tube vibration - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 19th January 2006, 01:44 AM   #1
smak is offline smak  Canada
diyAudio Member
 
Join Date: May 2003
Location: Toronto, Canada
Default tube vibration

heya,

i aquired a vintage heathkit amp that has been upgraded and recapped by a forum member less than a week ago.

there seem to be a few issues with it though.. one of which is that there is sometimes a low pitched vibrating sound coming from the chassis or tubes themselves.. kind of sounds like dry ice on a spoon if you have reference to that.

i was told the amp had a hot plating issue at one time but it was supposedly resolved. could this be that issue reappearing?

i'm also getting occasional popping through the speakers.. sometimes left channel, sometimes right and sometimes both.

it has blown a fuse also.. the power fuse from the back. i was told to switch to a 2 amp slow blow and it probably wont happen again.. to be on the safe side i replaced with a quick blow like it came with and its been okay so far. (1 day)

i thought the problems may be heat related but i've taken extensive measures to make sure the amp gets plenty of air now and it is running cool but problems persist.

otherwise the amp plays very nicely. i am getting some sweet mid-highs, although the low end is a but lacking but i hear this is somewhat common with tubes.

do these symptoms sound familiar to a certain problem tubes or tube amps run into? do they sound like minor issues you guys would just live with or do you think they should definatly get looked after before something worse crops up.
  Reply With Quote
Old 19th January 2006, 02:22 AM   #2
testlab is offline testlab  United States
diyAudio Member
 
testlab's Avatar
 
Join Date: Dec 2005
Location: Grand Rapids MI
Due to the age of the amplifier, I would be very suspicious of every electrolytic capacitor in the unit. For reliability reasons, I would replace those as a preventive maintenance measure.

As for the "hot-plating" issue and limited bandwidth, it sounds like signal path coupling caps. Probably the ones following the phase inverter. They sometimes short and pull plate current through grid of the power tube(s). The power tube plates will glow because they are not biased.

These are speculative ideas since I am not intimately farmiliar with the unit and, do not have a schematic to look at.

Regards,
Al
__________________
It's not whether you win or lose, it's how you lay the blame.
  Reply With Quote
Old 19th January 2006, 02:33 AM   #3
smak is offline smak  Canada
diyAudio Member
 
Join Date: May 2003
Location: Toronto, Canada
so is that vibration what "hot plating" is?

all the origional caps have already been replaced.. the tubes glow orange during normal operation anyways.. how can you tell if the bias issue is causing a glow?

thnx for the reply btw..
  Reply With Quote
Old 19th January 2006, 04:33 AM   #4
diyAudio Member
 
hagtech's Avatar
 
Join Date: Mar 2002
Location: Hawaii
Default crackling

I'd guess maybe a bad connection or broken solder joint. Are the tube sockets tight?

jh
  Reply With Quote
Old 19th January 2006, 04:40 AM   #5
smak is offline smak  Canada
diyAudio Member
 
Join Date: May 2003
Location: Toronto, Canada
hrmm, well they're not loose.. but i'll take a closer took tomorrow in the light.
  Reply With Quote
Old 19th January 2006, 05:57 AM   #6
diyAudio Member
 
Join Date: Sep 2003
Location: London
Like the previous posters said, maybe you have two unrelated problems. I've found that intermittent popping can be bad contacts on the tube bases. Can be solved, as said, by tightening tube pins, replacing sockets or just going over all the pins again with a soldering iron - sometimes the solder cracks and you get an intermittent that you can't see with the naked eye. I guess hot plating - term I've never heard of before - means the plates of the output tubes once got hot, probably through a capacitor or resistor being out of spec or non-functional, so that's another problem.
  Reply With Quote
Old 19th January 2006, 07:23 AM   #7
john is offline john  Philippines
diyAudio Member
 
john's Avatar
 
Join Date: Aug 2001
Location: pasay city
Default tube vibration

Hi there!

What tubes are in use for that amp? I had an experience on tube amps fitted with modern production Sino and Sovtek power tubes. Something like a "PLinking" sound can be heard upon power "on" and power "off". May be this the same case as what you are having?

John
  Reply With Quote
Old 19th January 2006, 07:33 AM   #8
diyAudio Member
 
cogsncogs's Avatar
 
Join Date: Jul 2003
Location: Wayne, West Virginia
Quote:
Originally posted by: smak
kind of sounds like dry ice on a spoon if you have reference to that.
Sputtering?

Quote:
i'm also getting occasional popping through the speakers.. sometimes left channel, sometimes right and sometimes both.
Many things could cause these symptoms. From your description it sounds like an intermittent connection as others have posted, either and/or bad sockets, bad/cold soldier joints, failing coupling/PS smoothing/bypass caps, bad tubes etc. Given the age of this dear to our hearts but old Heathkit; it may need a good overhaul! Especially replacing the PS caps and coupling caps, inspecting every soldier joint, checking for loose tube socket pins (not making good contact with the tube pins), off value resistors, those old carbon composition resistors are notorious for drifting off value with age and heat.

Quote:
so is that vibration what "hot plating" is?
Yes and no.
Hot plating...? is an over current condition i.e. under biased, too much current passing through the tube and exceeding the plate dissipation rating (watts). Now when in that condition you may hear a sputtering sound. Vibrating as you have described it; could it possibly be 'motorboating'...?, which is a very low frequency oscillation around 1Hz to 2 or 3Hz caused usually by a bad or failing power supply (PS) capacitor. A bad layout or circuit design can cause this but it's probably not applicable in your case unless someone before you has modified the amplifier circuitry.
As for 'popping' the fuse, this is indicative of excessive current being drawn. If you have a schematic or if not the model number; I may have the schematic as I have schematics for quite a few Heathkit amplifiers on my computer. Then we could possibly help you better. Also what and where any modifications/upgrades were done by the "other" forum member would be of great help!

Quote:
do they sound like minor issues you guys would just live with or do you think they should definatly get looked after before something worse crops up.
No! "We" would not live with this, no way! Some of us would end up in the hospital from beating ourselves up trying to figure out what's wrong or go crazy trying to live with it!
We would not consider these to be minor issues and if the output tube plates are glowing orange and popping fuses this would be a serious condition! And please don't be tempted to use higher rated fuses or bypassing them! From your post you have not been tempted to do so, very good!

So if you can come up with a schematic or model number that would be great! Hope I've helped you some way!

Cheers
Wayne
  Reply With Quote
Old 19th January 2006, 05:25 PM   #9
smak is offline smak  Canada
diyAudio Member
 
Join Date: May 2003
Location: Toronto, Canada
i dont think the tube plates themselves glow too much.. just the filiments of the tubes i guess so that sounds right.. the left channels 7199 tube filiments do seem to glow a bit dimmer than the rest though..

they are rogers, philco, rca, ge, sylvania and the it looks like no name "Japan" 6BQ5's brands.. all mixed together but the voltages or tube properties have been matched from what i have been told.

the tubes that are supposed to compliment this amp are 7199, EL84/6BQ6 and a GZ34/5AR4 but the ladder was replaced with something less powerful from what i understand due to avaliability issues.

the vibration i mentioned does not only occour when i turn the amp on and off.. it usually happens for 5 or 10 mins at a time, stops and starts again at some arbitrary moment.

the pop/crackle in the speakers occours wether the tubes are vibrating or not.. seems like at least once every 3-4 mins there is some kind of noise transmitted.

i've tried surge protected outlets as well as directly to the wall with no difference.

i think i'll take it back to the forum member and see if he cant figure it out.. hopefully it is just a minor tube or connection issue.
  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
Velcro as Vibration Isolator Buckapound Parts 5 9th May 2009 06:58 PM
tube anti-vibration mounting zigzagflux Tubes / Valves 19 9th September 2007 12:37 AM
Capacitor vibration ? ]|[ GorE Multi-Way 2 26th March 2007 10:26 PM
Vibration Control for UcD 700 serengetiplains Class D 9 4th January 2006 05:56 AM
Major Vibration Phrozen06 Car Audio 4 18th August 2005 02:36 AM


New To Site? Need Help?

All times are GMT. The time now is 07:11 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