[BUILD] 1176LN Rev D DIY

[college101]

OK..even better news

I just went and turned it on again, I turned the 1 K tone on, went to +4 and meter read 0 vu! Switched to GR mode...And shows 0 vu with the compression off, and -10 with compression on...It works... wish I had a scope to the distortion adjustment, just to tweak it some more....

 

[charlievela]

Has anyone had issued with their Rev D simply dying?  I finished mine last week and everything seemed to be ok.  I've been using it on a project and it sounded incredible.  I left the unit on for several days in my air conditioned studio thinking heat wouldn't be an issue..

Tonight I came up to do some mix revisions and the unit was dead.  Fuse looks fine and upon opening the unit nothing seems to be obviously fried. 

Any thoughts? anything i should check or double check?  I don't understand how this could have happend since the unit didn't move at all and none of my other gear seems to have been effected so i'm guessing it couldn't have been a power surge or anything like that. 

 

[charlievela]

Just double checked the fuse with my dmm and it appears to be the problem.  I'll replace it tomorrow and find out for sure.

 

[college101]

Im not entirely convinced that R44 is functioning within the circuit correctly!!?? I replaced the 5k back down to the 2k trimmer as per the schematic.

When I am dialing in the final stages of the step 3 GR tracking adjust, it does not move the needle per mnats video...Now I noticed parts of the video are CUT together...but, I am not sure if r44 has the same functionality as the input knob at the start of the calibration for step 3....To further explain, if the needle falls short of -10=turn the input up!  So you turn the input UP, but the needle does not move, it is really adjusting the needle movement when the compression is off! You follow me? Y/N?\

I was able to adjust the needle, by switching in and out of compression via the attack knob, I did notice small amounts of movent in compression, but I cant' be sure this is accurate since I feel the needle has a lot of drift...

I did go back threw my resistors and check each one in the GR meter tracking section, everyone tested, and was fine...

I then went a step further and started signal tracing the copper traces..joint to joint..everyone tested, and every trace was connected..

The only thing that still bothers me, is if I have done the calibration the right way...

I am able to to get -10 with compression on and 0 with compression off in GR mode

 

[college101]

Anybody?  Basically, mnats video makes me think, that the adjustment is supposed to allign the needle to -10 with compression on? Is this correct

I was able to set the q Bias correctly and had no problems with the 2nd step...just trying to verify the meter movement with the third step...

can somebody who has built the Mnats rev d 1176 push button version respond?

 

[spase]

can use edcor xs1100 transformers for input and outpot on this 1176 revisions?

 

[college101]

Ive pretty much given up on my rev D now...I thought I had it set correctly, but still seems like something is wrong..  its now a paper weight...

I thought I would get some help here but nobody is helping

this really is driving me crazy because I am supposed to be going to school for Electrical Engineering, and this just bums me out...

 

[canidoit]

college101, maybe have a break and come back to it. Most people I have seen on here, who has been frustrated over their builds problems, have eventually solved it after a cooling out period. Dont give up, it's a great sounding unit : )

Some have taken their units to technicians as well to solve their build problems.

 

[college101]

canidiot...I understand what your saying    I know I have put the parts in correctly, and measured everything. It is wired correctly! So frustrating

 

[canidoit]

canidiot...I understand what your saying    I know I have put the parts in correctly, and measured everything. It is wired correctly! So frustrating

I don't think that is possible?? Two positives will not equal a negative. If the parts are correct and you are getting the right measurements for everything, I do not think it would result in a unit that is not working properly. I do not think faulty parts, faulty pcb or faulty wiring would result in a correct measurement for everything?

I remember one member here went through so much frustration only to find out it was a simple resistor mistake that he kept on overlooking all the time he checked.

Sorry I couldn't help more. Can your teacher at school or another student who is cluey help you with troubleshooting?

 

[jandoste]

canidiot...I understand what your saying    I know I have put the parts in correctly, and measured everything. It is wired correctly! So frustrating

I don't think that is possible?? Two positives will not equal a negative. If the parts are correct and you are getting the right measurements for everything, I do not think it would result in a unit that is not working properly. I do not think faulty parts, faulty pcb or faulty wiring would result in a correct measurement for everything?

I remember one member here went through so much frustration only to find out it was a simple resistor mistake that he kept on overlooking all the time he checked.

Sorry I couldn't help more. Can your teacher at school or another student who is cluey help you with troubleshooting?

My unit was not working and that I found a few time later it was the wire connection[grn] was wrong and now it works !
Rock!


Edit: http://mnats.net/1176_reva-d_hairball_wiring_power.html

 

[college101]

Jandoste! what was your error in the wiring?  I have mine hooked up exactly as mnats wiring guide...and everything seems to test that it works!

Im going to put in a switch at the three pin terminal point...the jumper seems to be very loose, and not secure..A single pole, single throw should do the trick...atleast for getting R44 in the circuit... No one seems to have an answer for the question I continue to ask!!  WHICH IS> Does R44 really adjust the VU meter like r71 does?  I order'd a new match'd set of the 2n5 Fet's for Q1 and Q11... I believe this maybe  the problem... I also found the housing spacers to get the Fet's up off the board which I will install with some silicone...  the white silicone

After I drilled a hole into the clip on heatsink for the voltage regulator...things seem to be a lot cooler onm the board...Dont use the clip on heat sink! It doesnt regulate enough heat from VR1

 

[Biasrocks]

Anybody?  Basically, mnats video makes me think, that the adjustment is supposed to allign the needle to -10 with compression on? Is this correct

The calibration procedure can be confusing.

Basically you want the VU reading to agree with the GR reading, in other words if your doing 10db of gain reduction, the VU should show -10VU and the GR reading should show 10db of GR.

Look in the URIE manual on the JBL site, there are a number of calibration procedures contained in that manual near the end.

http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/UREI-1176LNmanual.pdf

Read the procedure until you understand exactly what is required and then do the procedure.

Mark

 

[jandoste]

Jandoste! what was your error in the wiring?  I have mine hooked up exactly as mnats wiring guide...and everything seems to test that it works!

All ground wire connction was wrong I guess you need to check all of them! We are human that sometimes we don't see what we are doing

cheers,

 

[college101]

Jandoste, what was wrong? I've seen a couple post's on people having the ground wrong in the case...The XLR's are grounded...the IEC is grounded, and then there is a ground off the input shield and a ground off the output shield...

The output transformer has a seperate ground...along with the power cap going to ground

Am I missing another ground somewhere?


Biasrocks! Hello!

I found page 40 in the manual from jbl pro site, which I completely overlooked.. Harpo even made a reference to me about pulling R44... BUT, I thought  the whole point of the three pin header was so that you didnt have to pull R44 back out of the circuit? maybe Im wrong though

I've been reading the calibration proccedures, and they seem similar to mnats video,  But...Even the jbl calibration info does not seem to directly reference the answer to my question...

Mnats video seems to give off the impression, that you will be able to directly adjust the vu needle by adjust R44 while in the circuit....

JBL PRO seems to give the impression that you will have to do trial and error to get the correct value of r44- by re-inserting it, and taking it out- and re-doing the first step of GR meter tracking calibration steps...until it meets all the requirements...

I have no choice but to try it, I just want an answer because Mnats video makes the 3rd step look super easy to calibrate, while If I have to take R44 in and out of the circuit, its gonna take a while

 

[Biasrocks]

I have no choice but to try it, I just want an answer because Mnats video makes the 3rd step look super easy to calibrate, while If I have to take R44 in and out of the circuit, its gonna take a while

No need to remove R44, that's what the jumper is for.

I know I had to go through the process a few times before I completely understood each step.

Are you getting compression?

Perhaps you could document here what exactly the results are for each step of the calibration process, starting with Q Bias.

Do you have a signal generator and an external VU meter; or a meter capable of reading AC voltages for the test procedure?

Mark

 

[edanderson]

there are two steps in the meter calibration for rev A-D: setting the meter circuit null (getting 0V across r74) and the GR meter tracking adjust (making it show 10db GR).

for setting the meter null, r44 must be out of the circuit.

for GR tracking adjust, r44 must be in the circuit.

during the GR tracking adjust process, r44 is the trimmer that you use to get the meter to read -10db in GR mode.  so yes, in answer to your question, r44 will change the amount of GAIN REDUCTION shown.  it will not affect the meter very much in VU mode where it is showing the signal level and not GR.  do not use r44 to adjust the meter in VU mode.

if your meter zero has shifted in VU mode after you are done with the the GR tracking adjust, you can do both steps again to correct for this.

if you can't make this process work, you may have a bad set of FETs, or a wiring/soldering problem.

ed

 

[college101]

Edanderson...Thanks for the response- I am not trying to adjust the vu meter in +4 mode....Only in GR mode- and it does nothing to the calibration...  I do use the +4 to monitor my signal, and the 20:1 ratio select button

Biasrocks...I have a digital multimeter(which is brand new) which I have been using for the current calibration. I have been using the VU of the 76 to perform the calibration.  I also bought a old school HP wide range oscillator(same one the mnats uses in his videos as his signal generator)

I first set up my multimeter to measure AC on the output of my Wide Range Oscillator, same one that mnats uses in the first step Q Bias calibration-  I read the info correctly and was able to perform this step with no problems... I measured the output of the trimmer to make sure the wiper was furthest from ground( basically as high as the trimmer will measure in ohms) then inserted it, and solder'd into place...

I then measured the output of my signal generator, and set it the same as mnats...1k or .775v into the input of the 76...

** I then do the normal controls, and turn the input up until the vu meter shows +1...which was very easy....I then turn the Q Bias down to turn the vu meter back to 0 vu... This step insured I had the correct setting for conduction.....

Take R44 out of circuit at this point....and turn off the signal generator

I then did the R74 measurement with no input signal, and adjusted till both conditions were met...O v across R74 and VU meter was at 0.... Then on to the step 3

I Put R44 back into the circuit here

This is where you go into vu mode, or +4 and feed the signal to the input..my needle jump to the right past +3 just like in mnats video! I have to turn down the output to re-zero the meter with compression off....I then turn compression ON...which I am getting compression, and the needle drops to around -7..SINCE it is short of -10, you have to turn the INPUT up per mnats video...I do turn it up, and then turn the compression back OFF....the needle jumps up again past +3 and I have to re zero the meter by again turning the OUTPUT down again..  I then turn COMPRESSION ON again, and the needle goes to -10....usually here, I can fine tune by repeating the last adjustment steps...but within 3 or 4 tries...its right on the money....with Compression off I am at 0 vu...and with compression ON...I am -10 vu..(this is of course all in +4 mode)


you then are supposed to go into GR mode, and re zero the meter with R71..which I do


I then leave the front panel controls as they are, and turn on compression....the needle drop to around -8 or -5 depending on the time I try to calibrate...  Here in mnats calibration video, he states to adjust the needle back to -10 by adjusting R44, BUT no amount of movement seems to do anything to move my needle at this point...  I  can turn off compression, and watch the needle drop to zero vu....This is what has been happening to my 76

I have gone through the mnats page wiring multiple times just to make sure my wiring is correct, and it is correct.. The only way it would be wrong, is if the pictures are wrong...

 

[edanderson]

the way you describe the calibration  in your last post sounds correct.

reading back through your earlier posts it looks like you had replaced r44 with a 5k trimmer and it was working, but then you switched it back to a 2k trimmer and it stopped working?  why?  are you sure the 2k trimmer you are using now is not broken?

you may need a 5k trimmer depending on the particular FETs you have -- some 2n5457s will work with a 2k but some need the extra range provided by a 5k trimmer.  alternatively, you could try a different 2n5457, but you may have to try a few to get one that works with a 2k trimmer.

ed

 

[college101]

Hey Edanderson....

  Yes..a few post's back, I thought I had it working...BUT I was wrong...it was not correct...  I found a page early in this thread where, they had begun using a 5k trimmer in the null adjust position...I havent had any problems with that pot in this circuit...  I placed the 5k trimmer in the R44 position, which still....did nothing to the circuit...

So far..no one has really answered my question directly....If you watch mnats youtube video on the third step of calibration, he makes it look like, R44 is supposed to move the needle..to adjust it to -10..if it is supposed to, mine does not work....if its supposed to do sometihng else, i need to know what its purpose is...  Functioning trimmer? Yes I always check all parts before installing, and record it my notes..Every new trimmer I have tried was first tested before going into be solder'd into place...

If you dont understand what I am talking about...Go to youtube, and watch the GR METER video...or 3rd step in the calibration video series from mnats...

I check'd each trimmer before I solder them into the circuit, and they all are working correctly...

I noticed in the 2nd calibration video, mnats has the ratio on 4:1 durring the meter null adjust! Is this right?