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

Instruments and Amps Everything that makes music, Especially including instrument amps.

Tube Arcing?
Tube Arcing?
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 29th March 2013, 04:07 AM   #21
nigelwright7557 is offline nigelwright7557  United Kingdom
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
Given the valves are new:
If the sound is sagging with volume then I would check the power supply electrolytics.
__________________
PCBCAD51 pcb design software. 2018 version out now. https://www.ebay.co.uk/sch/i.html?_f...nload&_sacat=0
  Reply With Quote
Old 29th March 2013, 04:09 AM   #22
ouimetnick is offline ouimetnick  United States
diyAudio Member
 
Join Date: May 2011
Location: Beverly, Massachusetts, USA
Send a message via AIM to ouimetnick Tube Arcing?
I will check the AC ripple tomorrow and report back.
  Reply With Quote
Old 29th March 2013, 08:13 PM   #23
ouimetnick is offline ouimetnick  United States
diyAudio Member
 
Join Date: May 2011
Location: Beverly, Massachusetts, USA
Send a message via AIM to ouimetnick Tube Arcing?
Took voltage measurements of the smaller filter caps, and here is the results

250VDC & 10mVAC (Should be 300VDC, but I have a 100W bulb in line with the power cord.)

170VDC & 15mVAC (Should be 200VDC, but I have a 100W bulb in line with the power cord.)

Can't measure the main 220mfd 300V caps because I can't reach the other side of the caps unless I desolder a bunch of wires and pull the board and jumper everything back in thanks to the MB's terrible design.

I don't think I really want to do the repair, but I do want to at least find the fault.
Attached Images
File Type: jpg photo 1.jpg (699.1 KB, 141 views)
File Type: jpg photo 2.jpg (579.8 KB, 86 views)
File Type: jpg photo 3.jpg (595.0 KB, 78 views)
File Type: jpg photo 4.jpg (764.2 KB, 74 views)
File Type: png PSU measurement Boogie.png (51.0 KB, 69 views)
  Reply With Quote
Old 30th March 2013, 06:07 PM   #24
ouimetnick is offline ouimetnick  United States
diyAudio Member
 
Join Date: May 2011
Location: Beverly, Massachusetts, USA
Send a message via AIM to ouimetnick Tube Arcing?
I checked all the power tubes and preamp tubes by putting them in my Epiphone Valve Junior. I tapped on each tube (both power and preamp) with a pen, and no static or ringing noises. In short, all the tubes work.

So we can rule out the tubes.
  Reply With Quote
Old 30th March 2013, 06:12 PM   #25
JMFahey is offline JMFahey  Argentina
diyAudio Member
 
JMFahey's Avatar
 
Join Date: Mar 2009
Location: Buenos Aires - Argentina
Quote:
Originally Posted by ouimetnick View Post
I checked all the power tubes and preamp tubes by putting them in my Epiphone Valve Junior. I tapped on each tube (both power and preamp) with a pen, and no static or ringing noises. In short, all the tubes work.

So we can rule out the tubes.
Excellent idea
  Reply With Quote
Old 31st March 2013, 02:55 AM   #26
ouimetnick is offline ouimetnick  United States
diyAudio Member
 
Join Date: May 2011
Location: Beverly, Massachusetts, USA
Send a message via AIM to ouimetnick Tube Arcing?
Looking at the schematic, it seems the speaker switch disconnects the preamp from the power amp.. Not the effects loop. So I could solder a wire to the input of the power amp and see if music makes it through cleanly, and isolate the issue? Or am I crazy?

In fact switching the SILENT RECORDING switch to MUTE cuts all noise, but it doesn't appear to disconnect the speaker or place a dummy load. Instead it looks like it is breaking the connection connecting the preamp to the power amp.

The manual says "This switch mutes all of the signal at the power section driver stage, removing the need for a speaker load IN THIS POSITION ONLY!

So you can run a tube amp w/o a load on the output transformer provided you do NOT have an input source? (in this case, the preamp)
Attached Images
File Type: png Screen Shot 2013-03-30 at 9.50.44 PM.png (46.6 KB, 21 views)
Attached Files
File Type: pdf 49062594-mesa-boogie-dual-caliber-dc-3-schematic.pdf (205.1 KB, 9 views)
  Reply With Quote
Old 30th April 2013, 02:34 AM   #27
ouimetnick is offline ouimetnick  United States
diyAudio Member
 
Join Date: May 2011
Location: Beverly, Massachusetts, USA
Send a message via AIM to ouimetnick Tube Arcing?
Still messing with this PITA. I decided to replace all electrolytic capacitors and diodes. I know shotgunning isn't recommended. As Enzo states "Its like throwing sponges at a rainstorm"

I didn't have high hopes that doing what I did would fix the issue, and sure enough it doesn't.

I know I've said it before, but the is a PITA!! Have to remove all pots, desolder nearly 20 different wires, and maneuver the board out with the stupid plastic nylon standoffs.

Besides sending it to Mesa Boogie.. any other suggestions?
  Reply With Quote
Old 2nd May 2013, 03:44 PM   #28
turk 182 is offline turk 182  Canada
diyAudio Member
 
Join Date: Oct 2012
ouimetnick
after checking out your you tube vid and the schematic and my failing memory i would be suspicious of the relays and their supply the fact that you get no sound on one channel and the weird fart noise on power down i remember this as clues in previous repairs that lead me to replacing relays only to discover bad zeners and bad 16 v filters in the switching matrix supply
  Reply With Quote
Old 2nd May 2013, 05:16 PM   #29
ouimetnick is offline ouimetnick  United States
diyAudio Member
 
Join Date: May 2011
Location: Beverly, Massachusetts, USA
Send a message via AIM to ouimetnick Tube Arcing?
Quote:
Originally Posted by turk 182 View Post
ouimetnick
after checking out your you tube vid and the schematic and my failing memory i would be suspicious of the relays and their supply the fact that you get no sound on one channel and the weird fart noise on power down i remember this as clues in previous repairs that lead me to replacing relays only to discover bad zeners and bad 16 v filters in the switching matrix supply
I replaced all the diodes. what do those relays actually do?
  Reply With Quote
Old 2nd May 2013, 07:31 PM   #30
turk 182 is offline turk 182  Canada
diyAudio Member
 
Join Date: Oct 2012
one of the relays is channel switching the other is selecting which channel the reverb is applied to.
i was wondering do you have the footswitch if i recall this amps lead channel won't work without it.
or was it something about push pull controls being set right, might be another model i'm thinking of ...

the matrix circuit in these can be finicky
did you in fact replace all the diodes because not all are the same type! which ones did you replace?

Last edited by turk 182; 2nd May 2013 at 07:35 PM.
  Reply With Quote

Reply


Tube Arcing?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
Preventing arcing on standby switch? infernal Tubes / Valves 6 21st June 2011 03:13 AM
Acoustat arcing problems The Peasant Planars & Exotics 5 27th August 2010 12:13 AM
ecc88 arcing at shutdown problem... pauldune Tubes / Valves 33 4th December 2009 06:21 AM
arcing in rectifier tube el capitan83 Tubes / Valves 8 9th January 2005 08:50 PM
the case of the arcing tube karma Tubes / Valves 12 29th April 2003 03:39 AM


New To Site? Need Help?

All times are GMT. The time now is 05:39 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki