Adding resistor to X2 capacitor - UK Vintage Radio Repair and Restoration Discussion Forum

Luxman1050 · 15th Nov 2019, 2:41 pm

Hi guys
just need to know if I can add a resistor onto an X2 safety cap. Situated on volume on/off switch but internal resistance is only 47ohms but I need 220r. Not been able to find a X2 0.047uf with internal resistance of 220r or above.

Any advice greatly appreciated.

Reason is the voltage is high by 40v should be 330v but its 370v so I would put this down to the X2 only having 47r.

Cheers Chris

GrimJosef · 15th Nov 2019, 2:45 pm

Normally X2 caps are used in the mains wiring (e.g. as click suppressors). When you say 'the voltage' should be 330V I'm afraid you need to be more specific. There are lots of voltages. Which one did you have in mind, and in what way do you think this capacitor/resistor combination is affecting it ?

Cheers,

GJ

Luxman1050 · 15th Nov 2019, 4:03 pm

Bit vague
just a snubber on mains on/off switch. It's a quad qc2 pre amplifier and originally it had a type of wax impregnated snubber on the on/off volume switch connected directly to the mains incoming AC voltage. It was a 0.047uf 220 ohm unit. So I am assuming it was there to couple and reduce voltage input. I have a 0.047uf 47 ohm X2 in place but re thinking the direct AC of mains is reading 137vac so not sure if that's right as it's not on schematic! But would assume it is not as I'm only using 47ohms as opposed to 220 ohms.
Now re thinking pin 3 on connecting plug to quad 2 mono amp its reading 370vdc but should be 330vdc according to schematic so it has nothing to do with snubber as I've just re thought and lies in the mono block amp obviously. So I would need to open up and measure voltages in their.
But going back to the pre amp could that vac be too high as I have no reference to the correct voltage so it could be high even though reading is relatively low.
Sorry about that got mixed up with both units as it's confusing as it is not one whole unit but split and directly coupled I think.

Cheers Chris

Station X · 15th Nov 2019, 4:11 pm

The value of the resistor connected in series with the class X capacitor will have no effect whatsoever on other voltages in the amplifier. I assume that you're measuring the voltage across the capacitor or the series resistor? Either way the reading is irrelevant.

If you want to maintain originality fit a 220R series resistor in series with a 0.047uF Class X capacitor.

Luxman1050 · 15th Nov 2019, 4:28 pm

Thanks Graham I've just worked that one out.

The mains going to R121 on my schematic but on other schematic is listed as R32 is 375v and drops to 317v but says should be 330v and drop to 240v.
I'll figure it out.
Also incoming mains direct from plug I have 133 vac on +very side and 98vac on -ve side so total of 231vac. So that makes sense as I usually get between 230 and 245 of mains supply. So those voltages are correct but the VDC obviously higher.

I'll need to take measurements all round.

Cheers Graham.

G8HQP Dave · 15th Nov 2019, 4:44 pm

An AC mains supply does not have a +ve or -ve side. It has line and neutral. The neutral will usually be near zero volts; if it is not then there may be a local fault, which should be reported to your electricity supplier.

It is not enough to take measurements. You need to understand what they mean.

GrimJosef · 15th Nov 2019, 5:19 pm

Quote:

Originally Posted by cdm1christopher

... Now re thinking pin 3 on connecting plug to quad 2 mono amp its reading 370vdc but should be 330vdc according to schematic so it has nothing to do with snubber as I've just re thought and lies in the mono block amp obviously ...

You're right that the voltage on pin 3 of the Jones plug depends only on what's happening inside the monoblock Quad II amp.

Unlikely as it may seem, the 330V number on Quad's schematic is just wrong. If you have a GZ32 rectifier in the amp then pin 3 will usually have 355-370V on it (depends on your mains voltage, the condition of the rectifier and how much current is being drawn by the rest of the electronics). If the rectifier has been upgraded to a GZ34 then you should be measuring 365-375V on pin 3. Your measured 370V is actually fine.

Cheers,

GJ

Luxman1050 · 15th Nov 2019, 5:30 pm

Good point I assumed these units along with others where designed to be plugged in either way round on the two pin bulgin from mains unless I'm getting confused. The unit is not earthed. I know the Jonese plug definitely needs to be the correct orientation otherwise major damaged would be done.
Its difficult with these units as you need the amplifier to run the pre amp which is a pain. Not like an ac/dc set with no mains transformer.

Still I'll look into that unless it's wired up wrong somewhere.

Luxman1050 · 15th Nov 2019, 6:20 pm

Ah that's great news as I just refurbed this one along with another.
I know you should not always go by the schematics as gospel as the ones I have do differ slightly on the capacitor and resistor readings as opposed to those originally installed from the factory.
I've used NOS valves everywhere except for the KT66 valves I do have the brown bear ones as reserves. I also replaced the ecc83 valve with a 12ax7 as it in my personal opinion improves bass response beautifully.
No used original mullard GZ32 not the 34 although I've heard it can improve sound quality I think that's right.
I did think things where fine as the sound is brilliant no distortion even near full volume and near zero hum.

Only problem with this one is the treble pot if you hear the contacts click as you turn the dial you'll get some crackling and slight increase in volume. I've cleaned thoroughly with contact cleaner which has helped but it's still there on occasion. I was going to open the pot up but not sure how internals are manufactured and unable to find any info on it so I don't want to dismantle and it's spring loaded and everything pops out. I have a feeling something has dropped inside and now and again maybe causing a short or one of the contacts is loose and is arcing.
If easy to open up let me know and I'll give it a go. I do like everything to be spot on.

Thanks guys all the input/help really appreciated.

Many thanks as always Chris

G6Tanuki · 15th Nov 2019, 7:30 pm

You can buy 'packaged' snubber-and-suitably-Class-rated capacitors from loads of suppliers.

My instinct - if it's a "glitch-suppressor" upside from a switch - would be to fit one of these 'packages' - the exact value of the resistor will always be a matter for disagreement but I'd be happy with anything between 40 and 500 Ohms.

15th Nov 2019, 2:41 pm	#1
Luxman1050 Octode Join Date: Apr 2019 Location: Margate, Kent, UK. Posts: 1,728	Adding resistor to X2 capacitor Hi guys just need to know if I can add a resistor onto an X2 safety cap. Situated on volume on/off switch but internal resistance is only 47ohms but I need 220r. Not been able to find a X2 0.047uf with internal resistance of 220r or above. Any advice greatly appreciated. Reason is the voltage is high by 40v should be 330v but its 370v so I would put this down to the X2 only having 47r. Cheers Chris

15th Nov 2019, 2:45 pm	#2
GrimJosef Dekatron Join Date: Sep 2007 Location: Oxfordshire, UK. Posts: 4,311	Re: Adding resistor to X2 capacitor Normally X2 caps are used in the mains wiring (e.g. as click suppressors). When you say 'the voltage' should be 330V I'm afraid you need to be more specific. There are lots of voltages. Which one did you have in mind, and in what way do you think this capacitor/resistor combination is affecting it ? Cheers, GJ __________________ http://www.ampregen.com

15th Nov 2019, 4:03 pm	#3
Luxman1050 Octode Join Date: Apr 2019 Location: Margate, Kent, UK. Posts: 1,728	Re: Adding resistor to X2 capacitor Bit vague just a snubber on mains on/off switch. It's a quad qc2 pre amplifier and originally it had a type of wax impregnated snubber on the on/off volume switch connected directly to the mains incoming AC voltage. It was a 0.047uf 220 ohm unit. So I am assuming it was there to couple and reduce voltage input. I have a 0.047uf 47 ohm X2 in place but re thinking the direct AC of mains is reading 137vac so not sure if that's right as it's not on schematic! But would assume it is not as I'm only using 47ohms as opposed to 220 ohms. Now re thinking pin 3 on connecting plug to quad 2 mono amp its reading 370vdc but should be 330vdc according to schematic so it has nothing to do with snubber as I've just re thought and lies in the mono block amp obviously. So I would need to open up and measure voltages in their. But going back to the pre amp could that vac be too high as I have no reference to the correct voltage so it could be high even though reading is relatively low. Sorry about that got mixed up with both units as it's confusing as it is not one whole unit but split and directly coupled I think. Cheers Chris

15th Nov 2019, 4:11 pm	#4
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Adding resistor to X2 capacitor The value of the resistor connected in series with the class X capacitor will have no effect whatsoever on other voltages in the amplifier. I assume that you're measuring the voltage across the capacitor or the series resistor? Either way the reading is irrelevant. If you want to maintain originality fit a 220R series resistor in series with a 0.047uF Class X capacitor. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

15th Nov 2019, 4:28 pm	#5
Luxman1050 Octode Join Date: Apr 2019 Location: Margate, Kent, UK. Posts: 1,728	Re: Adding resistor to X2 capacitor Thanks Graham I've just worked that one out. The mains going to R121 on my schematic but on other schematic is listed as R32 is 375v and drops to 317v but says should be 330v and drop to 240v. I'll figure it out. Also incoming mains direct from plug I have 133 vac on +very side and 98vac on -ve side so total of 231vac. So that makes sense as I usually get between 230 and 245 of mains supply. So those voltages are correct but the VDC obviously higher. I'll need to take measurements all round. Cheers Graham.

15th Nov 2019, 4:44 pm	#6
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: Adding resistor to X2 capacitor An AC mains supply does not have a +ve or -ve side. It has line and neutral. The neutral will usually be near zero volts; if it is not then there may be a local fault, which should be reported to your electricity supplier. It is not enough to take measurements. You need to understand what they mean.

15th Nov 2019, 5:30 pm	#8
Luxman1050 Octode Join Date: Apr 2019 Location: Margate, Kent, UK. Posts: 1,728	Re: Adding resistor to X2 capacitor Good point I assumed these units along with others where designed to be plugged in either way round on the two pin bulgin from mains unless I'm getting confused. The unit is not earthed. I know the Jonese plug definitely needs to be the correct orientation otherwise major damaged would be done. Its difficult with these units as you need the amplifier to run the pre amp which is a pain. Not like an ac/dc set with no mains transformer. Still I'll look into that unless it's wired up wrong somewhere.

15th Nov 2019, 6:20 pm	#9
Luxman1050 Octode Join Date: Apr 2019 Location: Margate, Kent, UK. Posts: 1,728	Re: Adding resistor to X2 capacitor Ah that's great news as I just refurbed this one along with another. I know you should not always go by the schematics as gospel as the ones I have do differ slightly on the capacitor and resistor readings as opposed to those originally installed from the factory. I've used NOS valves everywhere except for the KT66 valves I do have the brown bear ones as reserves. I also replaced the ecc83 valve with a 12ax7 as it in my personal opinion improves bass response beautifully. No used original mullard GZ32 not the 34 although I've heard it can improve sound quality I think that's right. I did think things where fine as the sound is brilliant no distortion even near full volume and near zero hum. Only problem with this one is the treble pot if you hear the contacts click as you turn the dial you'll get some crackling and slight increase in volume. I've cleaned thoroughly with contact cleaner which has helped but it's still there on occasion. I was going to open the pot up but not sure how internals are manufactured and unable to find any info on it so I don't want to dismantle and it's spring loaded and everything pops out. I have a feeling something has dropped inside and now and again maybe causing a short or one of the contacts is loose and is arcing. If easy to open up let me know and I'll give it a go. I do like everything to be spot on. Thanks guys all the input/help really appreciated. Many thanks as always Chris

15th Nov 2019, 7:30 pm	#10
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: Adding resistor to X2 capacitor You can buy 'packaged' snubber-and-suitably-Class-rated capacitors from loads of suppliers. My instinct - if it's a "glitch-suppressor" upside from a switch - would be to fit one of these 'packages' - the exact value of the resistor will always be a matter for disagreement but I'd be happy with anything between 40 and 500 Ohms.