Ipsofacto

Help. No sound from valve preamplifier.

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Hello to the board.

OK, be gentle please as the following is way above my pay grade.. Fired up the hi-fi this morning to be greeted with no sound except for some small bleed through coming from the speakers. Lifted the lid off the pre to see that both valves in the line stage weren't glowing. Please note the pre was upgraded two months ago so these are effectively 'new' valves. The valves in the line stage are ECC99s (there were 83s prior to the upgrade).

There is power into some of the tubes (power/voltage regulator?)

b0r7h.md.jpg

The line stage valves are both dead.

b0hVs.md.jpg

Can I plug in some ECC83s into the line stage to double check the problem isn't with the valves? A quick google this morning advised that ecc83s and 99s were interchangeable 'sometimes', but 'not always' which wasn't exactly helpful. I can also confirm that taking the pre out of the chain and plugging my monos directly into the CD player gives me sound.

Kid gloves please! Thanks in advance.

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I wouldn't do that. I also wouldn't panic. No power to the filaments (ie. No glow) suggests a power supply issue. Unplug the mains, wait 5 minutes, then check if there are fuses in the amp. Report back...

Sent from my BLA-L09 using Tapatalk

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Also, what amp is it, and who upgraded it, the manufacturer? Looks a bit like a Croft.

Sent from my BLA-L09 using Tapatalk

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The ecc99 is a supercharged ecc82 it takes more than twice the heater current and around 10 x the anode current as the anode impedance is a lot less, so may well stress the power supply

Hopefully a fuse or the turn on surge has tripped something out? 

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Looks like the VR is up and running so B+ appears OK. Heater circuit left to check...

Sent from my BLA-L09 using Tapatalk

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Thanks for the rapid replies everyone. Very helpful. Yes, the pre ampifier is a croft R with external power supply.

OK, I found a fuse on the external power supply and removing it and looking by eye it looks fine (I don't have the equipment to check it electrically).

Given I am way out of my depth on this and without any tools (or knowledge on how to use them!), I think in the first instance I will send Glenn an email and see what he says and whether it needs to go back (which I suspect it will).

Thanks all for your input. I will keep you updated.

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6 minutes ago, awkwardbydesign said:

When you can, buy a (cheap?) digital multimeter.  Almost anything would do to check voltages and continuity (fuses).  Just remember there are high voltages inside valve amps.

Now on my to-do list!

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Lidl were selling a digital multimeter  two weeks ago for £9.99, complete with battery, leads and a small screwdriver to undo the battery compartment, my local branch still had some when I did a bit of shopping on Monday 23rd, well worth trying to find one. 

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Super Wammer
45 minutes ago, Ipsofacto said:

Bulls eye! 

Fuse blown?

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