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 September 2006, 06:50 PM   #1
mcelaj is offline mcelaj  United States
diyAudio Member
 
Join Date: Nov 2003
Location: N/A
Default RCA R35, 39 & 57 Terminal Usage...

Hi,

As I have no technical know-how of how tube amplifiers work, I ask here, the following:

I have an RCA R35, 39 or 57 amplifier, not sure the exact model number, but on the Nostalgia Air website there is a schematic which coincides with all three models. This schematic perfectly matches the tube amplifier that I have and I am asking about.

The schematic can be viewed at:

Nostalgia Air

or more specifically:

Nostalgia Air RCA schematic

Now on the second page of the PDF file is the schematic. To the right is the schematic for the amplifier and power supply, which is in one chassis (the unit I have), and to the left of the schematic is the radio, which is on another chassis. The two chassis' are interconnected with a terminal strip which has 8 connections, as seen on page two of the schematic between the two units. I set up the amplifier and assumed that connection 4 is to be used as the positive input and either 5-8 as the negative input. I tried all combinations and only got music when either powering up the amplifier or turning the amplifier off. I don't have the field coil speaker that is in the schematic so i threw in a transformer (+/-2k ohm resistance) in its place and the voltage readings at the corresponding terminals where in order, as stated on the bottom of page one of the schematic. The output transformer measures 10 ohms and I used an 8 ohm speaker when testing.

Am I using the wrong terminals for input? Which terminals should I use. There is a 227 tube acting as the 1st Audio Stage (preamp I guess) in the Radio (left side of the schematic), perhaps I need a preamp before connecting to the amplifier? I tried connecting straight from my laptop output, whose output can be controlled through the laptops volume control. Maybe my tubes (245 tubes) are bad (don't own a tube tester)? The 280 tube must work as I get the DC voltage readings specified on the bottom of page one of the schematic. Maybe the 8 ohm test speaker is the fault?

I hope I did a good job of explaining my situation and hope someone can help me.

Regards,
Mehmet
  Reply With Quote
Old 3rd September 2006, 11:14 PM   #2
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Mehmet,
You have a pair of #45 tubes in push pull with a chassis mounted output transformer. You should use a choke instead of a transformer, but your voltages are correct (the transformer is okay to test with).

The original speaker may have been any impedance, including 16 ohm. That will not matter just yet. You should still get pretty good sound. Do you have the original speaker? If so, use it's field coil and use the other speaker if the cone or voicecoil is damaged. Off centered voice coils can sometime be adjusted by loosening the screw in the center, repositioning and retightening the screw.

The first thing I would do is test the tubes. Be careful as the 45's are expensive to replace. Replace the coupling caps and the filter caps and check the resistors are in tolerance (+- 20%), or at least in the ballpark.

By this point in time you should have the power supply, amplifier and radio working. Your MP3 will work once you get the rest working.

-Chris
  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
3 terminal regulator with 3 terminal shunt reference BWRX Power Supplies 11 17th January 2013 09:08 AM
EQ usage skooter Car Audio 29 30th December 2007 09:28 PM
usage of line out trans. robertc Tubes / Valves 2 25th June 2006 02:58 PM
Usage of BUZ71A ?? SM7UYJ Solid State 8 28th December 2005 05:18 AM


New To Site? Need Help?

All times are GMT. The time now is 10:59 PM.


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