Power Transformer for 6V6 SE Amp Question - 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 19th January 2008, 09:30 PM   #1
zxx123 is offline zxx123  United States
diyAudio Member
 
Join Date: Aug 2003
Location: ca
Default Power Transformer for 6V6 SE Amp Question

I bought used one from ebay for my 6v6 SE Amp Project.
The seller said it would be perfect one.

When I got and measured secondary taps without rectifier, the tester showed 330V. You know it is too high for 6V6 SE Amp. I claimed to the seller, but he said "the voltage will be ok when you connect it to tubes."

Well, I cannot understand his reply. For instance its heater taps is measured as exactly 6.3V. According to his logic, the heater voltage will also go down, when I attached it to 6V6 SE circuit.

Thanks.
  Reply With Quote
Old 19th January 2008, 10:01 PM   #2
BudP is offline BudP  United States
diyAudio Member
 
BudP's Avatar
 
Join Date: Feb 2007
Location: upper left crust, united snakes
We would need to know what type of rectifier is used for the B+, SS or Tube and what rectifier circuit is used, full wave bridge, full wave center tap, or some hybrid. Do you have a copy of PSUD2 you can model the power circuit with? By entering the measured no load values and what your power supply is built like you will bet a very accurate number for DC on the B+.

Typical cheap power transformer will show from 10 to 15 % loss of voltage under load for B+, but usually not more than 5 to 7% for the heater voltages, so you will probably be close to needs for both, just as a general note.

Bud
  Reply With Quote
Old 23rd January 2008, 05:16 PM   #3
diyAudio Member
 
Join Date: Jun 2005
Location: USA
Send a message via AIM to ThSpeakerDude88
330v is probably no load voltage, if your windings resistance is high ( IE the transformer cannot supply very high current) than it will most certainly drop when a load is attached.

For instance: I have a SMALL power transformer from an old organ. Its about the size of a 1-2 amp 12 transformer. Its outputs measure at 350-0-350vac with 123v input, but with a load that drops to around 270vac on each leg. My no load output voltage from the 5Y3 rectifier is around 380vdc, but when the amp is switched on that drops to a more comfortable 340vdc, which the 6V6 CAN and WILL handle just fine. Just watch your bias current.

Try measuring your secondary resistances to the CT. 150-250 ohms means you have a relativley low current transformer, 50-100 means it can supply quite a bit of current. The less winding resistance the more current it can pass, the higher the winding resistance the less current it can pass and the more a load will affect how much voltage is put out.
__________________
always preach the gospel-
and when necessary use words.
  Reply With Quote
Old 25th January 2008, 02:06 PM   #4
zxx123 is offline zxx123  United States
diyAudio Member
 
Join Date: Aug 2003
Location: ca
Default ...

Quote:
Originally posted by ThSpeakerDude88
330v is probably no load voltage, if your windings resistance is high ( IE the transformer cannot supply very high current) than it will most certainly drop when a load is attached.

For instance: I have a SMALL power transformer from an old organ. Its about the size of a 1-2 amp 12 transformer. Its outputs measure at 350-0-350vac with 123v input, but with a load that drops to around 270vac on each leg. My no load output voltage from the 5Y3 rectifier is around 380vdc, but when the amp is switched on that drops to a more comfortable 340vdc, which the 6V6 CAN and WILL handle just fine. Just watch your bias current.

Try measuring your secondary resistances to the CT. 150-250 ohms means you have a relativley low current transformer, 50-100 means it can supply quite a bit of current. The less winding resistance the more current it can pass, the higher the winding resistance the less current it can pass and the more a load will affect how much voltage is put out.
Thanks for your advice.
  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
Power transformer question keithgreenhalgh Tubes / Valves 4 6th August 2008 07:37 AM
Power transformer voltage question hbarki Parts 3 24th October 2005 07:53 AM
transformer power question needtubes Parts 2 9th April 2004 11:13 AM
i am new, power transformer question i_drives Parts 1 25th November 2003 12:53 AM
power transformer question Bill Fitzpatrick Solid State 5 8th June 2001 04:22 AM


New To Site? Need Help?

All times are GMT. The time now is 10:06 PM.


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