Problems with Pultec PSU

Hi

I´m building the Pultec SRPP-Version from Jakobs site.
(great site Jakob :thumb: )

my problem is that the psu give me 350V for the anode.
I use a 230V to 230V transformer.

Any hints or comments how to reduce the voltage?
I changed the 3.3k restistor to 10k, but there was no effect..

thank you
JanW

You will need to measure the psu under load - that is, with tubes mounted and running. Then you'll see the effect of changing the series resistor..

Jakob E.

I mesured the psu with the tube mounted. it is still 350V with the 3.3k restistor.
Will the voltage drop down when I use a 10k resistor?

thank you
JanW

Now I changed the resistor from 3,3k to 10k.
With tube I mesured 360V at pin 6.
I think this is not ok.

thank you
JanW

A larger resistor WILL give you a lower voltage.

Does the tube heat up at all?

Are you sure it draws current?

..at some 5mA, a 10K resistor should drop around 50V..

Jakob E.

hmm maybe I am wrong.
I changed to the 10k resistor and mesured between:

gnd and:

tube pin1 : 250V
tube pin2 : 0V
tube pin3: 0,4V
tube pin4: 6,3V
tube pin5: 0V
tube pin6: 360V
tube pin7: 245V
tube pin8: 250V
tube pin9: 3,0V

I use a ECC81 for testing but I thing that does not matter... or am I wrong? :?:

thank you
JanW

[quote author="JanW"]
I use a ECC81 for testing but I thing that does not matter... or am I wrong? :?:

thank you
JanW[/quote]

Hmm, not sure how much it matters w.r.t. the ECC88, but if you happen to have a ECC82 around I'd use that one.
Jakob originally used that '82, but not sure though if the resistors were adapted for the ECC88.

[quote author="JanW"]
I use a ECC81 for testing but I thing that does not matter... or am I wrong? :?:[/quote]

First, the heater voltage for ECC81 should be 12.6V if you are using pins 4 and 5.

[quote author="moamps"][quote author="JanW"]
I use a ECC81 for testing but I thing that does not matter... or am I wrong? :?:[/quote]

First, the heater voltage for ECC81 should be 12.6V if you are using pins 4 and 5.[/quote]

Nice one.

I've been wondering why the internal shield of the ECC88 (pin#9) wasn't used (floating i.s.o. grounded on the PCB) but now it indeed comes in very handy: that 3V @ pin#9 giving away the incorrect heating situation with something else than a '88.
So please skip the ECC82-suggestion: without modifications of the heater-connections it won't work either.

ohh, ok now I see my fault: :?

if I want to use a ECC82 or ECC83 or something like that I have to connect Pin 4 and 5 to +12,6V and Pin 9 to gnd.
If I want a ECC88 tube I have to connect Pin 4 to +6,4V and Pin 5 to gnd.

Am I right?

ECC81/ECC82 are not heater pin compatible with the ECC88?


thank you
JanW

Nope, no heater compability.

And you really need an ECC88/6DJ8 to get this circuit to make sense. Yes, you could probably get it to pass sound with other tubes, but it won't be much good.

Or possibly get a PCC88 - which should be easier to find cheap - but this needs adjustment of the heater supply to a bit higher voltage (consult tube data sheet)

Jakob E.

[quote author="gyraf"]Nope, no heater compability.

And you really need an ECC88/6DJ8 to get this circuit to make sense. Yes, you could probably get it to pass sound with other tubes, but it won't be much good.

Or possibly get a PCC88 - which should be easier to find cheap - but this needs adjustment of the heater supply to a bit higher voltage (consult tube data sheet)

Jakob E.[/quote]

That's the beauty of the LM317 as used by Jakob: the heater-voltage easily changed by changing a resistor. :thumb:

Jakob, talking about the SRPP, FWIW I read such a circuit is to be optimized to work in a certain fixed load. In other words, according to the article it's hard to make an SRPP sound good for all loads from say 2k to 1M. Is this the reason for the 2k2 after the output-TX or is it more TX-related ?

Just curious...

O, the article (so much for articles of course, but this writer seems to know his stuff - to say the least) :
http://www.tubecad.com/articles_2002/SRPP_Deconstructed/SRPP_Deconstructed.pdf @ conclusions, p27,28

Regards,

Peter

Thank you all :grin:

I think I have to try the ECC88.
I thought I coud use an other tube than a ECC88....

thank you :guinness:
JanW

[quote author="JanW"]
if I want to use a ECC82 or ECC83 or something like that I have to connect Pin 4 and 5 to +12,6V and Pin 9 to gnd.[/quote]
Nope.

4 to 12.6V, 5 to GND, 9 is N.C.
or
4 to 6.3V, 5 to 6.3V, 9 to GND

If I want a ECC88 tube I have to connect Pin 4 to +6,4V and Pin 5 to gnd. Am I right?

Click to expand...

Yes.

Regards,
Milan

[quote author="JanW"]I think I have to try the ECC88.
I thought I coud use an other tube than a ECC88....
[/quote]

ECC88 / E88CC / PCC88 / 6DJ8 / E188CC / 6922 / 7DJ8 / 7308
(adjust heater-value were applicable)

With changing a few heater-connections that ECC82 will fit of course (for instance for testdriving, while awaiting the arrival of a ECC88).

[quote author="moamps"][quote author="JanW"]
if I want to use a ECC82 or ECC83 or something like that I have to connect Pin 4 and 5 to +12,6V and Pin 9 to gnd.[/quote]
Nope.

4 to 12.6V, 5 to GND, 9 is N.C.
or
4 to 6.3V, 5 to 6.3V, 9 to GND

If I want a ECC88 tube I have to connect Pin 4 to +6,4V and Pin 5 to gnd. Am I right?

Click to expand...

Yes.

[/quote]

ah, ok
maybe then I will try the ECC82 just for testing.

[quote author="clintrubber"]

ECC88 / E88CC / PCC88 / 6DJ8 / E188CC / 6922 / 7DJ8 / 7308
(adjust heater-value were applicable)

With changing a few heater-connections that ECC82 will fit of course (for instance for testdriving, while awaiting the arrival of a ECC88).[/quote]

just ordered one ECC88 :grin:

thank you
JanW

[quote author="gyraf"]Or possibly get a PCC88 - which should be easier to find cheap - but this needs adjustment of the heater supply to a bit higher voltage (consult tube data sheet)

Jakob E.[/quote]

FWIW:
Adapted the heater supply for the PCC88, just use a 2k43 i.s.o. the 1k8 and all is fine: it'll give you the required 300mA, or in terms of voltage: at around 7.8V for the four tubes I tried. For easier values try 2k7 // 22k or start tweaking the 470 as well to get two easy values.

You can also target for that 300mA by using a slightly altered '317-configuration (skip the 1k8, replace the 470 by a 4.2R 1W resistor, connect the heater to pin 2 of the regulator etc etc) but it'll be fine as done above, less hassle.

Bye,

Peter

Adapted the heater supply for the PCC88, just use a 2k43 i.s.o. the 1k8 and all is fine: it'll give you the required 300mA, or in terms of voltage: at around 7.8V for the four tubes I tried. For easier values try 2k7 // 22k or start tweaking the 470 as well to get two easy values.

Click to expand...

Peter, are you still doing ok with your modified heater voltage? I just scored a pair of cheap telefunken PCC88 and would like to use them in a g-pultec. Thanks for the above infos and cheers, Marten

[quote author="martthie_08"]

Adapted the heater supply for the PCC88, just use a 2k43 i.s.o. the 1k8 and all is fine: it'll give you the required 300mA, or in terms of voltage: at around 7.8V for the four tubes I tried. For easier values try 2k7 // 22k or start tweaking the 470 as well to get two easy values.

Click to expand...

Peter, are you still doing ok with your modified heater voltage? I just scored a pair of cheap telefunken PCC88 and would like to use them in a g-pultec. Thanks for the above infos and cheers, Marten[/quote]
It's not fired up here but it should just work, it's straightforward Ohms law. Check the result with a meter. Happy EQing,

Peter

ok, I'll report back when it is up and running, might take some time though, I'm kinda cheap and need time to find all the parts, maybe roll the inductors myself :roll: