[BUILD] 1176 Rev A - Back to the beginning...

[Spencerleehorton]

The problems im having are all due to not correct Q6 bias, also need to test psu for any ripple.

Spence.

 

[Spencerleehorton]

HI,

Right, i've finally made a break through!!!

R29 which was 1.2M i did change for 2M, i've now put a 2M pot with a 230K in series, i've twiddle the pot and hey presto the distortion goes!!! dont know whether i should also put a pot in for R32 and whether that would also help bias Q6?
Unit sounding passable now, bit of hiss which could be tamed to my ears.

regards

Spence.

 

[twentys7ven]

Hi all, I'm working on my second Hairball kit (first was a Rev D, now obviously an A) and it appears I've run into some trouble. I'm able to complete the first step of calibration (Q bias) but I'm unable to complete step 2 as my VU meter won't budge an inch no matter what I do. Any ideas of where potential trouble could be? I'm relatively new to DIY so I'm unsure how to check the voltages against the schematic or if that would even help narrow it down.

 

[Spencerleehorton]

My other findings led me to change R32 to 280 ohm as my DCR of the Pri B winding was 20 ohms giving me a total of 300 ohms which is same as when using other transformer.
Then twiddle R29 to bias Q6 and take away distortion.
Heat wise on Q6 this is much better than before.

 

[Potato Cakes]

My other findings led me to change R32 to 280 ohm as my DCR of the Pri B winding was 20 ohms giving me a total of 300 ohms which is same as when using other transformer.
Then twiddle R29 to bias Q6 and take away distortion.
Heat wise on Q6 this is much better than before.

Excellent!

I won't have access to my 1176 for the next couple of weeks, so I won't be able to do any more voltage checking until then should you need it. I'll still be checking back to see how you're progressing.

Thanks!

Paul

 

[Spencerleehorton]

Hi Paul,
I'm pretty sure my unit is operating  within the parameters it should now.
Need only to tweak the Vu meter side as I've used slightly the wrong meter so in normal setup it doesn't quite setup as it should, but unit is sounding gritty and has character which I like and for instance a parallel signal of bass guitar nice and clean one side and through the 1176 the other kicks some serious butt!!

 

[Potato Cakes]

Great!

Glad it's up and running. Nothing more frustrating than working really hard on a project only to not have it work properly, and then not knowing where the problem lies.

Thanks!

Paul

 

[Diamondj421]

Hey guys,
Finished my 1176 Rev D build and am having trouble with the q bias calibration. I have everything set as recommended but turning R59 from max (CW) to its minimum only results in a -.5 Db change. Has anyone had/dealt with this problem before?

 

[Spencerleehorton]

Wrong thread dude, this is for the Rev A.

Check your solder joints?

 

[kessconn1]

Hello all!

This is actually my first post to groupdiy so please pardon any  forum etiquette mistakes. Anybody who has ever done the hairball blue stripe build I am in dire need of some assistance. A friend of mine purchased the kit and attempted it about a year ago, he eventually gave up and the non functioning unit was given to me. I know my way around a soldering iron and multi meter so figured I could get it working.  So first off he made some pretty bad mistakes (ie backwards transistors incorrect resistor values) the fuse was blown. with replacement fuse power would not move past power transformer.

Soo, I decided to do a complete tear down, test and reassembly I opted to get a new pcb as well. Did not want to mess with his somewhat burnt original board. everything tested pretty well within tolerance except a few transistors, and maybe 1 cap... the only thing I was not able to properly verify were the two matched transistors on meter driver, and signal line amp. they passed voltage but i dont have a meter that will read transistors properly. all other transistors were replaced.

After my assembly was completed turned it on to verify signal and calibrate. All I got was hiss at around 10k . after some fooling i figured out that if i press all ratio buttons the unit passes signal. albeit very badly with hiss still there. The input pot did not seem to change the volume of this hiss, but output pot and meter seemed to be doing their job. attack and release knobs did nothing. I also noticed that if i put my hand over signal preamp the hiss geot much louder like there is a grounding issue.

I know this is a lot to throw at you guys but I would really like to get this running, and after tearing down and verifying every part I am a little lost.  do not think I made any mistakes, have went back and triple checked wiring.... any way If anybody wants to aid a novice in need I would greatly appreciate it!

 

[Echo North]

Hello all!

This is actually my first post to groupdiy so please pardon any  forum etiquette mistakes. Anybody who has ever done the hairball blue stripe build I am in dire need of some assistance. A friend of mine purchased the kit and attempted it about a year ago, he eventually gave up and the non functioning unit was given to me. I know my way around a soldering iron and multi meter so figured I could get it working.  So first off he made some pretty bad mistakes (ie backwards transistors incorrect resistor values) the fuse was blown. with replacement fuse power would not move past power transformer.

Soo, I decided to do a complete tear down, test and reassembly I opted to get a new pcb as well. Did not want to mess with his somewhat burnt original board. everything tested pretty well within tolerance except a few transistors, and maybe 1 cap... the only thing I was not able to properly verify were the two matched transistors on meter driver, and signal line amp. they passed voltage but i dont have a meter that will read transistors properly. all other transistors were replaced.

After my assembly was completed turned it on to verify signal and calibrate. All I got was hiss at around 10k . after some fooling i figured out that if i press all ratio buttons the unit passes signal. albeit very badly with hiss still there. The input pot did not seem to change the volume of this hiss, but output pot and meter seemed to be doing their job. attack and release knobs did nothing. I also noticed that if i put my hand over signal preamp the hiss geot much louder like there is a grounding issue.

I know this is a lot to throw at you guys but I would really like to get this running, and after tearing down and verifying every part I am a little lost.  do not think I made any mistakes, have went back and triple checked wiring.... any way If anybody wants to aid a novice in need I would greatly appreciate it!

Possibly a damaged a transistor.

What do your voltages look like?

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Mike

 

[tata]

can anybody please help me whats the best way to get less amplification at the last stage?
i would like to use the Output pot (almost) fully, but in practice i only use the first half of it.
(Output is A250k potentiometer)

is 1/2W a must for the Output pot?

thanks

 

[Potato Cakes]

can anybody please help me whats the best way to get less amplification at the last stage?
i would like to use the Output pot (almost) fully, but in practice i only use the first half of it.
(Output is A250k potentiometer)

is 1/2W a must for the Output pot?

thanks

Depends on how much equals "less." You could wire the first two secondaries of the output transformer parallel instead of in series. You could use a cable or XLR barrel that has a pad built inside of it. Outside of those two options, you would just have to find an appropriate place to add resistance before or after the transformer, but that may make for all kinds of weird impedance issues that unintentionally adversely affect the circuit. I'm not entirely sure why you want to have the output fully open.

Thanks!

Paul

 

[tata]

thanks Paul,

i got two reasons : learning about the stages, their differences in revisions, etc - and for "comfort" in real life use. i would prefer having a longer move on the Out pot, which hopefully would give me finer settings in the range i use it.

having less ampl. in the last stage maybe would mean a not-that-hot 3053, and maybe cleaner signal (RF, for eg? not that i have too much trouble with that atm, but i had issues with RF before.) i could be wrong tho.  so lets say 6dB less? 9?

 

[Potato Cakes]

It seems the less invasive permanent option to start with would be to wire the output transformer secondaries in parallel. But I would try just putting a pad inline after the output XLR and doing some comparisons with and without to see if you can hear a difference tonally or if there is a difference in the noise floor or RF interference. I've build a number of the A and D revisions and noise is an issue that I've not had with this circuit. I even have a stereo Rev D that I built and took it on tour and have had no problems, even with doubling the electronics crammed in the same size chassis as the single channel.

The other thing to consider is that the Rev A is not really a clean compressor. It's sought after for it's distortion characteristics which you probably already know and why you built an A instead of a D. Again, I'm not exactly clear for what you're after, but I am curious if you do discover an audible difference between the output wide open and halfway. I think it would be good information to share with everyone here.

Thanks!

Paul

 

[kessconn1]

Possibly a damaged a transistor.

What do your voltages look like?

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Mike

Hi Mike,

Thanks for the response ill see if i can test this tomorrow, will get back to you with results

thanks again

Conner

 

[kessconn1]

Possibly a damaged a transistor.

What do your voltages look like?

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Mike

Hello Again, was able to sit down and read all voltages on transistors, here are all voltages listed, the readings are in this order

1st reading is transistor lead closest to front panel, second is center lead, third is lead closest to rear, hopefully this is ample for providing info needed, if you need me to label voltages by ECB let me know. here are readings:

q1:  (-.32) (no rd)(no rd)
q2:  (1.50) (4.34) (6.91)
q3:  (6.41) (13.0) (6.4)
q4:  (0.81) (4.60) (12.9)
q5:  (2.72) (23.8) (2.9)
q6:  (2.11) (2.6)  (26.7)
q7:  (4.40) (16.5) (4.4)
q8:  (16.1) (29.2) (16.5)
q9:  (2.9)  (29.2) (16.5)
q10: (13.6) (13.9) (3.5)
q11: (-.12) (-.28) (3.17)
q12: (-1.2) (2.56) (-.66)
q13: (-1.2) (2.05) (-.67)

before you even respond i can see that some of the readings are a little off (q11-q13), but is till lack the know how to say what is causing this whether  it is a bad transistor or something else in the circuit. any input would be greatly appreciated,

thanks!

Conner

 

[tata]

It seems the less invasive permanent option to start with would be to wire the output transformer secondaries in parallel.
....
Again, I'm not exactly clear for what you're after, but I am curious if you do discover an audible difference between the output wide open and halfway. I think it would be good information to share with everyone here.

Thanks!

Paul

Paul, i think im looking for something similar to the 1108 Hi/Low gain option:

not sure, but i think the 1108 schemo shows the High gain (S1)?

 

[Echo North]

Hello Again, was able to sit down and read all voltages on transistors, here are all voltages listed, the readings are in this order

1st reading is transistor lead closest to front panel, second is center lead, third is lead closest to rear, hopefully this is ample for providing info needed, if you need me to label voltages by ECB let me know. here are readings:

q1:  (-.32) (no rd)(no rd)
q2:  (1.50) (4.34) (6.91)
q3:  (6.41) (13.0) (6.4)
q4:  (0.81) (4.60) (12.9)
q5:  (2.72) (23.8) (2.9)
q6:  (2.11) (2.6)  (26.7)
q7:  (4.40) (16.5) (4.4)
q8:  (16.1) (29.2) (16.5)
q9:  (2.9)  (29.2) (16.5)
q10: (13.6) (13.9) (3.5)
q11: (-.12) (-.28) (3.17)
q12: (-1.2) (2.56) (-.66)
q13: (-1.2) (2.05) (-.67)

before you even respond i can see that some of the readings are a little off (q11-q13), but is till lack the know how to say what is causing this whether  it is a bad transistor or something else in the circuit. any input would be greatly appreciated,

thanks!

Conner

I mean I'm not going to go through and compare all of these to the schematic, but if you say only Q11-Q13 is off you're probably OK.

Did you re-use the Q6 from the previous build?

Mike

 

[kessconn1]

I mean I'm not going to go through and compare all of these to the schematic, but if you say only Q11-Q13 is off you're probably OK.

Did you re-use the Q6 from the previous build?

Mike

Didn't expect anyone to go through the whole thing just thought maybe something would jump out to someone familiar with the build . yes all transistors were replaced except for q11 and q1. judging from my voltages that are off i would assume that these are the problem but i am not skilled enough to confirm this without replacing them. Which i will do but i would like to confirm these are my problem before replacing them. to confirm q 6 is brand new and all voltages off of it seem to read correctly

Conner