dropping heater voltage - Page 2

poobah · 21st September 2006, 12:12 AM

On second thought that is pretty bundled up... How many secondaries do you have there? You would have to cut all that up until you could see the coils.

The reason I ask... you will not see your final voltage until ALL your secondaries are operating at their target load. The need for resistors, at least an exact value, might be premature.

jarthel · 21st September 2006, 12:15 AM

Quote:

Originally posted by poobah

The reason I ask... you will not see your final voltage until ALL your secondaries are operating at their target load. The need for resistors, at least an exact value, might be premature.

hmm when I measured the voltage, I just connected the rectifier tube to the 5V secondary with nothing else connected. It was the same when I checked the voltage for the 6AS7 and 6SL7.

I'm assuming this is not the right way to do it?

poobah · 21st September 2006, 12:24 AM

Not wrong... but not exactly right... as all the secondaries are loaded up, you will see the voltages lower across the board. So you may not really have a problem.

You know... at this point, you are 10% high, which is within spec (barely). Why not proceed, knowing that you may need a resistor, in other words leave room, and get some more load on the trans? The voltage will come down some more.

jarthel · 21st September 2006, 12:41 AM

Quote:

Originally posted by poobah

You know... at this point, you are 10% high, which is within spec (barely). Why not proceed, knowing that you may need a resistor, in other words leave room, and get some more load on the trans? The voltage will come down some more.

thank you for the help. you've been very helpful to me

I'll follow your advice. I'll load up all the needed secondaries first before I buy the resistors

poobah · 21st September 2006, 12:48 AM

poobah · 21st September 2006, 04:33 AM

Sorry dude... forgot the "why".

The resistance of the primary winding effectively appears in series with the inductance coupled to the secondary. So, as output power increases, so does primary current. This in turn causes the drop across the primary to grow, and in effect, the primary winds up with less voltage; this in turn, means less secondary voltage.

jarthel · 21st September 2006, 04:45 AM

Quote:

Originally posted by poobah
Sorry dude... forgot the "why".

The resistance of the primary winding effectively appears in series with the inductance coupled to the secondary. So, as output power increases, so does primary current. This in turn causes the drop across the primary to grow, and in effect, the primary winds up with less voltage; this in turn, means less secondary voltage.

thanks for the additional info. unexpected but greatly appreciated.

poobah · 21st September 2006, 04:50 AM

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21st September 2006, 12:12 AM	#11
poobah diyAudio Member Join Date: Nov 2005	On second thought that is pretty bundled up... How many secondaries do you have there? You would have to cut all that up until you could see the coils. The reason I ask... you will not see your final voltage until ALL your secondaries are operating at their target load. The need for resistors, at least an exact value, might be premature.

21st September 2006, 12:24 AM	#13
poobah diyAudio Member Join Date: Nov 2005	Not wrong... but not exactly right... as all the secondaries are loaded up, you will see the voltages lower across the board. So you may not really have a problem. You know... at this point, you are 10% high, which is within spec (barely). Why not proceed, knowing that you may need a resistor, in other words leave room, and get some more load on the trans? The voltage will come down some more.

21st September 2006, 12:48 AM	#15
poobah diyAudio Member Join Date: Nov 2005

21st September 2006, 04:33 AM	#16
poobah diyAudio Member Join Date: Nov 2005	Sorry dude... forgot the "why". The resistance of the primary winding effectively appears in series with the inductance coupled to the secondary. So, as output power increases, so does primary current. This in turn causes the drop across the primary to grow, and in effect, the primary winds up with less voltage; this in turn, means less secondary voltage.

21st September 2006, 04:50 AM	#18
poobah diyAudio Member Join Date: Nov 2005

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