Weber 6m45p high pitch squeal

blionb · 8th November 2012, 08:57 PM

Hi Everyone! I am a first time amp builder with more digital experience than analog. I am building a Weber 6m45p kit and I am at the point of biasing the tubes. I am using the 1Ohm resistor method. The voltage on pin 5 of my power tubes start at 515V and as I watch the power across the 1Ohm resistor it starts a about 3mW, at around 7mW or so, it jumps to 11mW and it starts to squeal at a high pitch. From what I have read this is oscillation(?). Some of the methods I have read on line do not seem to fix my problem at all. I triple checked my wiring of the output transformer and all seems well. I am going to go over my wiring again to see if I missed anything. In the mean time, can anyone suggest tests, measurements, diagnostic things I could do to try to track it down? Thanks in advance. Links below:

http://taweber.powweb.com/store/6m45p_layout.jpg
http://taweber.powweb.com/store/6m45p_schem.jpg

DF96 · 8th November 2012, 09:22 PM

This should be in the Instruments and Amps section.

Temporarily disconnect one end of R31, the feedback resistor. If this stops the oscillation then you have probably wired the OPT wrongly.

blionb · 12th November 2012, 04:41 PM

I did have the OPT wired incorrectly. I swapped the blue and brown wires from the OPT to the EL34s and the oscillation stopped. Now I have a different problem/question, but I will take it to the correct forum this time. Thanks for your response!

kevinkr · 12th November 2012, 04:54 PM

Moved to Instruments & Amplifiers per forum policy, see below:

Quote:

Tubes / Valves All about our sweet vacuum tubes

Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

AND

Quote:

Instruments and Amps Everything that makes music, Especially including instrument amps.

8th November 2012, 08:57 PM	#1
blionb diyAudio Member Join Date: Nov 2012	Weber 6m45p high pitch squeal Hi Everyone! I am a first time amp builder with more digital experience than analog. I am building a Weber 6m45p kit and I am at the point of biasing the tubes. I am using the 1Ohm resistor method. The voltage on pin 5 of my power tubes start at 515V and as I watch the power across the 1Ohm resistor it starts a about 3mW, at around 7mW or so, it jumps to 11mW and it starts to squeal at a high pitch. From what I have read this is oscillation(?). Some of the methods I have read on line do not seem to fix my problem at all. I triple checked my wiring of the output transformer and all seems well. I am going to go over my wiring again to see if I missed anything. In the mean time, can anyone suggest tests, measurements, diagnostic things I could do to try to track it down? Thanks in advance. Links below: http://taweber.powweb.com/store/6m45p_layout.jpg http://taweber.powweb.com/store/6m45p_schem.jpg

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
High pitched squeal from DIY guitar amp	santonel	Instruments and Amps	6	20th April 2012 12:43 AM
high pitched squeal from tube amp	bassking	Instruments and Amps	9	20th January 2012 04:31 PM
High pitch tone from AlephMini	yoke	Pass Labs	1	15th February 2009 01:40 PM
My alpine amp makes a high pitch squeaking sound	weesatron	Car Audio	67	29th October 2008 09:49 PM
High Pitch Noise in tweeters	bigrubes24	Car Audio	2	28th April 2005 12:39 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


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

8th November 2012, 09:22 PM	#2
DF96 diyAudio Member Join Date: May 2007	This should be in the Instruments and Amps section. Temporarily disconnect one end of R31, the feedback resistor. If this stops the oscillation then you have probably wired the OPT wrongly.

12th November 2012, 04:41 PM	#3
blionb diyAudio Member Join Date: Nov 2012	I did have the OPT wired incorrectly. I swapped the blue and brown wires from the OPT to the EL34s and the oscillation stopped. Now I have a different problem/question, but I will take it to the correct forum this time. Thanks for your response!