7027A with tubelab simple se - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Tubelab

Tubelab Discussion and support of Tubelab products, prototypes and experiments

Reply
 
Thread Tools Search this Thread
Old 8th November 2009, 03:41 AM   #1
diyAudio Member
 
Join Date: Aug 2008
Default 7027A with tubelab simple se

Guess I'm a little confused with this.
I've read that the 7027A is a direct drop in for a 6L6GC with two extra pins in the base.
Other threads say that you need to re-wire the socket, but it seems as though they are saying that when regarding an amp made for the 7027 and wanting to switch to a different tube.
My simple se blew up the 5AR4 tube (and fuse) on turn on with the 7027A on initial turn on.
I guess this amp is not supposed to run these tubes?
Paul
  Reply With Quote
Old 8th November 2009, 08:15 AM   #2
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Take a look at the datasheets- the pin configuration is different.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 8th November 2009, 01:29 PM   #3
diyAudio Member
 
Join Date: Aug 2008
Pins 1 & 6 not normally used are used on the 7027A. Pin 1 is tied to Pin 4, and Pin 6 is tied to pin 5.
Could you just "cut off" pins 1 & 6 on the 7027 A?
Or, does anyone want some free 7027A's?
I'm not going to rewire any sockets or anything.
I already love the sound of this little amp with a variety of other tubes, I just wanted to hear some other tubes.
  Reply With Quote
Old 8th November 2009, 01:40 PM   #4
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
I'll take your 7027s!

They are actually identical to 6L6GC except for the base. I probably wouldn't start cutting pins- doing it sufficiently to prevent arcing to the socket will probably damage the tube. Check your socket wiring and pull off and move anything connected to pin 1 (often connected to pin 8!) and pin 6. These "spare" socket pins are often used as tie points in 6L6 amps.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 8th November 2009, 01:57 PM   #5
diyAudio Member
 
Ty_Bower's Avatar
 
Join Date: Mar 2007
Location: Newark, DE
The 6L6GC and the 7027A both have the heaters on pins 2 and 7. They both use pin 3 for the anode, and pin 8 for the cathode. So far, so good. Now comes the tricky part. The 6L6 has the control grid tied to pin 5, and the screen grid at pin 4. The 7027A uses pins 5 & 6 for the control grid. Pins 4 & 1 are for the screen grid.

On the Simple SE circuit board, pin 6 has no connection to anything. However, pins 1 and 8 are tied together. I believe this is necessary to get EL34 tubes working correctly. The EL34 has the suppressor grid connected to pin 1, while the 6L6 types have it connected to the cathode internally.

When you plug in your 7027A, now you've got the screen grid shorted to the cathode. That's sure to be bad news. If you have easy access to the bottom side of the board, you could probably just cut through the trace between pins 1 and 8, and then I'd expect the 7027A would work fine. Just remember the EL34 tubes won't work after you make this modification, unless you've got some way to put back the jumper from 1 to 8.
  Reply With Quote
Old 8th November 2009, 01:58 PM   #6
diyAudio Member
 
Ty_Bower's Avatar
 
Join Date: Mar 2007
Location: Newark, DE
Quote:
Originally Posted by pforeman View Post
Or, does anyone want some free 7027A's?
Heck yeah! Send them to me!
  Reply With Quote
Old 8th November 2009, 02:20 PM   #7
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
How about just using a 6L6GC and calling it a day?
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 8th November 2009, 02:21 PM   #8
diyAudio Member
 
Join Date: Aug 2008
Sy or Ty,
first one to tell me where to send em, and their yours
  Reply With Quote
Old 8th November 2009, 02:27 PM   #9
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
As several other observers have pointed out the 7027A is a 6L6GC on steroids. It does however have this issue with the extra pins. The problem arises with the G2 connection to pin 1. Yes, pin 1 is connected to the cathode to allow EL34's to work. Simply plugging a 7027A into the Simple SE connected the screen grid voltage to the cathode. This shorts the B+ to the cathode resistors. It looks like the fuse and the rectifier tube were the only casualties, but the screen stopper resistors and the cathode resistors probably got a quick surprise too!

7027A's can be made to work in the Simple SE by cutting pin 1 off of the tube (not recommended) or by cutting the trace on the back side of the PC board that connects pin 1 to pin 8 on the output tubes. If you do this, you can not use the board for EL34's. Since there is a bunch of voltage between these two pins make sure that you remove about 1/8 inch of copper between the two pins.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 8th November 2009, 02:30 PM   #10
diyAudio Member
 
Join Date: Aug 2008
or you can email me address to pforeman@wideopenwest.com
  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
Tubelab Simple P-P booangler Tubelab 601 6th September 2014 10:00 PM
Electrolyticless Tubelab Simple SE nic6paul Tubelab 26 20th August 2013 12:56 PM
Tubelab Simple SE v.2 nic6paul Tubes / Valves 3 1st November 2009 12:59 PM
Second Tubelab Simple SE board done budmaestro Tubes / Valves 0 24th July 2008 12:18 AM
Tubelab Simple SE & Edcor waam68 Tubes / Valves 2 6th March 2008 12:15 PM


New To Site? Need Help?

All times are GMT. The time now is 07:20 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