Echo North
Well-known member
Chrome Heart said:
Could be a million things. See if you can get the qbias full negative. If it still oscillating, you need to go through everything.
[BUILD] 1176 Rev A - Back to the beginning...
- Thread starter mnats
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Help Support GroupDIY Audio Forum:
Could be a million things. See if you can get the qbias full negative. If it still oscillating, you need to go through everything.
Echo North
Well-known member
junkface said:
That's pretty normal. Usually it's that shielded wire to pin 7 or the wiring to the output. Cleaning that stuff up and getting it away from the PCB should eliminate it. I may also just be caused by having the lid off. Either way it's not your main issue (the oscillation at max output).
If you can't get a 10dB drop I would expect something off in the GR amp. Maybe try switching out the semi's?
Mike
Echo North
Well-known member
junkface said:
True.
I'm pretty stumped. I'd have to see it at this point I think. Maybe one of your FDH333 diodes is dead. Just a wild guess at this point.
Chrome Heart
Well-known member
OK so, color me red, my sine wave WAS oscillating. Dont know why but it went away after a reboot of the mac. Strange.Hairball Audio said:
At any rate Im having trouble with the null adjust, I cant seem to get the voltage to zero without running out of room on the trimpot. As I recall I matched the 3707's so I dont know what else it could be. I built it in 2013 but Ive been experiencing some problems lately.
jonathanmorbin
Well-known member
- Joined
- May 25, 2012
- Messages
- 67
Hi, I'm having a few issues and I'm a bit stumped at the moment. Basically my first issue seems to be that i have a clipped sine wave at pad 15. Its fine one side of R16 but on the 2n3707 side it has a clipped top half of the sine wave. All my voltages in that area of the circuit are pretty much bang on. I was able to Q Bias adjust but i cant do the next step. Voltages in the GR Meter circuit are pretty much bang on or at least will be once i can do that part of the calibration.
2nd problem is that i don't have GR. My ratio boards are working correctly. however as soon as i connect Pad 22 i loose my AC signal going in to the GR Circuit. at least it drops to almost 0. This part of the circuit i have voltages that are off. some are as much as 10v higher than they should be. They are all fairly relative however for example at Q7 i have 15v, 14v and 22v. My 30v rail is correct however at 29.8v.
I built 3 boards at the same time and they all have the same faults. I feel like I've exhausted all the options in testing. Any one got any ideas?
2nd problem is that i don't have GR. My ratio boards are working correctly. however as soon as i connect Pad 22 i loose my AC signal going in to the GR Circuit. at least it drops to almost 0. This part of the circuit i have voltages that are off. some are as much as 10v higher than they should be. They are all fairly relative however for example at Q7 i have 15v, 14v and 22v. My 30v rail is correct however at 29.8v.
I built 3 boards at the same time and they all have the same faults. I feel like I've exhausted all the options in testing. Any one got any ideas?
Spencerleehorton
Well-known member
Echo North
Well-known member
Chrome Heart said:
Are the voltages in that section looking ok referring to the schematic with voltages?
Echo North
Well-known member
jonathanmorbin said:
You can always send them (or one) in for repair.
http://www.hairballaudio.com/build-support-services
If none of them work I'd suspect basic build error like cold solder or damaged components from static electricity exposure. Just guessing.
Chrome Heart
Well-known member
Im gonna put it back on the bench tomorrow night and check it out, I double checked all the component values when I had it open to see if I made some simple mistake but everything is right.Hairball Audio said:
Spencerleehorton
Well-known member
Hi All,
so did anyone take a look at the wiring for the 4 gang switches i posted in previous message, i think ive wired it right?
regards
Spence.
so did anyone take a look at the wiring for the 4 gang switches i posted in previous message, i think ive wired it right?
regards
Spence.
Spencerleehorton
Well-known member
Echo North
Well-known member
Spencerleehorton said:
Did you not use switch PCBs?
Checking that would take more time than I have, but you could always just give it a try. Nothing will blow up.
Mike
blackartmixing
Active member
- Joined
- Dec 18, 2013
- Messages
- 34
Hi i'm just putting together my first 1176 rev A from hairball audio. just a quick check before i proceed, i'm getting 29.5 on the 30V rail and -9.6 on the -10V rail. does this look acceptable or should i go back and check what i've done? if so, what do i need to look at? my soldering skills are not the best at the moment but i don't know if this could be a problem so far. many thanks
Chrome Heart
Well-known member
i think your in good shape with that.blackartmixing said:
Spencerleehorton
Well-known member
Chrome Heart
Well-known member
Ok. All of the voltage readings look good. I have a 1.2 circuit board and a 1.2.5 voltage chart but everything is certainly within 10%. The hfe is matched at q12 and q13. The null adjust voltage gets to .067 when the trim pot is bottomed out. Is this a concern or should I switch the trim pot out to a 5 k?
Chrome Heart
Well-known member
A 21 turn 5k did the trick.
Spencerleehorton
Well-known member
Chrome Heart
Well-known member
So how different sonically, is the Hairball Rev D from the Rev A? Has anyone build both? It looks like they use the same Tx's in the kit.
