G-PULTEC problems, please help!

[tedsorvino]

Hi everyone. Haven’t finished housing the project yet. I’m abouttp use 2 transformerms of 220v :12v 1.5A each. I would like to connect a power led on one of them. I have several 3v-5v ones. Some consume up to 180mA (the red ones) some just about 30mA (the blue ones). Which line of the transformers should I prefer, which leds should I go for and what resistor value should I go for (ok the equation is pretty obvious for that one)?

 

[ruffrecords]

Remember LEDS do not like a high reverse voltage so you will need to wire a diode of opposite polarity across it if powering from ac. Assume the LED drops 1 or 2 volts and calculate the resistor from ohm's law for the required current.

Cheers

Ian

 

[HerbertR]

Hi everyone. Haven’t finished housing the project yet. I’m abouttp use 2 transformerms of 220v :12v 1.5A each. I would like to connect a power led on one of them. I have several 3v-5v ones. Some consume up to 180mA (the red ones) some just about 30mA (the blue ones). Which line of the transformers should I prefer, which leds should I go for and what resistor value should I go for (ok the equation is pretty obvious for that one)?

Personally I would tend to tap after LM317 at the regulated 6.3V DC Heater rail from the PSU Makeup Mainboardand and bring the Voltage 2-3V down directly via a resistor to the desired Voltage. Easy and safe. But 180mA is a lot.... Are you sure? Most small 2-5mm leds have something about 5-30mA.

 

[tedsorvino]

Personally I would tend to tap after LM317 at the regulated 6.3V DC Heater rail from the PSU Makeup Mainboardand and bring the Voltage 2-3V down directly via a resistor to the desired Voltage. Easy and safe. But 180mA is a lot.... Are you sure? Most small 2-5mm leds have something about 5-30mA.

Cheers for the advice. I will follow that. The 180mA value is true for two older red leds, weirdly enough, measured with the same supply that gives me about 20mA on most other leds.

 

[tedsorvino]

Remember LEDS do not like a high reverse voltage so you will need to wire a diode of opposite polarity across it if powering from ac. Assume the LED drops 1 or 2 volts and calculate the resistor from ohm's law for the required current.

Cheers

Ian

I think i will take the small regulated voltage line.

Ps. Actually the enormous current, was due to excessive voltage. 2v are enough and just draw 7mA. From the 6 volts line a 560 small resistor does the job perfectly fine.

 

[tedsorvino]

Hi everyone and merry christmas.
Just to clarify something since it’s the first time i’m using an ecc 88.
Firstly without the tube i was measuring 300v on the high voltage socket pin, apparently this seems normal for the built.
My socket is quite stiff and while i was pushing the tube with no power on, there was a momentary spark. After that with the power on and the tube fully in, i didn’t have any glow in it and the pin still shows 300v. Grounding is ok and the heater pin shows 6v ( i mean even if it’s not 6.3v it should still show some life around the tube).
Is the tube burnt or faulty or should i change a resistor or something?
Cheers

Ps. Is it normal to have continuity on all pins of the secondary on the output transformer with no power and no other pcb connected ( i mean pins 10, 9, 7, 8)?
Does it fix itself when it’s powered, connected with the other pcbs, and there is signal?
I’m using oep transformers and i ‘ve followed the pinout layout ( ll 5402 - oep) that can be found in the thread.

 

[tedsorvino]

Hi everyone and happy New year.
After replacing the tube and the fuse the board now seems fine. The filament was broken and it was needing a higher than 0.5 slo blo fuse. The problem is that now i have something like 285vdc on the Ht pin. I think that’s way too high, even if i haven’t connected any of the control boards.
Can i add some resistance in series with the 3k3 2 w to drop the voltage or should i replace the resistor?
What value would you recommend for around 240- 250v?

 

[solkatten]

Hi everyone and happy New year.
After replacing the tube and the fuse the board now seems fine. The filament was broken and it was needing a higher than 0.5 slo blo fuse. The problem is that now i have something like 285vdc on the Ht pin. I think that’s way too high, even if i haven’t connected any of the control boards.
Can i add some resistance in series with the 3k3 2 w to drop the voltage or should i replace the resistor?
What value would you recommend for around 240- 250v?

Try 10K you should be just fine in the 200-250v range

 

[tedsorvino]

Try 10K you should be just fine in the 200-250v range

Thanks for that. Actually i tried a 12k 1/2w one in series with the 3.3k 2w one and the results were around 260v.
Should i increase the wattage of the extra resistor in series or take the 3.3k completely off the circuit and stick a 10-12k 2w one?

 

[solkatten]

You should probably use 2-3 w range. Use a Ohm law calculator. Type in resistance and voltage drop over resistor, then you get watt and current

 

[tedsorvino]

Hi again. So far so good. I’m nearly there. But i have a problem. No signal on the out. Checked with oscilloscope. The signal nearly disappears on the junction of the 1k resistor and the 4.7u/250v poly cap. On the one end of the 1k the signal is fine. The resistor is fine. Doubt bad soldering. Maybe the oep tranformer connections? Should i take the output transformer out?

Ps. Dropped the voltage down to a working 250vdc with a 20k 5w resistor. Maybe a 12k 3w one could do better. Maybe a 27k 5w equally good. But it’s ok for the time being.

 

[solkatten]

Hi again. So far so good. I’m nearly there. But i have a problem. No signal on the out. Checked with oscilloscope. The signal nearly disappears on the junction of the 1k resistor and the 4.7u/250v poly cap. On the one end of the 1k the signal is fine. The resistor is fine. Doubt bad soldering. Maybe the oep tranformer connections? Should i take the output transformer out?

Ps. Dropped the voltage down to a working 250vdc with a 20k 5w resistor. Maybe a 12k 3w one could do better. Maybe a 27k 5w equally good. But it’s ok for the time being.

Try swap the tube if you have a spare one

 

[tedsorvino]

Try swap the tube if you have a spare one

I don't think it's the tube, since the signal right after the tube is good. Unless the tube has to amplify the signal ( I don't think it works that way). It's something right after the 1k resistor.

 

[solkatten]

I don't think it's the tube, since the signal right after the tube is good. Unless the tube has to amplify the signal ( I don't think it works that way). It's something right after the 1k resistor.

Maybe the theres something wrong with one half of the tube? Your 22k dropping resistor implys theres little current going trough the tube.

Maybe your spark was a cathode heather break down in the upper half of the tube

 

[tedsorvino]

Maybe the theres something wrong with one half of the tube? Your 22k dropping resistor implys theres little current going trough the tube.

Maybe your spark was a cathode heather break down in the upper half of the tube

Thanks for the help Solkatten. The thing is that this tube is a brand new one. I replaced the one that sparked. Of course it may also be a faulty one, or there’s something wrong with the socket. Or something around there.
But I need to have a solid idea on how to find out about the issue otherwise i will pay all my valuable money on not so common and not cheap tubes.
And I repeat. The amount of signal that enters the tube anode, comes out of the tube cathode. No drastic change there. Is this a sign of a bad tube?

 

[solkatten]

Thanks for the help Solkatten. The thing is that this tube is a brand new one. I replaced the one that sparked. Of course it may also be a faulty one, or there’s something wrong with the socket. Or something around there.
But I need to have a solid idea on how to find out about the issue otherwise i will pay all my valuable money on not so common and not cheap tubes.
And I repeat. The amount of signal that enters the tube anode, comes out of the tube cathode. No drastic change there. Is this a

Thanks for the help Solkatten. The thing is that this tube is a brand new one. I replaced the one that sparked. Of course it may also be a faulty one, or there’s something wrong with the socket. Or something around there.
But I need to have a solid idea on how to find out about the issue otherwise i will pay all my valuable money on not so common and not cheap tubes.
And I repeat. The amount of signal that enters the tube anode, comes out of the tube cathode. No drastic change there. Is this a sign of a bad tube?

If its not resistor, cap or bad solder joint or tube.
Look for short curcuit in the OPT besides the side that should be grounded

 

[tedsorvino]

That's something I suspect. Actually I think I may have put the OPT the wrong side. Since I placed both transformers the same side. Also since I'm using an oep transformer with external wires, things can happen.
So to start with I think removing the output transformer connections next to to the 4.7uf would make my life easier.
If nothing then I would go backwards up to the point of the tube cathode.

Ps. All good as far as testing goes. It was a short right after the OPT. Showed me signal on the ground too. Took both transformers out tested unbalanced up to the out of the 4.7uf poly cap. Much bigger and smoother signal. Changed the resistor to a 27k /5w one. Took the voltages down to 240vdc and 105vdc so now…it’s a matter of good OEP transformer connections and all will be fine.
Thanks for your help and input.

 

[tedsorvino]

Finished my built. Succesfully. All working good and sounding very good.
Working voltage at HT 235vdc (taken down from 300vdc, with a 27k/5w resistor). About 110vdcat the cathode. Used Creativ Clowns pcbs and OEP A262A2E (in mu cases). Tube used, just a cheap common ECC88.

Please be careful. (At least for these pcbs and at least in 2023) The pinout comparisons between this OEP model with the Lundahls that existed in this thread (before this post) are wrong and can cause major troubles.

Best is to check with a multimeter, read carefully the schematic, compare carefully the transformers’ manuals and datasheets regarding windings and pinouts. If possible work with an oscilloscope and always discharge the high voltage caps, before working the pcb.

In order to provide some help i will give you my working pinouts. The lundahl is a 2+2 : 1+1 transformer. The OEP is a 1+1:2+2 which means that the Oep has to be turned upside down and be glued on the pcb in order to work easier with the pcb holes. Connection wires have to be used from the pcb to the transformer pins. After soldering each wire check carefully with a multimeter for any short (especially on the mu metalic body of the transformer).

The screen pin on the OEP has to be towards the top of the pcb . It’s obvious to see what hole is considered 1 on the pcb (top right).

So on hole 1 (top right)of the pcb goes pin B3 of the transformer.
On hole 2 of the pcb goes pin B1 of the transformer.
On hole 3 of the pcb goes the screen pin at the top side of the transformer.
On hole 4 of the pcb goes pin B2 of the transformer.
And on hole 5 (bottom right) of the pcb goes pin B4 of the transformer.

That’s it for the right side (B-secondary of OEP , A-primary of Lundahl).

The left side of OEP (A-primary), counts from the bottom to the top (that’s very important to notice) and the connections go like this.

On hole 6 (top left) of the pcb goes pin A2 of the transformer.
On hole 7 of the pcb goes pin A4 of the transformer.
On hole 8 of the pcb goes pin A3 of the transformer.
And on hole 9 ( bottom left) of the pcb goes pin A1 of the transformer.

That’s it for the left side (A-primary of OEP, B-secondary of Lundahl).

That’s all. Working Oep A262A2E transformer connections.

I have to repeat. Please read the reference datasheets and manuals. If you ‘re not sure just buy the lundahls. It’s not the improvement of the sound that worths the extra 30 euros, but you save yourself from sone serious troubles. If you can read them, well done. Great results for about 50 euros cheaper.

Thanks again the kind people in this thread for the help. Excellent project Gyraf. Already a classic diy take on a legendary piece of gear.

 

[solkatten]

Great to hear that your pultec is up n kicking

 

[MiamiBoy]

I just found out that there's no input transformer inside my gPultec, as it's "optional" -(the guy who built this was on a save-spree).
obviously its working.. but what am I missing out on, without it?
And what will happen if I install one?