Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Colas LeGrippa on November 22, 2020, 07:11:49 pm
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Hi my friends!
I plan to build a high gain amplifier (another one hey hey ) with DC heaters. The power supply is already designed as it is not the first nor the 2 nd time I do that. The difference this time is that I want to elevate the ground ref. to 50-70 v.
Oops the door bell is ringing I ll be rigjt back
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OMG ! You won't believe this !!!! Linda my neighbour was ringing my door bell completely naked, (that's no lie I swear to God ) , trying to hide her breasts and p......the best she could while I was trying to look into her eyes and figure out where was my wife Nancy. The spring hinges of her front door had shut it up while she was picking up her shoes on her welcome mat.
Then I threw her my winter coat so she could get dressed the time she crosses my apt. to the back door sharing the same balcony as her own backdoor, luckily unlocked. Once in her apt, I tried to calm me down ( you know how I can get nervous sometimes don t you ? ) and when Nancy got out of the bath she realized I was very excited......."you're lovely , Jacques" You too, my darling.... Now I have to get back my winter coat......
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GEE MY HEATERS POST !!!!
....ok so I want to elevate my DC heaters gnd ref.
12.1 V at pin 4 or 5
70 V at pin 5 or 4.....
That makes no sense to me !
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You will need to float your 12.6v heater supply. This means none of it can be connected to chassis ground. Now connect the 12V positive and negative leads to pins 4 and 5. Wire all your 12A?7 tubes together but pin 9 will have no connection to anything. Tubes should light up and be functional. You should be able to measure 12V ***BETWEEN*** pins 4 and 5 but there should be no voltage between pins 4 or 5 and chassis ground.
Now, use a couple resistors to form a voltage divider on one of your B+ nodes. Experiment to get the elevator voltage you want. When you have it right, connect a wire from the junction of the voltage divider resistors to pin 9 of one of the 12A?7 tubes. This should "elevate" all the 12A?7 tube filaments you have wired together..
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So I don't have to connect all pins no 9 to the voltage divider in order to elevate all the heaters ?
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> I don't have to connect all pins no 9 to the voltage divider in order to elevate all the heaters ?
They are tied-together like ladies undergarments on a clothes-line. You can elevate the clothes-line pulleys from the 1st floor to the 10th floor balconies and all the clothes will elevate together.
> none of it can be connected to chassis ground.
Right: none of the undershorts can be hooked to the picnic table. Something will rip.
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It s obvius for me to keep the clothes line floating if not the pic nic table will be destroyed
Under garments or no garments at all, I prefer to see the reality. Naked.
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When wiring my dc regulated supply, I always end up with 12.1 volts, because of the12v voltage regulator. Always worked fine BUT how can we get 12.6 V ? I use 4,700 uF in and out, the middle pin of rhe reg. tied to gnd with a common diode like the 4007.
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Which reg chip?
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Colas
Did you get your winter coat back? :laugh:
Back on topic I have used both of the following schematics very successfully. The LM317T is my preferred because you can adj you Heater voltage accurately and the regulation specs for LM317T are tighter. Extra Diodes are an overkill, but I'm paying for them :icon_biggrin:
Be aware of Regulator's maximum limits for current and avoid excessive input voltage. Good starting point is Raw DC input 3V above desired output as dissipation with heater currents can get away on you. I have often just put DC heater on V1, unless it is a critical piece of test gear.
Trust this helps
Kind regards
Mirek
Forgot to mention: I find modern manufactured fixed regulator voltages a little sloppy, +/-0.2V is not uncommon. Should be +/-0.05V :icon_biggrin:
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Sluckey: the voltage regulator part of the heaters regulated power supply
Glass54: yes I did get it back, with a large smile
In bonus, Thanx for schematics
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Sluckey: the voltage regulator part of the heaters regulated power supply
Yes, I believe that is correct. Now tell me which number it is? IE, 7812, LM317, etc.
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Oops sorry buddy, I misunderstood your question ! I was the one lost, not you !!!! :l2:
7812.
. But they re so cheap, I can get whichever
is better
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The 7812 is a fixed output VR chip, ie, the output is 12V ***IF*** the reference pin is connected to ground (0V), as is normally the case. But if you connect the reference pin to let's say 2V, the output will now be 14V. Or, if we connect the reference pin to 0.6V, the output will now be 12.6V.
Here's a simple mod that allows you to adjust the 7812 output from 12V to about 14V. Use a 10-turn trimmer pot if you need precision. Or, replace the pot with a 1N4007 diode for a fixed output of 12.6V (may actually be 12.7V).
I suggest you get the filament voltage set as you like ***BEFORE*** messing with elevation. And remember, none of this regulator circuit can touch chassis ground if you elevate.
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Hola, southern man .
The only thing I don t get :BangHead: is the pin no.9.
I know there s an inside connexion between 4-5 and 9 for the filaments to light. But all the pins 9 have to be tied together if I want to elevate all the heaters no ? Like PRR analogy with the pulleys and clothes line... I know I m dumb but you have to deal with it :laugh:
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....I find modern manufactured fixed regulator voltages a little sloppy, +/-0.2V is not uncommon. Should be +/-0.05V
I've never been promised such tight spec on LM78xx types. 4% to 5%.
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Another reason for low output voltage is low input voltage. Colas, what are you putting IN to the regulator?
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The only thing I don t get :BangHead: is the pin no.9.
I know there s an inside connexion between 4-5 and 9 for the filaments to light. But all the pins 9 have to be tied together if I want to elevate all the heaters no ?
It'll be OK buddy. You don't have to get it. Just do it. :icon_biggrin:
OK, a little more info. Try this. You have other amps that are wired for 12VDC heaters? So, that means you applied 12V to pins 4 and 5 and strung several tubes together. Pin 9 was connected to nothing. Use your ohm meter to check resistance between pin 9 of one tube and pin 9 of any other tube. You will measure some low resistance.
So, how can that be? None of the pin 9s are connected to anything? It can be because pin 9 connects to pins 4 and 5 ***INSIDE*** every tube. And you have pins 4 and 5 connected to pins 4 and 5 of every tube. Think about this for a moment. It will make sense.
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i'm saving my 1,000 words for later :icon_biggrin:
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Let's say there are only three pairs of panties on the clothesline and they are right in the middle of a saggy line. You get up on the picnic table, grab the middle pair by the crotch and lift them up in the air. What do you think is going to happen? The neighbor lady's husband is going to blacken both your eyes because your wife has an electric dryer. Also, the other two pairs of panties are going to move up in the air along with the middle pair.
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OMG I don t want that happen !
Her husband weoghs at least 300 pounds, full of tattoos in his arms chest neck and front, he owns many HD motorcycles and always carries a magnum357 ( or is it a 45 ? ). One thing is sure:
according to what I ve seen last night, his wife has got a pair of 45 herself , which are as dangerous weapons ....but much more fun to play with....I guess :laugh:
PRR: 16 VOLTS to the input of the 7812
Sluckey: got it right this time amigo
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I knew you could. Just had to clear your mind of tits and ass. :l2:
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Yeah it gets me confused.....
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Colas
Just be aware you may need a heatsink on your 3Terminal Reg, eg 3Volt drop at 300mA (2 tubes)=0.9Watts. Doesn't sound like much but put your finger on the metal tab :icon_biggrin: Heatsink MUST NOT touch chassis/Ground as Sluckey advised.
PRR
I dream and live in hope (maybe just delusional :laugh:)
I like my regulators very close to the nominated (designed) voltage. Important in calibration equipment and thus my preference for LM317T and 337T. You also get potentially better regulation and lower noise-floor but requires extra component and cermet trimmer.
Just attaching a snapshot from OnSemi 78xx offering 3 different tolerances.
Kind Regards
Mirek
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Got to learn how to elevate heater voltages and a dose of "Penthouse Forum" In one thread!
:laugh:
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Yeah it s the 2 for 1 monthly special !
Check out my next thread !
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Glass 54, I ll definitely need a heat sink since 4tubes will have their heaters DC powered. Of course this circuit will have to be isolated from the rest of the amp. Thanks for image.
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curiosity;
is this a problem looking for a solution, or a solution looking for a problem :dontknow:
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You re too much curious
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You know how it is Shooter, you start asking a simple question and when people reads the word "naked" in a post, they start answering non related questions just to hang around , waiting desperately ( good word ??) to see a pic ofmy neighbour Linda, naked..
:laugh:
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Stay focused! If you ever finish this heater mod you can call it the Colas ICATT mod.
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...Just shows you the serious side effects of Covid 19 :laugh: :laugh:
But on a serious note, its an opportunity to see how our colleagues do things and possibly learn something new.
Just want to say thank you to all, as isolation with this forum has certainly been helpful and occasionally stimulating (man opening door, naked lady in distress standing in doorway :think1: and thus the elevated heater problem)
Kind regards
Mirek
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It would be funnier if you'd explain ICATT
But LEMME GUESS : Icatt get no satisfaction ?
Icatt on top of a tree ?
Icatt erpillar in a field ?
Or: I Caught A Traynor Transformer,
....my english is not good enough to keep on going... :dontknow:
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people reads the word "naked"
I spent 39yrs in the hospitals, naked doesn't even faze me :icon_biggrin:
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It would be funnier if you'd explain ICATT
Don't overthink this. Just spell it out slowly. Repeat until you get it. :l2:
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SHOOTER : :worthy1:
Sluckey : I tried, I tried, but all I could get is :
I see a t t...
Teetee for me has no signification :w2:
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Poor Colas. You're gonna need your neighbor to help. But turn it around a bit. Ask her to look down her shirt and spell "attic".
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I already asked her, she s willing to let me do it w!hen her bouncer is out with his gang. Thanks for the suggestion. Hoping there s no spiders in the attic....
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:laugh:
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Maybe it was the other Colas mod?
IC2TT's ? :laugh: :laugh: