Valve heater glow at power-up. - UK Vintage Radio Repair and Restoration Discussion Forum

PaulR · 19th Sep 2006, 7:29 pm

I bought a Rogers HG88 Mk111 amp for my son from Ebay and was fairly confident that I would be able to repair any faults that arose. I have replaced the caps in the power supply and all the coupling ones.

The problem is that when it is first switched on something in all the valves glows brightly for an instant. As the heaters warm up this disappears. As you can imagine, this puts me off trying it as I am scared of burning out the valves. The pilot lamp is OK so it doesn't seem to be a problem with the heater supply itself. I am fairly sure I have wired up the replacement HT caps OK, the only difference being that I replaced the 16uf ones further down the line with 22uf ones.

As this was a birthday and "going to Uni" present to my son I would be very grateful for any help or suggestions.

Many thanks

Paul

Kat Manton · 19th Sep 2006, 7:40 pm

Hi,

This seems to be normal for some types of valve - basically a small part of the heater that's outside the cathode tube lights up like a lightbulb when power is first applied and the cathode tube itself is cold. As the cathode warms up the heat dissipated in the heater evens up.

It is alarming, and I do wonder about valve longevity - but it's something I've seen happen with several bits of valve gear and never had a valve heater fail. The EF86s in my Quad IIs did this, none ever failed.

It happens with most of the valves in my Sondyna TV set - with 25 valves in there it lights up like a lighthouse when first powered up. I'm thinking of a small mod involving a relay switching out a series resistor after a time delay - just for my own peace of mind, really.

Regards, Kat

mickjjo · 19th Sep 2006, 8:00 pm

Hi Paul, I have a Rogers Cadet 111 and that does the same , At switch on, the bottom parts of the ECL86 heaters glow like light bulbs (

) , before settling down

. Seems to be perfectly normal with these valves so nothing to worry about

.

Regards, Mick.

PaulR · 19th Sep 2006, 8:06 pm

Thanks both.

It is very scary and as I had done some work on it I assumed it was something I had done. In fact I panicked so much I didn't think of the obvious and simple test of removing the DC fuse!!! Er - yes I know!

I have just done this and guess what - they still glow like bulbs when first switched on!

Right - off I go to find out what else is wrong. What would I do without this forum?

Many thanks

Paul

19th Sep 2006, 7:29 pm	#1
PaulR Dekatron Join Date: Oct 2003 Location: Southport Lancashire, UK. Posts: 3,233	Valve heater glow at power-up. I bought a Rogers HG88 Mk111 amp for my son from Ebay and was fairly confident that I would be able to repair any faults that arose. I have replaced the caps in the power supply and all the coupling ones. The problem is that when it is first switched on something in all the valves glows brightly for an instant. As the heaters warm up this disappears. As you can imagine, this puts me off trying it as I am scared of burning out the valves. The pilot lamp is OK so it doesn't seem to be a problem with the heater supply itself. I am fairly sure I have wired up the replacement HT caps OK, the only difference being that I replaced the 16uf ones further down the line with 22uf ones. As this was a birthday and "going to Uni" present to my son I would be very grateful for any help or suggestions. Many thanks Paul Last edited by Darren-UK; 23rd Jun 2007 at 2:07 pm. Reason: Made more specific.

19th Sep 2006, 7:40 pm	#2
Kat Manton Retired Dormant Member Join Date: Jul 2005 Location: West Yorkshire, UK. Posts: 1,700	Re: Rogers HG88 Mk III HELP! Hi, This seems to be normal for some types of valve - basically a small part of the heater that's outside the cathode tube lights up like a lightbulb when power is first applied and the cathode tube itself is cold. As the cathode warms up the heat dissipated in the heater evens up. It is alarming, and I do wonder about valve longevity - but it's something I've seen happen with several bits of valve gear and never had a valve heater fail. The EF86s in my Quad IIs did this, none ever failed. It happens with most of the valves in my Sondyna TV set - with 25 valves in there it lights up like a lighthouse when first powered up. I'm thinking of a small mod involving a relay switching out a series resistor after a time delay - just for my own peace of mind, really. Regards, Kat

19th Sep 2006, 8:00 pm	#3
mickjjo Rest in Peace Join Date: Jul 2004 Location: Dartford, Kent, UK. Posts: 1,661	Re: Rogers HG88 Mk III HELP! Hi Paul, I have a Rogers Cadet 111 and that does the same , At switch on, the bottom parts of the ECL86 heaters glow like light bulbs () , before settling down . Seems to be perfectly normal with these valves so nothing to worry about . Regards, Mick.

19th Sep 2006, 8:06 pm	#4
PaulR Dekatron Join Date: Oct 2003 Location: Southport Lancashire, UK. Posts: 3,233	Re: Rogers HG88 Mk III HELP! Thanks both. It is very scary and as I had done some work on it I assumed it was something I had done. In fact I panicked so much I didn't think of the obvious and simple test of removing the DC fuse!!! Er - yes I know! I have just done this and guess what - they still glow like bulbs when first switched on! Right - off I go to find out what else is wrong. What would I do without this forum? Many thanks Paul