KEL 84 Strange Noises

[bob orbell]

Aha, you'r just a wimp Philip, but a nice wimp.

[bob orbell]

Originally Posted by deepdown130

I cycle mainly as a means of getting to the railway station to be honest. Not sure I get much pleasure out of it (due to other road users generally). I work in London and sometimes in Bath so it makes little sense to have a car at the moment.

I'm impressed you aim for 100 miles a week - you must be fitter than the proverbial butcher's dog!

Yes I know what you mean about other road users and cycles, but I do most of my miles on country lanes and some off road stuff, I started cycling big time about 4 years ago after a knee replacement, it was the best exercise for the knee and to get my power back after 15 years of pain and limping . BOB

[bikerhifinut]

Just to stray back on topic.........lol lads dont lynch me.

Don't labour under a misconception that Edicron ECF80's as a replacement next time will be the same. Edicron are a well known rebrander and none the worse for that but there's no guarantee another pair will be the same origin.
Now I don't know if anyone else has broached this but what sort of DC heater supply have you got to the ECF80? If its the Schottky mod, then you really must have the pi filter in place as the voltage can get rather high. This might possibly stress the heaters and cause valve problems. I had a similar issue with a KEL84 that I bought used where the schottky mod hadn't had the pi filter with it. out of both sets of ECF 80 that came with it one of each pair was noisy and I figured the overvoltage on the heaters was the cause. After fixing it and getting the heaters down to 6.3v it stayed good. I used a set of generic Foreign made ECF80 and they seemed just fine to me. I think they originated from the service dept at the old radio factory in Southend (Ecko?) according to the friend who donated 4 to me. He'd got them from an old timer who worked there.
Anyway if you're happy with the way your edicrons work stick with them and dont worry about "spares" if you have them working inside their parameters they'll last years.

Andy.

[Richard]

Yes, as Andy says, check heater voltages.

If schottkies are used, part of any advantage would be from them being a low noise diode, and part of the advantage is in them dropping less voltage during rectification, so we end up with a bit under 1V extra. This can then be dropped in a pi filter which lowers noise further.

This info and the suggested 1R dropper resistor for KEL84 are in the faq, http://www.world-designs.co.uk/forum...read.php?t=573

[deepdown130]

Thanks for the further guidance chaps. I'm certainly learning a lot about the way my amp because of this "problem".

I measured the heater voltages on the 2nd May and they were both at 6.2V. That has drifted up 0.3V since I built it (although I'm guessing that could just be down to natural variations in the mains supply voltage).

My KEL is standard build from the original print - no mods.

Taking your advice about the valves lasting years I think I'll leave it as it is and have a tinker when they finally wear out.

I really do appreciate the advice, offers and help I've received (despite my tetchy moment - now deleted).

Thanks again

Gavin