MixBuzz1 Build/Support thread

[Igor]

Great, have a fun and make music! Pictures?

 

[Benny]

I'll post pictures when everything is checked,. I just realized that RP1 on the PSU board gets very hot when the unit is turned on for about half an hour. Is it too much current draw from the LEDs and relais?

 

[Igor]

What is the voltage across RP1?
LED's (including LED meter) are not not drawing many current.
What is the coil resistance of relays used?

 

[Benny]

I'll have to check that voltage. All parts were from your parts kits.

 

[Benny]

The voltage across RP1 is about 4V without MIX and 5,8V with MIX activated.

 

[Igor]

Relays in kits are 940...980 Ohm coil resistance, should not be a prob.

5.8/47=about 130ma max; power dissipation is about 0.75W.
Check the voltage at 2200uf cap; if within 23...26V, OK;
if 47R is 1W, change it to 2W 47R resistor.

 

[Benny]

OK then. Voltage at 2200uF cap is between 25-26V. I'm already using a 2W resistor so everything should be within specs. I'm gonna keep an eye on the resistor over the next hours to check if it's still too hot.

EDIT: I left the unit with power on for about an hour now and it seemed like the resistor would be at a normal temperature first. But after switching on the MIX option the resistor quickly heats up to a level where I can smell it and can't even touch it. Definitely too hot IMO.  ???

 

[Igor]

Put some oil on resistor, to prevent eye to be burnt, like in the pan  ;D

(Start eat with the eyes, (C) Addams Family)

Well... Try to put a pair of 2W, 100 ohm in parallel.

BTW. Do you have an incandescent lamp of EAO or something else in-circuit when MIX is ON?

 

[Benny]

BTW. Do you have an incandescent lamp of EAO or something else in-circuit when MIX is ON?

I'm only using LEDs. I broke the lamps glass and soldered LEDs in. Works nice!
I'll try the parallel resistors. Can anything be damaged if I just try to use bigger resistors, eg. 5W?

P.S. Let's see if I can get a tiny little steak on that thingy?!? Jummy  ;D

 

[Igor]

BTW. Do you have an incandescent lamp of EAO or something else in-circuit when MIX is ON?

I'm only using LEDs. I broke the lamps glass and soldered LEDs in. Works nice!
I'll try the parallel resistors. Can anything be damaged if I just try to use bigger resistors, eg. 5W?

P.S. Let's see if I can get a tiny little steak on that thingy?!? Jummy  ;D

Again, check what is the wattage dissipated at 47R. Up to 1W is absolutely fine.
LED is used with something like 2k2...4k7 in series, right?
I use LED's with EAO pushbuttons too.

Steak....Ooooum.......Yammie!!!!!

 

[Benny]

The wattage dissipated at RP1 (47ohms/2W) is about 0,7325W. (5,86V across resistor with 47ohms=0,125A)

The power LED is fed directly from the 12V outlet on the PSU thru a 2k4 resistor and the Bypass LED is fed from the Bypass connector on main pcb thru the onboard 2k4 resistor.
So that should be o.k. I think. Perhaps I'll check it again without the Power and Bypass LEDs. Just the relais and Meter.

 

[Igor]

100% within the specs.

 

[evilcat]

There's definetly DC offset @XLRs inputs when the comp is switched ON :
-8V between pin 1 and 2.
-2.7V between pin 1 and 3.

Dat's crazy! Is the star ground on motherboard connected to chassis?

And at the output of the comp, only when it's switched ON : 0.8 and 1 mV @ OP 1, and 2.3 and -3.9 mV @ OP 2.

Some DC offset within +/-2 mV at the outs of THAT1646 etc is acceptable,
Please check the DC voltages between AGND (starground at PCB) and pins of input balanced line receivers (INA137 or THAT1246):

INA137/THAT1246
PIN VOLTAGE

1  0v
2  0v
3  0v
4  -15v
5  0v
6  0v 
7  +15v
8 not connected

As well, try to pull out balanced line receiver chip and check the voltages without it, on socket
(maybe a contamination? 1% from 100, but, everything can be)

Maybe, dead chip (BOTH same???? Strange!), but I think it is ground issue.

OK so, my new rapport !

1st, the star ground on motherboard IS connected to chassis, as my pins 1 of all my XLRs, it's the only difference with your builds. Could it be a problem ?

2nd, XLRs Inputs measures : I/P 1 pin 2 -5.2V
                                              I/P 2 pin 2 -8.1V
                                              I/P 2 pin 3 -2.6V
All measures with comp engaged only.

3rd, 1246 measures :
1  0V
2  0V
3  -5.2V
4  -17.65V
5  -2.6V
6  -2.6V
7  +17.7
8  0V
FOR THE INPUT 1 RECEIVER

1  0V
2  -2.6V
3  -8.1V
4  17.6V
5  -2.7V
6  -2.7V
7  17.7V
8  0V
FOR THE INPUT 2 RECEIVER

And 4th, voltages with 1246 unplugged are ok except pins 5 and 6 whose have 2/300mV then it slowly decrease to 0V.

So, please, what should I do now Igor ??? Thanks.

Ben

 

[evilcat]

bump...
Igor, anyone ??? Any idea ?

Thanks,

Ben

 

[Igor]

Mmm...
Looks way strange.
You have to check the contact between power supply starground and pin1 of i/o XLR's. Should be 0 Ohm.
Otherwice, input line receivers are (maybe) dead. Let's do this check and see.

 

[evilcat]

Thanks Igor, I will.
The compressor could works (it's my case) even with line receivers dead ?

 

[Igor]

Or half-alive 
In any case, I think it is the ground issue.
Should be OK if receivers are not dead and pin1 of XLR have absolutely same potential as compressor's starground.

 

[evilcat]

Ok, thank you Igor, I'll let you know.

 

[Igor]

Been asked several times about how to implement attack/release with 11 position switches.
Here it is.

 

[Igor]

evil: any news? I impatiently waiting about a week. Curiosity, aye!