1176 VU Meter Substitution Question

[Echo North]

1k does not equal .775V RMS.

1K is the frequency ( the amount of cycles per second). The amplitude (or voltage) is a separate control.

What are you using to generate your signal?

Mike

 

[maxwall]

great general information regarding VU meters , thanks for the post and replies.

 

[3nity]

i'm using a function generator!

 

[3nity]

alright i made it sit at 0dB!
You;re right i did played with the amplitude and i got it!

So i could assume its working then i got something wrong with my 1176!
Argh!

You still think we;ll need to change some resistors to work perfectly in there??

Thanks

 

[Echo North]

Hey,

You need to get your signal generator sending out .775rms at 1K (good general frequency). Depending on your generator, the voltage may display as Peak-Peak, Peak, RMS, or in the case of my genrator...say it's p-p but actually show p.

Either way hook a DMM up to your signal generator and adjust the amplitude to read .775 on you DMM.

Now see what your VU reading is. In my case, with that meter it's +2.

A 910 ohm resistor in series to the meter should fix that and put it right at 0. See Keith's post about resistors in parallel to fine tune it.

Is your zero adjust working in your 1176?

Mike

 

[3nity]

Actually my 1176 is not compressing neither the VU;s is working!!

I have some troubles making my VU meter sits at zero.

Thanks Mike, dont worry its not the VU thats making default!

Jorge

 

[JW]

Can the PM1K meter bulbs be lit properly by the mnats power board?

 

[Echo North]

According to the PM-1000 schematic the lamps need +13v DC for proper illumination. So basically you can treat the meter as a SIFAM 12v lamp version.

Here is a great bit from Jacob about using the secondary to light a 12v lamp:
http://www.groupdiy.com/index.php?topic=275

Or you can use 2W resistors off of the lamp power section on the board. If I recall correctly that point is around +32V DC. There are a few post laying around on resistance in this scenario.

Mike

 

[glide 1]

Sorry to dig this up but i thought i'de post it here in case someone had the same issues i am having.

My unit is the Mnats rev h/j with a Sifam AL29WF. I think i have it calibrated ok and has been working very good for 2+years now. I have issues though that i never got around fixing...not sure if it is critical to the unit's performance or not.

I'm having a hard time keeping my VU set to "0". I find that if i adjust the release pot, the "0" setting that i had moves to +- -3db....more if i set it to a slower setting. Also sometimes when i turn the unit off and on, it does not always sit at "0" and takes a few min to "settle" at "0". Could this possibly be due to tolerance or quality of the trimpot i'm using for R55 (zero adjust)? If so what type trimpot do you recommend using for this. I'm looking at Bournes trimpots but not sure which particular 1 to use.

Any help would be appreciated, thanks in advance


glide 1

 

[Echo North]

My unit has always taken about 15 min to hit "0" spot on. It usually starts about 1/2 a db south of zero and slowly makes it's way up. It's a good idea to only set the "O" adjust after the unit has been powered for a good 30min.

My meter also sways with a twist of the release pot. Only about +/- a quarter of a db though.

Sounds like your issues maybe a little beyond this though.

Mike

 

[glide 1]

I also have these Denon VU's i plan on using for my next 2 units. Anyone familiar with these? And if they will work?

Still have to do tests using the sifam as reference not sure how to. Will update here on how things go.

Thanks to all who posted here, very informative thread.

 

[glide 1]

[quote author="Echo North"]My unit has always taken about 15 min to hit "0" spot on. It usually starts about 1/2 a db south of zero and slowly makes it's way up. It's a good idea to only set the "O" adjust after the unit has been powered for a good 30min.

My meter also sways with a twist of the release pot. Only about +/- a quarter of a db though.

Sounds like your issues maybe a little beyond this though.

Mike[/quote]

I was hoping a simple trimpot replacement would do. i understand +-3db is a lot, and would like to fix this. Thanks a lot Mike

 

[glide 1]

Ok just checked its +- 1db and not 3db variation in the VU. I let it warm up for 30min, set to zero and left it like that.

 

[gyraf]

Here's surely something missing in this thread?

Jakob E.

 

[JW]

Sorry to bring this one up again guys.

Just wanted to clarify concerning lighting the PM1K bulbs. I have a dual 1176 that I'm working on here with the PM1K meters (which call for 13V DC) and I'm using Mnats' p.s. board.

Should I take this from the +30V DC output of the power supply, and run the meters in series, with a little resistence? Or should I take it from the secondary of the transformer? (about 27V's AC on both secondaries)

Will DC bulbs like this be okay with AC? 

Thanks,
JW

 

[RedNoise]

great general information regarding VU meters , thanks for the post and replies.

+ 1 !

 

[3nity]

Do you think i could crack open this meter, change the lamps for leds and then power the leds from the 1176 main board?

 

[pstcho]

Hello Guys, ive built a G1176 long ago and i finally decided to debug every problem around the working state of it ( compresses perfectly )

i used a random Vu Meter that manages to make the  perfectly from GR position but doesnt really show -20 when it compresses 20db 8....4....

also in By pass it doesnt show any movement
to finish it shows a very very little motion while in VU position when the input is extremely loud

any idea, advice ?

thanks

 

[gyraf]

..have you looked at all the related/similar problems in the giant 1176-thread?

/Jakob E.

 

[pstcho]

Dear holy Jakob, i believe i went through all of it the last 2 months, i managed to fix many small issues like some very low hum ( adding soldering all over the ground PCB fixed the problem )

i managed to make the vu meter work more or less ok, but i didnt manage to find answers for those problems :/