WEM Dominator MK3 amplifier. Lamp and Transistor (actually a resistor) Enquiry - UK Vintage Radio Repair and Restoration Discussion Forum

pebbles123 · 7th Jun 2016, 9:02 pm

Hi, learning as I go ---

Problem with a on/off lamp on a WEM Dominator MK3 amplifier..
Here's a couple of pics.

Does anyone know where I could purchase a replacement lamp, or would I have to salvage the parts..
The problem is I don't know how much voltage the lamp draws, whether it's the lamp or transistor that's at fault..

Any info much appreciated as always.

Pebs

paulsherwin · 7th Jun 2016, 9:10 pm

Transistor? It appears to be a mains neon and series resistor.

No offence, but please be careful if your expertise is limited. There are high voltages around which at best can give you a nasty belt and at worst can kill you.

G6Tanuki · 7th Jun 2016, 9:14 pm

That is a simple neon lamp with series-resistor.

Assuming it is powered by 200-250V AC then the lamp itself is replaceable with a "NE2"

http://www.jaycar.co.uk/Active-Compo...-Neon/p/SL2690

and the resistor is probably something like 220K or 330K Ohms.

threeseven · 7th Jun 2016, 9:30 pm

Yup, standard neon lamp with series limiting resistor. They can be found on ebay for not alot.

peter_sol · 7th Jun 2016, 9:31 pm

iT does not look faulty and just goes across the normal 240 or 230 volt mains.
What makes you think it is at fault?

pebbles123 · 7th Jun 2016, 10:03 pm

Thanks for replies,

Yes I'm careful as I go, I'm not delving into the amp too much, just wanted to replace this light that's been niggling me.

It doesn't light when the amp is powered. I gathered the neon lamp had blown and needed replacing. What would you think is best solution??

Does anyone think it hasn't been wired correctly to the volt mains?

threeseven · 8th Jun 2016, 8:41 am

If the amp is a 240 volt version then the indicator lamp will be suitable for that voltage. The resistor could well have gone high value or open circuit but neons do not last forever.
New replacement neons can be had for very little on ebay so replacement would seem the most expedient solution. If you don't have or know how to use a multimeter, there is no way of knowing if the resistor is defective, so replacement of that is also the best solution.

vidjoman · 8th Jun 2016, 8:59 am

Photo 2 seems to show the wire from the neon to the resistor has not been soldered.

ionburn · 8th Jun 2016, 9:13 am

Looks like an 82K resistor - Isn't that somewhat smaller than usual?

TonyDuell · 8th Jun 2016, 1:19 pm

82K seems to be about right for a 115V supply. Perhaps it runs off a tap on the mains transformer so the same neon lamp assembly can be used for all mains voltages.

Station X · 8th Jun 2016, 1:29 pm

peebles123.

Can you post a clear picture of the resistor so we can see its colour code and determine its value.

Then if you have a meter you can check that its value hasn't drifted. Failing that just fit a new resistor and neon. If that doesn't work the fault is elsewhere.

pebbles123 · 13th Jun 2016, 10:34 pm

Hey guys, I believe the problem lays with the resistor as I'm getting no reading of multimeter...

Click image for larger version

Name: resistor.jpg
Views: 82
Size: 39.0 KB
ID: 126024

Resistor colours are orange - red - and what looks like light blue to my eyes.
Can someone tell me the value plesae?
Take into account this amp was built in the 70's...

The amplifier voltage is set to 240v, couldn't tell you whether it runs off a tap..

Station X · 13th Jun 2016, 11:09 pm

I'd say it's actually grey, red, orange which indicates a value of 82,000 ohms or 82k.

This agrees with what ionburn says in post #9

Top Cap · 13th Jun 2016, 11:32 pm

It runs off the 220V tap.

This one from Cricklewood would appear to be a close equivalent.
http://www.cricklewoodelectronics.com/NERR.html

pebbles123 · 14th Jun 2016, 12:09 am

Excellent - That's almost an exact copy...Thanks folks!

7th Jun 2016, 9:02 pm	#1
pebbles123 Diode Join Date: Jun 2016 Location: Birkenhead, Merseyside, UK. Posts: 4	WEM Dominator MK3 amplifier. Lamp and Transistor (actually a resistor) Enquiry Hi, learning as I go --- Problem with a on/off lamp on a WEM Dominator MK3 amplifier.. Here's a couple of pics. Does anyone know where I could purchase a replacement lamp, or would I have to salvage the parts.. The problem is I don't know how much voltage the lamp draws, whether it's the lamp or transistor that's at fault.. Any info much appreciated as always. Pebs Attached Thumbnails

7th Jun 2016, 9:10 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,975	Re: WEM Dominator MK3 amplifier. Lamp and Transistor Enquiry Transistor? It appears to be a mains neon and series resistor. No offence, but please be careful if your expertise is limited. There are high voltages around which at best can give you a nasty belt and at worst can kill you.

7th Jun 2016, 9:14 pm	#3
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,010	Re: WEM Dominator MK3 amplifier. Lamp and Transistor Enquiry That is a simple neon lamp with series-resistor. Assuming it is powered by 200-250V AC then the lamp itself is replaceable with a "NE2" http://www.jaycar.co.uk/Active-Compo...-Neon/p/SL2690 and the resistor is probably something like 220K or 330K Ohms.

7th Jun 2016, 9:30 pm	#4
threeseven Octode Join Date: May 2010 Location: Worcestershire, UK. Posts: 1,880	Re: WEM Dominator MK3 amplifier. Lamp and Transistor Enquiry Yup, standard neon lamp with series limiting resistor. They can be found on ebay for not alot. __________________ BVWS member

7th Jun 2016, 9:31 pm	#5
peter_sol Octode Join Date: Aug 2003 Location: Welwyn Garden City, Herts. UK. Posts: 1,906	Re: WEM Dominator MK3 amplifier. Lamp and Transistor Enquiry iT does not look faulty and just goes across the normal 240 or 230 volt mains. What makes you think it is at fault?

7th Jun 2016, 10:03 pm	#6
pebbles123 Diode Join Date: Jun 2016 Location: Birkenhead, Merseyside, UK. Posts: 4	Re: WEM Dominator MK3 amplifier. Lamp and Transistor Enquiry Thanks for replies, Yes I'm careful as I go, I'm not delving into the amp too much, just wanted to replace this light that's been niggling me. It doesn't light when the amp is powered. I gathered the neon lamp had blown and needed replacing. What would you think is best solution?? Does anyone think it hasn't been wired correctly to the volt mains?

8th Jun 2016, 8:41 am	#7
threeseven Octode Join Date: May 2010 Location: Worcestershire, UK. Posts: 1,880	Re: WEM Dominator MK3 amplifier. Lamp and Transistor Enquiry If the amp is a 240 volt version then the indicator lamp will be suitable for that voltage. The resistor could well have gone high value or open circuit but neons do not last forever. New replacement neons can be had for very little on ebay so replacement would seem the most expedient solution. If you don't have or know how to use a multimeter, there is no way of knowing if the resistor is defective, so replacement of that is also the best solution. __________________ BVWS member

8th Jun 2016, 8:59 am	#8
vidjoman Dekatron Join Date: Jun 2013 Location: East Sussex, UK. Posts: 3,327	Re: WEM Dominator MK3 amplifier. Lamp and Transistor Enquiry Photo 2 seems to show the wire from the neon to the resistor has not been soldered.

8th Jun 2016, 9:13 am	#9
ionburn Heptode Join Date: Dec 2014 Location: Lincoln, Lincolnshire, UK. Posts: 583	Re: WEM Dominator MK3 amplifier. Lamp and Transistor Enquiry Looks like an 82K resistor - Isn't that somewhat smaller than usual?

8th Jun 2016, 1:19 pm	#10
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,225	Re: WEM Dominator MK3 amplifier. Lamp and Transistor Enquiry 82K seems to be about right for a 115V supply. Perhaps it runs off a tap on the mains transformer so the same neon lamp assembly can be used for all mains voltages.

8th Jun 2016, 1:29 pm	#11
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: WEM Dominator MK3 amplifier. Lamp and Transistor Enquiry peebles123. Can you post a clear picture of the resistor so we can see its colour code and determine its value. Then if you have a meter you can check that its value hasn't drifted. Failing that just fit a new resistor and neon. If that doesn't work the fault is elsewhere. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

13th Jun 2016, 10:34 pm	#12
pebbles123 Diode Join Date: Jun 2016 Location: Birkenhead, Merseyside, UK. Posts: 4	Re: WEM Dominator MK3 amplifier. Lamp and Transistor (actually a resistor) Enquiry Hey guys, I believe the problem lays with the resistor as I'm getting no reading of multimeter... Resistor colours are orange - red - and what looks like light blue to my eyes. Can someone tell me the value plesae? Take into account this amp was built in the 70's... The amplifier voltage is set to 240v, couldn't tell you whether it runs off a tap..

13th Jun 2016, 11:09 pm	#13
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: WEM Dominator MK3 amplifier. Lamp and Transistor (actually a resistor) Enquiry I'd say it's actually grey, red, orange which indicates a value of 82,000 ohms or 82k. This agrees with what ionburn says in post #9 __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

13th Jun 2016, 11:32 pm	#14
Top Cap Octode Join Date: Mar 2006 Location: Watford, Hertfordshire, UK. Posts: 1,270	Re: WEM Dominator MK3 amplifier. Lamp and Transistor (actually a resistor) Enquiry It runs off the 220V tap. This one from Cricklewood would appear to be a close equivalent. http://www.cricklewoodelectronics.com/NERR.html __________________ Whether the Top Cap is Grid or Anode - touching it will give you a buzz either way!

14th Jun 2016, 12:09 am	#15
pebbles123 Diode Join Date: Jun 2016 Location: Birkenhead, Merseyside, UK. Posts: 4	Re: WEM Dominator MK3 amplifier. Lamp and Transistor (actually a resistor) Enquiry Excellent - That's almost an exact copy...Thanks folks!