sr1200
Well-known member
well, once you get to a certain level, the unit isnt compressing anymore since you're below the preset threshold. Def check the input stage.
[BUILD] 1176LN Rev D DIY
- Thread starter mnats
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Help Support GroupDIY Audio Forum:
pittsburgh
Well-known member
I can't get a 0db reading when my meter is set at +4. I've got my input and output controls cranked to 10 and I'm getting -6 on the VU meter. Could something in the ratio circuit be the culprit?
pittsburgh
Well-known member
On Friday I noticed the three unused connections on the bottom of the vu meter. A member that I was responding to at the time incorrectly informed me that the unit would not compress without those connections , and in the process of taking out and replacing the front panel, I broke off the solder point on pad six of the ratio board that leads to the output pot. I attempted to resolder and question wether or not I have been adequately able to fix it. While returning the unit to it's original order my level pots now need to be set to full to get any reading on the +4 meter setting. Before this teardown I could easily get 0VU with both pots set at half.
I've gone over the schematic, and it looks like connection six, should have audible continuity with R22, R 21, R20, R19, and R 78 Is that right? If I've ruined this trace for pin 6 is the best idea to just order a new PCB and resistors?
<img src="http://web.me.com/natesbasement/HARRISON_PHOTOS/PHOTOS_files/IMG_0352_1.jpg"/>
<img src="http://web.me.com/natesbasement/HARRISON_PHOTOS/PHOTOS_files/IMG_0353_1.jpg"/>
I've gone over the schematic, and it looks like connection six, should have audible continuity with R22, R 21, R20, R19, and R 78 Is that right? If I've ruined this trace for pin 6 is the best idea to just order a new PCB and resistors?
<img src="http://web.me.com/natesbasement/HARRISON_PHOTOS/PHOTOS_files/IMG_0352_1.jpg"/>
<img src="http://web.me.com/natesbasement/HARRISON_PHOTOS/PHOTOS_files/IMG_0353_1.jpg"/>
sr1200
Well-known member
the way i usually do it when a pad goes bad (hey that rhymed) is just go about 3mm from the pad (following the trace) and scratch off the protective coating over the trace (GENTLY) with a small flat head screwdriver. After you scrape away the coating the copper trace will be exposed and you can easily solder directly to the trace. If the trace is led on both sides of the board, you may have to run a tiny lil jumper wire THRU the existing hole( (talkin HAIR like wire.. kinda stuff you see on little transformers) or you can run a thicker wire around the board and have that wire connect to the trace or existing pad on the top.
Reason for going a little bit PAST the pad and not scraping RIGHT after the bad pad (hey another rhyme) is so the trace doesnt pull off the board where the pad fell off.
I dont have a revD open infront of me to see if the trace is led on both side (my assumption is its NOT, but we know what happens when you assume). Will work just as good as the pad, but dont try to solder and unsolder a bunch of times or you'll start to pull the trace off the board. If that happens, its time to call hairball. Best of luck!
Reason for going a little bit PAST the pad and not scraping RIGHT after the bad pad (hey another rhyme) is so the trace doesnt pull off the board where the pad fell off.
I dont have a revD open infront of me to see if the trace is led on both side (my assumption is its NOT, but we know what happens when you assume). Will work just as good as the pad, but dont try to solder and unsolder a bunch of times or you'll start to pull the trace off the board. If that happens, its time to call hairball. Best of luck!
pittsburgh
Well-known member
Thanks SR.
earth tones
Member
- Joined
- Mar 7, 2011
- Messages
- 20
When applying any of the multiple ratio settings on the pushbutton Rev D (4+20, all in), is it normal for the metering to become highly erratic....needle flying around, off the scale?
Majestic12
Well-known member
Yes, it goes full right, nothing to worry about.
I have a question about the PSU board that mnats offers. http://mnats.net/psu.html
Please excuse the newb question.
Would it be better to have the trim pots in or just the resistors on the psu board, and if I do put in the trim pots....how do I go about calculating the value for the resistors. This is for a 2-1176.
I am using the power tranny from Hairball Audio:
Dual Primary (115V/230V) Toroidal 2X25 30VA Power Transformer
[30VA-PT]
Avel Lindberg 2X25 30VA dual primary/secondary toroidal power transformer.
Specs:
TRANSFORMER, 30VA, 2 X 25V
Voltages, primary:0-115, 0-115
Voltages, secondary:0-25, 0-25
Power, per secondary winding:15VA
Approval Bodies:EN60950, EN60742, UL Recognised
Current rating:0.6A
Diameter, bolt hole:5mm
Diameter, RoHS Compliant: Yes
Thanks.
Please excuse the newb question.
Would it be better to have the trim pots in or just the resistors on the psu board, and if I do put in the trim pots....how do I go about calculating the value for the resistors. This is for a 2-1176.
I am using the power tranny from Hairball Audio:
Dual Primary (115V/230V) Toroidal 2X25 30VA Power Transformer
[30VA-PT]
Avel Lindberg 2X25 30VA dual primary/secondary toroidal power transformer.
Specs:
TRANSFORMER, 30VA, 2 X 25V
Voltages, primary:0-115, 0-115
Voltages, secondary:0-25, 0-25
Power, per secondary winding:15VA
Approval Bodies:EN60950, EN60742, UL Recognised
Current rating:0.6A
Diameter, bolt hole:5mm
Diameter, RoHS Compliant: Yes
Thanks.
Echo North
Well-known member
Calculator here and formula here:
http://www.reuk.co.uk/LM317-Voltage-Calculator.htm
R1=120Ω on the MNATs I believe.
I'd use static resistors.
http://www.reuk.co.uk/LM317-Voltage-Calculator.htm
R1=120Ω on the MNATs I believe.
I'd use static resistors.
I expected to find this in the search but did not.
on mnats wiring pages the ORANGE and RED wire of the avel lindberg power transfomrer from hairball are tied together and sent to a terminal strip.
these are said to be center tapped I guess but it also says 0v is center tap which the transformer says BLACK and ORANGE are 0v
RED and YELLOW are 25v
So am I creating a center tap with BLACK (0V) and ORANGE (0v) for MY transformer which is different than the one in the wiring pages?
I thought he was saying it was the same?
on mnats wiring pages the ORANGE and RED wire of the avel lindberg power transfomrer from hairball are tied together and sent to a terminal strip.
these are said to be center tapped I guess but it also says 0v is center tap which the transformer says BLACK and ORANGE are 0v
RED and YELLOW are 25v
So am I creating a center tap with BLACK (0V) and ORANGE (0v) for MY transformer which is different than the one in the wiring pages?
I thought he was saying it was the same?
Echo North
Well-known member
number2 said:
The transformer diagram (on the transformer) is misleading. 0V is simply showing the polarity of the windings.
Read through these responses:
http://www.groupdiy.com/index.php?topic=20058.msg594943#msg594943
Echo North said:
I apologize I am very new to this. Where did you see R1=120ohms? I looked at the schematics for the psu and it doesn't give a value. on the (http://mnats.net/psu.html) page it gives a calculated value for R1 to be 390 ohms and R2 to be 1500 ohms with a power supply of +30/-10 volt (which is what I think I have). When I put the voltage (30v) and the R1 value (390) it doesn't give me the 1500 ohms for R2 as calculated on the Mnats site. I must be doing something wrong...hahahaha. I just don't want to blow my stuff up so I am being very cautious and asking alot of questions. Thank you for your help.
Dan
Echo North
Well-known member
R1 on the calculator.
R6 and R4 on the MNATs schematic.
R6 and R4 on the MNATs schematic.
Echo North
Well-known member
Look at the circuit diagram on the calculator link.
Positive rail:
R1 on the calculator is R4 on the MNATs schem (120Ω). If you do the calculator you'll get 2760Ω which matches MNATs calculated 2.7K value.
now do the same on the neg rail and you'll get 840Ω.
Mike
Positive rail:
R1 on the calculator is R4 on the MNATs schem (120Ω). If you do the calculator you'll get 2760Ω which matches MNATs calculated 2.7K value.
now do the same on the neg rail and you'll get 840Ω.
Mike
pittsburgh
Well-known member
I'm running into the problem of not being able to get a zero db reading on the VU meter when in +4 mode. When I made a post the other day I was having an issue with the ratio board. I made a jumper for pin six to address that issue, and I also found that pins three and four were seeing each other. After fixing both of these issues I'm still having the same problem. What else should I check?
sr1200
Well-known member
If you follow the MNATS guide to a tee, you can't go wrong unless you have a bad board or component. Then its schematic time. Just make sure you read the fine print on his site. Especially when it comes to the transformer wiring. He has a separate section for the hairball kit which includes EXACTING directions.
MNATS "Test continuity between the ground pin and chassis. If there is a reading any greater than 1 Ohm figure out why and correct the problem before proceeding."
I have a $30 DMM and I get between 0.3 and 1.2 ohms (average is 0.9 ohm)
The reading from screw hole to adjacent screw hole in the chassis is about the same. do I just have a crappy DMM?
Figuring out why: There's really only 3 reasons right?
1) cheap MM
2) poor soldering
3) not enough surface area on countersunk bolt hole.
It must be fine and I'm over-analyzing but this is "the most important connection".
I have a $30 DMM and I get between 0.3 and 1.2 ohms (average is 0.9 ohm)
The reading from screw hole to adjacent screw hole in the chassis is about the same. do I just have a crappy DMM?
Figuring out why: There's really only 3 reasons right?
1) cheap MM
2) poor soldering
3) not enough surface area on countersunk bolt hole.
It must be fine and I'm over-analyzing but this is "the most important connection".
