andyfromdenver

please critique my regulated tube heater circuit
« on: December 12, 2016, 03:10:19 PM »
Hi solder-slingers.

Data: using a 115V barely loaded PT for the 6N1P tube Bass DI.
wall voltage ~121VAC
Single tube drawing ~300mA Heater current.  *edit: actual stated draw is 600mA +/-*

Plan: rectify 6.3VAC PT secondary (which is actually closer to 7. somethin' V due to see above).
feed 7805 (1A) with two diodes in series from center pin, raising the regulated voltage to obtain 6.4VDC


Questions: if I am using a large uf cap post bridge, do I still need the 0.3uf on the in from the datasheet, and do I need more than the datasheet 0.1uf on the out?

The PT has no heater center tap, if i exclude the chassis ground after the rectifier, will it work but hum? 

assuming need, where do you like to ground on tube circuits post rectifier? ground the tube pin and circuit, and  just run one wire to the other tube pin?  or ground at the circuit to chassis and still run two wires to pins?

Lastly, what would you do to improve this design? 

Bonus: need I worry about adding heat dissipation to my 7805 running less than a third of it's rating?
Bonus 2: should I fuse it pre bridge rectifier? 1A sloblo? 500mA sloblo?

Thank you!

Andy

« Last Edit: December 12, 2016, 06:07:25 PM by andyfromdenver »
my la2a scratch build: https://groupdiy.com/index.php?topic=65716.0
my orig tube DI w/ EQ build: https://groupdiy.com/index.php?topic=73834.0
2020 fav artist: Kate Bush


andyfromdenver

Re: please critique my regulated tube heater circuit
« Reply #1 on: December 12, 2016, 03:12:08 PM »
working test circuit is as shown in above scheme, with readings marked in above scheme.
my la2a scratch build: https://groupdiy.com/index.php?topic=65716.0
my orig tube DI w/ EQ build: https://groupdiy.com/index.php?topic=73834.0
2020 fav artist: Kate Bush

ruffrecords

Re: please critique my regulated tube heater circuit
« Reply #2 on: December 12, 2016, 04:38:40 PM »
Hi solder-slingers.

Data: using a 115V barely loaded PT for the 6N1P tube Bass DI.
wall voltage ~121VAC
Single tube drawing ~300mA Heater current.

Plan: rectify 6.3VAC PT secondary (which is actually closer to 7. somethin' V due to see above).
feed 7805 (1A) with two diodes in series from center pin, raising the regulated voltage to obtain 6.4VDC


Questions: if I am using a large uf cap post bridge, do I still need the 0.3uf on the in from the datasheet, and do I need more than the datasheet 0.1uf on the out?
You won't need any more. Just follow the datasheet
Quote
The PT has no heater center tap, if i exclude the chassis ground after the rectifier, will it work but hum? 
You don't need a centre tap with a bridge rectifier. The -ve of the smoothing cap goes to signal 0V.
Quote
assuming need, where do you like to ground on tube circuits post rectifier? ground the tube pin and circuit, and  just run one wire to the other tube pin?  or ground at the circuit to chassis and still run two wires to pins?
Check out my grounding 101.pdf document in the power folder of the DIY tab of my web site for how to connect chassis, signal 0V and safety earth:

http://www.customtubeconsoles.com/diy
Quote
Lastly, what would you do to improve this design? 
Use a 7806.
Quote
Bonus: need I worry about adding heat dissipation to my 7805 running less than a third of it's rating?
Bonus 2: should I fuse it pre bridge rectifier? 1A sloblo? 500mA sloblo?

Thank you!

Andy

 Thermal resistance junction to ambient is 65 degrees C per watt for a 7805.  7805 needs at least 2 volts across it to regulate.  With a load of 0.3A the dissipation will be a t least 2 x 0.3 = 0.6W . Temperature rise is therefore 0.6 x 65 = 39 degrees C so tab temperature is ambient (25) +39 =  64 degrees C which is hot but within the ratings.

Question is, do you have 2V needed to regulate? 7VAC is 9.9V peak. Allowing 1.3V drop in the rectifiers means you may have 8.6V peak into the 7805. Load current is 0.3A and rectifier cap is 3300uF so 120Hz ripple (from CV = it) is 0.76V pp  Minimum volts across regulator is therefore 8.6 - 0.76 - 6.4 = 1.44 so you do not have enough volts to regulate.

If you want to use this transformer you need to use a low dropout regulator

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

andyfromdenver

Re: please critique my regulated tube heater circuit
« Reply #3 on: December 12, 2016, 06:06:37 PM »
Ian, thank you so much for your time and the analysis.

I pulled the 300mA Heater current draw from some dark incorrect corner of my memory  ;D.  the data sheet sez 600mA +/-, I can plug that into your calculations.  Does that warrant something more substantial than 1n4007s? 

Would this item from mouser be a more elegant solution, w/ the given info on the Power Transformer (an older Hammond 269EX w/ 115V option only)?
http://www.mouser.com/ProductDetail/ROHM-Semiconductor/BA60BC0T/?qs=sGAEpiMZZMsGz1a6aV8DcBWz2LI05ySJNZ9Pab1TR00%3d

also, I was thinking if I didn't need the voltage boosting diodes on the 7805, I could ground the TO220 case to the chassis? is that a good solution?  I know you stated a chassis ground is not needed (if that was my correct understanding).  i have perused your grounding file before, I think, and will again this evening :-)

Three cheers!
Andy
my la2a scratch build: https://groupdiy.com/index.php?topic=65716.0
my orig tube DI w/ EQ build: https://groupdiy.com/index.php?topic=73834.0
2020 fav artist: Kate Bush

ruffrecords

Re: please critique my regulated tube heater circuit
« Reply #4 on: December 13, 2016, 02:04:56 AM »
Ian, thank you so much for your time and the analysis.

I pulled the 300mA Heater current draw from some dark incorrect corner of my memory  ;D.  the data sheet sez 600mA +/-, I can plug that into your calculations.  Does that warrant something more substantial than 1n4007s? 
They might be marginal. Probably worth looking for a standard 3amp bridge rectifier device.
Quote
Would this item from mouser be a more elegant solution, w/ the given info on the Power Transformer (an older Hammond 269EX w/ 115V option only)?
http://www.mouser.com/ProductDetail/ROHM-Semiconductor/BA60BC0T/?qs=sGAEpiMZZMsGz1a6aV8DcBWz2LI05ySJNZ9Pab1TR00%3d
Yes, that looks a better choice. Minimum regulation voltage drop is 0.5V.
Quote
also, I was thinking if I didn't need the voltage boosting diodes on the 7805, I could ground the TO220 case to the chassis? is that a good solution?  I know you stated a chassis ground is not needed (if that was my correct understanding).  i have perused your grounding file before, I think, and will again this evening :-)

Three cheers!
Andy
With 600mA current you will definitely need to heatsink the regulator. You can use the chassis for this even if the tab is not at chassis potential. You can buy an insulating kit for TO220 devices that consists of a mica spacer and a small plastic insulating washer that fits into the TO220 hole. With the addition of a little thermal paste, this allows you to make a thermal connection to the chassis but also to insulate it electrically. You should do this anyway so that you can control the point at which heater 0V, HT 0V , chassis and safety earth get connected together.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

andyfromdenver

Re: please critique my regulated tube heater circuit
« Reply #5 on: December 13, 2016, 08:36:28 AM »
noted all around Ian!

side note, how do you/ folks feel about 5.7v tube heaters? I couuuuuld plod ahead with the initial plan and use only a single diode, to buy my 2V over regulation.

I have some 3A 1kV diodes, and the parts to isolate the regulator tab. and some wings too.

I think a better option is to take stock of some needed supplies and make a big mouser order, though.


Also, another super smart friend has been detailing the bias conditions and paralleled vs individual cathodes, for CJs 6N1P schematic. he has some thoughts that I may implement given my PT choice option for a higher than 170 supply voltage, I asked him if I could copy and paste our emailing, and may do so with his permission.

tbc!!!

I really appreciate your thoughts and input! 1,000 kudos to you!

Andy
« Last Edit: December 19, 2016, 08:54:46 AM by andyfromdenver »
my la2a scratch build: https://groupdiy.com/index.php?topic=65716.0
my orig tube DI w/ EQ build: https://groupdiy.com/index.php?topic=73834.0
2020 fav artist: Kate Bush

ruffrecords

Re: please critique my regulated tube heater circuit
« Reply #6 on: December 13, 2016, 12:51:12 PM »
noted all around Ian!

side note, how do you/ folks feel about 5.7v tube heaters? I couuuuuld plod ahead with the initial plan and use only a single diode, to buy my 2V over regulation.

The idea of dc heaters is to reduce (to zero) the ac voltage across the heaters. A regular 6.3VAC heater voltage is 17.8V rms. If you just rectify and smooth the heater voltage (no regulation) you significantly reduce this value. With your 3300uF capacitor and a 0.6A load, the peak to peak 120Hz ripple is 1.5V which is 21dB lower than the original ac. Just a thought. The ancients actually used this technique in some broadcast mixers.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

andyfromdenver

Re: please critique my regulated tube heater circuit
« Reply #7 on: December 13, 2016, 02:23:07 PM »
Thank you!!!

side note, I have really been enjoying your tube mixer blog. I'm very grateful for your input. 
my la2a scratch build: https://groupdiy.com/index.php?topic=65716.0
my orig tube DI w/ EQ build: https://groupdiy.com/index.php?topic=73834.0
2020 fav artist: Kate Bush

Re: please critique my regulated tube heater circuit
« Reply #8 on: December 13, 2016, 04:44:07 PM »
Might be enough or not, but you can squeeze half a V more from the bridge with schottky diodes. 

ruffrecords

Re: please critique my regulated tube heater circuit
« Reply #9 on: December 13, 2016, 04:53:40 PM »
Thank you!!!

side note, I have really been enjoying your tube mixer blog. I'm very grateful for your input.

No Problem. I see you are from Denver. I am a big fan of the Denver football team ever since John Elway was quarterback. It was great to see them win the Super Bowl last year.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'


trobbins

Re: please critique my regulated tube heater circuit
« Reply #10 on: December 13, 2016, 07:41:15 PM »
Did you try just using an AC heater, with due care for layout and valve socket with centre spigot and extra screening if needed.   Your B+ may like you for that, especially if you take care with rectifying it.

andyfromdenver

Re: please critique my regulated tube heater circuit
« Reply #11 on: December 13, 2016, 10:24:39 PM »
I'm a fan of AC heaters and good layout.
I got several Hammond 269exs free from a friend.
some have the 125V primary hook up option which gets me ~6.7 for this project.
some only have the 115, that heater voltage is too high.

the rent is too damn high  ::)


@Ian, i'm such a fairweather am football fan, haha!  I did enjoy a win for the city though :-). lots of the mary juana was wafting through the air that night i'm sure  :o
I've been in Athens Georgia for the longest now, the never never land of broke musicians. it's great!
my la2a scratch build: https://groupdiy.com/index.php?topic=65716.0
my orig tube DI w/ EQ build: https://groupdiy.com/index.php?topic=73834.0
2020 fav artist: Kate Bush

trobbins

Re: please critique my regulated tube heater circuit
« Reply #12 on: December 13, 2016, 11:05:12 PM »
I'm a fan of AC heaters and good layout.
I got several Hammond 269exs free from a friend.
some have the 125V primary hook up option which gets me ~6.7 for this project.
some only have the 115, that heater voltage is too high.

First post indicates +5% mains voltage (121V) being applied to rated transformer primary gives 'too high' a heater voltage on a 6.3V 2.5A rated winding.  Your last post indicates -3% mains voltage (121V) applied to 125V tap gives 6.7V heater.

Perhaps you should load the heaters for rated current and retest, and then remove load and put on your applications heater load and retest.  6.3V +10% = 6.93V.  Is your meter reasonably accurate for those voltage measurements?  You will always run in to some mains voltage variation.  It just seems like a huge effort, and risk, to bypass the simplest heater power configuration.  Even the thought of dumbing the heater voltage down a titch with a power resistor seems so simple compared to your proposed path.

PRR

Re: please critique my regulated tube heater circuit
« Reply #13 on: December 13, 2016, 11:19:33 PM »
> You will always run in to some mains voltage variation.

I just found an IEEE voltage drop budget. Class A (lamps, all residential work) should be inside 127V and 108V. The budget apportions this to pole transformer, service wires, and circuit wires, but at the wall outlet you only need to account for possible 127V-108V range. You do not (generally) know what other loads may be on the system. While my last house was pretty solid 121V-117V, this house will go 125V much of the day, 117V in evening,  and 109V when laundry is run (electric water heat and dryer).

EmRR

Re: please critique my regulated tube heater circuit
« Reply #14 on: December 13, 2016, 11:40:41 PM »
 I'll add that a pair of low ohm power resistors in series will drop a bit of AC nicely.   It's a given that a higher current rating in the transformer than is drawn will yield a higher voltage. 
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

andyfromdenver

Re: please critique my regulated tube heater circuit
« Reply #15 on: December 14, 2016, 01:04:54 PM »
Awesome,  Thanks everyone for the input :-) 
just ordered some ldo 6v regulators and a few values of resistors in range to drop a little V.  we'll see.  I've not used resistors to drop V on heaters before, largely cause the tube amp repair guy I apprenticed with, way back, wasn't a fan.  However,  that doesn't mean it's not a viable solution.   I am a fan of simple and elegant, so Trobbins  (sorry if you prefer a different means of address) and Doug, I can appreciate what you advise.
« Last Edit: December 14, 2016, 01:11:56 PM by andyfromdenver »
my la2a scratch build: https://groupdiy.com/index.php?topic=65716.0
my orig tube DI w/ EQ build: https://groupdiy.com/index.php?topic=73834.0
2020 fav artist: Kate Bush

EmRR

Re: please critique my regulated tube heater circuit
« Reply #16 on: December 14, 2016, 01:21:00 PM »
10 parts versus 2, so 5x as many, same multiplier for failure points. 

Sometimes it's worth it, but here we're talking about a very low gain amp, so it's hardly a sonic consideration.  As I always say, I make records for clients running an army of vintage tube preamps with AC filament, no hum problems. 

DIY, any (well most) experiment is worthy as a learning point.  Good luck with it.
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

andyfromdenver

Re: please critique my regulated tube heater circuit
« Reply #17 on: December 14, 2016, 02:50:03 PM »
Thanks Doug!  This is the fourth of the now legendary (lol) 6N1P tube di, with CJs custom fat azz iron.  The other three are all AC heaters and sound superb, completely undetectable noise floor at working levels, they all got snatched up by friends.  This last one is staying at my lil home studio, so I feel better about getting a little more experimental w/ the circuit.  I've only done one other regulator circuit, a multi voltage, bipolar output box for some opamp and synthesizer circuit experiments.  I like to make little handwired eyelet boards and junk and try to make it look purty...  :o ;D

side note: thank you for listening... ::)
my la2a scratch build: https://groupdiy.com/index.php?topic=65716.0
my orig tube DI w/ EQ build: https://groupdiy.com/index.php?topic=73834.0
2020 fav artist: Kate Bush

EmRR

Re: please critique my regulated tube heater circuit
« Reply #18 on: December 14, 2016, 03:01:30 PM »
Gotcha!
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

CJ

Re: please critique my regulated tube heater circuit
« Reply #19 on: December 16, 2016, 04:59:18 AM »
here is a link to heater circuits>

https://groupdiy.com/index.php?topic=57166.msg728663#msg728663

ditch the regulators unless you like replacing them once a year.

tubes have their own voltage regulators built in them anyway,

this is done by choosing the right steel for the heaters,

you could probably get away with 1N400x diodes for a single 6N1P

Peavey does it in their Valveking,   four 6L6 tubes in series, 25 volts at 0.9 amps,

this means the tubes have to match up somewhat as far as individual heater current/voltage/temp

a 3 amp heat sinkable bridge sounds better as mentioned before,

maybe offer info on the current Reddi on a less public format (ie: PM) so we do not put people out on the street or get the GroupDIY folks in trouble, nothing wrong with blogging out a 1940's preamp, eh?
can't believe i said that, must be getting old,   :D

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html