[BUILD] 1176LN Rev D DIY

[Echo North]

That doesn't seem right.  You might have short to ground there (bad C21?).  On the - side of C21, you should see a neg voltage ranging from say -6 to -1 (roughly) depending on what ratio is selected.

What are your DCV's on either side of R61, R62 and R63?  All on the ratio.  Shouldn't matter what switch you have activated.

 

[HMPS]

replaced C21, problem remains

R61 -0.6, -0.5
R62 -0.5, -370 mV
R63 -370mv, 0

 

[HMPS]

side note, where should the orange, ground and yellow wires of the output transformer(EA-5002) go to?  just loose?

 

[Echo North]

side note, where should the orange, ground and yellow wires of the output transformer(EA-5002) go to?  just loose?

Orange and yellow get tied together.  Ground can do to your chassis ground at pin one.

It's covered here. 
http://mnats.net/1176_reva-d_hairball_wiring_meter_circuit.html

I think you have wiring issues.  I'll explain more after lunch, but you need to re-read the wiring guide.  Especially if you missed the yellow/orange part.

 

[HMPS]

The page says to tie them together.  They were tied out of the way, I should solder them together?  The ground is already connected to chassis.

Enjoy lunch lol!

 

[Echo North]

The page says to tie them together.  They were tied out of the way, I should solder them together?  The ground is already connected to chassis.

Enjoy lunch lol!

Yes solder them together.  In this case tie means twist the leads together.

 

[Echo North]

Alright here you go....read this as well but note it's rev a so some values (DC and component) will be different.
http://www.groupdiy.com/index.php?topic=29981.msg615080#msg615080

Print off the rev D schematic from the MNATs site.  Now go to the rev A schematic and write in the pad numbers from there on to your Rev D schematic...20,21,18 and so on.

Now here is one of your issues....you have no DC voltage at pad 21.  Here is how you get that voltage.  Look at your schematic, R64 connects to your -10V rail and then to pad 20.  From here is runs up to the ratio board and feeds the R63, R62, R61, R58 divider network and back down to the Qbias wiper where it connects to ground closing the circuit.  Looking at the schem R64 is 1.5K and the rest of the R in the chain are like 2K all together.  So you'll a sizable drop across R64.  Rail on one side (-10V) and something like -6V on the other.  If you don't at least have this with PAD 20 disconnected you have a main board issue at R64.  Edit: With pad 20 disconnected you'll have no path to ground...so no voltage drop accross this R.  Just make sure you have that side of the R64 going to the raio PCB pad 20. [End edit] Now this 6V gets connected to that R network with pad 20.  Now if you follow those resistors in order you should see a stepped drop -6V -> -4V -> -3.2V -> -2V (real roughly) until you get to the other side of R58 where it should be near fairly low, like -1V.

Now the switch just taps off those stepped voltages 6V -> -4V -> -3.2V -> -2V and feeds them to pad 21.

You've got basically no voltage anywhere in that chain I just described.  If you have -6V or whatever on the on side of R64 and not at pad 20 on the ratio, then you have wiring issues.  Likely it's miss wired, which would also help explain your voltage sag.

Good luck.

 

[HMPS]

I'm working on it, since 20 is measuring 0 DCV could there be something grounding it out?

 

[Echo North]

I'm working on it, since 20 is measuring 0 DCV could there be something grounding it out?

With the pads connected?  If you have pad 20 connected you should have -10VDC on one side of R64 and something like -6(ish) on the other side (same as pad 20).  If you have -10 on both sides, your missing your path to ground.  If you have -10 on one side and 0 on the other (pad 20) you have a short.

 

[HMPS]

Voltage Returns to -9.7 VDC when 18, ground, 22, 21 & 19 are removed

putting 18 drops voltage at 20 to -7.2
-10V rail still measures -9.7

plugging ground in drops 20 to 0vDC and -10 rail to -8.5

The other wires have no effect on the voltages


So Brown Drops it down and the ground & red(18) drop it to zero which are connected to the attack pot

 

[HMPS]

Is the path to ground before or after pad 20?  With 18 ground & 22 disconnected the voltage reads the same on both sides of R64

 

[Echo North]

Is the path to ground before or after pad 20?  With 18 ground & 22 disconnected the voltage reads the same on both sides of R64

You need to have 20 and 18 connected.  Check my edit shortly after I posted above.

This is a REALLY simple part of the circuit.  You have the -10V supply that enters through R64 and then pass through 4 resistors on the ratio PCB then out to the wiper of R59 and out one leg to ground.  You need to have this circle complete, then you'll get -10V drop to ground in steps through each of those resistances.  It's the most basic of series circuits.

 

[HMPS]

Ok will do hopefully we can get to the bottom of this today.

These might seem like silly questions but have to ask!

Ratio board is soldered to the switch is this correct? 

There is no insulation between the knobs and chassis, also correct?

 

[HMPS]

Thanks for helping me with this Echo

here's the measurements, do these look OK? or off?

with 20 and 18 plugged in

-10v rail reads -9.56

R64 -9.56, -7.16

Ratio board resistors

R4(63) - -7.16, -4.79
R3(62) - -4.79, -3.92
R2(61) - -3.92, -3.17
R1(58) - -3.17, -2.94

 

[HMPS]

also pad 18 reads -2.9 VDC

If those voltages look good to you then it must be something in the attack or release knob.

 

[HMPS]

Well I figured it out, I figured it had to be related to the attack knob by cause and effect.

I removed the wire going from attack to ratio board and it worked without it hooked in.  Hooked it back up and unit works!

Calibrated all 3 steps correctly.  Going through it again, when I press GR with no signal it is showing < 0

Thanks for helping through this Echo North, I really appreciate your time

 

[rokus666]

I still don't understand at what position should be "0" set pot when soldered to the board?

 

[andydiy]

Hi!

286-240-RC, There Substitutes?

Mouser Part #: 286-240-RC
Manufacturer Part #: 286-240-RC
Manufacturer: Xicon
Description: Metal Oxide Resistors 240ohms 5% Tol

 

[HMPS]

I got through all 3 calibration videos.

However when going through it again on the 3rd calibration when I click on attack it will drop in decibels, then when i re-adjust turning the attack back off has no change in the meter.

Should I do the calibrations as instructed on the JBL site?  Or just the 3 calibration videos?

Thanks!

 

[john12ax7]

Are you looking for a substitute for this part?

Any 240 ohm 5W resistor will do, either metal oxide or wirewound

Hi!

286-240-RC, There Substitutes?

Mouser Part #: 286-240-RC
Manufacturer Part #: 286-240-RC
Manufacturer: Xicon
Description: Metal Oxide Resistors 240ohms 5% Tol