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 Forum index » DIY Hardware and Software » Thomas Henry designs
SN VOICE TROUBLE>...ouch
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loss1234



Joined: Jul 24, 2007
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PostPosted: Thu Dec 13, 2007 11:48 am    Post subject: SN VOICE TROUBLE>...ouch Reply with quote  Mark this post and the followings unread

I rewired my sn voice (in hopes of making it fit on the panel) and now all i can get out of it is the triangle output.

I am hoping there might be an easy and quick way to test the circuit to make sure my chip isnt now dead. so i am looking for a pin number or something to just quickly test for noise or vco....could it be the cmos chip?



i am crossing my fingers that i can get this working again..triangle sure sounds good though

thanks all

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Scott Stites
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PostPosted: Thu Dec 13, 2007 8:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

If you have the triangle wave, then at least part of your IC is working.

I'd suggest going through and making sure the right points on the schematic connect to the right points on your panel controls and connectors.

Do you by any chance have an SN76477 datasheet? If you don't, I can PM you one.

Cheers,
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loss1234



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PostPosted: Fri Dec 14, 2007 8:05 am    Post subject: Reply with quote  Mark this post and the followings unread

its a strange problem...i got the vco working when its in envelope lock mode. BUT as soon as i switch it to envelope and then back to lock, all the sound goes away. Now I finally got sound by touching some of the pins on the SN chip with my +voltmeter tip. And when i switch into the envelope mode (WHICH is quiet because i am not yet sending it gATE) the sound dissapears which makes sense. BUT when i then go back to lock mode (which should make sound) i get nothing UNTIL i touch the voltmeter to the pins again...

what is going on here? something about some part of the circuit needing to be pulled high?

at least the chip seems to be ok mostly


thanks

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fluxmonkey



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PostPosted: Fri Dec 14, 2007 9:11 am    Post subject: Reply with quote  Mark this post and the followings unread

loss1234 wrote:
its a strange problem...i got the vco working when its in envelope lock mode. BUT as soon as i switch it to envelope and then back to lock, all the sound goes away. Now I finally got sound by touching some of the pins on the SN chip with my +voltmeter tip. And when i switch into the envelope mode (WHICH is quiet because i am not yet sending it gATE) the sound dissapears which makes sense. BUT when i then go back to lock mode (which should make sound) i get nothing UNTIL i touch the voltmeter to the pins again...


bad ic/socket connection? i had a similar problem once... when tracing it out, it always tested fine... turned out that everytime i poked the ic leg w/ my meter probe, it jostled it enough to make the connection, but w/out the probe it went back to open. had me stumped for quite a while. i think heisenburg had something to say about that.

b
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loss1234



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PostPosted: Fri Dec 14, 2007 10:40 am    Post subject: Reply with quote  Mark this post and the followings unread

hmmmm


but what i dont get is this...if its a bad socket connection than why does it work fine for as long as i want after that, UNTIL i flip the switch back and forth from envelope mode back to one shot mode?

this is a real wold situation and thats why i tested it....i will often go from one shot to envelope and then back again...if that wont work maybe i will just forget the envelope Sad

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PostPosted: Sun Dec 16, 2007 1:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey, Loss,

Did you figure out the problem? I can send you that PDF. It's the old Rat Shack version of the data sheet (it's a bit over 400K IIRC).

Cheerios,
Scott

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Danno Gee Ray



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PostPosted: Sun Dec 16, 2007 1:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

Would it be possible to post it? There might be a few of us that would find it useful.
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PostPosted: Sun Dec 16, 2007 3:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Or I could just post it. Laughing

Here it is.


276-1765.pdf
 Description:
Old Radio Shack SN76477 Datasheet

Download
 Filename:  276-1765.pdf
 Filesize:  402.39 KB
 Downloaded:  2106 Time(s)


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Danno Gee Ray



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PostPosted: Sun Dec 16, 2007 3:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank you Scott. Very cool to read through.
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loss1234



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PostPosted: Sun Dec 16, 2007 5:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

scott

yeah i have the datasheet
thanks though

i also have some old info on the chip...the strange thing is, as i said, all seems to work fine until i flip that switch.

i might just have to tear down the whole board and start over Sad

so sad because it was working fine till i decided to put shorter wires to the panel....

for me this project is much bigger panel wise than anything i have ever done
and with this many wires to test,etc it can be boggling to try to narrow down the issue

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PostPosted: Sun Dec 16, 2007 7:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
i might just have to tear down the whole board and start over Sad

so sad because it was working fine till i decided to put shorter wires to the panel....


No no !! Don't do that. Your so close, just take your time and check all your panel wiring to the board. It stands to reason that if the process of shortening the wires made things "break" then it's a simple wire error.

Make a copy of the panel wiring schematic, get a green pencil then check one wire at a time and mark the wire run green with the pencil. This is called green lining and it works. It helps to organize the isolation process. It helps you keep track of hat you have checked so you don;t keep checking the same things.

Take my advice, OK?

Report back to us your findings when you're done .... Very Happy Very Happy

Bill
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loss1234



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PostPosted: Mon Dec 17, 2007 5:02 am    Post subject: Reply with quote  Mark this post and the followings unread

bill

well let me ask you something. with the issues i am having, are there any specific wires i should check? it seems like a logic issue right? thanks for your advice.


its just that this happened to me with a ray wilson noise module too, i got it all working but then i decided to clean up the wiring and now that one isnt working either!!

there is no worse feeling than getting a module to a point where you dont know how to fix it. or dont have the spirit left to try!

so this weekend i built a new module, the ssm2044 from fonik and its working well. and that made me feel good again about electronics...

so i will give the sn voice a try today

thanks ALL

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fonik



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PostPosted: Mon Dec 17, 2007 8:30 am    Post subject: Reply with quote  Mark this post and the followings unread

i understand how you feel. such things can be frustrating sometimes. but let me emphasize the "green lining" method mentioned by state machine, it would be the logic conclusion.

try to find it out yourself first. IMHO this will be very satisfying.

sometimes we just need patience and endurance as well. several times i had to live with the fact that i don't knew how to fix a module for the moment, or rather: i had to put it aside for a day or two, and then look at it again...

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loss1234



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PostPosted: Mon Dec 17, 2007 9:01 am    Post subject: Reply with quote  Mark this post and the followings unread

point well taken

i suppose this is just part of the learning process

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State Machine
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PostPosted: Mon Dec 17, 2007 9:02 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
well let me ask you something. with the issues i am having, are there any specific wires i should check? it seems like a logic issue right?


Well, you are having issues with th envelop switching. I would check to see that your switch wiring is correct. I dont have the schematic in front of me but I believe the switch either grounds one MIX control bit or the other. make sure the correct pins on the 76477 are grounded when you flip the switch from one position to another. Also, check the pull up resistors going to these pins. these resistors will pull the pin high when left open circuited. These are important.

Did you mention that the module was working completely before you made you modifications to the wire lengths or was it working partially?

Bill
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loss1234



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PostPosted: Mon Dec 17, 2007 11:05 am    Post subject: Reply with quote  Mark this post and the followings unread

before i decided to rewire the module (due to cramming too much stuff into too small a space and too much tangled wiring) things were working great.

BUT when i rehooked everything up, i did get some quick magic smoke, which i reacted to right away and turned off the unit. its possible that during the magic smoke i burned a resistor or pot i dont know about. the sn chip and all the lf444s seem to be fine though. (i did try switching out the opamps and no difference)

but i think this is most likely a wiring thing but what do i know !!

thanks

i will take another stab at it tommorow

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State Machine
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PostPosted: Tue Dec 18, 2007 7:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
before i decided to rewire the module (due to cramming too much stuff into too small a space and too much tangled wiring) things were working great.


OK, thats what I thought .......

Quote:
BUT when i rehooked everything up, i did get some quick magic smoke, which i reacted to right away and turned off the unit. its possible that during the magic smoke i burned a resistor or pot i dont know about.


Sometimes no matter how fast we react, which is fairly slow by electronic standards, IC's can blow in a microsecond and if you saw the "magic smoke" than there is certainly some damage somewhere. This you know, I am sure.


Quote:
the sn chip and all the lf444s seem to be fine though. (i did try switching out the opamps and no difference)


Yes, but did you swap out the SN76477 with another. Suppose damage was done to hte MIXER select section of the IC?? Before any IC's are swapped though, you should resolve you wiring issues to avoid just burning up more things, THEN, if things still don't work, it's time to get another 76477 IC in the socket.

Quote:
but i think this is most likely a wiring thing but what do i know !!


Oh, for sure it is and I would do the GREENLINING as I said in another post. Also, check for an open POT, bad switch .... Put that ohm meter to work ... Wink

Thanks for your feedback BTW, we will help you as much as we can ........ Very Happy

Bill
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State Machine
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PostPosted: Tue Dec 18, 2007 7:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
had to put it aside for a day or two, and then look at it again...


Sometimes a good session on the toilet helps also to solve those really gritty problems !!!!!!!! Very Happy Shocked Very Happy Very Happy

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loss1234



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PostPosted: Tue Dec 18, 2007 8:28 am    Post subject: Reply with quote  Mark this post and the followings unread

although if the sn is on a +5 v regulator, wouldnt the regulator blow before the sn?

anyway, quite a few of my modules have gotten split seconds of magic smoke at some point. thats why i always have those 20r resistors in line with the + and - v. (smoke is from them not the other stuff) its rare that i have fried anything that quickly...but alas the SN might be far more sensitive.

but i was wondering if maybe i couldve blown a resistor or something related to the mixer circuit.

i hope its not the sn as that chip is too expensive! if thats the problem i might be putting this to the side for a long time Sad

but when i have time this week i will do a real greenline.

thanks for the advice

building a blast fed disaster for an xmas present right now so i will get back to this tommorow

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RF



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PostPosted: Tue Dec 18, 2007 5:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

If it was a resistor that smoked you should be able to see evidence of it being hot - get out the magnifying glass.
Good luck, loss1234!
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PostPosted: Sat Dec 22, 2007 11:08 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey loss, any luck ?????

Bill
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