G-PULTEC problems, please help!

[Tommy Radonicus]

Nice Work .. Have you Fired it up yet and if so how is it sounding ??

 

[audiophreak]

nice Build jordan s 

 

[sonicwarrior]

I have a weird problem with my MEQ PCBs: The 680N (Wima MKS-4 or MKS-2) won't fit:

Does anyone know a narrower 680N preferably available @Mouser? (I only found even bigger 680N capacitors there if the data-sheets don't lie but maybe I'm not able to read them)

 

[audiophreak]

could you solder in on the other side ??

 

[gyraf]

..or extend the pins with wires?

 

[sonicwarrior]

Thanks for the ideas. I'll try soldering it on the solder side first. 

 

[miklos]

Hi,

I'm just find this site today and i'm very exciting about what is possible. I just see all this community full of capacity and knowledge doing nice pro-gear by their hands and i really want to try to take this train, and the Eq seems "quite" easy.
Well I say "quite", cause looking at this board, it seems that it's not that easy, and that's frighten me a little. My last electronic lesson was 20 years ago, and yes, i know and do XLR from time to time and like to do that but i'm not sure i can really read and understand the electronic diagram for the G-Pultec.

So, i spend the day to find out some things over the internet but there are a lot of questions that i can't find easily ; maybe it's part of the beauty of making his own gear like that ?
Here are a few questions :

Is there a simple step by step somewhere where i can find :
- what is the best way to begin with (is that english ??) ?
- what are the good and improves components needed to go ? (http://www.don-audio.com ??)
- Where to find a nice PCB ? (https://pcbgrinder.com/index.php?route=product/product&path=59_70&product_id=61 ?)
- Where to find a nice case ? and how to print over metal as i see in this topic ?

Well, a lot of questions, and sorry if this very newbie questions, i didn't have time to search in all the forum but it seems to have a lot of informations, but maybe a little help would be very appreciate.
Thanks a lot

 

[imloggedin]

Here's some shots of my build:

Very nice. Where did you get the front panel and knobs?

 

[synnys]

Finished my build, very happy with the result, one problem though: The boost (hi) on the left channel doesn't do anything, on whatever frequency, it doesn't do anything.
What would be the first place to look? faulty pot meter? or something else?

Also my noise floor is around -82dB at 50Hz and -84dB at 100Hz. I find this very acceptable, but was just wondering what the noise floor of your pultecs are?

here are some pics of my build.

update: i checked all pot meter values against the right channel, both are the same. problem is somewehre in the filter board cause the left filter board on the right channel gives me the same error.

 

[synnys]

I'm aware of the thread in the pultec meta thread, which describes JW's exact same problem, only he had his amp/filter board wired incorrect and mine is absolutely wired correctly.

I'm replacing all the inductors now to see if that changes anything.

Edit: all inductors replaced, no difference.

stiil no hi boost. (q and freq also don't work for that matter)

 

[miklos]

Hi,

I've read all the topic and a few others and i thin i will try to build two units. But before trying to do it i want to clarify a few things that aren't still very clear.
On the power supply board, there are 2 units marked B350C1500 (350V/1.5A) and a 4700/25, are there trafo also ?

As seen on message 151, using the Edcor audio trafo could mean to have a specific PSB ?
And last one ; is anyone know a good electronic audio supplier here in France ?

thanks and excuse for my english

 

[synnys]

Hi,

I've read all the topic and a few others and i thin i will try to build two units. But before trying to do it i want to clarify a few things that aren't still very clear.
On the power supply board, there are 2 units marked B350C1500 (350V/1.5A) and a 4700/25, are there trafo also ?

As seen on message 151, using the Edcor audio trafo could mean to have a specific PSB ?
And last one ; is anyone know a good electronic audio supplier here in France ?

thanks and excuse for my english

B350C1500 is just a bridge rectifier (two diodes ) (this one is fine)
4700/25 = 4u7 poly capacitor 250v (very large capacitor)  try this one

try musikding.de for a supplier, they send through the whole of europe and they're cheap, fast and reliable.

 

[miklos]

B350C1500 is just a bridge rectifier (two diodes ) (this one is fine)
4700/25 = 4u7 poly capacitor 250v (very large capacitor)  try this one

try musikding.de for a supplier, they send through the whole of europe and they're cheap, fast and reliable.

Thanks a lot !
musikding seems to have a lot of things !

 

[synnys]

Ok so i replaced all pots, all inductors, all capacitors, all wiring between the filterboards and the wires between filter and amp board.

And stillll no freaking hi boost... someone care to shine a light on this, i don't understand where the problem could be left... i feel like i rebuilt the entire thing for nothing.

 

[mitsos]

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

 

[synnys]

When i measure the hi boost pot (10k) i get only 0.88k ohm when it's connected to the circuit. When disconnected i get a perfect 10k, so the pot is working proper.

When i measure the same at my working channel, i get about 3.88k ohm connected and 10k disconnected.

So what can cause this drop in resistance? All resistors on the filterboard are correct.

Also, i changed the hi boost pot to a 50k, and the resulted in a volume drop, so the signal does pass that pot. I also switched the Q pot from the working channel, didnt matter.

correct me if i'm , looking at the schematic, the signal goes thru the hiboost to the high freq switch, then to hi Q and then via bypass to the amp.
And since the pots are working and i replaced ALL caps and inductors, can i conclude the problem lies within my rotary switch? seems like the only component that could break the signal path... (nope that wasn't it either...)

 

[Harpo]

4700/25 = 4u7 poly capacitor 250v (very large capacitor)  try this one

or better not.  ??? (you'd need 1000 of these 4u7 caps in parallel to get to 4700uF)
Heater supply calls for a 4700uF cap with a 25V min.voltage rating.
This will not be a poly cap, but an electrolytic capacitor.

 

[synnys]

4700/25 = 4u7 poly capacitor 250v (very large capacitor)  try this one

or better not.  ??? (you'd need 1000 of these 4u7 caps in parallel to get to 4700uF)
Heater supply calls for a 4700uF cap with a 25V min.voltage rating.
This will not be a poly cap, but an electrolytic capacitor.

huh what are you on about?

the schematic clearly states a 4u7 250V polycap.

 

[synnys]

oh wait, we're not talking bout the same cap

sorry your right, i thought he meant the other one  :-[

 

[miklos]

I was talking about the other one labeled : 4700/25 with a "+".

Is that really the same as 4u7 250 ?