Cornet 2 - red light, oh no!

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MaskdBagel

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Cornet 2 - red light, oh no!
« on: 31 Jan 2015, 06:31 pm »
Hi all-

I have a few happy years on my Cornet 2, but it may need its first real maintenance. The LED isn't going from red to green. I've left it on for about an hour now, and the 5Y3 and the transformer are both still cool. I think replacing the tube might be a good first step, but I'd like to troubleshoot a little before buying one. Any advice on where to measure or what to look at?

Thanks!

poty

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Re: Cornet 2 - red light, oh no!
« Reply #1 on: 1 Feb 2015, 09:17 pm »
Do you see any sign of glowing inside 5Y3? Do you have any DVM on hand?

MaskdBagel

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Re: Cornet 2 - red light, oh no!
« Reply #2 on: 1 Feb 2015, 10:28 pm »
Thanks for the reply! No glow at all. I do have a DVM - where should I start?

poty

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Re: Cornet 2 - red light, oh no!
« Reply #3 on: 2 Feb 2015, 07:43 am »
You said you have the red LED on, then at least the mains voltage is connected to the transformer. It's good.
Turn off the Cornet 2. Pull out all four tubes (remember their positions!!!). Set the DVM to measure AC voltages (often it is marked as ~) in the range of >10V, switch on the Cornet 2 and put the probes to pins 2 and 8 of V100 (5Y3). Pins are counted from the key to counterclockwise direction (if you look at the tube side). It should read around 5V. Switch the DVM to the measurement range >700V and measure the voltage between pins 4 and 6. It should read more than 550V. If the voltages are on - then the problem is in the 5Y3 (replace). If not - there should be either the transformer problems (unlikely) or bad connections between the transformer and the PCB. We'll test that further.

MaskdBagel

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Re: Cornet 2 - red light, oh no!
« Reply #4 on: 3 Feb 2015, 12:42 am »
Huge help, thanks! All tested OK. Replaced the tube and all is well. Thanks!

Grinnell

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Re: Cornet 2 - red light, oh no!
« Reply #5 on: 7 Feb 2015, 03:40 pm »
I had the same situation last year

rectifier went bad  light turned green for a sec then red