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

Too high transformator voltages...
Too high transformator voltages...
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 29th December 2008, 09:06 AM   #1
Skorpio is offline Skorpio  Denmark
diyAudio Member
Join Date: Mar 2004
Location: Denmark
Default Too high transformator voltages...


I have an old amp from the 60' I am trying to fix. The first problem I have found is the secondary voltages on the mains transformer. They are a bit high. 420VAC, 55VAC and 7.2VAC for HT, bias and heaters.

I think there are two reasons: Amp is made for 220V mains and we now have 230V and also that transformator is unloaded.

If still too high, heater supply can be controlled by a series resistor, but what should I do with the HT supply? Would a series resistor here be a good idea also?
  Reply With Quote
Old 29th December 2008, 12:22 PM   #2
Stixx is offline Stixx  Germany
diyAudio Member
Stixx's Avatar
Join Date: Sep 2003
Location: Southern Germany
Your voltages will go down some once you connect a load.

You can use a series resistor in the HV as well...just pay attention to current draw and the resulting heat dissipation in the resistor (Ohm's law comes to mind ). When your psu uses a choke (common in older amplifiers), just add a RC block after the choke to drop the voltage.
On the other hand tubes can easily tolerate 10% of deviation in the HV supply...

Put in some tubes and measure your voltages again...
  Reply With Quote
Old 29th December 2008, 01:21 PM   #3
Ty_Bower is offline Ty_Bower  United States
diyAudio Member
Ty_Bower's Avatar
Join Date: Mar 2007
Location: Newark, DE
There are some good tips on building a buck autoformer here:
  Reply With Quote


Too high transformator voltages...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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Replacing transformator in X-540 dviry Parts 2 11th December 2011 01:26 AM
Can 6AK6's take high voltages? PRNDL Tubes / Valves 5 20th January 2009 11:06 AM
ST35 voltages WAY too high! ThSpeakerDude88 Tubes / Valves 13 14th April 2008 09:50 PM
Step-Up Transformator Silberlot Swap Meet 0 30th April 2006 02:15 PM
diy transformator JayV Parts 5 8th July 2003 01:19 AM

New To Site? Need Help?

All times are GMT. The time now is 11:13 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio