[BUILD] 1176LN Rev D DIY

[mnats]

As Ed mentioned earlier I have been working on an input transformer PCB. Since most of the modern input transformer options seem to be PCB mount I wanted to provide a tidy way of nailing them down without resorting to vero/perf board. The boards will accept the following transformers:

Altran C-3837-1 - O-12 clone
CMMI-2PCA - Cinemag's substitute for the O-12
CMLI-15/15B[PC] - as used in some of the reissues
Lundahl LL1540 - for a G1176 style input but wired 2:1 stepdown
OEP A262A2C - wired reversed for 2:1 stepdown

There is an option on the boards for an H-Pad as used on some of the reissues described by W O'B and neatly drawn by ed. This might provide a low-cost alternative for those unable to get a T attenuator.

Of course, you can also use a T attenuator at the input or use a potentiometer following the transformer ala G1176.

I'll post the files for a home etch, but will also have a batch made that can be distributed with the Altran transformers that ed is going to offer.

 

[kazper]

Hopefully Ed gets a few more than he went with on the Cinimags. I would definitely like 2 units with the altrans.

 

[ap123]

[quote author="kazper"]Hopefully Ed gets a few more than he went with on the Cinimags. I would definitely like 2 units with the altrans.[/quote]

Same here. I'm wondering if I might be able to bump up the quantity on this round of production. $25.75/unit at 25 pieces.

 

[BladeSG]

[quote author="Lowfreq"]I just paralleled two 100pf caps.[/quote]

Thanks. :thumb:

That's probably what I'll end up doing too.

 

[Stagefright13]

Here's a couple pics:

 WOW! that little black board seems to have an attitude just sitting there doesn't it? Too bad we can't make cases out of transparent aluminum ala Star Trek...
 Gonna fire mine up later this week. I went to radio shack to look for some knobs for another project. And saw that $3.99 1:1 transformer that Aaron used to test his so I broke the budget and procured it.
 I would like to thank Mnats for all his hard work. That input tranny board looks great. Also like to thank Ed and Aaron for helping all of us get the parts we need! And special thanks to Kato and his parts list for those of us that are new to the Mouser and Digikey catalog. Altho I am getting better with those bible things now. This project has turned into a great team effort. Looking forward to that uneasy feeling of hitting the power button lol...
 Speaking of power... What size fuse do ya think I should use?

John

 

[BladeSG]

[quote author="BladeSG"]Hi all... quick question.

I'm having a little trouble finding ceramic caps in 200pF (C3,C6). If I use 220pF is that going to cause problems? (I'm thinking it shouldn't matter)

Thanks in advance

P.S. If anyone has any 2N3391 transistors spare that you'd like to sell me, pls PM.

Steve[/quote]

It only occured to me today that a 220pF cap is only +10%.... duh!!

 

[ap123]

Just a note... Leeds Radio in NYC just got a shipment of NOS Mallory T600s (probably off ebay, doh!). The price is $36+shipping. Not sure how many they have.

You can order by telephone (718 963-1764) , fax, (718 963-1963) or email sales a/t leedsradio d/o/t com.

Note to moderator: I didn't want to post this on the black market as I'm not the seller.

 

[kazper]

What is the deal with the R-OPT1 Threshold Pot on the threshold board?

I searched around and must have overlooked it.... anyone have any clues on if we should put like a 2K pot there and adjusted it to read zero... for later..?

Kevin

 

[ap123]

[quote author="kazper"]What is the deal with the R-OPT1 Threshold Pot on the threshold board?

I searched around and must have overlooked it.... anyone have any clues on if we should put like a 2K pot there and adjusted it to read zero... for later..?

Kevin[/quote]

I probably have little place even taking a stab at this; but I believe it is an optional pot that allows you to tweak the threshold that is otherwise dependent on the ratio. If you look at page 10 of the urei manual (pdf page 13...ugh) there is a chart titled "1176LN Transfer Characteristics." It also says:

The transfer characteristic graph also indicates the region of the threshold.  Signals at levels below the threshold will not be affected by the compression/limiting action.  Higher signal levels will cause a controlled decrease in amplifier gain resulting in a change of dynamic range.  The 1176LN input level control adjusts the amount of signal to be processed above the threshold, and hence the degree of compression or limiting.

I cannot determine to what degree you could adjust the threshold and with what pot...but I would be very interested in some hints :grin: I would also be curious to see what the nuke/all-in setting looks like on the transfer characteristic graph.

 

[mnats]

[quote author="kazper"]What is the deal with the R-OPT1 Threshold Pot on the threshold board?[/quote]
First raised by Jakob in the big 1176 help thread as a response to some people saying that the threshold on their G1176 was too low. Turn the board over - you have to cut the trace indicated in order to use it. Leave the trace alone and the board works just like a regular G1176 rotary ratio board as is.

I think that by chasing a higher threshold you run the risk of putting too hot a signal through the FET, thus increasing distortion, but I thought others might want to experiment.

 

[Skylar]

mnats,

...couple of questions:

Will your pushbutton boards work with the Rev D project?
If so, will the wiring need to be done differently from your other 1176 projects?
Details are not absolutely necessary, I can figure it out when I get the boards ...just looking for a clear and distinct "yes" or "no".

Thanks

 

[Stagefright13]

I'm up to the pushbutton thing myself. I have the original style latching type. I am looking into it now. I haven't built the G1176 so haven't done this before. After looking at the schematic I can't tell which switch is which. Like top to bottom etc. I guess I can find the info eventually unless someone has a link they can post.
On another note I did power up my board and ps is looking good did voltage check and all and after 2 hour warm up.
30-0-30 toroid 34ac in, 44 after rectifier, 29.7 after reg. Running normal temps. R87 is a little hot but is about norm I believe. Prolly 160 degrees F ? Didn't hook anything else up yet tho... Waiting on pot from Aaron for last part (Besides input tranny)
I do have to make 4 small aluminum parts on milling machine to hold pushbuttons to the case studs tho. Guess I'll do that Friday. Then figure how to wire them this weekend.
But it passed the smoke test!!! Woohoo!!
:green:

 

[Skylar]

Okay, I just octuple-cross-referenced...

mnats' pushbutton layout
mnats' wiring guide
mnats' Rev D schematic/layout
mnats' Rev F layout
Urei Rev D/E schem
Urei Rev K schem (on which gyraf's G1176 is based)
Gyraf's G1176 layout
Purple MC76 schem

Looks like mnats' pushbutton boards will work fine for his Rev D boards, though you might want to follow the schematic closely during the build.

 

[usekgb]

[quote author="ap123"][quote author="kazper"]Hopefully Ed gets a few more than he went with on the Cinimags. I would definitely like 2 units with the altrans.[/quote]

Same here. I'm wondering if I might be able to bump up the quantity on this round of production. $25.75/unit at 25 pieces.[/quote]

I'd sure be in for a couple of these as well.

Cheers,
Zach

 

[Stagefright13]

I'm doing the pushbuttons p2p. I got the GR one done. Took a while because of all the jumper wires etc. The Purple schematic was a great help. Should be testing it tomorrow with tha "Greenbud" lol.
Only problem is Fedex sent my output pot to the front desk at a hotel. But they say they will get it to me tomorrow... We shall see! And free shipping. :green:

 

[Stagefright13]

Mines up and running. No gain reduction tho. Probably something to do with the bypass. Will fix it tomorrow. No noise or hum tho. Had to uses 3 schematics to get the wiring right. The purple schematic was much better when wiring the GR push switches because it say what button is what. Then used the urie schematic to get meter wiring,
Would be nice to have it all in one...

 

[sintech]

Stagefright13, this maybe helpful as a reference point.

I pulled an original Urei 1176 apart and copied out the point to point for interconnects, meter and ratio switch banks. This was for the Purple MC76 so some PCB pads may be labled differently.

Purusha redrew the switchbank, and is much clearer in this format.

 

[Stagefright13]

WOW thank you! Can't go wrong with that. Appreciate the help. It's very close right now and sounds fine except some kind of wiring problem. I will check it against that diagram.

btw I used a .022 cap on the pot...

Thanks again,
John

 

[timmygrimm]

forgive the rather basic question, but i'm wondering if this power transformer will work for a dual rev d.

Digi-Key Part Number TE62065-ND
Manufacturer Part Number 62065
Manufacturer AMVECO MAGNETICS
Description TRANSFRMR 22V 1.136A WITH WIRES


thanks!

tim

 

[Stagefright13]

I used the 30-0-30 (60 ct) 1.3 amp one from digikey.

In that drawing shouldn't the 10 meg resistor be wired on the 20:1 side?

OOPS the toroid I used was from mouser. Hammond 546-182K30
that's the part number.