Etherwave maximum input voltage

My first experience with split power supply so have mercy. If half wave rectification gives less than 50% of the transformer peak voltage why in this configuration is the voltage so high across the filter capacitors. I expected the board to use much less current than it does and more current flowing in the ground wire.  What am I missing?

This is important to me because I want to power my 386 pitch preview amp from the positive regulator, though my board does have its own regulator so I can get power directly off the big cap plus there are pads for another 2200 uf on my second 3 x 3 board if needed. I am aware of T0-92 style heat sinks, cute. There is a tiny bit of warmth on both 12v regulators.

The 5-pin din of the Hot Rodding schematic seems miss numbered?

AC at the plug = 14.9vac unloaded  14.6vac loaded

Across both 2200uf cap = 18.5 vdc

 2.1 ma measured on the ground connection.

32.7 ma positve regulator   

34.7 ma negative regulator

This latest board uses big radial capacitors on their side, my previous used axial so they do make changes to the PCB more than I thought.

Christopher, one thing to be aware of is that for AC volt readings, a lot of DMMs (those that aren't "true RMS") measure the peak voltage and scale this to give the equivalent RMS.  This method only works if the waveform is a sine wave.  The scale factor is one over the square root of 2 (0.707).  So if you measure 14.6 VAC at the transformer (definitely a sine wave), multiply this by the square root of 2 (1.414) and subtract the diode drop (0.7V) to find the approximate filter capacitor voltage:  (14.6 * 1.414) - 0.7 = ~20V.  Lightly loaded power supplies act like peak hold circuits.

Based on the LM78L12 datasheet I'd expect the quiescent current to be a few mA at most (regulators unloaded).  I suppose I believe the ~2 mA you see on the ground connection, but not the ~30 mA on pos and neg.  Put a 1 ohm or so resistor in series and look at the voltage across it with a scope, I believe it is a peak value that, averaged over the entire cycle, would be more like a couple of mA, and your DMM is badly misleading you here.  Even RMS DMMs can freak out when the duty cycle is too small.  With a light load, power supply diodes only conduct for a very brief period during each cycle.

Your right dew, I checked the transformer on my scope unloaded and found 40v p-p. This would be 20 volts using the single diode peak and the transformer would be called a 14 v which is a rough RMS estimate .707 x 20v.

Thank you I think I got that part now, never looked into it before.

Now low ground current I understand is because each side neutralizes the other as far as measuring the average current flow.

May be a coincidence but my 2 ma ground current may be the difference of the two current sources. Just guessing.

Christopher

In my thinking I evaluate everything with electron flow while others go opposite with current flow (holes) which camp are you in? My bet it will be holes as we are opposites, you go the direction of the arrows and I am anti-establishment. 

"In my thinking I evaluate everything with electron flow while others go opposite with current flow (holes) which camp are you in?"  -- Christopher

Few things get my grump on like the historical mistake of current flow.  Why not fix things so future generations don't have to deal with past BS?  But silicon NPN BJTs and NJFETs are superior and look nice on schematics with the mistake, so I suppose there's that.  I always wonder what a more methodical alien species might think of us based on our upside down schematics.

From the previous discussion I realize it is better to not use the EWS positive regulator to power my 386 pitch preview amplifier. Thermally the regulators operate on the edge.

On page one of this thread Thierry gives a good analysis of EWS input voltage and heat dissipation.

A power resistor outside at the AC transformer to shave off some of the overhead voltage of higher voltage transformers would be a good idea. A value large enough to dissipate heat externally but small enough not to affect proper filtering to the regulators.

As ILYA mentioned previously, I do not like this heat dissipated in an unvented wood box. Room temperature is rather stable but after placing my finger on a EWS regulators I have concern about the temperature rising in the box after a period of time.

It would seem to me the box needs gentle ventilation? For this reason have vent slots on each side of the EWS wood box?

Christopher

Edit: Chimney is funny, being holes for the Plus plugs are drilled in the bottom already I thought taking the plastic plug out of the top of the Pitch antenna was interesting.

"As ILYA mentioned previously, I do not like this heat dissipated in an unvented wood box. Room temperature is rather stable but after placing my finger on a EWS regulators I have concern about the temperature rising in the box after a period of time.

It would seem to me the box needs gentle ventilation? For this reason have vent slots on each side of the EWS wood box?" -- Christopher

Yeah that would probably be a good idea.  Though breezes could then make it inside and perhaps change things short-term?  Best I think is to have a tallish "chimney" type box with holes at bottom and top, and with the hot power stuff located at the top and heat sensitive stuff below it.  Or put the hot power stuff and heat sensitive stuff in separate boxes (my cunning plan).

"" Как ИЛЬЯ упоминалось ранее, мне не нравится это тепло, рассеиваемой в невентилируемом деревянной коробке. Температура в помещении достаточно стабилен, но после размещения мой палец на EWS регуляторов у меня есть озабоченность в связи с повышением температуры в поле после определенного периода времени. Казалось бы, мне нужна коробка нежный вентиляции? По этой причине имеют вентиляционные прорези на каждой стороне дерева коробки EWS? »- Кристофер Да, это, вероятно, будет хорошей идеей Хотя бризы может затем сделать его внутри и, возможно, изменить положение вещей краткосрочный Лучшее, что я думаю, что это есть.? довольно высокий "дымоход" Тип коробки с отверстиями в нижней и верхней, и с горячим материалом питания, расположенный на верхней и тепловой чувствительный материал под ним. Или "поставить горячий материал электрическую и тепловую энергию чувствительные вещи в отдельных коробках (мой хитрый план).

Приветствую всех участников форума! Много раз я был здесь и много читал, но зарегистрирован только сейчас. Очень рад, что здесь была моя картина электроснабжения терменвокс. Я надеюсь, что это было полезно. Что касается нагрева регуляторов напряжения есть идея: использовать элементы L7812cv и L7912cv, которые имеют большую мощность и будет менее теплой. Чтобы сделать это, отпайки старые регуляторы и припаять новые. Они прекрасно умеют работать в Etherwave. Я уже проверил это на практике. Я думаю, что это хорошая идея.  

P.S. I wanted to attach picture, but failed. Something not so loaded...

Let me help with your first post

Valery said,

"" Ilya mentioned earlier, I do not like is the heat dissipated in the unventilated wooden box. The room temperature is quite stable, but after placing my finger on EWS regulators I have a concern about the rise in temperature in the box after a certain period of time. It would seem that I need a box of gentle ventilation? For this reason, have ventilation slots on each side of the tree EWS box? "- Christopher Yes, it will probably be a good idea Although breezes can then make it inside, and possibly a short-term change things the best I think it is.? fairly high "chimney" type box with holes in the bottom and top, and hot food material, located on the top and heat sensitive material underneath. Or "put hot stuff electricity and heat-sensitive items in separate boxes (my cunning plan).

I greet all the participants of the forum! Many times I was here, and read a lot, but only now registered. I am very glad that there was a picture of my theremin power. I hope this was helpful. As for the heating voltage regulators has an idea: use the elements and L7812cv L7912cv, which have more power and will be less warm. To do this, the old branch line regulators and solder the new. They are perfectly able to work in Etherwave. I've tested it in practice. I think it is a good idea.

The EtherWave Standard would need a good trick for the pads to be easily adaptable. I like using the larger regulators in my own designs with loading resistors. In my thinking a regulator that is dissipating heat would still be the same amount of heat on a larger regulator but it would seem cooler because it is spread over a larger area. dewster mentioned a chimney, drill and place a plastic tube through a 1/2" (13mm) hole down over the two regulators?

The engineer in me: 35ma x 12 volts + reg 230 mw = ~650 mw  Better to stick with the vents.

Christopher

Thank You, Christopher! So my entry would be more accurate!

hi valery,

yes your picture also brings up some questions about that pin2. i opened my wallwart, wich came with the instrument some years ago, two prong no grounding. and obviously, there are the two cables from the secondary side of the transformer going to the din-jack. no shielding, no third cable. pin two is not connected at all.

my question is: if i want to provide ground by the power supply instead of the amp, using a three prong instrument cable, i think it's C13 or C14 type, could i route the incoming ground directly to pin two? i thought about adding a ground-lift switch too. or would that just cause a hilarious short?

uups, hit the post button accidently. i'm having some troubles too to upload a picture. maybe transatlantic-cable-overload.