About 1176 Mnats board - some questions

Hi all,
I'm a newbye and for the very first time I'm doing my 1176 with a mnats board rev H.

There's some points that I don't understand as well about the components in his list. :?

http://www.geocities.com/m_natsume/1176_bom.html

1) [...] (R*,R*1 if using Lundahl input transformer - note: Lundahl suggests 12k in this application rather than the 10k suggested in Jakob's version). Why this?

2) the component 37 in the b.o.m. is a "resistor carbon" with a value of 2M2. Is it a 5% 0,25W or a 1% 0,25W?

3) Can I use a trim pot of 2K2 instead of 2K in the list?

Thank you so much,

maalexx

1) Because Lundahl says so

2) Either

3) Yes

I'm gonna build a dual 1176 from mnats rev J boards. Which kind of GR meter do I have to use? I already read it has to be AC reading. I don't want to use sifam cause they seem pretty expensive to me. So which technical facts do I have to know to choose an other one?

Regards

Ben

Ptownkid:

thank you very much :green:


Benny:

you need a REAL vu meter, that has a germanium diodes system. Try to search through this forum, you'll find a lot of useful infos about it.


maalexx

O.K. Real VU meter then with germanium diode rectification.
But how much uA/mA does it have to be? That is the only last thing I need to know now. :green:

If you look at the board there is a area that don't need it''s parts if you do transformer inputs. there is also some Resistors and a few caps that are there for using a input transformer.

2M2 = 2.2 M Ohm
22R = 22 Ohms

look for Greg's BOM as well as the other one. There a good bases to go off, greg didn't give you locations which helps out allot and the other bom is based on Mnats board.

Use 1% if you buy them, 5% if you have them lying around or gan get for cheap local. Radio shack sells a 1% and 5% kit for about $13 that has allot of the needed values but not all of them

Any Trim pot above the value will work fine.

Just buy the sifam meters there really not that expensive at $60 shipped and there is no messing around to make it work, plug and go. There is other meters around on the web, I will look through my bookmarks and give you some good inexpensive links if you wish for some others that should work fine as is like the sifams. the sifams are top notch meters and you can get them on ebay every once in a while for decent prices.

check out http://www.tawelectronics.com/ for your resistors cheap, they also stock all the wima caps. There min order is like $10

I have both resistors, metal film at 1% 2M2 and carbon film 5% 2M2.
I used the first in my board.

In revision H of mnats board there is a little error, that he fixed in revision J: Lundahl LL1540 input transformer doesn't fit as well to the beginning area of R*, then I soldered R* under the pcb, I think it's good this too.

- I used to put R* and R*1 of 12K as Lundahl suggested, instead of 10K.

- C*1, C*2, C*3 and C* don't need to be placed, aren't they?

- component no. 66 in mnats b.o.m.: 3,6K, R51 and R59. R51? Where's R51 place?

[quote author="Benny"]O.K. Real VU meter then with germanium diode rectification.
But how much uA/mA does it have to be? That is the only last thing I need to know now. :green:[/quote]

http://www.jlmaudio.com/VU Buffer.htm - best solution if you don't want to pay for a real VU meter

With regard to the VU Meters:

If you want a cheaper option either buy the one from Mouser, and do the mods that someone here posted

For those of you wishing to use the inexpensive Modutec VU meters from Mouser (http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=291437).

I have found replacement resistor values that make this work.

change R59 to 240ohms
change R58 to 82Kohms

This allows the gain reduction to be set properly.

for the +4dbU output level:
Insert the rectifier that came with the meter between points X&Y on the main and meter board. You will also need to remove R51 (replace it with a short). This gets the output reading almost exactly correct, mine runs about 0.25dB higher on the VU meter than it should. You might try playing with a valus for R51 to adjust this.


Good Luck and I hope this helps!

Click to expand...

Here is the Mouser link: http://www.mouser.com/search/ProductDetail.aspx?R=3MAS-AVU-000virtualkey54100000virtualkey541-3MAS-AVU-000-AW

OR

Another option I used for VU meters was to find some used ones on eBay. There tend to be a lot, and you can get a bonafied VU for around $30.

I can't see why you would go through all the trouble just to save $25 and not just buy the sifam's and be done. In the end you have a nice peice and it's still a boatload less then buying a real 1176.

I personally have a SIFAM AL-29, I just soldered my board and now I'm going through wiring up. Any notice about R51?

R51 is the only resistor on the small meter board.

I had to wait till I was at home and could look at a unstuffed board. It rang a bell with me because I had a hard time finding one of them also.

kazper,
I've just seen R51 in the little board. I didn't see it because my choose went to the original pushbutton bars, that I ordered from Peigenesis.com.

maalexx

on the 1176D thread is a very easy to understand how to setup switches for a 1176. I think it's the same on both units the F/H and the D versions.

make sure you understand the issues associated with r26 in some configurations are just in general.

for all the community, I'm doing an order for the questions... this thread continue in "the lab" with this title: "mnats 1176LN board - wiring up step by step"


thanks for your help,


maalexx