My secondaries for the heaters are high even with load.
5.6V for the 5V secondary. and 7V for the 6.3 secondary.
I can go the cheap route and use .1ohm on 1 secondary wire and a .22ohm resistor on the other wire. But I've seen replies saying the resistor values must be the same but I'm not sure if this applies to my situation.
The tubes connected to the heaters are for the power supply. the 5V secondary going to the 5*4 rectifier and the 6.3 secondary going to the 6as7/6sl7 tubes used for the voltage regulation.
thank you for the help
5.6V for the 5V secondary. and 7V for the 6.3 secondary.
I can go the cheap route and use .1ohm on 1 secondary wire and a .22ohm resistor on the other wire. But I've seen replies saying the resistor values must be the same but I'm not sure if this applies to my situation.
The tubes connected to the heaters are for the power supply. the 5V secondary going to the 5*4 rectifier and the 6.3 secondary going to the 6as7/6sl7 tubes used for the voltage regulation.
thank you for the help
poobah said:You're on the right track Jarthel,
If these were center tapped secondaries, and the CT was "referenced", one could make a small case for balancing the resistors. In your case though, it shouldn't matter. You can even use ONE 0.33 Ohm if it makes life simpler.
both secondaries are CT secondary and I intend to reference the CT to 1/2 B+.
And unfortunately, I cannot find any .33ohm resistor locally. I need to go to Farnell or RS for such a value.
Yep,
It could be argued that this might induce some hum... very doubtful, although in principle the resistors should be matched.
Why not go ahead and get things moving with the resistors you have... leave the resistors easy to remove... don't wind the leads around the eyelets 5 times... just poke 'em in and so9lder them. Order the correct resistors next time you place an order... so you don't have to spend $15 for 2 ******* resistors.
It could be argued that this might induce some hum... very doubtful, although in principle the resistors should be matched.
Why not go ahead and get things moving with the resistors you have... leave the resistors easy to remove... don't wind the leads around the eyelets 5 times... just poke 'em in and so9lder them. Order the correct resistors next time you place an order... so you don't have to spend $15 for 2 ******* resistors.
Heater voltage..
I have a similar problem, and a 'different' cure....
I have a Toroid that is supposed to be 25V @4.5A loaded O/C volts is 27.8 and loaded by 3.5A is arond 27.5.
Im using it to supply two series wired 6C33C-B heaters.--27.5 is too much.
A simple 'mod' I did was to measure the turns/volt by looping test-lead through toroid core and back to meter. It was .5Vac or thereabouts....
I wound 6 turns More on the core, and connected it in Anti-phase to the original secondary. It was all insulated after with good quality tape. This dropped the voltage to 24.5, which Im happy with.
Its been working well for many months with no heating or other issues.
--No hot resistors or hard to find values, or waste of power. Easy with a toroidal Tx, but maybe not possible with an E I type Tx as there may not be room on the bobbin and sometimes hard to insulate if there is room for an additional couple of turns....
For your centre-referenced Tx, you'll need to join two coils of half the number of turns each to each end of your existing secondary, Both in Anti-phase. Use wire the same thickness as the secondary coil wire OR slightly thicker....
I have a similar problem, and a 'different' cure....
I have a Toroid that is supposed to be 25V @4.5A loaded O/C volts is 27.8 and loaded by 3.5A is arond 27.5.
Im using it to supply two series wired 6C33C-B heaters.--27.5 is too much.
A simple 'mod' I did was to measure the turns/volt by looping test-lead through toroid core and back to meter. It was .5Vac or thereabouts....
I wound 6 turns More on the core, and connected it in Anti-phase to the original secondary. It was all insulated after with good quality tape. This dropped the voltage to 24.5, which Im happy with.
Its been working well for many months with no heating or other issues.
--No hot resistors or hard to find values, or waste of power. Easy with a toroidal Tx, but maybe not possible with an E I type Tx as there may not be room on the bobbin and sometimes hard to insulate if there is room for an additional couple of turns....
For your centre-referenced Tx, you'll need to join two coils of half the number of turns each to each end of your existing secondary, Both in Anti-phase. Use wire the same thickness as the secondary coil wire OR slightly thicker....
poobah said:Actually Jarthel,
An R-core would probably provides the simplest way just to remove some turns!
Has your trans been dipped in varnish?
I have to look if it has been dipped in varnish. but in any case, can you tell me how it's done?
not sure if it's important but here's 2 pics of the transformer:
http://img156.imageshack.us/my.php?image=pict0004ty5.jpg
http://img82.imageshack.us/my.php?image=pict0005ne7.jpg
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.
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.
poobah said:
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?
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.
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.
poobah said:
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
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.
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.
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