Bad tube in old record player? - 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 17th September 2011, 04:45 AM   #1
rman is offline rman  Canada
diyAudio Member
 
rman's Avatar
 
Join Date: Oct 2007
Default Bad tube in old record player?

Hi.

I found a crescent 1601 record player at the recycle depot so I naturally had to take it home. OK it is a cheap old p.o.s, but it looked so forlorn waiting for it's final demise. I managed to order a schematic with voltages marked. I tried it carefully tried it out. I can plug it in to a dead wall socket at my work bench and turn it on with the light switch. It hummed loudly and had low distorted output, so I changed the filter cap, hum is gone, but still low and distorted output. The circuit connections check out and resistance values are close enough, and voltages on the input stage seem OK. The output stage, (50B5 pentode) Has about 12 volts on the grid, it should be zero. I then changed the coupling cap thinking it might be leaky. No change. The grid is properly connected to ground by way of the 500k tone pot. Disconnecting the coupling cap also makes no difference.(to the voltage) I also checked for shorts in the tube with my meter. The grid voltage is actually higher than the cathode voltage.

Anyway, I was wondering if this could be the tubes fault as I have no other ideas left.

Cheers.
Rolf.
  Reply With Quote
Old 17th September 2011, 05:20 AM   #2
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Schema?

It could well be a tube, it is likely 50 some years old. I have some 50C5, i'd be happy to send a couple for cost of post.

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 17th September 2011, 05:55 AM   #3
rman is offline rman  Canada
diyAudio Member
 
rman's Avatar
 
Join Date: Oct 2007
Hi Dave.

Thank's for the offer. I just looked in my tube manual. The 50B5 and 50C5 seem to be the same except for very different pinout. I'll see if main electronics has some.

I have no way to get schematic into computer, but it is pretty simple. I think I described everything relevant.

Thank's again.
Rolf.
  Reply With Quote
Old 17th September 2011, 08:20 AM   #4
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Different pinout? I assumed 50A5, 50B5, 50C5 were all just revisions of the same tube...

I looked thru my box of 50c5, no errant 50B5/ Might be some in the unsorted tubes, but that is somewhere i don't have time to go.

you could use the OPT for 50c5 or 50eh5, but that would require more work.

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 17th September 2011, 11:13 AM   #5
diyAudio Member
 
Globulator's Avatar
 
Join Date: Aug 2004
Location: Cambridge, England.
Most likely to be a coupling capacitor IME.
There can't be many so you may as well change them all!
  Reply With Quote
Old 17th September 2011, 04:58 PM   #6
rman is offline rman  Canada
diyAudio Member
 
rman's Avatar
 
Join Date: Oct 2007
Dave.
Main electronics in Vancover lists them on their site so should be easy to get.
Globulator.
You are right about there not being many. There is the input cap which can't be the problem and the interstage coupler I already changed.

I don't know how a tube could fail in this way. I was hoping someone could tell me if they can. It is not an expensive tube so I will try it anyway.

Cheers.
Rolf.
  Reply With Quote
Old 17th September 2011, 05:08 PM   #7
diyAudio Member
 
Frank Berry's Avatar
 
Join Date: Sep 2003
Location: Midland, Michigan
The old tube is probably gassy.
__________________
Frank
  Reply With Quote
Old 17th September 2011, 05:25 PM   #8
rman is offline rman  Canada
diyAudio Member
 
rman's Avatar
 
Join Date: Oct 2007
Frank.

Thank you. that makes sense. I will definitely change the tube.
  Reply With Quote
Old 18th September 2011, 05:01 AM   #9
rman is offline rman  Canada
diyAudio Member
 
rman's Avatar
 
Join Date: Oct 2007
So I changed the tube and a cathode resistor that read 245 ohms instead of the specified 150. The amp seems to work fine now.
I wasn't expecting Hi-Fi but the sound is pretty bad. It was kind of fun to crank Willie Nelson to 78 rpm.
Since I have gone this far, I ordered two new needles. The cart flips over for 78's.

Cheers.
Rolf.
  Reply With Quote
Old 30th September 2011, 02:54 AM   #10
rman is offline rman  Canada
diyAudio Member
 
rman's Avatar
 
Join Date: Oct 2007
Default Update

Just to add some closure, With a new needle, it tracks and sounds much better.
It still sounds wretched but probably a level of wretchedness that was acceptable to a teenager in1956. Or even some today

Just wondering, it doesn't auto return but it is obviously a changer so it should right?

Cheers.
Rolf.
  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
Hello record player maniacs talder Introductions 3 29th August 2011 03:57 AM
Telefunken Tube Receiver, Magnetophon 97 (Tube R2R) and Record Player Dredfred Swap Meet 1 3rd April 2011 02:12 AM
Old record player Rucyrius Everything Else 0 24th March 2011 03:35 PM
Free: PYE - garrard mono tube record 33/78 player MichaelPublic Swap Meet 0 24th July 2008 04:47 PM
New and Cheap Record Player rtarbell Analogue Source 1 27th February 2006 05:32 PM


New To Site? Need Help?

All times are GMT. The time now is 05:27 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