SSL 9K & 4K (E Series) 500 / 51X NEW BOARDS Mic Pre Thread 2011

[fishdrop]

maybe anybody can help me with one of my 4k5s.

had it in operation for some months. mainly on snare. great sound  ;D
when i switched it on today the meters went in the red area right away.
when i listened to the signal with headphones it sounded heavily distorted.
every couple of seconds it turned back to normal state, but most of the time it sounds heavily distorted. not usable for recording.

any advice how i can find the problem?

gain knob was close to minimum. HPF not engaged. no pad and no 48V activated.

want to check the unit tomorrow afternoon. i have a scope and a multimeter.
thought about removing ICs and checking the voltages first.
what do you think?

 

[culteousness1]

I once got problems with my 4K5 caused by a faulty (read scratchy) gain pot.
Gain went up instantly and then back to normal in the next seconds.
Could be fixed by moving the pot back and forth for a while...

Did you already inspect the board visually?

Cheers,
Carsten

 

[fishdrop]

I once got problems with my 4K5 caused by a faulty (read scratchy) gain pot.
Gain went up instantly and then back to normal in the next seconds.
Could be fixed by moving the pot back and forth for a while...

Did you already inspect the board visually?

yes i already inspected the PCB. no visually blown parts.
i removed all the ICs and measured for right voltages. everthing alright here.

i put all the ICs back into place.

a friend of mine said that it could be a malfunction within the feedback loop. he said my problem description would be a hint into that direction. saw three strange looking slder joints in that area. i resoldered the joints, but it didn't solve the problem.

he told me how to check the function of the feedback loops. I'll do that later.
yeah gain pot is also involved in the feedback loop. any idea how to check it??

don't want ta take the whole unit apart.

 

[culteousness1]

yeah gain pot is also involved in the feedback loop. any idea how to check it??

I don't have the schematic at hand right now. But, I would check the resistance first.
Then connect your DMM between the wiper and one other end and check resistance while
turning the pot. Look for the open circuits (Leerlauf).

Carsten

 

[fishdrop]

problem solved.  ;D

Feedback Loop of IC 30 was defective.
i put a 20k resistor on Pin 6 and Pin 2 while having signal on my headphones.
after touching the pins, the preamp was dead quiet.

after that i changed the two 10k resistors R17 and R115 for new ones.
after carefully soldering them in place and switching the unit on the problems disappeared.

while turning the gain to different settings for about a minute the problem came back for a moment and was gone the next moment. so maybe changing the pot is a very good idea as well.

fingers crossed for next recording session this weekend.

 

[fishdrop]

puh..... i think i have to change the gain pot too.
long time testing yesterday night revealed problems there, too.

 

[fishdrop]

puh..... i think i have to change the gain pot too.
long time testing yesterday night revealed problems there, too.

Alright.
i had a faulty gain pot. after changing and long time testing everything works like it should.

gain pot seems to be a weak link...

 

[fishdrop]

question on SSL 9k parts:

is a standard ceramic cap alright for the 3p3F cap?
or is a multi layer one recommended?

 

[Vac11]

Gentlemen,

may I introduce you to my beautiful twins :

Both were working properly from first power up.

Thanks to Bruno2000 for a really nice project, to Gustav for those beautiful boards
and to Frank (NRG Recording) for the front panels!

I am already considering another pair...

Cheers,
Carsten

Hi Carsten,

where you bought the big gray 2.2 uF, 100V, 5% tol. capacitors and small toggle switch? Where can I get this in Europe?

Thanks

Vac11

 

[culteousness1]

These are actually rated K = ±10%. IIRC, I ordered these at Farnell, e.g. #1215545. But using
Farnell's parametric search, LS = 22.5MM and C = 2.2µF, brings up a few with a even smaller tolerance.

My later 9K5s all used these, as they are dirt cheap 

Cheers,
Carsten

 

[Vac11]

And the small toggle on-on switches?

Thanks for your help!!!!

Vac11

 

[culteousness1]

Again, I used Farnell #9473017. But I remember that these switches didn't align with my front panel.
So I had to solder them in floating off the board. No biggie though  8)

 

[dipfrik]

Hello,

i start sourcing all the parts for some pcb's i have here.

Short question: Is this one, a LM 294 TO - NPN Transistor a valid replacement for the MAT-2H?
http://www.reichelt.de/ICs-LM-LS-/LM-394-TO/3//index.html?ACTION=3&GROUPID=2912&ARTICLE=10511&OFFSET=16&

Thanks in advance, Sven

 

[culteousness1]

Assuming you are referring to the LM394, I wouldn't recommend it as a suited replacement part.
Even though Reichelt seems to have some stock, the parts is obsolete for a > 1 year now.

Would suggest the Analog Devices MAT12 instead. Will shoot you a pm...

Cheers,
Carsten

 

[dipfrik]

Thanks!

 

[Vac11]

There is a picture here.  If you look at that pad with a magnifier, you will see that there is a connection there (right at the top of the picture, not visible in the picture.  All you have to do is cut till the pad isn't connected to the plane any more.  Mine was two tiny slices with a razor.

this is my first message here... and first message on a forum !
I'm a new diyer, i have build a VP26 without problem ( it's really easy, isn't it ?), and now i build a SSL9K5, and i have some problems. My first test was - in part- good, without the led meter.

My first problem :

With the led meter, R1 is destroyed... OK it's because there is a shortcut. Bruno 2000 says "there is an unwanted connection between the power eyelet and the top ground plane of the meter board."
Another try without the meter board... ok. So i have to cut the extra copper but i don't know how and where to do that. have i to cut on 1 or 2
or both ?

My second problem :

The HPF. Big saturated bass between 15Hz and 110 Hz and after, it's like a band pass filter, or a HPF with a big bell.
Maybe the trimmer is the solution?
I have record this ugly noise but i don't know how to put it here 

So, you understand that i need help...

thanks

ledada

Hi,

I have one PCB, revision 4.2, purchased a month ago ...

It is still necessary to fix the meter board?

M.

 

[culteousness1]

Dunno really. Better use your DMM to check for continuity between the eyelet and GND (eyelet below).

Carsten

 

[tzman]

There is just one version. So you'll still need to modify it and also do the polarity swap.

 

[Vac11]

Hi,

what knobs shaft did you use on the pots from audiomaintenance.com? Knobs with 6 mm shaft or 6.35mm (250) shaft?

This weekend I finished building the preamp. After 2 hours of normal use suddenly burned resistors R1 and R2. I do not understand it. Everything went two hours in order. After replacing the same.

I'll try it yet properly checked and measurement.

Vac11

 

[tzman]

Audio Maintenance states the shafts are 1/4", so that would 6.35mm. You could always use a caliper to confirm this...

R1 and R2 burning indicates a short somewhere. I see you did cut the trace on the meterboard, but I would start looking around that area.
Another possibility is that you might have put the module in a 51x rack and didn't insert it properly so pin 12 - 15 would have shorted (assuming you removed pin 17 and 18 from the PCB...).