tube amp no sound only buzz - diyAudio
Go Back   Home > Forums > Live Sound > Instruments and Amps

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

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
Reply
 
Thread Tools Search this Thread
Old 14th June 2013, 07:38 PM   #1
ba3jar is offline ba3jar  England
diyAudio Member
 
Join Date: Mar 2012
Default tube amp no sound only buzz

Hi

i hope someone could guide please , my tube amp that i built dont give a sound when i turn it , the only sound i can get through the speakers is a buzz sound and when i turn the volumes the buzz get louder , when i plug a guitar it wouldnt give any sound but if i touch the strings it make a click sound , can anyone help ?

thanks
  Reply With Quote
Old 14th June 2013, 07:45 PM   #2
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Let me look in my crystal ball for you. The mist is fading . . .

It says you probably have a wiring error.

To get further than this we need more information: circuit diagram, some hint of your level of experience and available test equipment.
  Reply With Quote
Old 14th June 2013, 09:29 PM   #3
ba3jar is offline ba3jar  England
diyAudio Member
 
Join Date: Mar 2012
the amp is a kit by weber the schematics below
https://taweber.powweb.com/store/lauren_schem.jpg

i did add another stage of pentode ef86 preamp below

https://taweber.powweb.com/store/ef86_schem.jpg

but without the capacitors and tone pot , just a coupling cap and then to volume

the output tube changed from 807 to 6l6 tube didnt change the cathode resistor 300ohm i kept everything as it is , the voltage on plate of the output is 427 v and the screen 327 v

i did check all the wiring , everything seems to be in its place
  Reply With Quote
Old 15th June 2013, 01:37 AM   #4
diyAudio Member
 
indianajo's Avatar
 
Join Date: Jan 2010
Location: Jeffersonville, Indiana USA
when you touch the meter to the input grid on the output tubes, does it go "POW" in the speaker? If not, whynot? Back up one stage. Same test. Etc.
Warning, make measurements with one hand at a time. Connect the meter ground to the chassis with a clip lead to make this possible. Don't work high voltage alone. use a lot of light and don't work distracted by a cell phone etc.
You can work your way in from the input jack with an analog meter with a 2 VaC scale, and a 20 VAC scale. When you exercise the input with a FM radio on a rock station, can you see the beats of the music on the meter pointer? this requires a >450 V capacitor in series with the meter input, as AC analog voltmeters will read DC if you don't block it off.
Or a scope, but an analog voltmeter is a lot cheaper, and doesn't require 60 new electrolytic caps like the scope I bought on craigslist. The one where the boards are all glued in to the frame by the control rods and switches.
After you've proved the music goes in the first tube grid, does it come out the plate capacitor? Why not?
__________________
Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,1.3K, SP2-XT's, T-300 HF Proj's, Steinway console, Herald RA88a mixer, Wurlitzer 4500, 4300
  Reply With Quote
Old 15th June 2013, 02:05 AM   #5
lexx21 is offline lexx21  United States
diyAudio Member
 
Join Date: Mar 2011
Location: North Carolina
Wait.... you said that you replaced the 807 with a 6l6? What did you do with the anode lead? Did you remove it and wire it to the anode of the 6l6?

Also, you are running that 6l6 at darn near maximum plate voltage (450 is max per the JJ data sheet), so don't expect that tube to last very long the way you are running it.

You also said that you didn't change the cathode resistor. Is the bias still going to be the same for the 6l6 as the 807? I wouldn't think so since you are running at vastly different "normal" voltages.

What IndianaJo suggested is a great idea. Make sure you have a source going into it (cd player would be good). Do not run your amp without a load on the output.
  Reply With Quote
Old 15th June 2013, 09:05 AM   #6
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Does the EF86 stage replace the original ECC83 input stage or does it come before it? If the latter then you may just have too much gain.

By the way, this should be in Instruments & Amps forum.
  Reply With Quote
Old 15th June 2013, 11:35 PM   #7
ba3jar is offline ba3jar  England
diyAudio Member
 
Join Date: Mar 2012
i used the meter on the input grid of the output tube and it gave me such sound (pow) then went to the input grid of the 12ax7 V1A it gave me a scratch sound like but very light not like the (pow) ,on the V1B input grid gave me the (pow) sound , the ef86 in its input just scratch sound , the ef86 stage is not replaced with the 12ax7 and not after it actually i made it separately as in the schematic shown above one input but it has a coupling cap without the tone knob ,then goes to a volume and the output of the volume is connected to the driver 12ax7 V1B input grid , the V1A has two inputs and a tone a volume same as shown in the schematic of the amp its output volume connected to the input grid of the V1B driver .
however i did make measurements on the plate , which i did connect the blue lead that suppose to go to the 807 plate i connected to the plate of the 6l6 on that plate it gave me plate = 429v on the screen grid = 325v on the cathode that connected to the cathode resistor 300 ohm , it gave me 23v
i made my calculation i hope i'm right about it
429V - 23V = 406V
23V / 300 ohm = 0.076 ( 76ma )
0.076 * 406V= 31.12 watt
using 6l6GC , i know its limit is 30watt so yes in this case i'm taking it to its maximum , i know that i need to work on the cathode resistor and make it above the 300 maybe 400 ohm or even 500ohm , or maybe i change the tube to a KT88 cause it can take a 45watt max in this case but still the question is the amp dont make sound because i'm taking the 6l6 to its limits? i only hear buzz sound going up every time i turn the volume up and when i turn the volume down the buzz goes down .
  Reply With Quote
Old 15th June 2013, 11:51 PM   #8
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
All guitar amplifier threads belong in Instruments & Amplifiers by forum policy. Moving it.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 15th June 2013, 11:53 PM   #9
diyAudio Member
 
indianajo's Avatar
 
Join Date: Jan 2010
Location: Jeffersonville, Indiana USA
Excess plate dissipation wattage on the output tubes will eventually burn holes in the plates, but not make it not sound until it does. Suggest you do as you indicate and take action (like bigger cathode resistor) to increase the postive voltage of the input grid of output tubes versus the cathode. I notice you didn't say you touched the input grids of the output tubes with your meter, and listen for the bang. Suggest you do so. No bang, some sort of wiring error is possible.
update.
Notice moderator has been busy. Welcome to the outer darkness with wailing and knashing of teeth. On I&A if Enzo and Salas are busy at work, you're often stuck with me, and my prefered instrument amp is the Hammond organ. Suggest you join music-electronics-forum.com where everybody works on guitar amps and organ amp owners like me are banned. Obviously, organ "music" is not music. Or maybe Hammonds don't use electrons, they use positrons or something.
__________________
Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,1.3K, SP2-XT's, T-300 HF Proj's, Steinway console, Herald RA88a mixer, Wurlitzer 4500, 4300

Last edited by indianajo; 15th June 2013 at 11:59 PM.
  Reply With Quote
Old 16th June 2013, 01:01 AM   #10
ba3jar is offline ba3jar  England
diyAudio Member
 
Join Date: Mar 2012
thanks indianajo , yes i did touch the input grid of the output tube with the meter and it did give that paw sound
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Decware Zbox - looking for Tube buffer mods to reduce buzz speakerfritz Tubes / Valves 18 18th February 2012 10:06 PM
Decware Zbox - looking for Tube buffer mods to reduce buzz speakerfritz Tubes / Valves 0 17th February 2012 04:42 PM
Crackling Noise in Tube Amp (only) & PC Sound Card LinuksGuru Digital Line Level 3 17th May 2009 04:45 PM
Crackling Noise in Tube Amp (only) & PC Sound Card LinuksGuru Tubes / Valves 3 17th May 2009 04:44 PM
Melos triode and computer as source: BUZZ BUZZ BUZZ zigo3 Tubes / Valves 4 28th November 2007 02:11 AM


New To Site? Need Help?

All times are GMT. The time now is 07:35 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2