Heater regulator for guitar amp? - Page 4 - 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 7th July 2012, 11:35 AM   #31
diyAudio Member
 
Join Date: Jul 2005
Location: North Derbyshire
Quote:
Originally Posted by Enzo View Post
I made a case for it earlier. A common problem in guitar amps is the high current connections for 6.3VAC burning up on the inter-board wiring and even the transformer wires plugging onto the board. By running them in series like that, they need only a 0.9A connection, and the resulting higher voltage winding can be lighter.
Proper construction prevents that happening anyway, so essentially it's a penny pinching measure by shoddy manufacturers

Quote:

Commercial amps are not designed for running with tubes missing. Many do run that way, but they are not designed with that in mind. When they want to disable a tube, they turn it off via the active elements, not the heaters.

Those particular tubes may not have been designed for series strings, but it works fine and causes no problems, at least in the examples we see.
Series/parallel connections have got to be a bad idea, where one heater going O/C will cause the other parallel ones to do the same (so three valves blown where just one failed). Even if one of the 0.9A valves fails, then the amp is completely dead - one output valve failing in a conventionally wired amp will leave it still working for the gig (at least to some extent).
__________________
Nigel Goodwin
  Reply With Quote
Old 7th July 2012, 08:55 PM   #32
Simon B is offline Simon B  United Kingdom
diyAudio Member
 
Join Date: Dec 2011
Location: North-East England
Quote:
Originally Posted by darkskeptic View Post
All your help was awesome in this, and even the more heated discussions bring other knowledge and viewpoints out.....

"even the more heated discussions"

Penny has finally dropped, better late than never I suppose!
__________________
Engineer: One who can do for 10 shillings what any fool can do for 10 pounds.
  Reply With Quote
Old 7th July 2012, 09:05 PM   #33
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
yes, if one tube heater fails, then either they all go dark or one of the preamp tubes is gone and the others will run hot. However, the VAST majority of tube failures do not involve the heaters. I haven;t seen an open heater 6L6 in decades. I am sure it happened to someone somewhere yesterday, but for most, it just isn't an issue. When tubes do fail, it is generally power tubes shorting between elements. That takes out high voltage fuses most times, and so heater issues become moot.

In an amp like we are discussing, all three of those preamp tubes (I include the phase inverter for convenience) are needed for amp function, so the only case in which a dead tube would leave the amp playable would be a failed power tube. And that leads us back to the almost never happens condition.

I have seat belts and air bags in my car in case I am involved in a collision. Perhaps I should also install ceiling air bags in case a circus elephant tries to stomp my car. Sorry, that was flippant. My ceiling bags might protect me from a tree falling on my car. That actually happens now and then. But not very often, the recent wind storm we had over here being an example.

As to penny pinching, well, one man's penny pinching is another man's not wasting money. Molex connectors have a current rating that limits their use. A manufacturer of amps could use multiple molex connectors, or find some different larger connection materials, sure. Or they could simply do this. And by doing this they allow themselves to use the common connectors they use for everything else.
  Reply With Quote
Old 8th July 2012, 12:29 AM   #34
Simon B is offline Simon B  United Kingdom
diyAudio Member
 
Join Date: Dec 2011
Location: North-East England
FWIW, and as the original proponent of current regulation for heaters in this thread:

Out of the uncounted but certainly many hundreds of dead valves that have gone through my hands in the last 30 years or so, I think I've noticed perhaps three or four with open circuit filaments. The rock'n'roll christmas lights idea grew out of my noticing that the filaments usually still worked.

Switch-on and switch-off stress on the electrode structures and the glass-metal seal
s contributes to valve failure. What portion of guitar amp valve failures are caused by this is unknown - I've known guitarists who it didn't apply to at all, their failures were more that the envelope melted.......

Returning to the OPs question about using a regulator to feed this particualr heater chain, one idea is this:

Use three LM317T regulators, wired as current regulators, in parallel, each carrying 0.3A.

For each regulator, to get the required 1.25v drop across the resistor in the output path, downstream of which the reference ("adj") terminal is connected, R = 4.17 ohms, so 3R9 + 1R2 is close enough. 0.6w metal film should be fine, the 3R9s dissipate 0.351w.

Three regulators to ease heatsinking and increase reliability, the silicon works out cheaper than fancy heatsinks. Should be cheap and reliable, even into a dead short, disspation per regulator is 10w, so heatsink for that and it should be fine.


__________________
Engineer: One who can do for 10 shillings what any fool can do for 10 pounds.
  Reply With Quote
Old 8th July 2012, 12:12 PM   #35
diyAudio Member
 
Join Date: Jul 2005
Location: North Derbyshire
Quote:
Originally Posted by Simon B View Post
Out of the uncounted but certainly many hundreds of dead valves that have gone through my hands in the last 30 years or so, I think I've noticed perhaps three or four with open circuit filaments.
Like I said in post #29

O/C heaters are VERY rare, I've probably seen more O/C heaters on CRT's than valves? - usually where just one of the three heaters goes O/C so you lose one colour totally. Obviously you can't read it as O/C as they are paralleled, but by careful observation you can spot one has gone out.
__________________
Nigel Goodwin
  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
how to wire 6.3VDC heater on a heater with center tap (12.6V series, 6.3V parallel)? jarthel Tubes / Valves 9 14th April 2012 06:36 PM
Zener heater regulator arold19 Tubes / Valves 18 28th July 2010 07:56 AM
Regulated Heater on the 6SN7 Aikido Plate to Heater question john65b Tubes / Valves 6 24th November 2009 06:44 AM
A better LDO heater regulator astouffer Tubes / Valves 6 10th November 2006 07:02 AM
6.3v Heater Regulator Schematic cantskienuf Tubes / Valves 3 29th April 2005 01:20 PM


New To Site? Need Help?

All times are GMT. The time now is 02:25 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