Pick up and Valve problems - UK Vintage Radio Repair and Restoration Discussion Forum

Bufo Bill · 15th Aug 2019, 10:47 pm

Hi I bought an AKG P8ES stylus and cartridge assembly recently, and I found the left channel low on volume compared to the right hand channel. Then today I decided to do a bit of fault tracing, and the GZ32 Valve in my Quad II Amp was not working upon switching the system power on. I run a mono system, ie a Quad II and QCII Preamp. Could the low volume of the left channel be accounted for as an early symptom of the valve failure, or do you think I am dealing with two unrelated problems that just coincidentally happened at roughly the same time? I would like to hear your opinions either way, although a link appears unlikely to my uneducated mind.
Regards from Bill.

Nuvistor · 15th Aug 2019, 10:55 pm

Swap the connection over from the cartridge and see if the fault follows the amp or the cartridge.

Bufo Bill · 15th Aug 2019, 11:32 pm

Hi Frank, none of my inputs work through the amp, there is definitely a fault there. I was about to swap channels on the pick up when the amp malfunctioned. I have sourced another valve, but currently do not have a way of checking the cartridge, this being my only amp.
Regards from Bill.

Edward Huggins · 16th Aug 2019, 7:32 am

Am I reading this correctly? How can the OP tell about the difference in stereo cartridge voltage outputs if he is only using a mono amplifier?

Also I can't see any possible connection between a rectifier failure and issues with a cartridge.

Station X · 16th Aug 2019, 8:48 am

Quote:

Originally Posted by Bufo Bill

the GZ32 Valve in my Quad II Amp was not working.

Regards from Bill.

How do you know that?

Bufo Bill · 16th Aug 2019, 10:56 am

Edward: my speaker is a Quad ESL, I can clearly hear the instruments on the left channel on a stereo record are not as loud as they should be. I can't see why there should be a link either, it just seemed odd that the two faults occurred in quick succession, so it made me wonder.
X: the valve doesn't warm up over time. It shows no sign of activity at all. It does seem odd that the valve failed, can I check some other component that could cause the valve to be inactive?

Edward Huggins · 16th Aug 2019, 11:14 am

If the valve does not warm up or glow over time then it has failed. A new rectifier in your Quad would be no bad thing anyway especially considering its liekly age. Easily sourced.

GrimJosef · 16th Aug 2019, 11:14 am

The GZ32 contains two separate heaters - one for each diode. Failure of one heater, obvious by there being only one bright orange spot visible from the top of the valve (if you can see through/round the silver getter), is not uncommon. But for both heaters to fail in the same valve is rare. It can be due to a solder contact failure inside one of the pins on the valve's base. But it may also indicate a failure in the amp's wiring somewhere between the 5V secondary on the mains transformer and the GZ32 socket. If you make any measurements here do remember that this part of the wiring is connected to the GZ32 cathode which, when the valve is working, will be at about 370V DC relative to the chassis !

Cheers,

GJ

Bufo Bill · 16th Aug 2019, 11:37 am

Thanks GJ, will have a look later on.
Bill.

G8HQP Dave · 16th Aug 2019, 12:20 pm

If you are using a stereo cartridge connected to a mono amp then low sound from one channel can only come from the cartridge or the cartridge wiring.

Bufo Bill · 16th Aug 2019, 12:27 pm

Quote:

Originally Posted by G8HQP Dave

If you are using a stereo cartridge connected to a mono amp then low sound from one channel can only come from the cartridge or the cartridge wiring.

Yes, thought that was the case, but wanted to check with more experienced enthusiasts. Many thanks for your help.
Bill.

Bufo Bill · 17th Aug 2019, 3:43 pm

There were actually a couple of crusty bits of solder. Plugged everything back in and we have power. Will let the esl charge up for a bit and get back to you later if there's any more trouble or interesting developments. Thanks for the advice everyone.
Bill.

15th Aug 2019, 10:47 pm	#1
Bufo Bill Heptode Join Date: Jan 2016 Location: Wolverhampton, West Midlands, UK. Posts: 777	Pick up and Valve problems Hi I bought an AKG P8ES stylus and cartridge assembly recently, and I found the left channel low on volume compared to the right hand channel. Then today I decided to do a bit of fault tracing, and the GZ32 Valve in my Quad II Amp was not working upon switching the system power on. I run a mono system, ie a Quad II and QCII Preamp. Could the low volume of the left channel be accounted for as an early symptom of the valve failure, or do you think I am dealing with two unrelated problems that just coincidentally happened at roughly the same time? I would like to hear your opinions either way, although a link appears unlikely to my uneducated mind. Regards from Bill.

15th Aug 2019, 10:55 pm	#2
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	Re: Pick up and Valve problems Swap the connection over from the cartridge and see if the fault follows the amp or the cartridge. __________________ Frank

15th Aug 2019, 11:32 pm	#3
Bufo Bill Heptode Join Date: Jan 2016 Location: Wolverhampton, West Midlands, UK. Posts: 777	Re: Pick up and Valve problems Hi Frank, none of my inputs work through the amp, there is definitely a fault there. I was about to swap channels on the pick up when the amp malfunctioned. I have sourced another valve, but currently do not have a way of checking the cartridge, this being my only amp. Regards from Bill.

16th Aug 2019, 7:32 am	#4
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,324	Re: Pick up and Valve problems Am I reading this correctly? How can the OP tell about the difference in stereo cartridge voltage outputs if he is only using a mono amplifier? Also I can't see any possible connection between a rectifier failure and issues with a cartridge. __________________ Edward.

16th Aug 2019, 10:56 am	#6
Bufo Bill Heptode Join Date: Jan 2016 Location: Wolverhampton, West Midlands, UK. Posts: 777	Re: Pick up and Valve problems Edward: my speaker is a Quad ESL, I can clearly hear the instruments on the left channel on a stereo record are not as loud as they should be. I can't see why there should be a link either, it just seemed odd that the two faults occurred in quick succession, so it made me wonder. X: the valve doesn't warm up over time. It shows no sign of activity at all. It does seem odd that the valve failed, can I check some other component that could cause the valve to be inactive?

16th Aug 2019, 11:14 am	#7
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,324	Re: Pick up and Valve problems If the valve does not warm up or glow over time then it has failed. A new rectifier in your Quad would be no bad thing anyway especially considering its liekly age. Easily sourced. __________________ Edward.

16th Aug 2019, 11:14 am	#8
GrimJosef Dekatron Join Date: Sep 2007 Location: Oxfordshire, UK. Posts: 4,311	Re: Pick up and Valve problems The GZ32 contains two separate heaters - one for each diode. Failure of one heater, obvious by there being only one bright orange spot visible from the top of the valve (if you can see through/round the silver getter), is not uncommon. But for both heaters to fail in the same valve is rare. It can be due to a solder contact failure inside one of the pins on the valve's base. But it may also indicate a failure in the amp's wiring somewhere between the 5V secondary on the mains transformer and the GZ32 socket. If you make any measurements here do remember that this part of the wiring is connected to the GZ32 cathode which, when the valve is working, will be at about 370V DC relative to the chassis ! Cheers, GJ __________________ http://www.ampregen.com

16th Aug 2019, 11:37 am	#9
Bufo Bill Heptode Join Date: Jan 2016 Location: Wolverhampton, West Midlands, UK. Posts: 777	Re: Pick up and Valve problems Thanks GJ, will have a look later on. Bill.

16th Aug 2019, 12:20 pm	#10
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: Pick up and Valve problems If you are using a stereo cartridge connected to a mono amp then low sound from one channel can only come from the cartridge or the cartridge wiring.

17th Aug 2019, 3:43 pm	#12
Bufo Bill Heptode Join Date: Jan 2016 Location: Wolverhampton, West Midlands, UK. Posts: 777	Re: Pick up and Valve problems There were actually a couple of crusty bits of solder. Plugged everything back in and we have power. Will let the esl charge up for a bit and get back to you later if there's any more trouble or interesting developments. Thanks for the advice everyone. Bill.