higher current bulbs behave like a constant current source that attempts to force the higher current through the lower current bulb, causing the voltage across it to rise to a high value in excess of its voltage rating and making it blow.

Conversely, when replacing a bulb in a low current string by a high current one, the constant current provided by the string will result in a low voltage appearing across the replacement, making it glow dimly.
Thank you - both the scenarios you describe are things I have experienced on this journey !

Now I am understanding more about the different bulbs I have.
Tinker1966 is offline   Reply With Quote
Old 19th Jan 2024, 9:51 pm   #7
duncanlowe
Nonode
 
Join Date: Jan 2016
Location: Stafford, Staffs. UK.
Posts: 2,529
Default Re: Christmas light problems - help please !!!

This reminds me of a discussion when I worked in Woolies. Someone brought back some tree light bulbs, saying they all failed very quickly, though they were the correct voltage for their string. I did query whether they were the correct wattage and they got quite stroppy telling me they had some random qualification, and that only the voltage was important, so what did I know. Store manager decided he knew better. Maybe he did, as it probably wasn't worth the argument, and maybe I should have known better myself.
duncanlowe is offline   Reply With Quote
Old 20th Jan 2024, 11:21 pm   #8
chris.oates
Triode
 
Join Date: Apr 2020
Location: Northallerton, North Yorkshire, UK.
Posts: 36
Default Re: Christmas light problems - help please !!!

I have a large collection of used low voltage filament bulbs salvaged from Christmas fairy lights donated by friends and relatives when almost all of the rest of the world went led. In the annual December get the lights working session I have found a bench variable power supply invaluable in determining the power rating as well as the voltage rating of individual bulbs. Before I owned the power supply I used to use a simple rheostat and measure the voltage and current with two multimeters. As others have said matching the power rating is important to get even illumination and avoid blows.

Chris
chris.oates is offline   Reply With Quote
Old 20th Jan 2024, 11:53 pm   #9
The Philpott
Dekatron
 
The Philpott's Avatar
 
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,081
Default Re: Christmas light problems - help please !!!

...and just occasionally, a sealed packet of NOS spares will be found to have a rogue lamp of the wrong voltage or wattage, a situation exacerbated by the fact that some (and the push-ins in particular) have no markings. Reputation means nothing, i found one in a packet of Woolies lamps!

Dave
The Philpott is offline   Reply With Quote
Old 22nd Jan 2024, 1:16 am   #10
bionicmerlin
Heptode
 
bionicmerlin's Avatar
 
Join Date: May 2010
Location: Warminster, Wiltshire, UK.
Posts: 682
Default Re: Christmas light problems - help please !!!

Ii always used to find the Woolworths bulbs were always a bit on the bright side and hence didn’t used to last as long as other makes.
Probably we shouldn’t of mixed different makes. Maybe if you used all of one make this wouldn’t happen. I assume between makes there is a slight wattage difference Andy
__________________
I bet that car doesn't have a suppressor.
bionicmerlin is offline   Reply With Quote
Old 22nd Jan 2024, 11:49 am   #11
GMB
Dekatron
 
GMB's Avatar
 
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 3,086
Default Re: Christmas light problems - help please !!!

Slow starting helps. I started doing that (with variac) to ours when I ran out of spares.

It's the same issue as series valve heater chains - if you have differing thermal inertias then during the startup some lamps are overloaded until it all reaches the operational current - the reason they added thermistors in TVs.

I am considering adding a capacitor dropper but I need to recheck what happens during the startup with that.
GMB is offline   Reply With Quote
Old 22nd Jan 2024, 4:06 pm   #12
Tinker1966
Triode
 
Join Date: Nov 2014
Location: Leominster, Herefordshire, UK.
Posts: 25
Default Re: Christmas light problems - help please !!!

Well thank you to everyone who commented. Both issues are now sorted out.

Firstly I was mixing my voltage and wattages which as everyone clearly explained leads to blown bulbs … I now have a string of 3w 20v bulbs and a string of 7w 16v bulbs.

And secondly I found one of the milk glass bulbs was indeed a flasher bulb causing the whole string to flash ! I hadn’t ever realised these flash bulbs were around at the time of milk glass bulbs!


So now they’re up and running so thanks to all.
Tinker1966 is offline   Reply With Quote
Old 22nd Jan 2024, 9:38 pm   #13
dave walsh
Dekatron
 
Join Date: Jan 2006
Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex.
Posts: 5,814
Default Re: Christmas light problems - help please !!!

I had two sets of twenty 12v bulbs. I thought those were too bright and when some failures occured I built a chain of thirty which worked out at 8 volts each. It wasn't a very sophisticated set-up but [to my surprise] it was quite bright enough and lasted about thirty years. They were only replaced out of family members wanting a change in the end

Dave W
dave walsh is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 10:58 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.