Testing OT taps?
Moderators: pompeiisneaks, Colossal
Testing OT taps?
Any way to test output transformer taps to make sure which one is 8 ohm and which one is 4 ohm?
My playing here: http://www.youtube.com/user/dovemanvideo?feature=mhsn
Re: Testing OT taps?
Apply 6VAC to a primary winding, and measure the secondary voltages. The 8 ohm output will generate a higher signal level than the 4 ohm
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Stevem
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Re: Testing OT taps?
Just install it in the amp and measure the ac voltage output , your not going to hurt anything by having a mismatched load on the OT for a short amount of time and at less max power output!
Also most 8 ohm taps will resistance wise measure on more than .7 ohms and not less than .4, but for thses small measurements on a ohm meter you can not hold the wire ends to make the measurement as a modern meter will read thru you and the OT winding!
Also most 8 ohm taps will resistance wise measure on more than .7 ohms and not less than .4, but for thses small measurements on a ohm meter you can not hold the wire ends to make the measurement as a modern meter will read thru you and the OT winding!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Testing OT taps?
Actually both suggestions are fine. If the transformer is outside the amp, go with trobbins' suggestion. Apply a low AC voltage to one winding, measure the voltage on the other. The 8 ohm winding will have 1.4 times the voltage of the 4 ohm winding.
As a side note, a 16 ohm winding will have two times the voltage of a 4 ohm winding.
If it's inside an amp Stevem's suggestion is is the way to go. You will not damage anything testing a speaker on a mismatched tap.
The way to distinguish the approaches is by the Principle of Maximum Laziness!
As a side note, a 16 ohm winding will have two times the voltage of a 4 ohm winding.
If it's inside an amp Stevem's suggestion is is the way to go. You will not damage anything testing a speaker on a mismatched tap.
The way to distinguish the approaches is by the Principle of Maximum Laziness!
Re: Testing OT taps?
It's in the amp ... I just want to verify it ...
Am I measuring at the speaker ... not sure how to measure ... what to measure with the meter.
Thanks in advance.
Am I measuring at the speaker ... not sure how to measure ... what to measure with the meter.
Thanks in advance.
My playing here: http://www.youtube.com/user/dovemanvideo?feature=mhsn
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Testing OT taps?
Yes, a meter set for AC volts if your going it by voltage, the higher the impedance of the tap, the higher the voltage will be by a factor of some 30%.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Testing OT taps?
When set to 4 ohm = 45 mVStevem wrote:Yes, a meter set for AC volts if your going it by voltage, the higher the impedance of the tap, the higher the voltage will be by a factor of some 30%.
When set to 8 ohm = 80mv
Measured with meter set on voltage. Red lead on + tab of speaker and Black lead on - tab of speaker with the amp idling with no signal.
So I think if I did this right that I have confirmed the taps are labeled correctly. Sound right?
My playing here: http://www.youtube.com/user/dovemanvideo?feature=mhsn
Re: Testing OT taps?
Normally, a low input signal would be applied, eg. from a sinewave oscillator, or a mp3 file with a sine wave. Such that output voltage would have a low level of signal generated (eg. 1Vrms).
Re: Testing OT taps?
I have a sine wave generator on my iPad ... I can try that.trobbins wrote:Normally, a low input signal would be applied, eg. from a sinewave oscillator, or a mp3 file with a sine wave. Such that output voltage would have a low level of signal generated (eg. 1Vrms).
My playing here: http://www.youtube.com/user/dovemanvideo?feature=mhsn