Superlite TMB Schematic Voltages

[Riffmonster]

Hey guys,

I did not wanna open a new thread for this cause it is kinda the same topic.

If I want to build the Superlite tmb, can't I just aim for the voltages of the lite 2b? I wanna build the Superlite tmb with tube rectification, so I would take the same power section of the lite 2b and just add the 27k 2 watt resistor to get node D. Is there anything wrong about going that way? I can't really see why it should. Thanks!

[Daviedawg]

Yes you can. All 18 watts which aim for the 18 watt tone will have similar voltages at key points.

Dd

[JMPGuitars]

Hey guys,

I did not wanna open a new thread for this cause it is kinda the same topic.

If I want to build the Superlite tmb, can't I just aim for the voltages of the lite 2b? I wanna build the Superlite tmb with tube rectification, so I would take the same power section of the lite 2b and just add the 27k 2 watt resistor to get node D. Is there anything wrong about going that way? I can't really see why it should. Thanks!

Yeah, like Dd said, they're mostly the same. If you look in the downloads section you'll see my Lite 2/Superlite TMB voltages use the same sheet. viewtopic.php?f=25&t=24418

Tube rectified or solid state, you still want the same B+.

Thanks,
Josh

[Riffmonster]

Thanks Josh, can't wait to build it!

[kinmike]

So I used a 130 ohm, 12 watt resistor and got the B+ down to 343 volts at 120 vac. Pin 3 of power tubes is 11.48. Are these close enough or do I keep chasing it?

Thanks,

Mike

[JMPGuitars]

So I used a 130 ohm, 12 watt resistor and got the B+ down to 343 volts at 120 vac. Pin 3 of power tubes is 11.48. Are these close enough or do I keep chasing it?

B+ is great, leave it there. Now you should get your Pin 3 (cathode) voltage up to 12V. What's your cathode resistor now?

Thanks,
Josh

[kinmike]

Josh,

Well, being impatient, since my last post and seeing your last post I went from 180 to 220 on the cathode resistor. The voltage at pin 3 of the power tubes is now 12.48 but the B+ went up to 352.

Maybe I need two decade boxes to get this straight. Looks like another week is needed for me to order more parts. I guess I need to order multiples in the range of each resistor. I see you suggested that already.

Mike

[JMPGuitars]

Well, being impatient, since my last post and seeing your last post I went from 180 to 220 on the cathode resistor. The voltage at pin 3 of the power tubes is now 12.48 but the B+ went up to 352.

Do you have two 100 ohm 5W or higher resistors? You can put them in series at Pin 3 and see what voltages you get.

Thanks,
Josh

[geoff 1965]

006.JPG

i made this little test box Mike,it's 2 wirewound variable resistors "colvern" and it's been one of the most useful test pieces i've got!
i used it for the sag resistor,adjusting B+,el84 biasing and fine tuning voltage dividers.
you simply patch it in and adjust it till you get the exact voltage you want then remove it and measure the resistance.
with a 150R bias resistor i had exactly 12V on pin 3 but my dissipation was just over 12 watts so i've got 180R now with 12.7V on pin 3 and dissipation of 11.5 watts and to be honest both values sounded just as good.

[kinmike]

Do you have two 100 ohm 5W or higher resistors? You can put them in series at Pin 3 and see what voltages you get.

Thanks,
Josh

I actually had the wherewithal to order a 200R 5 watt resistor last time. I installed it, but with the 130 ohm dropping resistor my B+ is still 356. Pin 3 was 12.3v.

Dang, I was hoping to get this solved.

Mike

[kinmike]

006.JPG
i made this little test box Mike,it's 2 wirewound variable resistors "colvern" and it's been one of the most useful test pieces i've got!
i used it for the sag resistor,adjusting B+,el84 biasing and fine tuning voltage dividers.
you simply patch it in and adjust it till you get the exact voltage you want then remove it and measure the resistance.
with a 150R bias resistor i had exactly 12V on pin 3 but my dissipation was just over 12 watts so i've got 180R now with 12.7V on pin 3 and dissipation of 11.5 watts and to be honest both values sounded just as good.

Yeah, looks like I could use something like that.....

[JMPGuitars]

I actually had the wherewithal to order a 200R 5 watt resistor last time. I installed it, but with the 130 ohm dropping resistor my B+ is still 356. Pin 3 was 12.3v.

Dang, I was hoping to get this solved.

Mike

Throw that 200R in place to drop the B+. Put a 180R on the cathode and check your voltages.

Please also post a photo of how you have it setup.

Thanks,
Josh

[kinmike]

OK, I put the 200 ohm in with a 180 ohm cathode resistor and my B+ is 340 with 11.4 volts on pin 3.

I assume I need to still get closer to 12 volts. Back to 200 on there as well?

I know I need to change out the 5 watter to 10 later on.

Thanks,

Mike

[JMPGuitars]

OK, I put the 200 ohm in with a 180 ohm cathode resistor and my B+ is 340 with 11.4 volts on pin 3.

I assume I need to still get closer to 12 volts. Back to 200 on there as well?

I know I need to change out the 5 watter to 10 later on.

Thanks,

Mike

Yeah, give it a shot and see what happens. 11.4 isn't terrible, but if you can get it closer to 12 it would be better on your tubes. The truth is plenty of people have their 18 watters biased there or hotter, but it's not ideal.

TBH 5W is fine there too, 10W is overkill. That's why people often use 10W there (for overkill). I think the minimum for the voltage you're dropping is around 1.5W, so 5W is pretty safe for now. 10W is better because it shouldn't get as hot (assuming the 5W actually gets hot).

Thanks,
Josh

[kinmike]

Ended up using 220 ohm 5 watt for the dropping resistor and 200 ohm for the cathode resistor. B+ is 337 and pin 3 of power tubes is 11.6.

I could probably try 220 for the cathode to get a little closer but that is another Mouser order.

Mike

[JMPGuitars]

Ended up using 220 ohm 5 watt for the dropping resistor and 200 ohm for the cathode resistor. B+ is 337 and pin 3 of power tubes is 11.6.

I could probably try 220 for the cathode to get a little closer but that is another Mouser order.

Mike

Drop the B+ to 200ohm. 337 is too low. You want 340 to 345. Then test cathode again. If those are the only resistors in the ballpark, put the 220 on the cathode, and the 200 on B+ and test.

Thanks,
Josh

[kinmike]

Josh,

Just from my experience lately of the interaction between the two resistors I was thinking just changing to a 220 ohm cathode resistor would increase both the B+ and the power tube pin 3 voltage. Do you think that would be worth a try?

Thanks,

Mike

[JMPGuitars]

Josh,

Just from my experience lately of the interaction between the two resistors I was thinking just changing to a 220 ohm cathode resistor would increase both the B+ and the power tube pin 3 voltage. Do you think that would be worth a try?

Thanks,

Mike

Sure, why not? Small changes aren't going to hurt anything.

Thanks,
Josh

[kinmike]

220 ohm cathode resistor got me a B+ of 346 and power tube pin 3 voltage of 12.2. I guess I can call it good. I'll post all voltages tomorrow.

Thanks for all the help. I'm just slow in every sense of the word.

Mike

[JMPGuitars]

220 ohm cathode resistor got me a B+ of 346 and power tube pin 3 voltage of 12.2. I guess I can call it good. I'll post all voltages tomorrow.

Thanks for all the help. I'm just slow in every sense of the word.

Mike

That is good! How does it sound??

Thanks,
Josh