All things G1176 - the new "repost" thread.

[helterbelter]

This time I have even triple checked for solderingshorts. None.

I doubt if I would have seen it when I would have checked for soldershorts for a fourth time.... But there was one after all.

So, it's time to trim the controls, and set it up for stereo use !

Thanks !

Paul

 

[gswan]

You will need 4 small germanium or schottky diodes for each meter, arranged as a bridge rectifier, between the pair of meter wires and the meter terminals.

 

[emreyazgin]

You will need 4 small germanium or schottky diodes for each meter, arranged as a bridge rectifier, between the pair of meter wires and the meter terminals.

Geoff, will something like this work?

If yes, do I need the resistor and the capacitor and what values for the diodes?  any germanium? resistor 3.6k? Cap?

Cheer,s
Emre

 

[gswan]

The resistor is already in circuit in the 1176 metering section. It's a 3.6K for the +4dB setting.
The diodes can be OA91 (germanium) types or, if you find these hard to get, you can use a schottky like the BAT86.
The capacitor is optional and will alter the meter decay time, however I'd leave it out.

 

[emreyazgin]

The resistor is already in circuit in the 1176 metering section. It's a 3.6K for the +4dB setting.
The diodes can be OA91 (germanium) types or, if you find these hard to get, you can use a schottky like the BAT86.
The capacitor is optional and will alter the meter decay time, however I'd leave it out.

Perfect Thanks Geoff!

 

[W DeMarco]

Hey fellas,

Tryin to finish up another G, Its calibrated and working well outside of the fact that there is a nice loud buzz coming from the output.  This is with no input connected.  Im gonna try to change up the ground scheme a bit tonight.  Another odd thing is that this buzz nearly goes away with the output pot at halfway up.  Interesting...Any ideas?

Will

 

[gswan]

Grounding.

 

[emreyazgin]

Well, I have finally "finished" the 1176. Tested it..and of course not working properly.

Here is what happened:

- First time I tried, I left it ON for about 5 seconds and BD135 got VERY HOT. I thought its the BD136 first. I examined the PCB and found ot that R28's left leg was touching the Q5's metal cap. I don't know if that cap conducts electricity to inside? But to make sure I desoldered it and tested and the Q5 wasn't working. I think it blew up!..Before I took it off there was still audio, but the BD135 and 136 wasn't hot at all. Probably the current was cut because of Q5 blowing up..

-Now, I replaced the Q5 (BC107) and cautiously turned the unit on first for 1 second, then 2 seconds then 3 seconds and checked what is heating up and the BD135 is the one. It starts to heat up really high in a few seconds..

I don't even know how to start to troubleshoot this...I have checked the bottom and top of the pcb to see if there are any shorts and couldn't find any..

I really appreciate any thoughts as I don't know where to start..

 

[W DeMarco]

Emrey

No fears, you'll get her goin.  Doesnt sound right.  Start with your voltages.  Be careful.  there are some checkpoints noted on the top of your pcb.  Make sure these are on.  Thats a start.

 

[emreyazgin]

UPDATE: I have found out that an electrolytic was soldered + and - wrong side. The cap in question is Q30, thats one of the caps from the balanced input section. Could this be related to the heating BD136?

Also, thanks a lot for the encouragement but I am still scared that something will blow up before I could even meter anything as it takes 3 seconds for the BD136 to heat up...Any recommendations? (Of course meanshile I will resolder the cap that was wrongly inserted and test again)..

I think that capacitor explains why the audio was gradually increasing in volume until it was distorting...and sometimes it was cutting out and coming back..

 

[gswan]

Don't bother running audio through these units until they are fully tested and calibrated. You run the risk of breaking something.

Check all components and soldering around the output drivers and the transistors immediately preceeding these. Something's shorted or inserted incorrectly.

 

[emreyazgin]

Don't bother running audio through these units until they are fully tested and calibrated. You run the risk of breaking something.

Check all components and soldering around the output drivers and the transistors immediately preceeding these. Something's shorted or inserted incorrectly.

OK, sorry for asking every single thing but I need to ask which components are the output drivers.. :-[

EDIT: Sorry you already mentioned before : Q8 and Q9 sorry about that

 

[emreyazgin]

I am a novice so I might be doing something stupidly wrong, like wrong orientation or something similar and probably I can't even realize that its wrong! So if, please, someone can look at least around the output drivers, and the drivers themselves about orientation or any other obvious mistake I would be grateful.

Here are what I have used:

MULTICOMP BC107 NPN TO-18
STMICROELECTRONICS BD135 NPN TO-126
MULTICOMP BD136 PNP TO-126  (This one is PNP, for example I am JUST realizing this!...Any problems with PNP?..just brainstrorming)

And I basically followed the drawings on the pcb's for orientation..I could be totally wrong, I think its visible from the image how I put the two output drivers..I hope its as simple as just orientation problem..

Cheers,
Emre

 

[gswan]

Do you have anything inserted into the little link behind the driver transistors?

 

[gswan]

What did you use for Q6 and Q7?

 

[emreyazgin]

No the links are empty

 

[emreyazgin]

What did you use for Q6 and Q7?

FAIRCHILD SEMICONDUCTOR BC560  PNP, TO-92

 

[gswan]

Check the orientation of Q6 and Q7 against a data sheet and the PCB connections. Don't rely on the markings.

 

[casrec]

I would check all of your transistors. I ordered two different transistors from mouser and the data sheets were wrong. Shocking I know . Any who, you can use you DMM and the diode tester to easily check the orientation. Here is a link on how to test.

http://www.kilowattclassroom.com/Archive/AN0007.pdf

I kept frying R35 and Q5 was getting super hot because Q9 was the wrong way in.  

 

[emreyazgin]

Check the orientation of Q6 and Q7 against a data sheet and the PCB connections. Don't rely on the markings.

Data sheet and my orientation matches.

I would check all of your transistors. I ordered two different transistors from mouser and the data sheets were wrong. Shocking I know . Any who, you can use you DMM and the diode tester to easily check the orientation. Here is a link on how to test.

http://www.kilowattclassroom.com/Archive/AN0007.pdf

I kept frying R35 and Q5 was getting super hot because Q9 was the wrong way in. 

Thanks for the information, I will try this as well..