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Old 15th Aug 2019, 10:47 pm   #1
Bufo Bill
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Default 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.
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Old 15th Aug 2019, 10:55 pm   #2
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Default Re: Pick up and Valve problems

Swap the connection over from the cartridge and see if the fault follows the amp or the cartridge.
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Old 15th Aug 2019, 11:32 pm   #3
Bufo Bill
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Default 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.
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Old 16th Aug 2019, 7:32 am   #4
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Default 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.
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Old 16th Aug 2019, 8:48 am   #5
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Default Re: Pick up and Valve problems

Quote:
Originally Posted by Bufo Bill View Post
the GZ32 Valve in my Quad II Amp was not working.

Regards from Bill.
How do you know that?
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Old 16th Aug 2019, 10:56 am   #6
Bufo Bill
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Default 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?
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Old 16th Aug 2019, 11:14 am   #7
Edward Huggins
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Default 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.
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Old 16th Aug 2019, 11:14 am   #8
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Default 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
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Old 16th Aug 2019, 11:37 am   #9
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Default Re: Pick up and Valve problems

Thanks GJ, will have a look later on.
Bill.
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Old 16th Aug 2019, 12:20 pm   #10
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Default 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.
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Old 16th Aug 2019, 12:27 pm   #11
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Default Re: Pick up and Valve problems

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Originally Posted by G8HQP Dave View Post
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.
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Old 17th Aug 2019, 3:43 pm   #12
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Default 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.
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