Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Unknown PP output transformers
Unknown PP output transformers
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
Thread Tools Search this Thread
Old 6th December 2010, 01:49 PM   #1
ellejammer is offline ellejammer  Italy
diyAudio Member
Join Date: Feb 2009
Default Unknown PP output transformers

Hi everybody,

3 years ago I got on the bay a NOS pair of identical PP output transformers.
The end bells say respectively:
FT4725698-138305E and FT4725698-138217E
The core is a 1_3/4 inch stack of EI 1_1/8 inch lamination
Primary inductance is about 250H @ 5Vrms, 50Hz, plate to plate with a DC resistance of 125+125 ohm.
They weight 2.2Kg each and look like an A470, maybe a bit smaller...
Nominal impedances, from voltage ratio measurements, are:
Primary: 7.0 Kohm plate to plate
Second: 0-8-16-32 ohm, tapped

Does anybody know the manufacturer and their use ?
Thank you, Franco
  Reply With Quote
Old 6th December 2010, 07:48 PM   #2
Tom Bavis is offline Tom Bavis
diyAudio Member
Tom Bavis's Avatar
Join Date: Jun 2002
Location: Macedon NY
138 is Stancor - 1963 week 5 and 1962 week 17 (1952 and 1972 seem unlikely). Harman-Kardon had part numbers that started with "FT", so that's where I would look - one of their 6L6 or 7355 based amplifiers. Like A500, A700, HK-250, TA260...
  Reply With Quote
Old 7th December 2010, 05:56 AM   #3
ellejammer is offline ellejammer  Italy
diyAudio Member
Join Date: Feb 2009
OK Tom, I thank you for the very detailed info and fast answer !
I'm going to check with Harman-Kardon....
  Reply With Quote


Unknown PP output transformersHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Use 2X SE output transformers fo 1x PP speaker Tubes / Valves 4 25th February 2009 06:03 PM
amplifier for unknown output transformers? tonskulus Tubes / Valves 20 9th December 2007 11:36 AM
Dynaco Z-565 Output Transformers (PP EL-84/6V6) Flodstroem Swap Meet 3 4th April 2006 07:22 PM
testing unknown transformers cm961 Parts 2 9th January 2004 04:56 AM
Using PP output transformers for single ended amp SHiFTY Tubes / Valves 4 26th August 2002 07:18 PM

New To Site? Need Help?

All times are GMT. The time now is 03:42 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio