First go at submini tubes

[mnordbye]

I've bought some old 5977 sub mini tubes a while ago, and finally got around to try them out. I wanted to try them in a Marsha Valve type circuit http://www.aronnelson.com/gallery/main.php/v/vanhansen/marshavalve1_1.gif.html , but i've had no luck yet. Can't get a single sound out of it, so i wonder if i've connected the tube wrong.

The Marsha Valve schematic i linked is the FET version, but i tried using the Tube-to-FET conversion method over at RunOffGroove.com, to adjust the schematic to suit the tube. Can any give me an advise on this?

The datasheet for the tubes: http://frank.pocnet.net/sheets/137/5/5977.pdf

And one more thing. The heaters, should i connect them or not?

EDIT: Forgot to mention, these tubes are supposed to be similiar to the 6AK4 tubes.

[biggy boy]

Hi
The heaters need to be powered up for the tube to work, If that is what you are asking?

Glen

[biggy boy]

 


Looks like the heaters need 6 volts.

[mnordbye]

Yeah, the heaters need 6,3V for the tube to work, i tried that. Maybe i overlooked something, i'll try again.

[mnordbye]

Oh, and by the way. I'm using a 9V adapter, what is the best way of getting 6,3V to the heaters?

Would it be easier/better to use 12V?

[frequencycentral]

Hey Magnus, how are you deriving the 6.3v / 150ma for the heater? I would say pin 3 should be heater +ve and pin 6 should be heater ground. Pin 8 equates to drain in the Marsha circuit , pin 5 equates to source, and pin 1 equates to gate. Note that the tube pinout on the datasheet is looking at the tube from below. Why don't you post some voltages?

Oh, and by the way. I'm using a 9V adapter, what is the best way of getting 6,3V to the heaters?

Would it be easier/better to use 12V?

12v will give you more gain than 9v.

There are a number of ways to get the heater supply.

1. Use a 7806
2. Use a LM317 and a few resistors as in the Subcaster
3. Use a series resistor between your power source and the heater +ve pin.
4. Use some high current diodes in series between the power source and the heater +ve pin.

Series resistor:

From 9v supply: 18 ohm  1/2 watt
From 12v supply: 38 ohm  1 watt

Diodes:

Each diode drops 0.7v, so four would drop 2.8v for a 9v supply, and eight would drop 5.4v for a 12v supply.

............or you could use a 12v supply and just run two tube heaters in series:

+ve to tube 1 pin 3,
tube 1 pin 6 to tube 2 pin 3,
tube 2 pin 6 to ground.

[mnordbye]

Thanks Freq! I'll try all of those out.

[frequencycentral]

Thanks Freq! I'll try all of those out.

No problem. My fave way is using two heaters in series. Next fave is the series resistor way. Never tried the diode way, but it should work according to Valve Wizard. LM317 way uses too many components for my liking. 7806 is a neat solution, again never used that way, but some forum memeber have.

Check the link: http://www.freewebs.com/valvewizard/heater.html

[mnordbye]

A question. By using to heaters in series, how do you connect them?

Also, measured the Pin 3 heater now with a 22ohm resistor (didn't have 18), and it reads approx. 2 volts. The other heater is connected to ground. No sound still, so i wonder, at which voltage should i bias the Drain/Plate? It's at 4,5V now, and i'm using a trimpot for that.

[frequencycentral]

A question. By using to heaters in series, how do you connect them?

+12v to tube 1 pin 3;  tube 1 pin 6 to tube 2 pin 3;  tube 2 pin 6 to ground.

Also, measured the Pin 3 heater now with a 22ohm resistor (didn't have 18), and it reads approx. 2 volts. The other heater is connected to ground.

From what supply voltage? I think I got my math right........!?

No sound still, so i wonder, at which voltage should i bias the Drain/Plate? It's at 4,5V now, and i'm using a trimpot for that.

Once you have the heater sorted, tweak the trimpot until you get maximum gain and replace it with a fixed resistor. I would try 100K and 220K fixed resistors too.

[mnordbye]

A question. By using to heaters in series, how do you connect them?

+12v to tube 1 pin 3;  tube 1 pin 6 to tube 2 pin 3;  tube 2 pin 6 to ground.

Also, measured the Pin 3 heater now with a 22ohm resistor (didn't have 18), and it reads approx. 2 volts. The other heater is connected to ground.

From what supply voltage? I think I got my math right........!?

No sound still, so i wonder, at which voltage should i bias the Drain/Plate? It's at 4,5V now, and i'm using a trimpot for that.

Once you have the heater sorted, tweak the trimpot until you get maximum gain and replace it with a fixed resistor. I would try 100K and 220K fixed resistors too.

Okay, so if i was using 2 tubes, i could go with heaters in series, i see.

I'm still using the 9V adapter, i'm using that until i get it going.

Okay, i'll try the resistors after the heaters are up and running.

[frequencycentral]

Okay, so if i was using 2 tubes, i could go with heaters in series, i see.

I'm still using the 9V adapter, i'm using that until i get it going.

You need to be running at 12v to use two heaters in series. 

[mnordbye]

Okay, so if i was using 2 tubes, i could go with heaters in series, i see.

I'm still using the 9V adapter, i'm using that until i get it going.

You need to be running at 12v to use two heaters in series. 

Ahh, the dividing thing. Forgot about that. 

[mnordbye]

No luck yet, tried one of the other tubes too. A few observations though.

When i connect the second heater, the ground heater, to ground, i notice a drop in voltage from the adapter. It's not 9,18 anymore, which it usually is, it's slightly over 2 volts! When i disconnect the second heater again (pin 6, seen from the bottom), it jumps back to 9,18V. Why is this happening? Can it be that the tube must be read from above instead?

One other thing, will the tube light up when the heaters are connected?

Also, this is the first time that i find troubleshooting interesting. Almost like i don't want it to work just yet. I need sleep...

[frequencycentral]

The two series heaters really need to be powered from 12v not 9v. This will provide 6v to each heater. If you run them both off 9v neither heater will get what it needs. 

Just out of interest, what ma is your power supply rated at?

The heaters should glow a nice orange when powered. The tubes should also be warm to the touch.

Here's a diagram of how the two heaters should be connected, ignore the 6111 bit:

[mnordbye]

I'm not using the heaters-in-series methos, i'm using the series resistor method. A 18ohm (i have 15 and 22) between the 9V adapter and pin 3(first heater) and connected the other heater, pin 6, to ground, as suggested.

My adapter is rated for 1A

Well, the heaters are neither warm, nor to they glow. I guess it's connected wrong somehow. I've checked and reset the tube connections several times.

[mnordbye]

And  just to clear things up, 3 of the pins says "NC" on the data sheet, i guess that's "Not connected" ?

[frequencycentral]

I'm not using the heaters-in-series methos, i'm using the series resistor method. A 18ohm (i have 15 and 22) between the 9V adapter and pin 3(first heater) and connected the other heater, pin 6, to ground, as suggested.

My adapter is rated for 1A

Well, the heaters are neither warm, nor to they glow. I guess it's connected wrong somehow. I've checked and reset the tube connections several times.

OK, I misunderstood.

The 22 ohm will drop 3.3v, so you'll get 5.88 to the heater from your 9.18v supply, that's ok but not ideal. The 15 ohm will drop 2.3v, so you'll get 6.88 to the heater from your 9.18v supply, that's probably too high and could reduce the life of the tube in the long run.

1A should be fine on the adapter.

Make sure you're reading the pinout correctly, it's easy to get it the opposite way around. The pinout on the datasheet is viewed from below, looking at the pins.

Correct, pins 2, 4 and 7 are not connected.

[mnordbye]

Okay, thanks again Freq, i'll try it in the morning.

[Ripthorn]

I'm a big fan of using zener diodes.  You could either use one to drop to the correct voltage, or you get a 6.3V zener, put the anode to ground and make your heater voltage be from the cathode end.  Then you get a rock solid 6.3V regardless of input supply (as long as it is higher than 6.3V) as long as the power rating is sufficient (1W is easily enough I would think).  Be carefule though, once you get bit by the submini bug, the only cure is to purge it from your system by building several projects.