All things G1176 - the new "repost" thread.

[W DeMarco]

Right on,

I'll go through the resistors again and report back the results.. Shouldnt be to tough. I already checked all the interconnects as well. So whats hot down in Kent these days. Any good bands out there?>

Will

 

[enthalpystudios]

there's some cool stuff going on... there always seems to be a secret coalition of amazing music going on beneath the small college town veneer.

beaten awake is doing real well for themselves, play a fine show if you get a chance to see it.

i saw you recorded finless brown, very cool... used to play some shows with them before they moved.... i was in low in the sky and kind of honeypot and had played some shows with them.

to g1176 builders: sorry for getting Off Topic, espeically if this is the year 2010 and whoever's reading this is digging seriously deep down to find an answer.... sadly, I don't have it....

 

[W DeMarco]

So I found a few problems that I had hoped would clear up my GR mode peg, things like installing the ratio switch reversed, a couple of lame solder points...

The ratio switch probably solved my problem with the Q bias but it didnt help my gr mode vu problem.

Heres a big discrepancy I found between Gyrafs scheme and a bom I used. For the tracking Gyraf calls for a 500 k trim. In my bom I have a 100 k called for. That sounds like a big difference to me. At least if it was money it would be big diff! Im gonna hit the surplus shop and pick up a 500 k if their cool enough to stock it.

By the way I saw a killer weller solder station at hgr industrial surplus that the had listed for 90 bucks. However everythings on sale. I live about two miles away from the warehouse so if anyone ever finds something of use there I can check it out.

W

 

[W DeMarco]

I got a 500 k trim pot and installed which didnt help to much if at all. Meter is still pegged. This morning I did the resistor check which went, for the most part well. I have a led spelunkers light that complicated the issue. Playing tricks with my eyes.l; BTW what type of light works best for id'ing resistors?


So I picked up a bunch of FET's at electronic surplus: They are the 2n5457 type that Gyraf has listed for the substituted original. Noob alert: is it alright to use these? If it is and they are rare there are probably 100 more there!!

Anyone have a suggestion. Im real excited to get this monster up just a couple of gremlins to go!!

W

 

[enthalpystudios]

i think i used the 100k, but i cant remember for sure.... the 500k will be just fine, may be a little less range for the 'sweet spot' but it covers 0-100k, plus and extra 400 more k! will be fine.

for the meter, check the ratio board very carefully, and check the wiring to the ratio board...... the ratio board has quite a few things that affect the meter when set to GR mode. if there's a short on the ratio board, there are quite a few places that would cause the meter to peg one direction or the other. same goes of course for the meter switch, but since you started posting, i started remembering issues on my ratio board... i actually believe it turned out to be a little strand of wire wisping into another. gotta watch those guys. are you hard wired or using crimp pins to the frontpanel?

 

[enthalpystudios]

my folks are in town for the weekend, but i think i'll probably get a chance late tonight ( ;] ) to do a couple mods to one of my units for an A/B, which will require a recal

so that'll freshen me up, i can be a bit more helpful....

 

[W DeMarco]

I've been checking rechecking swapping things out and I still have a pegged VU in GR mode. I think its the only problem anymore.

I went through both switch pc's continuity is in place. Im gonna go through my pot connections again and see if that might be a factor.

Any other suggestions.

William

 

[byoung]

I have a question about using OEP's on Mnats board, the two R* and R*1 resistors are only changed from 10K to 12K if you use Lundahl wired 1:1, so for OEP's in either orientation I should use 10K, is this correct?

Also I'm curious, since this is my first project with transformers, what do I get from wiring them reverse, ie do I get more headroom, gain etc. on the input if wired 2:1 compared to 1:1 or how about on the output, less gain, more gain, less headroom? I'm just curious how the wiring of the transformers affects the unit and sound. If this has been talked about somewhere else can you point me too it? I couldn't find it via the search engine.

Thanks
Brian

 

[enthalpystudios]

hey brian... go for a 10k there.

the original revisions of the 1176 that the g1176 is based on had a 10db step up at the output, and this is why, on mnats board, the output transformer is wired 1:2, to get 6db extra gain to closer match the original.

to do that, on the output, just install the oep as it is on the board. If I remember correctly, the input transformer is wired 1:1. On the original, there was no input transformer. On previous revisions that *did* have an input transformer, it was wired 500:200. There are a lot of posts about all this, but basically, try it out as is.... see how you like it. If you feel you need to hit the compressor a bit lighter, you can try wiring the oep off board with a stepdown.

If you want, you can also install a couple pins on to the board so that you can use alligator clips on an upside-down oep while you try different windings and experiment before commiting with the soldering-iron.

its a picky issue, and you have to decide what you like and how you prefer to use the tool. if you haven't yet, print all the relevant material, like the schematic, the pcb layout from mnats site, and the oep datasheets from the oep site. these are invaluable while you are working on it, especially if you experiment with windings amd ratios

billy

 

[mnats]

[quote author="byoung"]so for OEP's in either orientation I should use 10K, is this correct? [/quote]
[quote author="enthalpystudios"]hey brian... go for a 10k there.[/quote]
You've tested this in both configurations?
[quote author="enthalpystudios"]to do that, on the output, just install the oep as it is on the board. If I remember correctly, the input transformer is wired 1:1. [/quote]
My last revision of my boards has options for different ratios on both the input and output transformer including 1:1 and 2:1 on the input; 2:1, 1:2 and 1:1 with the OEP on the output and the original 2:1 and modified 1:2 on the output. I did that to encourage experimentation, hoping that my fellow Lab Rats would try it out and post some results.

 

[enthalpystudios]

[quote author="mnats"]My last revision of my boards has options for different ratios on both the input and output transformer including 1:1 and 2:1 on the input; 2:1, 1:2 and 1:1 with the OEP on the output and the original 2:1 and modified 1:2 on the output. I did that to encourage experimentation, hoping that my fellow Lab Rats would try it out and post some results.[/quote]

sorry, didn't know that! i seem to only be able to pc-mount an oep in one direction at both input and output on my board.

so, if the oep is installed any other way at the input, i'm out of my element

sorry about that.....

 

[glide 1]

Sorry if this has been asked before.. Would these switches from ITT Cannon work on the Mnats 1176?

farnell order code 1701605 and 1701629


Also, i'm also looking for alternative pots to the Alpha (Taiwan) type used on Greg's BOM. 5M, 25k, 100k, 10k all from the same range and brand, just wanting them to all have the same feel /tension when turned. Thanks

 

[W DeMarco]

Make sure that you read the tech sheets. I noticed that the switches your asking about have solder lugs, youll want pc mount for Gyraf or MNATS boards. Basically the z in the manufacturers product number should be a c. Also you'll need to be able to program the switch to different position amounts. This is usually a small washer with a tab on it that you drop into the appropriate slot on the switch. The ones on the BOM that your using should give you some insight to what the paticular needs are.

 

[glide 1]

Thanks for pointing that out W DeMarco.

I see also that a 2pole 6pos switch is used on the 1176 but effectively only has 4 selectable ratios.... Is this what you mean by being "able to program the switch" so that only the 4 positions are used?

 

[glide 1]

I found a pair of VU Meters from an old Denon tape deck, it has 4 terminals; 2 for the meter (i believe, - have'nt tested), and 2 for the light (i know because i checked if the bulbs work with a 9V battery).

My question is, What can i do to check if it works and how do i know if it is the type that can be used for this project. Resistance on the meter terminals is 7.6kohm and on the light 6.6ohm. I'd post a pic of it but don't know how to do it here.

 

[W DeMarco]

Exactly what I meant by programming the switch. Check the early pages in this thread for info about the VU meter. The G1176 board uses 3.6 K on the meter if I remember correctley. Its the one resistor on the meter switch pcb. Heres a good vu thread http://www.groupdiy.com/index.php?topic=7628

W

 

[W DeMarco]

Also beware of the voltages coming off the meter light output. You don't want to go through bulbs if its to high for the light you mentioned.

 

[gevermil]

Anybody know the correct part for the 10V/1WZenor Diode
The parts list # dosent come up on mouser search Yet a bunch of others do ?
I think I ordered the wrong one

 

[W DeMarco]

[quote author="gevermil"]Anybody know the correct part for the 10V/1WZenor Diode
The parts list # dosent come up on mouser search Yet a bunch of others do ?
I think I ordered the wrong one[/quote]


Try this, taken from the parts sourrcing thread 10V/1W ZENER DIODE search 1N4740A at mouser when I did it came up with several options.

Will

 

[gevermil]

Yeah .... I wasnt sure which one to pick and in my haste I got a ZM4740A
It dosent have the solder leads
would rat shack have this ?