Olson AM-240 schematic needed - 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 1st April 2014, 05:48 AM   #1
diyAudio Member
 
Mosquito's Avatar
 
Join Date: Sep 2009
Location: Santa Fe, Argentina
Default Olson AM-240 schematic needed

Hi fellow forumers
I'm going to restore this amp for a friend of mine
this is the unit: AM-240 Ampl/Mixer Olson Radio Corporation; Akron, Ohio, buil
Obviously, the one I've in the bench is not in such a good shape, take a look:
Well, lacking the schematic the restoring job, while not impossible, becomes considerable more difficult. So If one good soul can share the circuit, it will help in an just and heroic cause.
Cheers
J.
Attached Images
File Type: jpg 010420141013x.jpg (94.4 KB, 65 views)
File Type: jpg 010420141014X.jpg (108.7 KB, 62 views)
File Type: jpg 010420141015X.jpg (124.7 KB, 62 views)
File Type: jpg 010420141017X.jpg (110.5 KB, 61 views)
File Type: jpg 010420141019X.jpg (147.0 KB, 55 views)
File Type: jpg 010420141021X.jpg (122.3 KB, 28 views)
File Type: jpg 010420141022X.jpg (103.9 KB, 25 views)
__________________
If I only had a dollar for every song I've sung...
  Reply With Quote
Old 1st April 2014, 12:43 PM   #2
diyAudio Member
 
Mosquito's Avatar
 
Join Date: Sep 2009
Location: Santa Fe, Argentina
addendum:
first and dirt measurements confirm that this circuit output stage works with 415V on plates, 400V on G2, and -20V fixed bias.
First decision: revolve heaven and earth to find the original 7189 tubes (a very difficult and expensive task in my neighborhood), or derate the B+ to a more maneageable level, in order to fit the humble 6BQ5's (standard flavour)?.
Since this unit is being powered through a 110 to 220 step down transformer, a proper 220V PT is likely to be purchased, so, adjusting to fit different tubes will not be a problem, but...
__________________
If I only had a dollar for every song I've sung...
  Reply With Quote
Old 1st April 2014, 01:24 PM   #3
infinia is offline infinia  United States
diyAudio Member
 
infinia's Avatar
 
Join Date: May 2005
Location: Californication
it's probably a knock off of a HH Scott design, so get a couple of their schematics might get you to 85%.
in the end looks like loads of work with an unknown quality result?
Attached Images
File Type: jpg 222C-C1.jpg (1.07 MB, 31 views)
__________________
like four million tons of hydrogen exploding on the sun
like the whisper of the termites building castles in the dust
  Reply With Quote
Old 1st April 2014, 01:25 PM   #4
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Jim McShane ships world wide and it's likely other reliable tube sellers can accommodate you too.

Fortunately, a good and affordable 7189 equivalent is in production. It's the Russian 6П14П-EB (6p14p-ev), AKA EL84M, is what you should buy.

Be careful to distinguish between the 7189 and the 7189A. 7189As are extinct and amps using it need socket rework and (perhaps) operating conditions adjustment to employ the 6П14П-EB.
__________________
Eli D.
  Reply With Quote
Old 1st April 2014, 02:02 PM   #5
diyAudio Member
 
Mosquito's Avatar
 
Join Date: Sep 2009
Location: Santa Fe, Argentina
Thanks Infinia and Eli. Much appreciated.
This weekend I'm going to check the amp against the Scott schemo, it will be fun.
I'm mostly concerned about some rotary switches, cables were cut off, and functions disabled, a real mess, ad opera some shitty incompetent TV repairman , for sure.
For what I saw, the tubes fitted (one is missing) are standard 7189's, not the "A" version.
I guess I'll take the 6П14П-EB route... Now I'm looking for some tubes on Mercado Chifle, our local version of Steals Bay
__________________
If I only had a dollar for every song I've sung...
  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
Olson-Morgan 6F6 Amplifier Info's needed. Tubologic Tubes / Valves 0 2nd September 2013 11:04 PM
Schematic needed panasonic RX-1230 schematic Buzzsaaw Analog Line Level 0 23rd April 2011 07:52 PM
Help needed on fullrange fostex with McIntosh mc 240. Audio Luddite Full Range 4 1st January 2009 04:10 AM
irf 240 or irfp 240 for the aleph scu Pass Labs 2 14th January 2002 06:49 PM


New To Site? Need Help?

All times are GMT. The time now is 06:00 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