No sound.... - Page 2 - 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 19th September 2012, 04:52 PM   #11
M Gregg is offline M Gregg  United Kingdom
diyAudio Member
 
M Gregg's Avatar
 
Join Date: Jun 2010
Location: UK
Just a guess,

Either HT (B+) open, OP Tx open or bad connection. Speaker lead or voice coil open..possible stand by switch fault or broken connection. The mains is OK because the heaters are working!

Do you have a multi meter?
If you don't know what you are doing then be guided by the guys here! Don't play with a live chassis it can kill you easily.
There are some tests you can do with it switched OFF!
High voltage..Take care..

Regards
M. Gregg
__________________
What is the sound of one hand clapping?

Last edited by M Gregg; 19th September 2012 at 04:56 PM.
  Reply With Quote
Old 19th September 2012, 05:08 PM   #12
TheGimp is offline TheGimp  United States
diyAudio Member
 
TheGimp's Avatar
 
Join Date: Aug 2009
Location: Johnson City, TN
Several things could be wrong with the amp.

First you need to be competent and comfortable with working around high voltage. According to the schematic, your B+ is 410V. It will be more likely 415-425V as line voltage is higher today than when the amp was designed.


Given that you can follow the appropriate safety procedures, you need to remove the chassis from the cabinet, and support it upside down on your bench.

I would check the continuity in the output of the output transformer first. If that looks good I'd go on to the voltage checks.

Since the tube heaters are on, the fuse and ac switch can be ruled out.

(By the way, you need to change the power cord to a three prong safety cord while you have the amp out of the cab.)

Your problem is most most likely in the HV section. You need to measure the voltage at the standby switch with it off and then on, and at the input and output of TR2. If TR2 is open (not likely) you will lose all high voltage to the preamp driver and screen voltage to the output tubes. No sound will ensue.

If you have appropriate voltages on both sides of TR2 (schematic values up to 1.05X schematic values) then the problem lies elsewhere than the B+.

Also check the B+ on the output tube plates (open OPT).

I doubt the bias voltage is sufficient to shut the tubes off completely, but it is also a possibility. Check the voltage at the two ends of the 10K balance pot. This is the same circuit as the Bassman 50 I just finished working on.

Bias voltage could be as high as -45V. I had to increase it in my case to -45V to get the zero signal tube current where it should be.

If it is greater than -45V I would look at a possible bad connection to the 15K or an open 15K resistor.
  Reply With Quote
Old 19th September 2012, 11:27 PM   #13
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
In post #2, Hollow asked the OP to check the speaker, but the OP merely restated the tubes were lit.

The speaker wiring may LOOK intact, but that tells us nothing about its integrity or whether the speaker itself works. Before ALL that other stuff, verify that the speaker and its wiring will function.

Your problem is zero sound, not poor sound or weak sound. So your trouble is not from some wrong voltage. EVen grossly wrong voltages will result in some sort of sound. COnsidering the general lack of internal fuses in Fenders, a loss of B+ is possible, but not at all common.

Unplug the speaker wire from the amp, get your ohm meter, and measure resistance from plug tip to plug sleeve. Open? Or some low resistance?
  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
Sony TA-VE215 cracking sound/sound cutting out crowdome Solid State 4 2nd October 2012 04:39 PM
Creative Sound Blaster X-Fi sound card w/upgrade GOWA Swap Meet 0 12th August 2012 10:05 PM
Kicker zx700.5 sub channel has humming sound and amp2 has echo like sound ivkata Car Audio 3 10th April 2012 10:23 PM
The Ultimate Sound Improving for Compact Disc's through Patent-Pend.CD Sound Improver tiefbassuebertr Digital Source 145 25th April 2011 08:39 PM
Eighteen Sound (18 Sound) NSD 1095N Compression Drivers and XT1086 Horns opc Swap Meet 6 1st May 2009 04:48 AM


New To Site? Need Help?

All times are GMT. The time now is 03:44 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