I recently just soldered the simple analog filter up and when I plugged it in… nothing. When everything’s connected, the output is extremely quiet and there is no change in the (extremely quiet) sound when I move the pots. Another thing is the leds flash as they should when there’s no input, but once I plug in an input the leds stop and only one is on. I’ve checked over my circuit multiple times and cant see anything. Could it be an issue with the lm13700? I had to use the SMD version.
Any help would be greatly appreciated!!
Sorry if there’s already a topic on this, I couldn’t see one!
Hi! I just took voltage readings
So I measured voltages at the power supply pins and the tl074 was giving the correct values. The lm13700 didnt have 12V on the +12 pin (pin 11). Thats most likely whats giving me the problem, but can you see anything else?
I had to condense my breadbord layout as I ran out of space
I just checked all my pins on the lm13700 and tl074. I did a continuity check and all the pins are connected to where they’re supposed to be. I went over my soldering but there are no shorts on the back. I’m starting to think either the tl074 or lm13700 (or both) is fried, so I’ll probably end up ordering both of them.
You say you don’t have +12 V on LM13700 pin 11. Maybe the chips are fried or maybe not, but even so that should not cause your +12 V to disappear. (If it were somehow shorting that pin to ground then you wouldn’t measure +12 V there, but you also would be shorting your power supply and presumably you’d have noticed that.) So there must be a problem elsewhere. With power off, do you have continuity from that pin to the +12 V wire? Presumably not, and in that case the fault should be easy to find: Check continuity from pin 11 to the red jumper wire (red on the diagram, anyway; I guess yours is orange?) and from the red wire to the +12 V wire. And for that matter, from the +12 V wire to the power supply.
Are the connections on the right hand side of the LM13700 correct?
Also, where is the 1nf to ground from pin 12?
Ah I’ve actually just realised you’ve used red for the ground wire, the colours make it quite difficult to compare against the diagram on a picture…
On the right hand side are your giant resistors definitely connected properly, and are the two resistors that overlap next to the transistors definitely not shorting to each other?
Hey Guys…
Re-soldered the +12 wire and now I’m getting 12v on the pin. Still same issue. I performed a full continuity test with my DMM on everything, and found that the 1nf cap connecting pin 12 to ground (its right underneath the smd board) did not make my DMM beep when connecting over it. Could this be the bad connection?
On the right side of the board where everything is condensed there appears to be no shorts. I also ran a razor between all the rails.
I was looking at your soldering, doesn’t look the best and I can see several cold joints on the board that I would suspect. But also that LM13700 soldering to the adaptor board, pins 9 & 10 look shorted and I think 13 doesn’t look soldered down, can you measure between each outer pin of the adaptor and the SMT chip pins, I always do this on any SMT adaptor board I use to check for good connections and shorts.
Those are output and input of one of the Darlington buffers and aren’t used in this circuit, so that shouldn’t be a problem if they are.
That’s the input to one of the OTAs. Audio signal should be present there, but at a very low amplitude. You can check with a scope, or an audio probe but it’ll be pretty quiet.
Hey guys,
I ordered the through hole version of the lm13700, soldered it, and now the cutoff works. The resonance, however, does not. Anyone run into this problem before?
