miniblok 1 voltage problem - 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 16th October 2010, 12:34 AM   #1
diyAudio Member
 
Join Date: Feb 2010
Location: calgary alberta tundra canada
Default miniblok 1 voltage problem

i built this amp a while ago and all the voltages checked out, i had 215 volts B+ but now the voltage has bumped up to 250 for some reason and i cant determine why that is. i guess there isnt enough voltage drop across R1 so that means that the tube isnt pulling up enough current, im not sure where to go from here. maybe i can just increase the value of R1 but that doesnt really solve the mystery...

any ideas?
thanks
Attached Images
File Type: gif miniblok.gif (8.1 KB, 66 views)
  Reply With Quote
Old 16th October 2010, 12:10 PM   #2
Cassiel is offline Cassiel  Libya
diyAudio Member
 
Cassiel's Avatar
 
Join Date: Sep 2004
Location: Madrid
Quote:
any ideas?
Yes, leave it alone.
  Reply With Quote
Old 16th October 2010, 12:44 PM   #3
diyAudio Member
 
Join Date: Feb 2010
Location: calgary alberta tundra canada
Quote:
Originally Posted by stalker View Post
Yes, leave it alone.
is that supposed to be a joke?
  Reply With Quote
Old 16th October 2010, 12:54 PM   #4
Cassiel is offline Cassiel  Libya
diyAudio Member
 
Cassiel's Avatar
 
Join Date: Sep 2004
Location: Madrid
No. No need to worry.
  Reply With Quote
Old 16th October 2010, 01:17 PM   #5
Brit01 is offline Brit01  United Kingdom
diyAudio Member
 
Join Date: Jul 2008
I guess if the tube's parameters are within optimum working levels then all should be ok?

Any change in current or sound? Has R2 or R3 drifted?


Have you measured the cathode voltages/current?

If R3 is pulling less current, the B+ is likely to rise.

Last edited by Brit01; 16th October 2010 at 01:19 PM.
  Reply With Quote
Old 16th October 2010, 01:30 PM   #6
diyAudio Member
 
Frank Berry's Avatar
 
Join Date: Sep 2003
Location: Midland, Michigan
The tube characteristics have changed for some reason. The output triode is pulling less current than it pulled originally. Perhaps it's gassy. Have you tried another tube?
__________________
Frank
  Reply With Quote
Old 16th October 2010, 01:55 PM   #7
diyAudio Member
 
Join Date: Feb 2010
Location: calgary alberta tundra canada
Quote:
Originally Posted by Brit01 View Post
I guess if the tube's parameters are within optimum working levels then all should be ok?

Any change in current or sound? Has R2 or R3 drifted?


Have you measured the cathode voltages/current?

If R3 is pulling less current, the B+ is likely to rise.

could it be the bypass cap (c8) next to r3? maybe it's voltage rating is too low because i have the same problem with the other channel's amp.

the sound has become distorted. im going to install a 1ohm resistor from the cathode to ground to measure current.
  Reply With Quote
Old 16th October 2010, 01:56 PM   #8
diyAudio Member
 
Join Date: Feb 2010
Location: calgary alberta tundra canada
Quote:
Originally Posted by Frank Berry View Post
The tube characteristics have changed for some reason. The output triode is pulling less current than it pulled originally. Perhaps it's gassy. Have you tried another tube?

i tried a different tube and the result is the same. i guess ill just start switching out parts until i hit the fawlty component
  Reply With Quote
Old 16th October 2010, 02:08 PM   #9
diyAudio Member
 
Frank Berry's Avatar
 
Join Date: Sep 2003
Location: Midland, Michigan
Is the bias voltage correct?
__________________
Frank
  Reply With Quote
Old 16th October 2010, 02:24 PM   #10
Brit01 is offline Brit01  United Kingdom
diyAudio Member
 
Join Date: Jul 2008
Give us some measurements.

Do you have a DMM?
  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
miniblok 2 distorted sound chopchip Tubes / Valves 3 7th October 2010 04:57 PM
Questions about tweaking the Miniblok SET... 69CamaroSS396 Tubes / Valves 11 9th August 2008 08:37 PM
Question about MiniBlok II Schematic pj_cow Tubes / Valves 2 5th March 2008 08:38 PM
High voltage problem jtrompetter Tubes / Valves 8 16th February 2008 05:28 PM
Voltage problem sith Tubes / Valves 10 7th January 2005 12:20 PM


New To Site? Need Help?

All times are GMT. The time now is 05:51 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