synnys

Re: G-PULTEC problems, please help!
« Reply #360 on: December 17, 2012, 01:02:17 PM »
no, what harpo said is right. its a 4700uf 25v electrolytic cap


synnys

Re: G-PULTEC problems, please help!
« Reply #361 on: December 17, 2012, 02:08:13 PM »
If it's only the high boost that doesn't work (but the rest of the controls work perfectly???)  that points to a problem between the wiper of your hiboost pot, the inductor(s), the hiboost caps and the BW pot.  These are all in series, if there is a break somewhere in this series circuit, there is no high boost.  Could be a bad component (but looks like you replaced everything?), miswired pot, broken wire, bad solder joint somewhere, anything.   You could try injecting a (music not tone) signal to the input, turn the high boost halfway up and probe along the above-mentioned parts until you find where the signal stops.

Take a look at the schematic, a simplified way to look at it is as if the "hi boosted" signal travels from the wiper of the high boost pot through the LC circuit, through the Bandwidth pot back to the rest of the circuit.   

good luck

Ok so i just did the following:

i duct taped the tip of the jack coming from my sound card out to a wire and soldered that to the IN on the filter pcb.

(i duct taped the sleeves of two jack cables together with some wire)

and now i'm touching all solder points on the filter pcb with the tip of the jack going into my soundcard. so i can hear the music playing thru the cable.

guess what? the signal NEVER stops. i can hear music on EVERY solder point on the filter pcb.
not every point has the same volume ofcourse, and some points (at the caps) sound EQ'ed. which makes sense.

But it seems the signal path is not broken, how come the high boost doesnt work then?

Harpo

Re: G-PULTEC problems, please help!
« Reply #362 on: December 17, 2012, 03:08:35 PM »
...and mine is absolutely wired correctly.
Maybe assume it is not.
I'd double check the bypass wire connections (sw2A from schematic = sw1B from pcb silkscreen) that might cause your low ohm reading.
A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.  -Douglas Adams

synnys

Re: G-PULTEC problems, please help!
« Reply #363 on: December 17, 2012, 03:11:37 PM »
bypass switch is good, it works so it must be good,

hi cut and lo boots/cut work fine. just the HFboost that keeps bugging me.

synnys

Re: G-PULTEC problems, please help!
« Reply #364 on: December 19, 2012, 09:13:23 AM »
Problem solved!

I found out while remeasuring everything, that the 1M resistor above the bypass switch was giving me 1M at both positions of the bypass switch while that should have been bypassed.

So it was a bad connection in the bypass switch after all, but i didn't think of that before because the lo freq circuit was bypassed all right by that same switch!

:D!


rooster21

Re: G-PULTEC problems, please help!
« Reply #365 on: January 09, 2013, 10:50:22 PM »
I've got a question for those using the #47 fender lamp.

I have some 60hz hum being introduced when my lamp is connected, a noise reading of [email protected] vs [email protected] with no lamp. I'm getting power from the 6.3v point on the PCB and dropping it with a 42ohm 2watt resistor.

Is anyone else getting similar values? Any other suggestions on how to power the lamp?

gyraf

Re: G-PULTEC problems, please help!
« Reply #366 on: January 15, 2013, 01:45:38 AM »
Take AC lamp power directly from one of the the 12V secondaries, with a suitable dropping resistor. That way you don't mess with the regulated DC heater voltages. Just keep the lamp leads twisted, and some distance away from the filter board.

Jakob E.
..note to self: don't let Harman run your company..

rainton

Re: G-PULTEC problems, please help!
« Reply #367 on: February 09, 2013, 02:54:49 PM »
hello everybody,

I also have two GPultecs here. But they are still from the time when I was not DIYing so a friend built them for me some years back.

Now I moved and so did the entire studio and it seems the pultecs didn't like moving too much:

They both work but with one of them when I switch the LoBoost to 100Hz the signal gets pretty loud and some frequency seems to be boosted -
but it's rather in the midrange - definitely way above 100Hz!

The other Pultec does the same thing when boosting at 16khz -> signal level raises and the boost is also somewhere in the midrange - definitely way below 16khz...

I just opened them up and was suspecting the caps at the respective frequency  selection points but a) this merely estimated and b) I don't know which cap is for which frequency...

some help would be highly appreciated

gyraf

Re: G-PULTEC problems, please help!
« Reply #368 on: February 11, 2013, 04:26:47 AM »
..check integrity and soldering of the capacitor that gets switched into circuit at the failing frequencies..

Jakob E.
..note to self: don't let Harman run your company..

rainton

Re: G-PULTEC problems, please help!
« Reply #369 on: February 24, 2013, 03:57:43 PM »
Thanks Jakob,
I unsoldered all the components in question and checked them with the DMM - they seem to be ok.
After soldering them back to the pcb both units seem to work again :)


Re: G-PULTEC problems, please help!
« Reply #370 on: March 06, 2013, 04:47:53 AM »
An output transformer question.

While yo can sub the correct Lundahl for and OEP, can i sub/swap in a Carnhill VTB1148 output transformer. Would this work?

The specs are

Turns Ratio; N1:N2 = 1+1:1.7+1.7 DC Coil Resistances: P1:P2:S1:S2 = 6:6:20:20 (Ohms)


I thought this might be of better quality than an OEP and half the price of the Lundahl.


Thanks for any light/help

Kind regards

Michael de A

gyraf

Re: G-PULTEC problems, please help!
« Reply #371 on: March 06, 2013, 09:50:00 AM »
Depends entirely on it's inductances - impossible to tell from those specs.

Jakob E.
..note to self: don't let Harman run your company..

Re: G-PULTEC problems, please help!
« Reply #372 on: March 16, 2013, 10:59:30 PM »
Hi Everyone!

This is my first post and I apologize if this has been answered elsewhere (many posts to weed thru!), but some of you may already know the answer...

I am planning on piecing together the G9 Mic Pre, G1176 and the G-Pultec to make a pseudo record channel for my home studio. I'll make them all separately of course, but I'm looking for one thing.  The G-Pultec DIY page doesn't include a list of components like the others, it just helps when ordering all the appropriate parts needed for the build, and also you all may have substituted better parts for the build.

Does anyone have a good current components list for the G-Pultec? I would greatly appreciate it and looking forward to this build, you may see more of me in the future! Thanks in advance!

synnys

Re: G-PULTEC problems, please help!
« Reply #373 on: March 17, 2013, 02:24:08 AM »
8   2x6 lorlin
4   10k lin
2   1k lin
2   100k log
2   2k2 lin
2   22mH
2   47mH
4   100mH
2   18n
2   12n
2   6n8
2   3n3
6   33n
4   47n
2   68n
4   100n
2   150n
6   220n
2   330n
2   22n
2   15n
2   10n
2   470n
2   680n
2   1u
2   2u2
4   10k
4   1k
2   75r
4   470r
2   1k8
2   2k2
2   470k
2   3k3 2W
2   LM317
4   220u 350v
2   4u7 250v
2   470u 16v
2   4700 25v
2   10u 25v
2   heatsink
8   3pin connector
4   LL5402
2   ecc88 / 6dj8
2   fuse 4at
4   bridge rectifier 350 1.5a


This is a list i made for a stereo pultec.

But all the components are on the silkscrene of the PCB

Re: G-PULTEC problems, please help!
« Reply #374 on: March 17, 2013, 04:11:43 PM »
Many thanks for the list... helps make sure I don't overlook anything. But I suppose I should just take my time with this as well.

gyraf

Re: G-PULTEC problems, please help!
« Reply #375 on: March 21, 2013, 03:07:02 AM »
Quote
4   10k lin

Circuit works best with one log(lf boost) and one lin(hf-boost).

Jakob E.
..note to self: don't let Harman run your company..

mrdarwin

Re: G-PULTEC problems, please help!
« Reply #376 on: April 24, 2013, 08:02:45 AM »
Hi everybody!
I just finished my first Gpultec with OEP A262A2e output transformers and unbalanced inputs, and it sounds great.
The output level is less 2,7dB than input level... Is it normal? because OEP instead Lundahl?
I'm confused with wiring transformers:
output: OEP 1:2 ,secondary and primary in series and the primary goes to output balanced, so the transformer works for 2:1, is it correct?
Do I have to wire the OEP in the same way like the lundahl(2:1 oep, 1:0.5 lundahl)? inverse?

If I want use balanced input, do I have to wire the OEP in the same way like the lundahl?

thanx!

frazzman

Re: G-PULTEC problems, please help!
« Reply #377 on: May 10, 2013, 03:43:55 AM »
Quick question - i've built a few of these with unbalanced input (so no input trafo).

Given that Pin1+3 are tied together for unbalanced input, should I still connect pin 1 on input XLR to star ground?

At the moment I have the star ground connected to filter PCB gnd and output pin1 terminal gnd, but I have not connected star gnd to XLR input pin1. Should I???

Everything seems to work fine but I am trying to minimise noise

Thanks

gyraf

Re: G-PULTEC problems, please help!
« Reply #378 on: May 11, 2013, 01:54:27 AM »
No simple answer. Try to see what works best in your case.

As always, interfacing to an unbalanced input depends on whether the previous stage is electronically or transformer balanced.

But you should connect xlrpin1 to ground in any case.

Jakob E.
..note to self: don't let Harman run your company..

frazzman

Re: G-PULTEC problems, please help!
« Reply #379 on: May 11, 2013, 02:25:41 AM »
No simple answer. Try to see what works best in your case.

As always, interfacing to an unbalanced input depends on whether the previous stage is electronically or transformer balanced.

But you should connect xlrpin1 to ground in any case.

Jakob E.

thanks Jacob, I ended up connecting both xlrs and filter gnd to star gnd and that seems to have given me the best rresult. zero noise in bypass and low boost, interestingly the first freq in the high boost is the most noisy but the rest of the high freq positions get quieter,  particular 6.8k which is just as quiet as bypass. I think others have also noted this finding


 

Related Topics

  Subject / Started by Replies Last post
4 Replies
1697 Views
Last post August 16, 2004, 02:08:36 PM
by frob
4 Replies
1949 Views
Last post November 13, 2004, 10:51:40 AM
by Adky
2 Replies
2236 Views
Last post May 23, 2006, 04:51:14 PM
by rubric
2 Replies
1654 Views
Last post November 17, 2006, 05:25:08 PM
by carloff