Cheap AndEasy 6.3 Volts

>"Veb is much higher with germanium, 20-30V. And inverting was done precisely to increase bandwidth, albeit at the cost of gain. "

I'll be damned. Just looked it up and Veb is like 25 volts. I would have never thunk it so high. Think germanium and you almost automatically think lower voltages. But there it is in my old spec  book fom Howard W. Sams back in the 1980s, maybe a but earlier. The 2N711 is not rated but the 2N1193 is. 

I doubt it will make the bandwidth but at least I can be more sure of the readings I take.

I already checked the power supply and all regulated voltages are fine, the unregulated voltages are all low but the line voltage is down to like 108 volts. That is true RMS so if the tops ad bottoms of the sine wave are clipped off it means even lower rectified voltages off the power transformer. but I temporarily turned off the electric heater running on the same extension ad the voltages came up, no change. 

>"you not got any germanium diodes? "

You mean to put across the emitter and base ? I don't have alot of confidence in that method. Maybe if I give it some resistance to the collector ? I dunno. It is a common collector stage so it should be able to handle a bit more gain. But 40 times as much ? I think that is asking alot. 

This book does not give a range or hfe versus HFE, it just specifies it at a certain collector current.

>"** Yep - charging and discharging an electro through it full voltage range 100 or 120 times per second is something you very rarely see as it approaches or exceeds the ripple current limit.
The part will likely run warm and have a short life. "

I have noticed that lower capacitance lytics handle less ripple current and have higher ESR. 

I don't even want to think about the real math but to rectify from 5 volts you get 7.07 volts. I think the total RMS is the vector sum of the CDC and the AC component, so the waveform has to droop lower than 6.3 volts. Off the top of my head I would say 4 point something volts. Now with a 600 mA current drain (estimated) how low a capacitance will it need ? Well it is going to make a sawtooth and not a really perfect one either. 

This sounds like a question at a good engineering school. The kids today in this country are lucky we have few because most of them would never pass. Like Thompson and a few others were discussing, they don't even want to pay new grads, they want them to intern to see if they know anything. And look at the thread from the guy who had no idea about negative feedback and instability in an amp stage. 

I wouldn't want to do the math either. But lytics have a sloppy tolerance and are affected quite a bit by heat. A regular one won't do it. A high temp precision is the only way to go. 

Like I believe I mentioned to tabb, I like the one resistor idea much better. 

Now I have to fix that vertical amp. i could really use one of those extenders to have the plugin hanging out to work on it. I looked ad there is no east way to dismount the plug opr anything. I it was a 7XXX series that would be different, because in "our" hold, meaning my buddy, we have extra plugins for those and an extra mainframe. An extender could be built from that. But nothing for the 5XX series. And if I buy one I can probably just get a working one and be done with it. Maybe I should have a look at Electronic Shithose's website. (that' ESI in Euclid, Ohio) It is hard to believe that all that surplus is on the web, but it is. But last time I was there I didn't see any 5X series anything. Maybe eBay.

I am setting it aside for now though, I am sick of fucking with it. I got wron voltages on a differetial set of transistors and am having trouble figuring out where it is coming from. Also the blocking oscillator for the chop mode does not run, the transistor there had a three way short. I replaced it and now it alternates, but intermittently. If anyone has too much time on their hands it is a Tektronix 561A with a 3B1 dual vertical amp and a 3B1 dual time base. The manuals for the vertical and the mainframe are on bama, but not the horizontal. But then I think the horizontal is fine. 

Tripped out working on that old thing, both tube and solid state hybrid. And it has some of those nuvistors that it's hard to tell the pinout. In fact I am no longer used to point to point wiring. I didn't like PC boards in the beginning but that changed. Now I find them easier to follow. 

And I definitely need a new pair of eyes. Reading glasses and a magnifying glass just barely gets me acceptable vision in one eye. No depth perception. Soldering is fun, think you're tinning a wire ? Nope, you are burning your hand. But I will have an appointment with an eye doctor within a couple months. I need an ophthalmologist, an optician can do nothing about this. 

What fun getting old !

I cannot see,
I cannot pee, 
I cannot smell,
I look like hell, 
The golden years have come at last,
The golden years can kiss my (_|_)

jurb...@gmail.com wrote:

------------------------

> >"** Yep - charging and discharging an electro through its full voltage
> > range 100 or 120 times per second is something you very rarely see
> > as it approaches or exceeds the ripple current limit.
>
> The part will likely run warm and have a short life. "
> 
>
> I have noticed that lower capacitance lytics handle less ripple current
> and have higher ESR. 
> 

** Yep, ESR goes up with voltage and down with capacitance.  

A rule that keeps PSU smoothing electros within maker's ratings is to operate them with a ripple voltage (measured p-p) that is never more than 20% of the DC rail voltage plus at least 10% under the cap's rated voltage. 

Same rule people have been using for eons.


....  Phil 

On Wednesday, 7 February 2018 06:36:42 UTC, jurb...@gmail.com  wrote:
nt:

> >"Veb is much higher with germanium, 20-30V. And inverting was done precisely to increase bandwidth, albeit at the cost of gain. "
> 
> I'll be damned. Just looked it up and Veb is like 25 volts. I would have never thunk it so high. Think germanium and you almost automatically think lower voltages. But there it is in my old spec  book fom Howard W. Sams back in the 1980s, maybe a but earlier. The 2N711 is not rated but the 2N1193 is. 
> 
> I doubt it will make the bandwidth but at least I can be more sure of the readings I take.
> 
> I already checked the power supply and all regulated voltages are fine, the unregulated voltages are all low but the line voltage is down to like 108 volts. That is true RMS so if the tops ad bottoms of the sine wave are clipped off it means even lower rectified voltages off the power transformer. but I temporarily turned off the electric heater running on the same extension ad the voltages came up, no change. 
> 
> >"you not got any germanium diodes? "
> 
> You mean to put across the emitter and base ? I don't have alot of confidence in that method.

I do. Don't forget that inverting will cane hfe as well. And you can put as many diodes on as you want. And I assume you know geranium diodes vary in their characteristics quite a bit. Some have pink flowers some have blue :)


NT

> Maybe if I give it some resistance to the collector ? I dunno. It is a common collector stage so it should be able to handle a bit more gain. But 40 times as much ? I think that is asking alot. 
> 
> This book does not give a range or hfe versus HFE, it just specifies it at a certain collector current.

Phil Allison wrote:

--------------------
>
> 
> ** Yep, ESR goes up with voltage and down with capacitance.  
> 
> A rule that keeps PSU smoothing electros within maker's ratings is
> to operate them with a ripple voltage (measured p-p) that is never
> more than 20% of the DC rail voltage plus at least 10% under the 
> cap's rated voltage. 
> 

** On reflection, that 20% figure could be too high in some cases. 

Electros rated at 10,000uF or more operating on continuous load should have no more than 10% p-p ripple. 



....   Phil

>"Electros rated at 10,000uF or more operating on continuous load should have no more than 10% p-p ripple."

I think even that is too high. Say you got 60 volts on it nominal, that is 6 volts of ripple. Figure for a pretty damn low ESR, say 1 ohm and the thing must be dissipating some power. The Xc of a 10,000 uF is so low at even 60 Hz that it is practically all resistive.

If you got 6 volts (just use RMS to make it easy) ripple across say one ohm ESR to use a shitty excample, what is the power dissipation ? It is 36 watts no ? I think that is a bit high and the cap won't last long. A half ohm is much more likely, that would be dissipating 72 watts. (actually it is going to be much lower, but just for  nice round figures...)

So actually I am agreeing with you, but agreeing more than you agree with yourself.

jurb...@gmail.com wrote:

------------------------
>
> >"Electros rated at 10,000uF or more operating on continuous load
> > should have no more than 10% p-p ripple."
> 
>
> I think even that is too high. Say you got 60 volts on it nominal,
> that is 6 volts of ripple. Figure for a pretty damn low ESR, say
> 1 ohm and the thing must be dissipating some power. The Xc of a 
> 10,000 uF is so low at even 60 Hz that it is practically all resistive.
> 

** Not on this planet - pal. 

The (100Hz) ESR of a good 10mF electro is about 20 milliohms and 0.25 ohms reactive. 

https://www.digikey.com/product-detail/en/kemet/ALS30A103DE063/399-11414-ND/4833245

At 10.8A rated ripple current, the cap dissipates 2W and warms a few degrees. 


> 
> So actually I am agreeing with you,
>


** Just does not look that way....




.....    Phil 

>"** Not on this planet - pal."
alright, it is unreasonable to think a 10,000 uF would have 1 ohm ESR, 0.020 is more realistic. 

So from 5 volts RMS (I assume) we will get 7.07 volts.Of course this is minus the Vf of the rectifier, let's say 0.6 volts, leaves us 6.47 volts. We are pretty much there really. So let's say we have a Schottky diode and the Vf is only 0.25 volts, that leaves us with 6.82 volts and just to be a pain we want it right at 6.3. 

Am I right so far ? Now this is where I get fuzzy. To get exactly 6.3 volts RMS, how much ripple voltage do we need ? Well the waveform is not going to be a sine or half sine, it will be a sawtooth, but it will be clipped at 6.82 volts DC plus AC.(assuming no loss from the transformer) 

While it may be more expedient to use a resistor in series with the filter, he wants to use the Xc of the cap. (I wonder if he is related to Rube Goldberg) So assuming practically no ESR in the cap, what value do we need to get the requisite ripple ? 

This may sound ridiculous, and it is for such an application.But in engineering instrumentation there is alot weirder shit they need to figure out. The whole thing sounds like an engineering test question. 

So the question becomes how do you sum the DC and AC components of this voltage output to get exactly 6.3 volts RMS ? 

Assuming the source resistance, the secondary of the transformer has zero resistance, that ripple waveform will be a sawtooth with the top of it being 6.82 volts. It should be symmertrical when it comes to voltage so since we need 6.3 out of 6.84, is that the P-P waveform rectified needs 6.82 - 6.3 which is 0.54 volts. 

I assumed 600 mA for the filament current off the top of my head. A 10 ohm resistor dropped a little over half of it, leaving about 6.2 volts IIRC. Just assume 600 mA filament current. 

I assume we need double the drop desired in ripple voltage, which would be 0.54 volts. Treating Xc as a resistance disregarding ESR, 600 mA drops 1.08 volts across 1.8 ohms, right ? 

So we need 1.8 ohms Xc, right ? Using the impedance nomograph for expediency, I get 757 uF assuming 120 Hz because this is the US. 

Am I right ? Off the top of my head 757 uF sounds too high, but the nomograph doesn't lie. I think. 

Have I fucked this all up or what ? Really, I don't really trust myself with this type of thing these days. It used to be so easy. Now I have trouble following unfamiliar circuitry, it used to be a piece of cake. 

I probably blew it, and it might be in my assumption of the required ripple voltage. But it could be anything. 

This is driving me crazy. It used to be so easy to figure shit like this out, but these days I catch myself in stupid errors. And I never tried this before, using ripple to reduce voltage on purpose. 

I also have trouble with saws and measuring. It used to be taking into account the kerf of the blade, now I err using the wrong inch mark. Like if the board has to be 6½" I might make it 7½" or 5½". This is not eyesight. I also built some cool shit out of wood, but now I have much trouble thinking in 3D. Like if I had a sheet metal brake it would take me a long time to figure out how to make a basic chassis. In the past I could do it almost without thinking. 

I've made a few stupid errors in the past few years. I am losing it. Maybe practice will help. It sucks.

jurb...@gmail.com wrote:

------------------------------

> >"** Not on this planet - pal."
>
> alright, it is unreasonable to think a 10,000 uF would have 1 ohm ESR,
> 0.020 is more realistic. 

> 
> Am I right so far ? Now this is where I get fuzzy. To get exactly 6.3 
> volts RMS, how much ripple voltage do we need ? 
>

** This would be best done by trial and error, starting with lowish value electros and working up.

An ordinary DC meter is all you need to monitor for 6.3V. 


.....   Phil  

On Friday, 9 February 2018 05:06:51 UTC, jurb...@gmail.com  wrote:
phil:

> >"** Not on this planet - pal."

> alright, it is unreasonable to think a 10,000 uF would have 1 ohm ESR, 0.020 is more realistic. 
> 
> So from 5 volts RMS (I assume) we will get 7.07 volts.Of course this is minus the Vf of the rectifier, let's say 0.6 volts, leaves us 6.47 volts. We are pretty much there really. So let's say we have a Schottky diode and the Vf is only 0.25 volts, that leaves us with 6.82 volts and just to be a pain we want it right at 6.3. 

Small BRs typically drop around 2v, 1v per diode. 0.6v is the knee voltage, not the typical Vf under load. A lot of EEs get that wrong.

> Am I right so far ? Now this is where I get fuzzy. To get exactly 6.3 volts RMS, how much ripple voltage do we need ? Well the waveform is not going to be a sine or half sine, it will be a sawtooth, but it will be clipped at 6.82 volts DC plus AC.(assuming no loss from the transformer) 
> 
> While it may be more expedient to use a resistor in series with the filter, he wants to use the Xc of the cap. (I wonder if he is related to Rube Goldberg) So assuming practically no ESR in the cap, what value do we need to get the requisite ripple ? 

a series R drops voltage. A parallel cap increases it by partly filling in the valleys.

> This may sound ridiculous, and it is for such an application.But in engineering instrumentation there is alot weirder shit they need to figure out. The whole thing sounds like an engineering test question. 
> 
> So the question becomes how do you sum the DC and AC components of this voltage output to get exactly 6.3 volts RMS ? 
> 
> Assuming the source resistance, the secondary of the transformer has zero resistance,

it doesn't of course, and with a small transformer delivering its charge over part of the cycle that will affect things

> that ripple waveform will be a sawtooth with the top of it being 6.82 volts. It should be symmertrical when it comes to voltage so since we need 6.3 out of 6.84, is that the P-P waveform rectified needs 6.82 - 6.3 which is 0.54 volts. 
> 
> I assumed 600 mA for the filament current off the top of my head. A 10 ohm resistor dropped a little over half of it, leaving about 6.2 volts IIRC. Just assume 600 mA filament current. 
> 
> I assume we need double the drop desired in ripple voltage, which would be 0.54 volts. Treating Xc as a resistance disregarding ESR, 600 mA drops 1.08 volts across 1.8 ohms, right ? 
> 
> So we need 1.8 ohms Xc, right ? Using the impedance nomograph for expediency, I get 757 uF assuming 120 Hz because this is the US. 
> 
> Am I right ? Off the top of my head 757 uF sounds too high, but the nomograph doesn't lie. I think. 
> 
> Have I fucked this all up or what ? Really, I don't really trust myself with this type of thing these days. It used to be so easy. Now I have trouble following unfamiliar circuitry, it used to be a piece of cake. 
> 
> I probably blew it, and it might be in my assumption of the required ripple voltage. But it could be anything. 

It's way easier to measure it! On load of course, which means adding caps starting very small & increasing as required.

Years ago I used this approach to create a filament lamp booster/economiser that didn't mess with the operation of CFLs.


NT

> This is driving me crazy. It used to be so easy to figure shit like this out, but these days I catch myself in stupid errors. And I never tried this before, using ripple to reduce voltage on purpose. 
> 
> I also have trouble with saws and measuring. It used to be taking into account the kerf of the blade, now I err using the wrong inch mark. Like if the board has to be 6½" I might make it 7½" or 5½". This is not eyesight. I also built some cool shit out of wood, but now I have much trouble thinking in 3D. Like if I had a sheet metal brake it would take me a long time to figure out how to make a basic chassis. In the past I could do it almost without thinking. 
> 
> I've made a few stupid errors in the past few years. I am losing it. Maybe practice will help. It sucks.