One of my ECC85 driver tubes causes just one channel to make a fairly loud pop every 15 minutes or so. None of my other driver tubes do this in the same amp. I've cleaned the pins and no improvement. Any idea what would cause this?
It is my favorite sounding tube so I hate to give it up as even ones of the same brand and supposedly same era don't sound as good to me.
It is my favorite sounding tube so I hate to give it up as even ones of the same brand and supposedly same era don't sound as good to me.
Did you try swapping the tubes from the channels to see if it actually is the tube causing the problem?
As the ECC85 was designed for VHF amplification, an odd valve to use as an audio amplifier with a knee point designed for class C and an oscillator up to 45MHZ.
Try replacing the valve as it sounds like it maybe is intermittantly shorting internally.
I would use a 6n2p-eb in its place but not a Chinesium version, they are poor quality.
Try replacing the valve as it sounds like it maybe is intermittantly shorting internally.
I would use a 6n2p-eb in its place but not a Chinesium version, they are poor quality.
The Philips PA amplifiers EL6405, EL6415, EL6416, EL6425, EL6426, EL6435, and EL6436 all have an ECC85 as the driver tube (and all have EL36's as power tubes). So there must have been some kind of advantage in using the ECC85 in atleast those amplifiers.
Attached are the schematics of the Philips EL6425 and four other amplifiers using the ECC85. Three of these five are intended for 'normal' use, so not (primarily) as PA amplifiers.
Attached are the schematics of the Philips EL6425 and four other amplifiers using the ECC85. Three of these five are intended for 'normal' use, so not (primarily) as PA amplifiers.
Attachments
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2 x EF86 triode + 2 x EF86 + ECC85 + 4 x EL36 pp (Philips EL6425).pdf
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0,5 x ECC85 + ECL84 + EL84 se (Amroh Duette Stereo).pdf
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2 x ECC85 + 2 x EL84 c-follower pp (Voima Radio A2-20).png -
2 x ECC83 + ECC85 + 2 x EL84 pp (Amroh Capriccio).pdf
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2 x ECC83 + EF86 dc-coupled + ECC85 + 2 x EL34 pp (Tesla Mono 50).gif
As a derivative of the 12AT7/ECC81 with not too significant differences plate curve wise between both, the ECC85/6AQ5 is well suited for audio purpose. The overlap between both is so big that, apart from the different pinouts, both would fit bilaterally.
Btw, according to the info on Frank Philipses' site, the Philips EL 6435 doesn't feature EL36's as finals, but PE06/40N's instead (~807's as real pentodes). Anyway, the point is it's low signal amplifier section, including the ECC85 LTP, which it shares with the EL6405/6415/6425.
Best regards!
Btw, according to the info on Frank Philipses' site, the Philips EL 6435 doesn't feature EL36's as finals, but PE06/40N's instead (~807's as real pentodes). Anyway, the point is it's low signal amplifier section, including the ECC85 LTP, which it shares with the EL6405/6415/6425.
Best regards!
thank you for the replies.
The screen between the anodes is grounded.
It is just this one tube that does it in the one channel. Sometimes it will go longer than 15 minutes without popping but I can run the amp all day with any of the other ecc85 tubes without any popping.
The screen between the anodes is grounded.
It is just this one tube that does it in the one channel. Sometimes it will go longer than 15 minutes without popping but I can run the amp all day with any of the other ecc85 tubes without any popping.