All things G1176 - the new "repost" thread.

[adoucette]

quick q, on the BD135 and BD136 transistors, which side is the front? Silver foil side or black with writing side? This data sheet shows the transistor but doesnt give any clues as to if this is the side with the silver foil or the other side..

so for example, if I were looking at the transistor from the silver foil side, reading the legs from left to right, how would they read? E.C.B, or B.C.E?

Thanks

 

[adoucette]

Datasheet im referring too:

http://www.fairchildsemi.com/ds/BD/BD135.pdf

 

[MartyMart]

Don't let that little "3D" photo confuse you, every data sheet I have for the
TO126/220 size items has the pin-out shown across the front of the device
which has the "numbers" on it , and never from the metal or plain back .

So across the front and pins down 1-2-3 E-C-B

Could be that you screwed your regulator when you had the Transformer wired
badly a page or so back, for the sake of 50 cents, I'd try a new regulator as well
as checking the parts around it as Geoff suggested previously.

I'm on my second 1176 and followed the Mnats site instructions VERY closely, this
saved me a lot of headache and gave me a working unit right away, which only
needed calibration - again following all the known instructions and tips.

Also, I've had parts that are marked incorrectly from major suppliers , such as 100
22k resistors that were 2k2's !! - so check EVERY one before fitting unless you are
100% sure that they are the correct value - check ANYWAY !

And don't get too down on yourself, it takes time and effort and lots of studying to
get all this stuff down, you WILL get there, just be patient as the rewards are SO
worth it in the end .

Marty.

 

[gswan]

[quote author="adoucette"]quick q, on the BD135 and BD136 transistors, which side is the front? Silver foil side or black with writing side? This data sheet shows the transistor but doesnt give any clues as to if this is the side with the silver foil or the other side..

so for example, if I were looking at the transistor from the silver foil side, reading the legs from left to right, how would they read? E.C.B, or B.C.E?
[/quote]

The metal side is always the back of the device. It's intended to be attached to a heatsink to dissipate the heat from the die.

 

[adoucette]

Thanks for the help guys, I checked the mounting of these transistors and they are mounted correctly. Still havent had time to trouble shoot any more, been crazy busy. I might just have to ship it home and keep going on it during my time off, we'll see.. would be nice to get it goin for this record though!

 

[JW]

Hey guys,
A couple questions.
I did a search of this thread, but didn't find any info about R46, the 10M ohm resistor.

There isn't a spot for it on Mnats version J board. I see where it is on the schematic, right next to r87, but then actually R87 in the Gyraf schematic appears to be different than R87 on the mnats board. Anyway, what's up with R46? Is it not needed?

Also, I have all the parts for both a transformer and IC based input. Has anybody wired up a switch whereby you could use both? It would obviously be a pretty complicated switch, as the input pot also is different.

I guess I could just have 2 input pots. and a simple double pole after the input jack. That would probably be silly though. Any ideas?

 

[kenrinc]

JW,

R46 is not on the rev J main board, it's on the ratio switch board.

There are others who have done the switched elec/bal input and trannie input. Don't know how they did it. I had read a bit about it in the 1176 threads here. I don't think there was much actual detailed info though ....

Ken-

 

[JW]

Hey Ken,
Thanks, technical mistake on my part.

I have it filled but I apparently didn't mark it off when I filled it, so at some point I couldn't find it. Still I don't remember putting a 10M in anywhere, so I'll have to check that value again and make sure.

Anyway, I'll start the long process of digging through the threads looking for possible switching info between inputs.

One more question, though.
This concerns the slam mode wiring tuturial on Mnats' page.

It appears that when the suggested slam mode switch (alpha stat) switch is wired into the ratio board, one spot on the ratio board is left unconnected that looks like it could be important. That point is between point "7" and one side of the attack pot. Is this how it's supposed to be or am I missing something?

 

[kenrinc]

Yes there is at least one spot on the ratio switch that looks like it should be connected to the pcb but isn't. In other words there is a solder pad left with no connection. I can't off hand remember which one it was but I believe it was one around the main perimeter. Wiring using the photos was difficult for me and I ended up doing it wrong ( I missed the two in the center ). The switch mnats shows is no longer available and although the new switch looks the same you have to watch where the "tab" is located when your wiring it up. The photos only show one side of the switch even though there is 6 or 7 photos.

Ken-

 

[JW]

Hey Ken,

Thanks. The wiring of the second side of the switch is symmetrical to the first side right?

Anyway, I followed the pictures, and my switch appears to be wired and soldered in the same as Mnats'

I think what might be confusing things is that in the second to last pic it appears the switch isn't finished. i.e. there isn't the wide sweeping connection between the last leg and the second story middle tab.

Mnats?

 

[kenrinc]

Jw, yeah you got it. The pins are offset (ie: one pin is missing in each set of 5) It's the last pin that is tied over to pin 4 of each side. If you look at the pics you'll notice that at least the first 8 pics only show the tabbed side of the switch. Only the last photos shows both sides but it's at a middle view so it's hard to ascertain what is what. For me personally, it's part of DIY, what can I say, you can't expect to have it all so sometimes you just got to try it and see if it works :wink: (directed at me).

If you'll notice there is only one picture that shows the two center pins and that's where I obviously didn't look clear enough. Really easy to miss.

Ken-

 

[JW]

Hey guys,

Concerning a switch to go between the IC and transformer input, I drew this up: http://img151.imageshack.us/img151/6318/switchtl3.jpg

Now, I don't really know a whole lot about how I should draw a switch, but if I could find something like this, I imagine it would do the job.

The middle row (top to bottom) would be the common connections to both the input pot and the input XLR. The first three rows (left to right) would be the pot, the last three the XLR.

Would this be called a 6 pole double throw?
I'm trying to find the correct switch at Mouser.

 

[gswan]

You probably don't need to switch the GND terminal. This can be left connected between the XLR connector and the IC input. It has no signal function on the transformer, since a transformer only uses the differential input.

 

[JW]

Okay,

I wasn't sure about that.

So, a 5 pole double throw? I'm not sure I've ever seen anything like this. Do they start becoming rotary switches generally, when you have that many poles?

 

[gswan]

You can use a 4pole double throw (you have two poles currently switching GND, which are not needed). This could either be a toggle (4PDT) or a rotary switch (6-pole 2 position is the usual standard).

 

[JW]

Cool.

I have it wired up now and it seems to be switching well between the two inputs.

Okay, now. . . FET matching.

I've been searching a bit here. This is a dual 1176 so I'll be trying to match 4 FETs. I starting trying to figure out how to build a proper test jig to match these, but can't you just use the 1176 circuit to match the FET's? In effect, isn't this the reason for the FET sockets?

Anyway, does anybody have a link to a page that discusses the proper front panel settings and measurements for FET matching using the 1176 circuit?

 

[gswan]

[quote author="JW"]Okay, now. . . FET matching.

I've been searching a bit here. This is a dual 1176 so I'll be trying to match 4 FETs. I starting trying to figure out how to build a proper test jig to match these, but can't you just use the 1176 circuit to match the FET's? In effect, isn't this the reason for the FET sockets?
[/quote]

I wouldn't bother with FET sockets, it's a point of failure when they start to corrode.

The matching of the GR FET and the metering FET assists in the calibration of the meter tracking to match the gain reduction. It's also useful to know a bit about the GR component (FET) if you need to perform diagnostics. Measuring its transfer characteristics is a simple task, and can't be done in the 1176 unit itself. Try here for some info:
http://www.axtsystems.com/index.php?view=article&catid=34%3A1176ln&id=46%3A1176lnfets&option=com_content&Itemid=62

Uses a couple of 9V batteries, some resistors and a pot. You only need to match the FETs in pairs, since the calibration and operation of the channels will be independent of each other.

 

[kenrinc]

I noticed on the 2nd channel of my 76 that when I switch into GR mode it takes the meter about 2 minutes to reach zero. Basically when first switched to GR mode it stays all the way to the left then slowly rises until at zero. Unit seems to work fine otherwise.

Ken-

 

[mich]

question about the attack time:
looking at the schematic ,it appears that for slower attack time one should increase the attack pot value ?
also,the schematic calls for 25K and the availble value (outside the usa) is 22K..maybe only the extra 3K will do the trick?
im sure this was discussed before - i cant find it in this massive thread..

 

[flintan]

My ouput pot is scratchy, gives a low freq noise while it's turned. I also have about 6V DC around it (between CW tab and CCW/ground).

Is it normal to have DC across the output pot? I guess not..or?