AC Elevated Heaters . . . .

RickyLee

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I hope the uptight remark was not for me. :)

I am watching.

It is nothing Bro. You're always helping me along as well as many others here man. It is very appreciated.

I know I can sound like a broken record sometimes, and lose some patience when it comes to studying up on this stuff before diving in. Yeah, I should not trust everything I see and read on the innerwebz.

I got frustrated with the filter calculators and just dived in by trial and error.

I still need to get that big cap outta there but no heff to do it right now. It is crammed tight in this mess I built. Maybe get back on it later if I feel up to it or maybe tomorrow after the football conf championship games . . . .
 

RickyLee

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I gave up on trying to run a 12AX7 on DC heaters. But was thinking, WTF would it hurt just to power the lone reverb 12AX7 on just below spec heaters. Reverb tone is nothing important and just a low percent in the mix anyway. But, powering it at 5.4VDC would be worse than at 5.4VAC, correct? I remember reading that. But of most importance, I do not want to bring in any added noise as it is quiet at this point.

I have some high current power supplies in stash, but they might be the switching type that I would not want to use. I think I have a 9VDC and an 18VDC.
 

mickeydg5

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It is nothing Bro. You're always helping me along as well as many others here man. It is very appreciated.

I know I can sound like a broken record sometimes, and lose some patience when it comes to studying up on this stuff before diving in. Yeah, I should not trust everything I see and read on the innerwebz.

I got frustrated with the filter calculators and just dived in by trial and error.

I still need to get that big cap outta there but no heff to do it right now. It is crammed tight in this mess I built. Maybe get back on it later if I feel up to it or maybe tomorrow after the football conf championship games . . . .
It is not only about trusting what you read. It is about applying but understanding first.

I am not positive I fully understand what you actually did but am suspicious you loaded the circuit down by the way it was set up.

There is much to learn about power supplies and supported components when designing circuits, especially lower impedance circuits.
 
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RickyLee

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It is not only about trusting what you read. It is about applying but understanding first.

I am not positive I fully understand what you actually did but am suspicious you loaded the circuit down by the way it was set up.

There is much to learn about power supplies and supported components when designing circuits, especially lower impedance circuits.

Did you get the drawing I sent you?

Would you even expect to be able to obtain and hold 6VDC from the 5VAC 3A tap on a power transformer running even one 12AX7 filament? This is not a separate aux/added filament xfmr, this is the Classic Tone PT in the amp that has that 5V for the Deluxe Reverb tube rectifier. I do not have a tube rectifier in this amp, in case anyone is wondering lol.
 

mickeydg5

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Did you get the drawing I sent you?

Would you even expect to be able to obtain and hold 6VDC from the 5VAC 3A tap on a power transformer running even one 12AX7 filament?
Man I forgot about that. I have to go get it since it is on an account I do not use too often.

It can be held if set up correctly.

Let me go look at that email account. I'll be back.
 

RickyLee

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OK. If you think it is possible, I will give it another shot again tonight. This 5V tap has no center tap of course.

I am somewhat limited on e'lytic cap values. I should have decent values to try direct on the BR positive OUT, and then put another value close or even direct across the tube socket/on load for gits and shiggels. I should have plenty of high voltage non polarized film caps as I read something around .1uF should be in between the two other cap locations.

If we do get a 12AX7 to hold at 6VDC, well then we will see if my channel switching 5V relay coil will affect this when it is powered on as well.

If I can get the 6VDC without the relay coil in there, that will work and I can then move the relay coil to be powered of my 6.3VAC heater tap. As long as putting that relay coil in the latter does not induce any noise, as that is of most importance. I want the amp to remain quiet first. This other crap is just icing on the cake.

And a reminder, my 6.3V tap has the faux center tap elevated about 52VDC . . . .
 

RickyLee

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Mickey, give a forum class on that BR filter cap calculator and the fields/values that need entered. The time field was where I was confused. Is that the time constant charge time?
 

mickeydg5

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Mickey, give a forum class on that BR filter cap calculator and the fields/values that need entered. The time field was where I was confused. Is that the time constant charge time?
I am looking at the stuff and see two issues.

But first tell me

1) where is this BR filter capacitor calculator? Link it please.

2) which Omron 5V relay? Part #?
 

RickyLee

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I am looking at the stuff and see two issues.

But first tell me

1) where is this BR filter capacitor calculator? Link it please.

2) which Omron 5V relay? Part #?

Crap, I looked at a few of those filter cap calculators. They seemed similar.

Here is the relay coil data sheet. But remember, I tried this all with no relay coil in the amp. So that is just secondary icing on the cake. The sketch I drew was with relay which I now have. But I could not get close to 6VDC with no relay in there yet.

https://omronfs.omron.com/en_US/ecb/products/pdf/en-g5v_2.pdf


OK. Looking for the calculator, I ran into this explanation for the time field.

"is the period of the full-wave rectified waveform, in seconds"

And now this makes sense lol. I found this calculator and did that calculation of 1/2 * 1/60 = 8ms.

Plug that into this calculator with 5V and 300mA for a 12AX7 and I get 480uF. I do have a 470uF cap lol.

https://electronicbase.net/smoothing-capacitor-calculator/

ADD: Or am I supposed to use the 6.4VDC figure?
 

RickyLee

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I don't even remember now if I started with 1000uF or the 470uF that I had there too. I remember that Studio 15 amp we messed with had a 470uF and I raised it to 1000uF and it worked out well.
 

RickyLee

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That calculator I posted seems much simpler than the ones I had initially looked at.

I want to try this experiment again without undoing too much of my work in this tight crammed space of a beotch amp.

I can do a test by jumpering together a test circuit with test leads I suppose. Clip in a 12AX7 to its heater pins. It would be simple to unsolder one leg of my power xfmr 5VAC tap inside the amp. Then use test leads to tap into the PT winding. I do not see an issue with my amp/relay coil being left attached to the other leg of the 5V tap, no? Relay coil power connection is open of course.
 

mickeydg5

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@RickyLee

First, you are dealing with 5VAC from PT secondary into rectifier with capacitive input filter. That is basically 1.414*5=7.07 volts. Your circuit is loading it down from there.

Second, the parallel tube heater has nothing to do with the charging current of the capacitor. The capacitor is in its own branch and is limited by its own internal resistances in this case.
Still under operating condition the capacitor will see about 412mA for ripple. NOTE that is just for ripple current.

Your relay is rated at 5V and 100mA. See where this is going? You are burning up the relay causing more resistance.
When the tube heater is added the circuit pulls even more current, loading the circuit even more which as you may have guessed drops the voltage more.

So you need to design a power supply for your needs.
Drop the 7VDC down to 6.3VDC to feed the tube heater(s). Then drop voltage (and current) again, preferably with a regulator, to power the 5V relay(s).

Or two regulators, a 6.2V and a 5V.
 
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RickyLee

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Hmmm. I do not see a regulator working in there for the 6V, as they do need that aprox 2V extra on the dropout. I remember seeing/reading about non dropout regulators, but I do not have any.

And I never seen anything close to 7V, which would be due to the voltage drop from the silicone diodes, correct?

Mesa Heartbreaker has an interesting heaters and relay coil circuit without using any regulators, but again, it is using the 6.3V tap. That one uses seven 6800uF caps in array.
 
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mickeydg5

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Hmmm. I do not see a regulator working in there for the 6V, as they do need that aprox 2V extra on the dropout. I remember seeing/reading about non dropout regulators, but I do not have any.

And I never seen anything close to 7V, which would be due to the voltage drop from the silicone diodes, correct?
Yes, right. Most available 6.2V regulators will need more like 8.2V to hold proper voltage.

It would be best or easiest to use a limiting resistor and 6.2V zener.
Actually the same could be done for the 5V section.
 
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myersbw

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RickyLee, now you have me really curious as to what all ya got in this thing? You said seven 12ax7's...??? So, I'll assume six by subtracting the needed phase inverter. Watcha doing with 12 stages? Give a little rundown...reverb or trem circuits? buffered FX loop? Or, multiple separate preamp channels? (maybe you could switch in cascaded circuits?) Got me curious...
 

RickyLee

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RickyLee, now you have me really curious as to what all ya got in this thing? You said seven 12ax7's...??? So, I'll assume six by subtracting the needed phase inverter. Watcha doing with 12 stages? Give a little rundown...reverb or trem circuits? buffered FX loop? Or, multiple separate preamp channels? (maybe you could switch in cascaded circuits?) Got me curious...

This is basically two high gain channels, each with their own respective tone controls and master volume. It will have tube driven reverb, but have not wired in the reverb transformer just yet, so that one 12AX7 is not in the amp at this time. So right now there is six of seven 12AX7's running. I still need a spring reverb tank.

Channel I is my take on the Boogie 2C+ lead channel only. Channel II is my take on the Slodowno SLO lead channel only. I did not use either of those designs FX loops. I did put a dedicated loop on the Boogie side and then from there that channel feeds to its MV and then relay switch. Slodowno side goes from its last 4th stage -> cathode follower -> tonestack -> MV then joins at the relay switch. After the relay switch is the global loop, which is not buffered, but just a simple old school insert point of send/return that is jumpered if nothing is plugged in. From there on to phase inverter/power amp which is just a standard Marshall 2203/4 circuit.

Transformers are capable of aprox 40W but running a pair of 6V6 push pull fixed/adjustable bias.

So basically, I am cramming two iconic lead channel circuits into a Deluxe Reverb home lol. It is very tight man. I used the standard Deluxe Reverb eyelet boards and then tried to lay this all out the best I could. I had to do quite a bit of point to point flying leads in there as there is just not enough circuit board there. The channels start out sharing the first stage V1A and branch/Y off from there having their own dedicated stages rest of the way. Just too far off from each other to share more stages then that, and then I do have the 1uF cathode bypass cap of 1st stage which is Soldano value, Boogie should have .47uF with switching to add in 15uF.
 
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RickyLee

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I want to do a test circuit of this 5V tap to rectified DC, but outside of the amp. I am going to unsolder only one leg of my 5V winding, leaving the other leg hooked up inside the amp to its bridge rectifier/cap/relay coil. I will then use test leads to plug into that 5V tap and make a new rectified DC circuit outside the amp to experiment. You guys see an issue with that one leg of that 5V tap being attached to the original bridge rectifier? Or will it still load/pull down even with one leg hooked up?
 

mickeydg5

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I want to do a test circuit of this 5V tap to rectified DC, but outside of the amp. I am going to unsolder only one leg of my 5V winding, leaving the other leg hooked up inside the amp to its bridge rectifier/cap/relay coil. I will then use test leads to plug into that 5V tap and make a new rectified DC circuit outside the amp to experiment. You guys see an issue with that one leg of that 5V tap being attached to the original bridge rectifier? Or will it still load/pull down even with one leg hooked up?
As long as the disconnected/tapped leg is the high/positive side it will be ok. That takes the one inside of the amplifier out of play by your description.
 


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