845 set bias. - 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 3rd August 2014, 01:10 PM   #1
diyAudio Member
 
Join Date: Feb 2013
Default 845 set bias.

Hello , this is my beginner question i have this integrated amp supose to be ongaku clone with 2×845 rca tube , 2×12sn7gt , 2×ecc83 and four rectifier tubes the amp was fully restored replaced all caps with solen , mundorf , auricap , after testing everithing is ok but it seems to me that the right 845 tube is a litter brighter than left i have a picture of a module to setup bias can any one explain to me how should i setup bias where to point the probes from voltmeter i must say i dont have any specs from amp or tubes.

I know there is a high voltage and im aware of danger.

Im posting a picture of bias plate.This pictures are from prevoius not restored amp.

THX for any help

regards
Attached Images
File Type: jpg IMG_4222.jpg (280.7 KB, 186 views)
File Type: jpg IMG_4224.jpg (266.1 KB, 187 views)
  Reply With Quote
Old 3rd August 2014, 05:56 PM   #2
Aleks1 is offline Aleks1  United Kingdom
diyAudio Member
 
Join Date: Nov 2004
Location: Manchester, Uk
How long is a piece of string?

Twice as long as half it's length.

Measure some things like plate voltage etc if you can, and get back to us.

Have fun.
  Reply With Quote
Old 3rd August 2014, 06:55 PM   #3
diyAudio Member
 
Join Date: Aug 2012
Quote:
Originally Posted by mcnaget View Post
...it seems to me that the right 845 tube is a litter brighter than left ...
What do you mean? Brighter sound or brighter light from the fillament?
The intensity of the light is not affected by the bias.
  Reply With Quote
Old 3rd August 2014, 07:52 PM   #4
diyAudio Member
 
Join Date: Feb 2013
Default 845

Quote:
Originally Posted by Parafeed813 View Post
What do you mean? Brighter sound or brighter light from the fillament?
The intensity of the light is not affected by the bias.
I mean brighter light . Im not sure but as im informed those tubes are 5-6 years old so are the rectifiers and 12sn7gt the 12ax7 ei niš was recent replacement.

thx

regards
  Reply With Quote
Old 4th August 2014, 03:47 PM   #5
jervill is offline jervill  United Kingdom
diyAudio Member
 
Join Date: Aug 2010
If it's the brightness of the filaments then maybe check the filament voltages. If one is way over or way under, it may explain the difference in brightness. As mentioned above, the bias shouldn't affect this.

If it is an Ongaku clone then there are examples of the schematics on the net. I would examine those and see if it tallies to what you have wired up in the amp. Regardless, it would be a good idea to give a good look at the amp and trace a schematic for it. Should help you work out where to probe and what readings to expect roughly, especially if your planning to examine it deeper. Good luck!
  Reply With Quote
Old 4th August 2014, 04:28 PM   #6
работник
diyAudio Member
 
Rod Coleman's Avatar
 
Join Date: Jul 2004
Location: Warwickshire UK
Definitely - you need to check the voltage across each filament. It should be 10V (9.5V to 10.5V). Outside of that range (esp. >10.5V), the lifetime of the tube is dramatically reduced.
  Reply With Quote
Old 5th August 2014, 08:45 PM   #7
diyAudio Member
 
Join Date: Feb 2013
Default 845

Thanks for advices and help , posting the picture after restoring i replace 12ax7 with sovtek lps there is a slight birghtness on 845 tube but the voltage is ok im leaving now amp for new parts to settle down .

regards
Attached Images
File Type: jpg 20140801_152410.jpg (836.3 KB, 67 views)
  Reply With Quote
Old 5th August 2014, 10:12 PM   #8
diyAudio Member
 
HollowState's Avatar
 
Join Date: Aug 2006
Location: Taxland, New Jersey
That's a nice project but I see one thing that needs attention. There are several places where wires are going through holes in the chassis. There are no rubber or plastic grommets. I know at this point it's a big job to add them, but it needs to be done. Especially with the voltages involved with tubes. You are taking a big risk because some of the through holes are pretty tightly packed with wires. They need to be enlarged and a protective grommet installed. And if the wire is Teflon™ it's all the more important because Teflon will cold form. That's what caused our space shuttle to burn up on the launch pad years ago killing all three astronauts.
__________________
"It is hard to imagine a more stupid or more dangerous way of making decisions than by putting those decisions in the hands of people who pay no price for being wrong." ~Thomas Sowell
  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
Mr. Lian 845 SET – more kit rather than commercial product. avp1 Tubes / Valves 3 27th April 2014 11:03 PM
music angel 845 SET PeterParsons Tubes / Valves 8 11th November 2013 03:12 AM
845 with kathode bias Dogie_Hogan Tubes / Valves 3 28th June 2011 09:20 AM
Help me to work on the damping factor of my 845 SET rdk845 Tubes / Valves 17 18th May 2009 02:04 PM
Tubes for Viva Solista 845 SET amp angeloitacare Tubes / Valves 9 19th September 2008 03:22 PM


New To Site? Need Help?

All times are GMT. The time now is 12:49 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