Am I splitting hairs?

12/17/2008 2:26:02 AMPeter G. Balazsy

I'm working on this little ole' Packard Bell 100a.
http://www.nostalgiaair.org/Resources/842/M0012842.htm

I'm having trouble trying to determine if the B+ loads are correct or not.

You'll notice that the B++ coming off the rectifier is shown as +126vdc and this goes to the 50L6 plate via the output transformer where it ends up at +120Vdc.

The rest of the B+ after the second section of the pi filter is shown at +105vdc.

That means there is a 21 volt drop across R8 the 1000 ohm 1-watt resistor shown in between the two filter caps.... right?

Ok... well doing the simple ohms law math 21 volts divided by 1000 ohms = 21ma of current.... right?

and 105 volts B+ at drawing 21ma means the B+ loads must be around 5000 ohms total... right?
105v/.021a = ~5000 ohms... right?

And to determine the proper wattage of that 1000 ohm resistor P=IxE

21v x .021a = .441 watts.. and double that for safety .88watts ...means a 1 watt resistor will be just fine... right?

Okay... so far so good.

But I noticed that my 1000 ohm 1 watt resistor was excessively hot.

So I decided to make some measurements and see why.

Well this led to my current question:
... Is there truly any excessive current or is it really normal?

Here's what I found:

I have typically slightly higher AC line voltage (125vac) resulting in greater B+ ... okay ....but I can't see that making such a difference.

I actually have 140vDC (B++) at the cathode of the 35Z5 and 108 volts DC on the other side of that 1000 ohm resistor.
That is a 32 volt drop. ( TEN 10 volts [i]higher[/i] than shown on the print)
I checked the resistor ( precision = 1000 ohms).. so that's fine.

But the problem is that a 32 volt drop means there is 32ma of current being drawn by the B+ loads. ... not the 21ma as indicated by the 21volt drop shown on the print.

Now since I actually have 140v B++ ...and [b]if there really was 5,000 ohms[/b] of B+ load... then the total voltage drop across that 1000 ohm resistor would still only be about 23volts.

But the way I'm figuring it all...the fact that I'm actually dropping 32 volts there across that 1000 ohm resistor means the total B+ loads must be way down around 3,375 ohms causing the extra 10ma current draw.

Why is this??

32 ma x 32 volts = 1 watt + ... and double that for safety means I really need a 2 watt resistor now .....not the 1 watter as shown in the print.

So what gives?

The B+ loads that I measured are :
1.) The oscillator section of the 12SA7
2.) The plate of the 12SA7
total = ~17ma

3.) The plate of the 12SK7 = ~16ma

4.) The plate of the 12SQ7 = .2ma

5.) the Screen grid of the 50L6 = 2.3ma

Changing out the 12SA7 and 12SK7 made no difference.

All capacitors are NEW

All resistors are in spec.

Are these loads excessive or normal?

If they are normal... I'll need to double the 1000 ohm resistor wattage to 2 watts...
But that conflicts with the logic of the schematic... right?

I feel something isn't quite right... but can't put my finger on it.

Any ideas?

12/17/2008 12:13:46 PMLewis Linson

Hi, Peter:
I agree with ypu that there is something wrong with the current in your Packard-Bell, and I would not replace the one Watt resistor with a 2 Watt. I am having another shut-in day, we have had a warm front stalled overhead for several days here, the warm temps (71 F. at 11:38 AM EST) are appreciated, but the humidity is opressive.

You say you've replaced C11, but what would happen if you disconnected C11B for a moment and checked the Voltage across R8? Probably a waste of time, but something sneaky like that has consumed a lot of my sanity over the years.

How 'bout pulling the tubes that are on the low side of that resistor and see what happens before the filament cools off.

More later,
Lewis

:I'm working on this little ole' Packard Bell 100a.
:http://www.nostalgiaair.org/Resources/842/M0012842.htm
:
:I'm having trouble trying to determine if the B+ loads are correct or not.
:
:You'll notice that the B++ coming off the rectifier is shown as +126vdc and this goes to the 50L6 plate via the output transformer where it ends up at +120Vdc.
:
:The rest of the B+ after the second section of the pi filter is shown at +105vdc.
:
:That means there is a 21 volt drop across R8 the 1000 ohm 1-watt resistor shown in between the two filter caps.... right?
:
:Ok... well doing the simple ohms law math 21 volts divided by 1000 ohms = 21ma of current.... right?
:
:and 105 volts B+ at drawing 21ma means the B+ loads must be around 5000 ohms total... right?
:105v/.021a = ~5000 ohms... right?
:
:And to determine the proper wattage of that 1000 ohm resistor P=IxE
:
:21v x .021a = .441 watts.. and double that for safety .88watts ...means a 1 watt resistor will be just fine... right?
:
:Okay... so far so good.
:
:But I noticed that my 1000 ohm 1 watt resistor was excessively hot.
:
:So I decided to make some measurements and see why.
:
:Well this led to my current question:
:... Is there truly any excessive current or is it really normal?
:
:
:Here's what I found:
:
:I have typically slightly higher AC line voltage (125vac) resulting in greater B+ ... okay ....but I can't see that making such a difference.
:
:I actually have 140vDC (B++) at the cathode of the 35Z5 and 108 volts DC on the other side of that 1000 ohm resistor.
:That is a 32 volt drop. ( TEN 10 volts [i]higher[/i] than shown on the print)
:I checked the resistor ( precision = 1000 ohms).. so that's fine.
:
:But the problem is that a 32 volt drop means there is 32ma of current being drawn by the B+ loads. ... not the 21ma as indicated by the 21volt drop shown on the print.
:
:Now since I actually have 140v B++ ...and [b]if there really was 5,000 ohms[/b] of B+ load... then the total voltage drop across that 1000 ohm resistor would still only be about 23volts.
:
:But the way I'm figuring it all...the fact that I'm actually dropping 32 volts there across that 1000 ohm resistor means the total B+ loads must be way down around 3,375 ohms causing the extra 10ma current draw.
:
:Why is this??
:
:32 ma x 32 volts = 1 watt + ... and double that for safety means I really need a 2 watt resistor now .....not the 1 watter as shown in the print.
:
:So what gives?
:
:The B+ loads that I measured are :
:1.) The oscillator section of the 12SA7
:2.) The plate of the 12SA7
:total = ~17ma
:
:3.) The plate of the 12SK7 = ~16ma
:
:4.) The plate of the 12SQ7 = .2ma
:
:5.) the Screen grid of the 50L6 = 2.3ma
:
:
:Changing out the 12SA7 and 12SK7 made no difference.
:
:All capacitors are NEW
:
:All resistors are in spec.
:
:Are these loads excessive or normal?
:
:If they are normal... I'll need to double the 1000 ohm resistor wattage to 2 watts...
:But that conflicts with the logic of the schematic... right?
:
:I feel something isn't quite right... but can't put my finger on it.
:
:Any ideas?

12/17/2008 4:12:49 PMPeter G. Balazsy

:Hi, Peter:
:I agree with ypu that there is something wrong with the current in your Packard-Bell, and I would not replace the one Watt resistor with a 2 Watt. I am having another shut-in day, we have had a warm front stalled overhead for several days here, the warm temps (71 F. at 11:38 AM EST) are appreciated, but the humidity is opressive.
:
: You say you've replaced C11, but what would happen if you disconnected C11B for a moment and checked the Voltage across R8? Probably a waste of time, but something sneaky like that has consumed a lot of my sanity over the years.
:
: How 'bout pulling the tubes that are on the low side of that resistor and see what happens before the filament cools off.
:
:More later,
:Lewis

Hi Lewis:
I lifted and measured the loads from AFTER the 2nd filter cap.. and the current is 30ma to all the B+ loads

I don't know wht you mean about pulling tubes since they are in series all will go dead.

12/17/2008 6:37:42 PMLewis Linson

::Hi, Peter:
::I agree with ypu that there is something wrong with the current in your Packard-Bell, and I would not replace the one Watt resistor with a 2 Watt. I am having another shut-in day, we have had a warm front stalled overhead for several days here, the warm temps (71 F. at 11:38 AM EST) are appreciated, but the humidity is opressive.
::
:: You say you've replaced C11, but what would happen if you disconnected C11B for a moment and checked the Voltage across R8? Probably a waste of time, but something sneaky like that has consumed a lot of my sanity over the years.
::
:: How 'bout pulling the tubes that are on the low side of that resistor and see what happens before the filament cools off.
::
::More later,
::Lewis
:
:Hi Lewis:
:I lifted and measured the loads from AFTER the 2nd filter cap.. and the current is 30ma to all the B+ loads
:
:I don't know wht you mean about pulling tubes since they are in series all will go dead.
:

12/17/2008 6:41:00 PMLewis Linson

:::Hi, Peter:
:::I agree with ypu that there is something wrong with the current in your Packard-Bell, and I would not replace the one Watt resistor with a 2 Watt. I am having another shut-in day, we have had a warm front stalled overhead for several days here, the warm temps (71 F. at 11:38 AM EST) are appreciated, but the humidity is opressive.
:::
::: You say you've replaced C11, but what would happen if you disconnected C11B for a moment and checked the Voltage across R8? Probably a waste of time, but something sneaky like that has consumed a lot of my sanity over the years.
:::
::: How 'bout pulling the tubes that are on the low side of that resistor and see what happens before the filament cools off.
:::
:::More later,
:::Lewis
::
::Hi Lewis:
::I lifted and measured the loads from AFTER the 2nd filter cap.. and the current is 30ma to all the B+ loads
::
::I don't know wht you mean about pulling tubes since they are in series all will go dead.

You will have a few seconds of normal operation of the tube before the filament begins to cool. I am just thinking weird stuff that most people don't think of, like wrong grid bias, but that wouldn't affect the 35L6, it's plate is before the resistor, but the screen isn't.
Lewis
::

12/17/2008 6:57:45 PMPeter G. Balazsy

FOUND the answer!

Seems it's all caused by the higher line voltage making the filaments hotter causing the tubes to operate more and drawing the extra current.

I used a 12v bucking transformer to drop the 125vAC down to about 115vAC... and then I get 123 volts DC at B++ on the 35Z5 cathode.
Then the 1000 ohm resistor drops only 23vdc.. as it should... with the B+ loads now only drawing 23ma.
That all makes perfect sense now...lol

Whew!
.. I was starting to really scratch my head with this one...lol

12/17/2008 7:04:14 PMLewis Linson

:FOUND the answer!
:
:Seems it's all caused by the higher line voltage making the filaments hotter causing the tubes to operate more and drawing the extra current.
:
:I used a 12v bucking transformer to drop the 125vAC down to about 115vAC... and then I get 123 volts DC at B++ on the 35Z5 cathode.
:Then the 1000 ohm resistor drops only 23vdc.. as it should... with the B+ loads now only drawing 23ma.
:That all makes perfect sense now...lol
:
:Whew!
:.. I was starting to really scratch my head with this one...lol

I was about to ask you if you had a VARIAC, and if so, see what happened at normal line Voltage.
Lewis
:

12/17/2008 11:10:29 PMwasnt that already sugested in a nother forum>?

:FOUND the answer!
:
:Seems it's all caused by the higher line voltage making the filaments hotter causing the tubes to operate more and drawing the extra current.
:
:I used a 12v bucking transformer to drop the 125vAC down to about 115vAC... and then I get 123 volts DC at B++ on the 35Z5 cathode.
:Then the 1000 ohm resistor drops only 23vdc.. as it should... with the B+ loads now only drawing 23ma.
:That all makes perfect sense now...lol
:
:Whew!
:.. I was starting to really scratch my head with this one...lol
:

12/17/2008 11:48:27 PMPeter G. Balazsy

Ummm Yeah .. (that's right ...I also posted question this on ARF).. if you read that then you already know that I took the suggestion offered there.
What's your point?

HOWEVER... update:

As it turns out it seems it is NOT just the filaments running on higher voltage and being hotter causing more current by increased conduction..

I decided to try to isolate exactly where the problem comes from.

So I added a 100 ohm 5watt resistor in the filament string right after the rectifier heaters to drop 15vac. This resistor droped exactly 15vac... bringing the filaments back in line. However the 1000 ohm resistor R8 in the pi filter STILL dropped 32 volts DC.

I even used another 12 volt tube filament instead of the 100 ohm resistor to look more like a 6 tuber.

Anyway.. the variation in the filament voltage did not have any serious effect on the 32volt DC drop on R8.

So the only thing that DID in fact cause it to drop
down to the normal 21vdc... was feeding the AC input with 115vac vs 125vAC.

So I guess somehow the higher B+ is causing the 10ma extra B+ current drain... but i'm not certain I understand exactly how.

12/18/2008 7:51:54 PMZ-

:So I guess somehow the higher B+ is causing the 10ma extra B+ current drain... but i'm not certain I understand exactly how.

There are good books on electronics theory. Many are online, I can supply a few links. A little theory may save a lot of "head scratching".

Syl

12/18/2008 7:48:28 PMZ-

:I used a 12v bucking transformer to drop the 125vAC down to about 115vAC...

I thought you found a "better" way using zeners to lower the AC voltage instead of a bucking transformer? What happened to that "idea"?

Syl

12/18/2008 8:43:07 PMi can see why u arent liked syl. jerk

::I used a 12v bucking transformer to drop the 125vAC down to about 115vAC...
:
:I thought you found a "better" way using zeners to lower the AC voltage instead of a bucking transformer? What happened to that "idea"?
:
:Syl

12/18/2008 9:16:43 PMPeter G. Balazsy

::I used a 12v bucking transformer to drop the 125vAC down to about 115vAC...
:
:I thought you found a "better" way using zeners to lower the AC voltage instead of a bucking transformer? What happened to that "idea"?
:
:Syl

Hey..Why are you asking that Syl?... I just did a quick test..with a bucking transformer.. duh
Why are you being so critical?
What's your point Syl..
....or do you just like to be snoty.. I don't understand your reasons for "jabbing" at people.

Care to explain?

12/18/2008 9:27:05 PMhes been kicked from lots of other sights

:::I used a 12v bucking transformer to drop the 125vAC down to about 115vAC...
::
::I thought you found a "better" way using zeners to lower the AC voltage instead of a bucking transformer? What happened to that "idea"?
::
::Syl
:
:Hey..Why are you asking that Syl?... I just did a quick test..with a bucking transformer.. duh
:Why are you being so critical?
:What's your point Syl..
:....or do you just like to be snoty.. I don't understand your reasons for "jabbing" at people.
:
:Care to explain?
:

12/19/2008 9:00:52 AMZ-

"sights's"?

Is this english?

LOL! No wonder you're posting anonymous.

Syl

12/19/2008 8:56:55 AMZ-

:::I used a 12v bucking transformer to drop the 125vAC down to about 115vAC...
::
::I thought you found a "better" way using zeners to lower the AC voltage instead of a bucking transformer? What happened to that "idea"?
::
::Syl
:
:Hey..Why are you asking that Syl?... I just did a quick test..with a bucking transformer..

Sheesh, who's snotty here?

Why are you so aggressive everytime I ask a question?

I just asked what happened to that "idea" as you did not follow-up in your original thread and answer the few questions that were asked.

Syl

12/18/2008 9:28:36 PMPeter G. Balazsy

Syl:

There are many good books on line about courtesy and diplomacy.
I can help supply some links if you'd like.

12/19/2008 8:58:51 AMZ-

:Syl:
:
:There are many good books on line about courtesy and diplomacy.
:I can help supply some links if you'd like.

Apparently you never read them. Now I see why many think you're a condenscending egotistic person.

Syl

12/19/2008 11:41:21 AMshove you crappy cartridge

rebuilds up your a$$

::Syl:
::
::There are many good books on line about courtesy and diplomacy.
::I can help supply some links if you'd like.
:
:Apparently you never read them. Now I see why many think you're a condenscending egotistic person.
:
:Syl

12/19/2008 11:47:14 AMHuh?

::Syl:
::
::There are many good books on line about courtesy and diplomacy.
::I can help supply some links if you'd like.
:
:Apparently you never read them. Now I see why many think you're a condenscending egotistic person.
:
:Syl

Why go berserk you two? If you perceive an insult, ignore it and it will go away. These little dust ups are just hair-trigger responses to nothing. Lighten up and enjoy life.

12/19/2008 2:58:08 PMZ-

:Why go berserk you two?

Errr...Not me. I ask simple questions and I get snide replies. On the other hand I do enjoy the anonymous retard's replies though.

Syl

12/19/2008 3:23:03 PMLewis Linson

If you ignore these children, they will get tired of being little pests and maybe settle in fot their afetrnoon naps.
Lewis

::Why go berserk you two?
:
:Errr...Not me. I ask simple questions and I get snide replies. On the other hand I do enjoy the anonymous retard's replies though.
:
:Syl

12/19/2008 3:22:59 PMVinny

Greetings,
Gentlemen, in a time when our young soldiers are coming home in pine boxes, family homes are being lost to the "almighty banks" (the banks that we are bailing out), jobs are being lost, children and families are starving and living in cardboard boxes and junk cars in freezing weather. We have a choice to make. It is natural to have personality conflicts with one another, our conflicts are microscopic compared to those mentioned previously and others. I have always learned and reaffirmed over the years that the one who degrades the other in public tells me about themselves, and nothing about the one who is being degraded.
It would be with wisdom, gentlemen like, intelligent and classy to ignore and walk away from any aggression and for any one to reverse their course of aggression. I am still relatively new to this website and in diapers at this hobby; however this website for me has been a great diversion to my personal and working life, it would be sad to see it polluted and torn down. So we should all do our part to preserve it’s dignity in the name of Dr. Lancaster and ourselves. It is wonderful to hear acts of kindness and relevance as one recently posted by Edd as he is helping an older woman with a disease.
So if anyone infiltrates this website with smut they are only telling us about themselves, and revealing their lack of attributes that you guys have.
Vinny

:::Syl:
:::
:::There are many good books on line about courtesy and diplomacy.
:::I can help supply some links if you'd like.
::
::Apparently you never read them. Now I see why many think you're a condenscending egotistic person.
::
::Syl
:
:
:Why go berserk you two? If you perceive an insult, ignore it and it will go away. These little dust ups are just hair-trigger responses to nothing. Lighten up and enjoy life.

12/19/2008 4:00:14 PMLewis Linson

Vinny, ny friend, I couldn't agree with you more. I am here to learn and to help (if I can), and enjoy.
I enjoy helping people, and I have been helped, and I enjoy working with people like the most of us. I have no desire to get into a Pixxing match, but we have some fun picking at each other. I hate to see a few doo doos ruining it for the rest of us.
Lewis

:Greetings,
:Gentlemen, in a time when our young soldiers are coming home in pine boxes, family homes are being lost to the "almighty banks" (the banks that we are bailing out), jobs are being lost, children and families are starving and living in cardboard boxes and junk cars in freezing weather. We have a choice to make. It is natural to have personality conflicts with one another, our conflicts are microscopic compared to those mentioned previously and others. I have always learned and reaffirmed over the years that the one who degrades the other in public tells me about themselves, and nothing about the one who is being degraded.
:It would be with wisdom, gentlemen like, intelligent and classy to ignore and walk away from any aggression and for any one to reverse their course of aggression. I am still relatively new to this website and in diapers at this hobby; however this website for me has been a great diversion to my personal and working life, it would be sad to see it polluted and torn down. So we should all do our part to preserve it’s dignity in the name of Dr. Lancaster and ourselves. It is wonderful to hear acts of kindness and relevance as one recently posted by Edd as he is helping an older woman with a disease.
:So if anyone infiltrates this website with smut they are only telling us about themselves, and revealing their lack of attributes that you guys have.
:Vinny
:
:
:
:
::::Syl:
::::
::::There are many good books on line about courtesy and diplomacy.
::::I can help supply some links if you'd like.
:::
:::Apparently you never read them. Now I see why many think you're a condenscending egotistic person.
:::
:::Syl
::
::
::Why go berserk you two? If you perceive an insult, ignore it and it will go away. These little dust ups are just hair-trigger responses to nothing. Lighten up and enjoy life.

12/17/2008 10:29:20 PMDan

Hi Peter
Check to see if the utility voltage at your main is way out of phase in relation of voltage to current

:I'm working on this little ole' Packard Bell 100a.
:http://www.nostalgiaair.org/Resources/842/M0012842.htm
:
:I'm having trouble trying to determine if the B+ loads are correct or not.
:
:You'll notice that the B++ coming off the rectifier is shown as +126vdc and this goes to the 50L6 plate via the output transformer where it ends up at +120Vdc.
:
:The rest of the B+ after the second section of the pi filter is shown at +105vdc.
:
:That means there is a 21 volt drop across R8 the 1000 ohm 1-watt resistor shown in between the two filter caps.... right?
:
:Ok... well doing the simple ohms law math 21 volts divided by 1000 ohms = 21ma of current.... right?
:
:and 105 volts B+ at drawing 21ma means the B+ loads must be around 5000 ohms total... right?
:105v/.021a = ~5000 ohms... right?
:
:And to determine the proper wattage of that 1000 ohm resistor P=IxE
:
:21v x .021a = .441 watts.. and double that for safety .88watts ...means a 1 watt resistor will be just fine... right?
:
:Okay... so far so good.
:
:But I noticed that my 1000 ohm 1 watt resistor was excessively hot.
:
:So I decided to make some measurements and see why.
:
:Well this led to my current question:
:... Is there truly any excessive current or is it really normal?
:
:
:Here's what I found:
:
:I have typically slightly higher AC line voltage (125vac) resulting in greater B+ ... okay ....but I can't see that making such a difference.
:
:I actually have 140vDC (B++) at the cathode of the 35Z5 and 108 volts DC on the other side of that 1000 ohm resistor.
:That is a 32 volt drop. ( TEN 10 volts [i]higher[/i] than shown on the print)
:I checked the resistor ( precision = 1000 ohms).. so that's fine.
:
:But the problem is that a 32 volt drop means there is 32ma of current being drawn by the B+ loads. ... not the 21ma as indicated by the 21volt drop shown on the print.
:
:Now since I actually have 140v B++ ...and [b]if there really was 5,000 ohms[/b] of B+ load... then the total voltage drop across that 1000 ohm resistor would still only be about 23volts.
:
:But the way I'm figuring it all...the fact that I'm actually dropping 32 volts there across that 1000 ohm resistor means the total B+ loads must be way down around 3,375 ohms causing the extra 10ma current draw.
:
:Why is this??
:
:32 ma x 32 volts = 1 watt + ... and double that for safety means I really need a 2 watt resistor now .....not the 1 watter as shown in the print.
:
:So what gives?
:
:The B+ loads that I measured are :
:1.) The oscillator section of the 12SA7
:2.) The plate of the 12SA7
:total = ~17ma
:
:3.) The plate of the 12SK7 = ~16ma
:
:4.) The plate of the 12SQ7 = .2ma
:
:5.) the Screen grid of the 50L6 = 2.3ma
:
:
:Changing out the 12SA7 and 12SK7 made no difference.
:
:All capacitors are NEW
:
:All resistors are in spec.
:
:Are these loads excessive or normal?
:
:If they are normal... I'll need to double the 1000 ohm resistor wattage to 2 watts...
:But that conflicts with the logic of the schematic... right?
:
:I feel something isn't quite right... but can't put my finger on it.
:
:Any ideas?

12/18/2008 1:31:42 AMPeter G. Balazsy

:Hi Peter
: Check to see if the utility voltage at your main is way out of phase in relation of voltage to current
:

but how do I test that?
...lol

12/19/2008 3:18:56 PMLewis Linson

::Hi Peter
:: Check to see if the utility voltage at your main is way out of phase in relation of voltage to current
::
:
: but how do I test that?
:...lol

My thinking would be that a phase angle would give you a lower actual E and I, resulting in a lower heating of the filaments, or lower actual Wattage; I think you might be barking at the wrong aquirrel here.

But, about those Zener diodes: do you think maybe the distorted input waveform might cause RFI on weak signals? After all, you are distorting a 125 Volt waveform, maybe a lot of harmonics??
Lewis