All things G1176 - the new "repost" thread.

[jho-audio]

Hi there,

I have a 66vct (33x2) toroid sitting here, 120VA. Is this too much for my two G1176 boards?

Thanks, Jason

 

[gyraf]

Jason,

I think it is too large. 160VA is huge overkill anyway. With the 33V, your regulators will probably get VERY hot.

Jakob E.

 

[jho-audio]

Thanks again Jacob! I found a surplus store close by with two 26x2 torroids and will grab those on my way home.

Cheers, Jason

 

[mfdu]

ok.

got my first 1176 on the test bench.

i had the bd135 and bd316 (Q8/Q9) in the wrong way around and they got *a little hot*. i think i fried them... testing unit with 1kHz signal, not giving any output.
also trying to get GR meter zero to behave - trimpot doesn't have any impact on GR meter level.
but apart from those *little* problems, very happy, and got unit #2 to fit into case as soon as i have fault fixed unit #1.

anyway, it LOOKS great, and will sound just as good real soon. lets see if i can get a photo linked :

 

[gyraf]

M.F.D.U.,

the transistors WILL fry if put in reversed. And what's worse, they will often also kill the previous (driver) transistor (s)

Jakob E.

 

[Piotr]

Hi, I've been considering for some time the construction of some Gyraf projects, I stumbled accross Mnats' 1176LN which seems a great addition but I still have one question remaining: how are the units interfacing with mixers ?

Depending on the mixer, inserts might be either at +4 dBu or -10 dBV, either balanced or not. Let me know if you've considered this question... What's the input and output of those projects ? Wouldn't it be a good idea to deal with this issue, for example by providing the usual switch to match the units I/O with the console's insert type.

I have a old Soundtracs Solo Logic 24 on which the inserts are unbalanced and at -10 dBV so I just fear gear that's only set to work with +4 dBu. Thanks, I am waiting for your opinions... Piotr

 

[orson whitfield]

Would anyone sell me a few matched BF245As? I only have time to DIY during the summers and I'd really like to finish my two G1176s.

 

[gyraf]

Piotr,

That shouldn't be necessary.

After all, the original 1176 never had -10/+4 switches, which nobody complained about..

Jakob E.

 

[mfdu]

the transistors WILL fry if put in reversed. And what's worse, they will often also kill the previous (driver) transistor (s)

hi gyraf. thanks for getting back to me.

yes - i done gone let the magic smoke out of Q8/Q9.

i guess i can assume Q7 (BC560) is toast too? what about the rest of the build and components?

well, she is passing audio with ample gain control thru the pots, so i guess that bodes well.

unit two hasn't suffered the same torments at my hands. that one hasn't been fitted into a case yet, so has had the BC135/136 direction corrected. before being powered up.

thanks again. will post when got both units firing (as opposed to smoking). next up - GSSL.

chris.

 

[cannikin]

Hey Guys,

I'm in the home stretch of building my G1176. the unfortunate thing is R36
100R resistor 1/4 Watt keeps frying... I have no idea what is causing this to happen..

any thoughts are greatly appreciated.

 

[mfdu]

i am assuming i have fried Q7 when i let the smoke out of Q8 and Q9.

i have been told the BC557 is an equiv replacement for the BC560 in Q7. seems like that may be the case - anyone care to confirm?

hope to hear from yerz . . .

i have yet to test unit#2 - too busy in sessions. i expect everything will be tickety-boo tho.

[edited]
unit #2 appears to be operating fine, but having some meter calibration issues which i'm working through (using http://www.altronics.com.au/index.asp?area=item&id=Q0490 and the info on that page is all i've been able to find on it)

chris.

 

[cannikin]

Hey guys;

I have the Mnats PCbs (version H) using Lundahl input and output transformers and omitted the components suggested on mnats site. Upon power up R36 (100R) keeps burning out within seconds of powering up the unit. I have checked for shorts, solder bridges and polarity of caps.. everything is correct.

I am using a 30Va Load, 25 + 25 Secondary V, .60A Secondary Current for the power trannie. and getting a reading of 29.9Vac and .65A DC out of the Power Trannie.

ANy thoughts as to why R36 is frying would greatly be appreciated.

 

[gyraf]

R36 burns if there's shorts, wrong resistors or transistors, or wrongly oriented (or failed) transistors.

Jakob E.

 

[mfdu]

gyraf

i suspect then that you have answered both my query and also cannikin's.

R36 is the weak point - no worries. so my Q7 should still be apples? well i'll be dropping in replacement Q8/Q9 tonight.

i now suspect the orientation of the two tantalum caps (C19/C20). will check this evening also. should be ok as i dont believe i let the magic smoke out.

now accumulating parts for the GSSL project.

chris.

p.s. my wife wishes to say thank you all for keeping me out of her hair and giving her a chance to read a couple of books!

 

[spacecho]

hey guys,

how important is it to 'match' the transistors? I read Gyraf mentioning that we will need sockets for the BF245 fets. Is this for swapping around (matching) purposes?

if yes, which ones?

is a multimeter okay when testing their values, and is their a desired reading for each transistor type? or is it more about matching particular transistor values with each other?

i have bought a whole heap of the transistors for a group diy with 4 of my buddies. We are building a pair each, but got a second pair for the future and a futher single set for contingency. So we have 25sets of parts to mix and match if necessary.

hi m.f.d.u

harry here (turtlerock forum)

will start building this week, i'm in the se suburbs too, so maybe we should catch up and compare, tech units if necesary.

thanks to Jakob and Mako for all their great work.

 

[cannikin]

thanks jakob, I'll check again :guinness: :guinness:

 

[gyraf]

Hi harry,

[quote author="spacecho"]
how important is it to 'match' the transistors? I read Gyraf mentioning that we will need sockets for the BF245 fets. Is this for swapping around (matching) purposes?

if yes, which ones?[/quote]

uhm... the BF245's?

I suggest you read the posts in the 1176-meta, we've covered this several times now.

The idea is to have FET's that track regarding gain reduction in GR and VCA positions, so that the meter (in gr mode) reflects what's going on. Also, if you want to be able to use the units as stereo tracking, you should match FET's for similar GR for a given input level.

thanks to Jakob and Mako for all their great work.

You're welcome - but who is Mako?

 

[cannikin]

[quote author="gyraf"]

thanks to Jakob and Mako for all their great work.

You're welcome - but who is Mako?[/quote]

Mako is mnats.

Ok I'm off to check my G1176 and find my errors...

Cheers
:sam:

 

[cannikin]

Ok after using a magnifying glass I found my silly error..

amazing how a solder bridge can ruin your day... not to mention your unit

I have a sifam meter which the lamp box is rated 12V 1/2W and I checked the Voltage coming off the VU Lamp terminals on the main board and it reads 38.5Vdc

what is the best to bring that voltage down to at least 12V?

 

[Greg]

Just use a series resistor. You can make the calcualtion or just use a pot and adjust... then measure and replace with a resistor. I usually just use a pot. Also, I'd recommend running a little bit under 12V... the bulb will last much longer.