All things G1176 - the new "repost" thread.

[gswan]

1K 1W carbon resistors are cheap and plentiful. You should be able to find one of these.

But what I need is 1.1K, can I use 1k instead of that?

Yes you can. It's a resistor used in the PSU to limit current to the zener.

 

[emreyazgin]

1K 1W carbon resistors are cheap and plentiful. You should be able to find one of these.

But what I need is 1.1K, can I use 1k instead of that?

Yes you can. It's a resistor used in the PSU to limit current to the zener.

Thanks.

I was looking at my Lundahl 5402 and it is missing two legs! I've checked its website and I think normally it should have 9 legs? (excluding 8)..Mine doesn't have the 1st leg as well.. Is it broken??

 

[gswan]

There should be 9 pins.
Two for each of 4 windings and one for the shield.

 

[Chrome Heart]

Ive looked in the thread to no avail, but is there a Mouser or Digikey number for an attack pot with an "OFF" position?

 

[gswan]

Ive looked in the thread to no avail, but is there a Mouser or Digikey number for an attack pot with an "OFF" position?

You are looking for a 25K pot with a SPDT switch on the back of it. Used to be very common in old TV sets for the volume control with power switch. You may have to look further afield than Digikey or Mouser though.

 

[Echo North]

Ive looked in the thread to no avail, but is there a Mouser or Digikey number for an attack pot with an "OFF" position?

Mouser:
315-2415F-25K

 

[emreyazgin]

A quick question about the rotary's. Can I solder them any way I want? I couldn't find information as to orientation

PS : The one on the ratio board actually says "A" so I matched that to the A on the lorlin. But on the meter board it doesn't say anything

 

[Chrome Heart]

A quick question about the rotary's. Can I solder them any way I want? I couldn't find information as to orientation

PS : The one on the ratio board actually says "A" so I matched that to the A on the lorlin. But on the meter board it doesn't say anything

Orientation should not make a difference unless your using a D shaft. In that case you might want to think about how its positioned.

 

[Chrome Heart]

And thanks for the part number HB. Also, the knobs that are on the way from your store. 8)

 

[Echo North]

Ive looked in the thread to no avail, but is there a Mouser or Digikey number for an attack pot with an "OFF" position?

So Echo, with regard to the switch above, It looks like one of the feeds is soldered to the back of the switch and then jumped over to the wiper tab. Please correct me if Im wrong.

Thanks

Mouser:
315-2415F-25K

Not sure what you mean.

It's a regular 25K pot (with three terminals) and it has a SPDT switch on the back of it (with it's own 3 terminals).  The SPDT is where you connect BLK, GRN and 22.

It has about 300º rotation with the switch in the off position.

Mike

 

[emreyazgin]

Ok, Ive completed the PSU section on the Rev J, I got the DC readings from suggested places and here are the results:

-10V pad shows exactly -10VDC
24V pad shows +28.8VDC

I am using a 30VA 230V AC > 25 0 25 0 in 25 0 25 configuration trafo

Is this ok?? Is it higher than 24 V because there is no load on it? By the way I am using a 1.1k 0.5W resistor as a temporary replacement for 1.1k 1W until it arrives from the shop, Ive only turned it on for a minute or so so that it doesn't heat up. Ive checked other components and they are not too hot as well. i don't know how its supposed to be though. Do you think all these sound OK?

Cheers,
Emre

 

[Chrome Heart]

Ok, Ive completed the PSU section on the Rev J, I got the DC readings from suggested places and here are the results:

-10V pad shows exactly -10VDC
24V pad shows +28.8VDC

I am using a 30VA 230V AC > 25 0 25 0 in 25 0 25 configuration trafo

Is this ok?? Is it higher than 24 V because there is no load on it? By the way I am using a 1.1k 0.5W resistor as a temporary replacement for 1.1k 1W until it arrives from the shop, Ive only turned it on for a minute or so so that it doesn't heat up. Ive checked other components and they are not too hot as well. i don't know how its supposed to be though. Do you think all these sound OK?

Cheers,
Emre

Sounds like your on the right track.

 

[Echo North]

Thanks Mike. I was looking at tha data sheet and I guess its just a picture of some other pot because it does not show a switch. The data pic pdf. shows a pot with the three terminals as usual, and then two more solder tabs on the back of the pot body.
[/quote]

That sounds like a SPST switch.

That part is the right one, I've used it on my builds.

Mike

 

[helterbelter]

Well, I finished my dual Gyraf 1176’s this week.  Checked the powervoltages, searched for bad solderings, caps and diodes in the right directions, etc. Then, powered them up to check if audio came through.

Badly.

Channel 1 [EDIT: now fixed, wrong type FET)
This channel runs audio, but low level comes out of the unit. ( I have to set the in- and outputpots fully cw, and even then there’s a few dB’s  gaindrop, with the outputtransformer wired as 1:1.  (I estimate 2 dB, maybe 3 dB).
The level is too low to even get a single dB of compression. Maybe the sidechain isn’t working at all, but I don’t know, because the level is just too low. What could be wrong ? (
- I have swapped all the BC107’s ( I had to do that anyway since I had used the A versions first, now I have fitted C’s).
- I compared the voltages with the referencevoltages in the schematic  from Gustav’s site, all is okay and decent.
For some reason, when I tap off the signal from the wiper of the inputpot, the signal appears to be louder than at the output, so the inputcircuit is fine.

Now  channel 2 :

It doesn’t pass audio at all. I have checked the voltages, and those  in the signal pre-amp were faulty. (check the picture).

(I didn't note it in this picture, but the voltage at the right side of R17 is 30v, which is correct)

I also have traced audiosignals, the audio is fine up to the inputpot, but there’s where it goes wrong. When I apply audio to the outputpot,  the signal reaches the output, so , the fault is likely to be in the signal pre-amp . I checked the 100 uF cap C7, and that one is fine. Also with this board, I have changed all the BC107’s to BC107C.

For both boards, I have the suspicion that the BF 245’s are defective, or more likely, a wrong version [Edit : They are the C version, not A ]. Can that be cause these errors ?

I have 2 pairs of matched FETs from Mike, but I don’t want to put these in before I’m sure the boards are okay.

 

[helterbelter]

Bump....
I hope to fix it today....  

Just came back from the local electronics store, the only FET they had was the BF245 C version...

any thoughts ?

 

[helterbelter]

Well well well...

In the channel that didn't compress, I've replaced the BF245C's with Mike's matched pair FET's, now it's working as it should. 

For the other channel, I'll take out the BF's, and measure the voltages again before I put the matched pair in.

 

[helterbelter]

So, I've taken out the FETs, and measured the voltages again. The voltages still have the same faulty values.

(I didn't note it in this picture, but the voltage at the right side of R17 is 30v, which is correct).

I also didn't note that the emitter of Q 4 has a voltage of 1.31 V instead of 11.5V....

So, any ideas what could be causing this defect ?

 

[jdbakker]

So, any ideas what could be causing this defect ?

If everything's OK on the right side of R17 but wrong on the left side, then either R17 is the wrong value, has bad solder joints or something to the left of R17 is drawing way more current than it should (ie: most likely a short). So I'd start by having a close look at R17.

More general hints:

All shunt-based compressors (including the 1176 and the LA-2A) effectively become line amps if you take out the shunt element. So the first test for such compressors is to remove the FET or the T4B and see if it passes signal.

The best possible debugging situation is when you have two identical units, one working and one not working. The same circuit nodes should have the same voltages (modulo parts tolerances). Use this plus a signal tracer to isolate the fault.

Good luck,

JDB.

 

[helterbelter]

Thanks for the reply !

Shorts and correct directions of caps and diodes are the first thing I check, always, before powering up the project for the first time. This time I have even triple checked for solderingshorts. None.

Yesterday evening I have checked the R17 already, and also R18, 19, 20, 12, and C4.  I have also measured the resistance to ground on the emitter of Q4, and compared with the (working) other channel. All are the same.

When I apply a signal to the emitter of Q4, the audio gets to the output, but sound distorted.

Anyhow, tomorrowevening I'll continue the checking of components, if I can't find it, I'll ask again.
Thanks so far!
Paul.

 

[emreyazgin]

A meter question. I got two Sony "VU" meters from ebay. They both work but I think they are not really AC meters, When I put a DC voltage of 1.5V through a 4k resistor it goes almost to +2db's..but with AC it just "trembles" in -20dB...Ive heard that I need a rectifier...Are these avilable in Farnell, RS etc? or is it something I need to build?