U47 with EF14 tube Build

[Spencerleehorton]

I’m only testing the pcbs work, I’m not using that power switch.
Waiting for a few more bits before I put in the cases.
Will finish off next week.
But yes, it all works, 36R I tested for the H+ and can wind it to 5.05v with no problem.
B+ I used a 180k and got 105v so just the other resistor to put on the B+ for the pattern relay.

 

[Cqwet Dbdfte]

If you are dropping out voltage in your regulator, you could also do this with series resistors with your rectifier diodes.

 

[Spencerleehorton]

Just waiting on some brass stand offs

 

[rock soderstrom]

No secondary fuses for the transformer?

Edit: I can't see a primary fuse either, have you installed one? I would fuse the transformer on both sides, I have seen a transformer burn down during a live show! Don't save money in the wrong places...

 

[Drosselmeier]

 

[Spencerleehorton]

Yeah I got a fuse in the iec as per previous pic, top one.

 

[rock soderstrom]

Yeah I got a fuse in the iec as per previous pic, top one.

Okay, I didn't see them because the socket is so slim , it was also a bit late yesterday... The fuse holders for the PCB are super cheap, I think they make sense, but of course it's your decision whether you use them or not.

Still proud to see my design in use.

 

[Spencerleehorton]

Stand offs have been delivered but I’m at work so will test over the next few days.
Got my laser heat tester and will put them through their paces!!

 

[Spencerleehorton]

Well disappointing at the moment as without mic connected and load resistors on, the psu seems to get the desired voltages but with the mic connected H+ only at 2v and B+ sits at 130v and will not drop when twiddled?
Using 20k, 20k, 25k trimmer on B+
3.8R, 3.8R, 3.8R for n H+
Will loose the first 3.8R on H+ and see where I get to and investigate why I can’t twiddle down B+?

 

[Khron]

You REALLY need to get your Ohm's law math sorted, man...

What value load resistors were / are you using?

Those 3.8R don't sound like a very standard value to me. Unless they're maybe from EIA96 series?


*** Later edit ***

I may or may not be speaking for all of us who've been trying to assist you through this, but it's becoming more and more frustrating to read how you are trying seemingly random attempts at solutions, with apparently no rhyme or reason, or justification, or clear measurements or basic maths, and just get presented with a half-ass description of "I tried this and it doesn't work" As mentioned before, i'm sure none of us here hold any ill will towards you, but you're definitely not making trying to help you, any easier...

 

[rock soderstrom]

Those 3.8R don't sound like a very standard value to me. Unless they're maybe from EIA96 series?

I think Spencer is talking about the series resistors in the H+ part.

I think it's a good plan to get the H+ PSU part up and running first.

Just to be on the safe side, what is your load at the moment, an EF800?
What voltages are dropped across the 3.8R series resistors? How much over the LM317? How much raw DC voltage do you have directly after the rectifier?

 

[rock soderstrom]

Will loose the first 3.8R on H+ and see where I get to and investigate why I can’t twiddle down B+?

Yes, you can bridge one of the series resistors with a crocodile cable as a test. The problems in B+ could be due to the tube being massively underheated at the moment...maybe the tube cannot emit its full anode current.

 

[Khron]

I think Spencer is talking about the series resistors in the H+ part.

I know / i understood that; they're still not a very standard value though. 3.9 in the E12 series (or perhaps even 3.6 in the E24 series) would be more... "familiar" to me.

 

[rock soderstrom]

I know / i understood that; they're still not a very standard value though. 3.9 in the E12 series (or perhaps even 3.6 in the E24 series) would be more... "familiar" to me.

Okay, I see. I would measure them,too. We need more numbers as mentioned above to see whats really going on...

 

[Khron]

Okay, I see. I would measure them,too. We need more numbers as mentioned above to see whats really going on...

seemingly random attempts at solutions, with apparently no rhyme or reason, or justification, or clear measurements or basic maths, and just get presented with a half-ass description of "I tried this and it doesn't work"

Indeed...

 

[Cqwet Dbdfte]

@Spencerleehorton
You are attempting to wire up a circuit without basic understanding of schematics and Ohm's Law. It is VERY simple.
Removing a load from an unregulated power supply will always increase the voltage, and vice versa.
The unregulated power supply has some series resistance, and can be viewed as a "current source" rather than a voltage source.
Once you install a voltage regulator it becomes a voltage source.

Download LTspice, easy to use, hit CTRL+N , hit R for a resistor (enter a number for it), V for a voltage (enter a number for it), G for grounds, Draw wires (F3) between the parts, hit Run, add some time, 1 sec is OK, and watch your results on a graph.
Grandma can do it.
Don't ask any more questions until you have done this.
https://www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html

 

[Spencerleehorton]

I’m going to ignore the you don’t know what your doing msgs, I do know the basics and normally there are simple errors I make.
Ef800 - 275ma
Unloaded.
The resistors I’ve used are 7.5R in parallel, that’s why I’ve got 3.8R.
On H+ after diodes I am getting 16v
After R1(3.8R) I’m getting 15v
Next 3.8R = ? Need to measure
Next 3.8R = 2.5v

I did post before what I used as load resisters and I did actually use ohms law to work it all out!!

 

[Khron]

I’m going to ignore the you don’t know what your doing msgs, I do know the basics and normally there are simple errors I make.

Well, if you really knew the basics (AND applied / used them), you might not be needing to ask for help here? Or rather, "actions speak louder than words" - if you really knew what you were doing, you "shouldn't" need our help with something this trivial, surely..? Once again, not trying to be mean or anything (despite your occasional attitude), just pointing out the disconnect between your claims and actions, that's all.

Ef800 - 275ma
Unloaded.

Well that right there is a contradiction of logic. Either you have the tube heater connected (ie. the circuit is loaded), or you don't (unloaded). So which is it?

On H+ after diodes I am getting 16v
After R1(3.8R) I’m getting 15v
Next 3.8R = ? Need to measure
Next 3.8R = 2.5v

How certain are you that none of the capacitors are shot?

1V dropped across 3.75R works out to 266mA or so - so far, so good.

13.5V dropped across 3x 3.75R in series works out to 1.2A (1200mA). So some capacitor's internally shorted, you've stuffed up some wiring somewhere, or the cables you're using (if any) are busted, or any combination of these. Or, for all we know, even some probing error somewhere...

A voltage reading between that second and third series resistor would be revealing, perhaps.

 

[rock soderstrom]

Ef800 - 275ma
Unloaded.

This part is indeed contradictory. Is the mic connected with the EF800 now?

Let's take a more relaxed approach to the whole thing. This is the current state (regarding H+), right?



I would be interested in the voltages at the two question marks. It seems that your LM317 is dissipating more than 10V, why?
Does the LM317 get very warm?

How have you populated R3 and VR1?

 

[Spencerleehorton]

I was just writing I was using the EF800 and it was 275mA as we all know don’t no why I wrote unloaded and then put the loaded voltages! Sorry.

Yes something is off, I’ll get more time over the next few days to investigate.
Appreciate all the help and you guys putting up with my ways!!