ROCKOAL JUKEBOX 1458 - 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 24th February 2012, 07:48 PM   #1
diyAudio Member
 
Join Date: Feb 2012
Default ROCKOAL JUKEBOX 1458

I AM WORKING ON A ROCLOLA JUKEBOX AMP.THE SCHEMATIC WHICH IS HARD TO READ USES A PUSH PULL OUTPUT.THE PLATE RESISTANCE IS 480 VOLTS.THAT IS TO HIGH.I THINK THE RESISTORS IN THE POWER SUPPLY ARE BAD.THEY ARE THE OLD SAND RESISTORS.WHAT CAN I USE TO REPLACE THEM?THEY USE A 12AT7 JUST BEFOR THE 6L6 TUBES.I CAN'T GET ANY SIGNAL THRU THE AMP.ANY HELP WOULD BE APPRECIATED.
  Reply With Quote
Old 25th February 2012, 12:07 AM   #2
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
Link us to the schematic

What makes you think 480v is too high?


Did you measure that 480v with the tubes removed? Or were they in their sockets and functioning?
  Reply With Quote
Old 29th February 2012, 08:08 PM   #3
diyAudio Member
 
Join Date: Feb 2012
I LOOKED UP THE TUBE IN MY RCA MANUAL AND THE MAX PLATE VOLTAGE WAS 400 VOLTS.WHEN I TESTED THE VOLTAGE THE TUBES WERE IN THE AMP AND WORKING.IF THE PLATE VOLTAGE IS TO HIGH WHICH IS RIGHT OFF THE RECTIFIER THEN ALL THE OTHER VOLTAGES WILL ALSO BE HIGH.THIS WOULD BE THE GRID ECT.THE TUBE WOULD BE OPERATING IN DISTORATION.THE SOUND FROM THE AMP IS BUBBLIE.THANKS FOR THE REPLY.I STILL NEED HELP.
  Reply With Quote
Old 29th February 2012, 09:01 PM   #4
diyAudio Member
 
Join Date: Mar 2011
Location: Jarna
Here´s a link to schematic.

http://www.thearcadeboneyard.com/Juk...0SCHEMATIC.pdf

Anode voltage should be 380V.
  Reply With Quote
Old 29th February 2012, 09:03 PM   #5
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Please stop shouting. All uppercase letters is the WWW equivalent of shouting.

The schematic shows a RC self bias network between the 6L6GB cathodes and ground. The plate to cathode potential difference is less than the measured B+ rail voltage. In any event, "old time" equipment makers frequently ignored published spec's.
__________________
Eli D.
  Reply With Quote
Old 29th February 2012, 11:23 PM   #6
diyAudio Member
 
aardvarkash10's Avatar
 
Join Date: Mar 2007
Location: Auckland, NZ
Bad resistors? You think? Are you SURE you should be in there doing this on a live circuit???

If you had some idea you would measure the pd across the ceramic resistors. As you haven't figured this out yourself yet, I'm going to play for safety and say get the f#ck out of that thing until you know what you are doing.

I hope I'm blunt enough here. Your questions indicate strongly that you are a danger to yourself and whoever lives with you, and any potential user of the equipment you are "fixing" at the moment.

Stop.
__________________
"Folks, you can't prove truthiness with information. You prove truthiness with more truthiness. In a process known as truthinessiness." - Stephen Colbert, The Colbert Report
  Reply With Quote
Old 1st March 2012, 09:26 PM   #7
diyAudio Member
 
Join Date: Feb 2012
i have been working on vac.tube radios for years.my father was also a radio repairman before tv was introduced to the public. i know what i am doing.i just wanted an answer to my question.i don't need your help.thank you
  Reply With Quote
Old 1st March 2012, 10:00 PM   #8
diyAudio Member
 
aardvarkash10's Avatar
 
Join Date: Mar 2007
Location: Auckland, NZ
well, you stated the plate resistance was 480 volts, you can't identify how to assess the actual voltage across the tube and you figured the ressistors in the power supply are bad, even though the B+ is taken straight from the rectifier - no resistor.

You may not need my help, but you definitely need help.

Heres a hint - are both output tubes conducting? Do you know how to check this?
__________________
"Folks, you can't prove truthiness with information. You prove truthiness with more truthiness. In a process known as truthinessiness." - Stephen Colbert, The Colbert Report
  Reply With Quote
Old 1st March 2012, 10:12 PM   #9
diyAudio Member
 
HollowState's Avatar
 
Join Date: Aug 2006
Location: Taxland, New Jersey
Quote:
Originally Posted by chucksue View Post
i have been working on vac.tube radios for years..... i know what i am doing.
You have me scratching my head. If you really do know what you're doing, you should be able to fix it. It seems like a simple circuit.

Quote:
i don't need your help
Then why did you ask for it twice? And you do need help with your grammar. Capitals at the start of a sentense, a space between sentenses and always capitalize a single i.
,
__________________
"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
Jukebox Iron mosfetmaniac Tubes / Valves 9 16th December 2009 10:18 PM
Jukebox relay? Austin Duggan Everything Else 6 19th April 2009 10:52 AM
DIY Jukebox!! ThSpeakerDude88 Tubes / Valves 36 30th December 2008 04:26 PM
Help With Jukebox Amp HYDEBEE Tubes / Valves 2 30th December 2005 11:03 AM
PC jukebox cougarz Digital Source 8 25th November 2005 03:07 AM


New To Site? Need Help?

All times are GMT. The time now is 03:19 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