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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 15th Oct 2017, 6:28 pm   #21
GrimJosef
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Default Re: Smoking Quad II.

Hmmm. Can you confirm the voltages measured at the two ends of the R EF86 anode load resistor. It's R6 in Keith Snook's picture of the tagboard about a third of the way down this page http://www.keith-snook.info/quad-ii-...amplifier.html. It would be most useful if you could actually touch your test probe to the wires going into the resistor ends rather than to the tags that those wires are soldered to. The resistor wire going towards the edge of the tagboard is meant to be connected to the valve's anode, which you say is at -1.28V. The wire at the other end of the resistor is meant to be connected to the E terminal on the main smoothing block, which you say is at 347V.

If you do indeed measure -1.28V and 347V at the ends of R6 then can you power down, swap the two EF86s swapped over, put the power back on and repeat the measurements. I wouldn't expect anything to change, but it's just possible that the strange readings will 'follow the valve'. If they do then that indicates that the valve is sick. If they don't then I'd power down immediately and we'll have to investigate the rest of the circuitry further.

Cheers,

GJ
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Old 15th Oct 2017, 8:25 pm   #22
Stanney2001
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Location: London, UK.
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Default Re: Smoking Quad II.

Breakthrough,

I pushed my probe into the end of the resistor and it budged.
Resoldered. And switched on again.

R5 is 122.4 V. And R6 is 106V
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Old 15th Oct 2017, 11:00 pm   #23
GrimJosef
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Default Re: Smoking Quad II.

Excellent news. Does it sound better ?

Cheers,

GJ
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Old 15th Oct 2017, 11:20 pm   #24
Stanney2001
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Default Re: Smoking Quad II.

I switched both ef86s
R5 is now 113.6
R6 is 116.8

It sounds a lot, lot better.
Saint Saens carnival of animals.

Thank you so much.
I really enjoyed that.

I can follow those tools for the other monoblock.
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