Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

Replaced pulled tubes with a resistor?
Replaced pulled tubes with a resistor?
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 4th May 2007, 02:58 AM   #1
Ty_Bower is offline Ty_Bower  United States
diyAudio Member
 
Ty_Bower's Avatar
 
Join Date: Mar 2007
Location: Newark, DE
Question Replaced pulled tubes with a resistor?

I've grown weary of trying to sort out my little single ended EL84 project, so I've turned to my Harmon Kardon A230 for a while. In case you are wondering, the SE amp is mostly working fine. It's still biased too high, but it runs fine if I keep it on the Variac with the line voltage turned down to around 115 VAC.

Anyhoo, I have a HK A230 which I picked up off eBay for cheap a couple years back. I'm not sure it has a whole lot of potential, but I'm still keen to make it work well enough for basement or garage duty. The OPTs have no 4 ohm secondary taps, and no screen taps on the primary. They look awfully small to me, too. All the coupling caps are ceramic discs - at least I can fix this.

Here's my question: I pulled two 12AU7 tubes and one 12AX7 tube which made up the phono preamp and tone control circuits. I don't intend to use these parts, so it made sense for me to just bypass them and remove the unused components. At least, it seemed reasonable until I realized what was supposed to be the 215V supply to the AF amp and phase inverter had jumped over fifty volts. Without the load of the phono and tone tubes, I've upset the power supply.

So, I've decided to "correct" this problem by sticking a 30k ohm, 5 watt cemented resistor where the missing tubes used to live. It seems draw the right amount of current, and the supply voltages appear to fall back in line.

Is this a big mistake? What am I overlooking?
  Reply With Quote

Reply


Replaced pulled tubes with a resistor?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Big transformer (pulled from Sony receiver) maurycy Swap Meet 0 1st December 2008 02:29 PM
Pulled Voltage Below 0?! flyinglemur Power Supplies 0 8th March 2008 08:21 PM
Pemoline pulled from market. Tweeker The Lounge 3 20th January 2006 05:41 AM
Fisher CA-272 pulled from trash heap... rev_psilocybe Solid State 1 10th July 2005 01:55 PM
Figuring plate resistor values or tubes 101 Burnedfingers Tubes / Valves 15 10th August 2003 12:13 AM


New To Site? Need Help?

All times are GMT. The time now is 01:37 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki