tube is flashing and glowing very bright!

pho_boi · 8th February 2006, 09:46 PM

Hello friends,

I've got a Cayin A-50T integrated amplifier, and I'm experiencing some very scary problems.

Out of nowhere, one of the EL34 tubes starts to flicker and glow a lot more than the others. My right speakers starts to make popping sounds too, this is when I switch everything off. It's happened 3 times over the past year or so.

I'm sure that its not the tube, because the first time it happened I changed all four EL34s and it's still occuring in that same tube position. The other three tubes have never had this happen, only happens in that one tube socket.

Any clue what is going on? I really wanna fix this because I don't want to ruin my speakers or the tubes.

Thanks everyone

karma · 8th February 2006, 10:11 PM

what shape are your tube sockets in? are thay new old?

SHiFTY · 8th February 2006, 10:11 PM

Does the grey metal structure (plate/anode) glow bright red? Or is it more of a sparking in the tube?

If it is glowing red, then you have either a bad coupling capacitor or no bias voltage.

If it's sparking you might have no screen voltage or a faulty connection.

pho_boi · 8th February 2006, 10:21 PM

Quote:

Originally posted by karma
what shape are your tube sockets in? are thay new old?

It's a pretty new amplifier, the socket are just the regular 8 socket ones for el34s.

Quote:

Originally posted by SHiFTY
Does the grey metal structure (plate/anode) glow bright red? Or is it more of a sparking in the tube?

If it is glowing red, then you have either a bad coupling capacitor or no bias voltage.

If it's sparking you might have no screen voltage or a faulty connection.

It's the filaments (i think), they normally glow like regualr tubes. But that particular tube starts flicker and glowing a lot brighter than the others.

I've checked the bias, and they are all at 0.35v or 35ma.

karma · 8th February 2006, 10:24 PM

ic well shifty covered the rest

cheers

pho_boi · 8th February 2006, 10:44 PM

I've found a link with pictures of my amps underside, can someone point out to me which ones are the coupling caps?

http://www.sanyue.net/read.php?tid=11067

Thanks

Alastair E · 9th February 2006, 05:03 PM

Not really easy to see in the pics postd, They take ages to load, and you cannot see even then..........

Best get the schematic and check there........

Svein_B · 9th February 2006, 06:44 PM

You can find some excellent photos at store.acousticsounds.com
Select the <large images for high bandwidth users>

I do not have a circuit diagram, but from memory:
Input 12AX7 (both triode halfs in parallel), direct coupled to 12AU7 phase splitter in LTP configuration. Coupling caps are .22uF (RealCap) mounted on bias reg circuit board.

Svein_B

pho_boi · 9th February 2006, 09:16 PM

I'll go get some replacement caps soon.

Would there be anything else that would be causing these symptons?

8th February 2006, 09:46 PM	#1
pho_boi diyAudio Member Join Date: Nov 2004 Location: Brisbane	tube is flashing and glowing very bright! Hello friends, I've got a Cayin A-50T integrated amplifier, and I'm experiencing some very scary problems. Out of nowhere, one of the EL34 tubes starts to flicker and glow a lot more than the others. My right speakers starts to make popping sounds too, this is when I switch everything off. It's happened 3 times over the past year or so. I'm sure that its not the tube, because the first time it happened I changed all four EL34s and it's still occuring in that same tube position. The other three tubes have never had this happen, only happens in that one tube socket. Any clue what is going on? I really wanna fix this because I don't want to ruin my speakers or the tubes. Thanks everyone

9th February 2006, 05:03 PM	#7
Alastair E diyAudio Member Join Date: Feb 2004 Location: South Wales	coupling caps..... Not really easy to see in the pics postd, They take ages to load, and you cannot see even then.......... Best get the schematic and check there........ __________________ Das Beste Oder Nichts

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
7591 is glowing RED	dognut	Tubes / Valves	2	1st March 2009 06:16 PM
Problem: Really Bright glowing 6CA7	gary f	Tubes / Valves	14	21st July 2006 09:42 PM
Tube flashing	safetyman	Tubes / Valves	15	7th September 2005 02:26 PM
Flashing Rectifier Tube- Bad Thing?	Sherman	Tubes / Valves	46	19th August 2005 12:00 AM
Blue glowing tube	Gabster	Tubes / Valves	24	27th September 2002 04:08 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read

8th February 2006, 10:11 PM	#2
karma diyAudio Member Join Date: Feb 2003 Location: hamilton,ontario	what shape are your tube sockets in? are thay new old?

8th February 2006, 10:11 PM	#3
SHiFTY diyAudio Member Join Date: Jul 2002 Location: New Zealand	Does the grey metal structure (plate/anode) glow bright red? Or is it more of a sparking in the tube? If it is glowing red, then you have either a bad coupling capacitor or no bias voltage. If it's sparking you might have no screen voltage or a faulty connection.

8th February 2006, 10:24 PM	#5
karma diyAudio Member Join Date: Feb 2003 Location: hamilton,ontario	ic well shifty covered the rest cheers

8th February 2006, 10:44 PM	#6
pho_boi diyAudio Member Join Date: Nov 2004 Location: Brisbane	I've found a link with pictures of my amps underside, can someone point out to me which ones are the coupling caps? http://www.sanyue.net/read.php?tid=11067 Thanks

9th February 2006, 06:44 PM	#8
Svein_B diyAudio Member Join Date: Oct 2005	You can find some excellent photos at store.acousticsounds.com Select the <large images for high bandwidth users> I do not have a circuit diagram, but from memory: Input 12AX7 (both triode halfs in parallel), direct coupled to 12AU7 phase splitter in LTP configuration. Coupling caps are .22uF (RealCap) mounted on bias reg circuit board. Svein_B

9th February 2006, 09:16 PM	#9
pho_boi diyAudio Member Join Date: Nov 2004 Location: Brisbane	I'll go get some replacement caps soon. Would there be anything else that would be causing these symptons?

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)