Trying to identify/find documentation on a 50EH5 amp - 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 23rd August 2007, 07:11 PM   #1
diyAudio Member
 
Rob.capone's Avatar
 
Join Date: Aug 2007
Default Trying to identify/find documentation on a 50EH5 amp

Hi all,

I'm new to the site and the hobby and I could use a little help. I've tinkered around with tube type Ham and Shortwave gear off and on for a couple of years, but this is my first attempt at audiophile gear.

I just purchased my first little amp. I got it off eBay for $25 shipped. it even came with the original speakers.

All I know for sure is that it is a Magnavox phono amp using 2 50EH5's and a 12AX7. Aside from the numbers printed on the chassis that you can see in thee pics, the following is stamped on top 636275- 4.

It came with a block diagram but no schematic. On the diagrams lower right corner is: EL 1484-1. I have searched the internet using all these numbers and found nothing. Does anybody have or know where I can get a schematic for this.

It works but of course needs to be recapped (has nasty hum) and I'm trying to avoid having to figure out all the components and hand writing a schematic myself if possible.

Any help would be greatly appreciated. Thanks,
Rob

Click the image to open in full size. Click the image to open in full size. Click the image to open in full size.
__________________
Of all the things I've lost, I miss my mind the most!!! ;-)
  Reply With Quote
Old 23rd August 2007, 07:40 PM   #2
r221b is offline r221b  United States
diyAudio Member
 
Join Date: Jul 2007
http://www.radiomuseum.org/tubes/tube_50eh5.html

sherlock
  Reply With Quote
Old 23rd August 2007, 07:46 PM   #3
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Rob,
Welcome to DiyAudio!

You can also look for those phonograph schematics, they should be close. One of the RCA tube manuals should also have a circuit that is close to yours.

Lose the ceramic caps straight off. It will sound better with a different type in there. All coupling caps need to be replaced as well.

-Chris
__________________
"Just because you can, doesn't mean you should" my Wife
  Reply With Quote
Old 23rd August 2007, 08:14 PM   #4
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Default Dangerous Amplifier Design



Something else needs to be mentioned immediately, and that is the lack of a power transformer to provide isolation from the power line.

Before you even think about plugging this thing in get yourself an inexpensive isolation transformer on eBay. A 100Va rating should be just sufficient.

Do anything else and you may end up electrocuting yourself or someone close to you.



We want to keep you around and healthy, that's how our hobby grows!
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 23rd August 2007, 08:30 PM   #5
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
YES!!!!!! the popular HOT CHASSIS design has one side of the line cord tied directly to the chassis, usually with a non-polarized plug . if you use grounded test equipment or connect the device to a preamp, etc... that has a grounded chassis, you will pop a breaker. if you touch the chassis you can get KILLED!!!!! you MUST use an isolation transformer with this device. if it has a non-polarized plug, you have a 50-50 chance of plugging it in correctly with the chassis connected to the outlet neutral. even if it has a polarized plug, many outlets have been known to be wired backwards.
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 23rd August 2007, 10:33 PM   #6
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Default You know what guys?

I knew that but completely missed it. I've repaired so many that these days I sometimes forget about new safety awareness.

Hi Rob,
Use an isolation transformer to make it safe. They are cheap on Eeekbay

-Chris
__________________
"Just because you can, doesn't mean you should" my Wife
  Reply With Quote
Old 24th August 2007, 04:57 AM   #7
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Welcome to the club/

http://www.t-linespeakers.org/tubes/SEP_50EH5.html

Click the image to open in full size.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 24th August 2007, 03:47 PM   #8
diyAudio Member
 
Rob.capone's Avatar
 
Join Date: Aug 2007
Thanks for all the info and advice.

I will update you on the progress of the rebuild.

__________________
Of all the things I've lost, I miss my mind the most!!! ;-)
  Reply With Quote
Old 24th August 2007, 03:47 PM   #9
diyAudio Member
 
Rob.capone's Avatar
 
Join Date: Aug 2007
OH, I forgot to ask, should i go with metal film resistors or are carbon comps sufficient?

and what caps do you guys think are best?

Thanks again,
Rob
__________________
Of all the things I've lost, I miss my mind the most!!! ;-)
  Reply With Quote
Old 24th August 2007, 04:38 PM   #10
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Rob,
Carbon composition types are only good in RF work. This includes grid stoppers. I like to use metal oxide types in most places and metal films in the input signal path, and feedback network. Both are easily available from the bigger supply houses.

-Chris
__________________
"Just because you can, doesn't mean you should" my Wife
  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
efuns.net DAC - documentation needed PrzemekE Digital Source 3 22nd August 2012 03:18 PM
Component ID from a 50EH5 Amp booangler Tubes / Valves 4 30th January 2009 11:26 PM
MN662720 documentation JacekPlacek Parts 0 29th November 2007 08:46 AM
MN662720 documentation JacekPlacek Digital Source 0 29th November 2007 08:44 AM


New To Site? Need Help?

All times are GMT. The time now is 09:14 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