Op amp overheating- Little Angel Chorus v4

[Steve Blackdog]

Dear all,

I can see that I am going to be one of those newbies who asks dump questions!

I have just built Rick Holt's v 4 LA chorus. When I connect the battery the op amp gets very hot very quickly.

I can't find any shorts, although I made a mistake of using a piece of vero from my parts bin, so it quite a few of the traces have had to be repaired.

Before I rip it up and start again with a new piece of vero or perf, is there an obvious culprit?  It is not the op amp, I have swapped it and same problem.

Here's a photo of front and back. Look away now if you can't stand the sight of bodges!

Cheers

Steve

[GibsonGM]

Hi Steve, welcome! There are no dumb questions at all, we all have had troubles at different times! 

Are your chips inserted in the proper orientation?  Pin 1 is really where pin 1 should be, not rotated 180 degrees?

It sounds like a short (of course).  What you can start with is to look around the base of the opamp and be sure that you are not 'bridging' your blobs - the solder on 1 trace must not connect the solder or copper of a trace next to it.  IC socket pins must not have continuity (must not be connected with no opamp in the socket).  Use a magnifying glass. If you find any touching, you'll have to re-flow the solder and use something like an Xacto knife to 'ream' between the traces til it's clean.   A solder sucker of some form can be very helpful here. 

Make sure each trace you were to cut is really completely cut thru!  Use your meter, set to continuity ("beep") and with no power applied to the circuit.  A look at how your negative battery lead is wired up to the 'switching jack' might help - if a + was somehow connected to that deal, it would short (should only be the grounds).

After you've done what you think you can do, use your meter to test for resistance between the battery clip terminals w/no power applied.  Take note of what happens - you should see a rising resistance, not simply some arbitrarily low resistance.  Low being 10s ~ 100 ohms, ballpark.

That will get you started, and I know you'll get more advice as people see your post!   We'll help you get it working, no worries  Most of these problems are build errors - we all do it, and still do even after years of building!

[antonis]

Although image is a bit blurry, I'd check some suspect points..



P.S.
I'd also check resistance between pin1 & GND and pin7 & GND..
(GND points not necessarily the circled ones..)

[antonis]

Are your chips inserted in the proper orientation?  Pin 1 is really where pin 1 should be, not rotated 180 degrees?

I think you've nailed it up, Sir..

[Steve Blackdog]

Thank you!  Will report back this evening.

[Steve Blackdog]

Thanks to "eagle-eyes" Antonis!  Yes the op amp was the wrong way around.  Swapped it around and now gets warm but not hot.

Will test tonight with something plugged in!

[GibsonGM]

Ahem, good call, Antonis, LOL    (laughing)

Are your chips inserted in the proper orientation?  Pin 1 is really where pin 1 should be, not rotated 180 degrees?

[antonis]

Ahem, good call, Antonis, LOL    (laughing)

I kneel in respect to your Highness, Sir..

[duck_arse]

is there a resistor missing from the upper ring?
is the cap in the lower ring backwards? hard to tell from photo.

also, it's nice to link to the layout you've used, so we don't have to go looking and end up with something different. circuit diagram? yeah sure, same applies.

and, probably, those opamps that were hot while in backwards - just chuck em in the bin and forget about whether they stilll good or not.

[Steve Blackdog]

Here's the layout and schematic.

So the hot op amp is sorted.

Like many before me, I just get the dry signal.

Here are my voltages. Btw, the battery voltage is around 7v.  Will test again with fresh battery.

PT

1- 4.99
2 - 2.44
3 & 4 - 0
5 - 2.77
6 - 0.22
7&8 - 3.63
9 -  0.15
10&11 - 2.44
12 - 0.16
13 - 2.43
14 - 4.7
15 - 0.06
16 - 0

5532

1 - 3.99
2 - 3.75
3 - 3.75
4 - 0
5 - 0.21
6 - 0.757
7- 1.36
8. 7.47

L7805

1- 6.7 (hence need to get with fresh battery 🤔)
2 - 0
3 - 4.99

[Steve Blackdog]

[Steve Blackdog]

[duck_arse]

ah haa! totally different layout.

anywho - your IC1B voltages are bad. hard to see from your pic, but, if your R2/R3 voltage divider had 100k and 4k7 fitted instead of 100k and 47k, your VC voltage would read low, somewhere about 220mV-ish. what's your pin 5 reading? also something amiss with the 2399 voltages - the right side should be 2V5-ish.

[edit : wrong number]