Brian Posted January 22, 2013 Share Posted January 22, 2013 What could I check please ? Set RV1 and RV2 to their middle position.Please measure the voltage on each +/-/out pin of the op-amps, U1, U2A, U2B, U3A and U3B and post the values here. Link to comment Share on other sites More sharing options...
sauce Posted January 22, 2013 Share Posted January 22, 2013 Ok I check everything with RV1 and RV1 to their middle position : First with the TL081CP :U1 (TL081CP) : pin 2 (-) :13.6Vpin 3 (+) : 12.3Vpin 6 (out) : 13.7V U2 LF353 : pin 1 (out 1) : 13.6Vpin 2 (- 1) : 13.6Vpin 3 (+ 1) : 12.3Vpin 7 (out 2) : 13.6Vpin 6 (- 2) : 13.6Vpin 5 (+ 2) : 12.8V U3 NE5532 :pin 1 (out 1) : 13.7Vpin 2 (- 1) : 13.6Vpin 3 (+ 1) : 13.6Vpin 7 (out 2) : 13.7Vpin 6 (- 2) : 13.7Vpin 5 (+ 2) : 13.7V Second with the NE5534P :U1 (NE5534P) : pin 2 (-) :15.3Vpin 3 (+) : 15.3Vpin 6 (out) : 26.6V U2 LF353 : pin 1 (out 1) : 16.6Vpin 2 (- 1) : 16.6Vpin 3 (+ 1) : 15.3Vpin 7 (out 2) : 16.6Vpin 6 (- 2) : 16.6Vpin 5 (+ 2) : 15.6V U3 NE5532 :pin 1 (out 1) : 16.7Vpin 2 (- 1) : 16.6Vpin 3 (+ 1) : 16.5Vpin 7 (out 2) : 16.7Vpin 6 (- 2) : 16.7Vpin 5 (+ 2) : 16.7V Just for info comclone is the clone of this : http://www.google.fr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CEUQFjAC&url=http%3A%2F%2Fwww.elfaforums.lv%2Fattachment.php%3Fattachmentid%3D768%26d%3D1226221211&ei=8sP-ULCsMYSS0QWvuoGADQ&usg=AFQjCNFF1TCmydVKiu0RjiGD4y7Ge-J0mg&bvm=bv.41248874,d.d2k&cad=rja I use both electret microphone (with R30) and dynamic (without R30). Link to comment Share on other sites More sharing options...
Brian Posted January 22, 2013 Share Posted January 22, 2013 U2 LF353 : pin 1 (out 1) : 13.6Vpin 2 (- 1) : 13.6Vpin 3 (+ 1) : 12.3V...This is odd. U2A is configured as a voltage follower. Pins 1 and 2 are joined, as the voltages show but they should have the same voltage on them as pin 3. The same with U2B, the voltages on pins 2 and 3, at DC, should be the same. Either this chip is broken or, maybe, your whole circuit is oscillating at a high frequency. The voltage at the output of the 5534 is also wrong. It looks like the output has latched up high. More later once I've cooked... Link to comment Share on other sites More sharing options...
sauce Posted January 22, 2013 Share Posted January 22, 2013 I'm going to try with the other intercom. Link to comment Share on other sites More sharing options...
Brian Posted January 22, 2013 Share Posted January 22, 2013 Thinking out aloud... 1) The NE5534 doesn't have a compensation capacitor fitted between pins 5 and 8 in the ComClone. In an ideal world it doesn't really need one but putting 22pF there won't hurt. 2) I can't help feeling the problems people are seeing is down to oscillations. 3) What happens if you terminate the audio line on the XLR. The proper way to do it is 200R in series with 4k7 and 10uF/50v in parallel. But for testing 2k2 to ground will work. Link to comment Share on other sites More sharing options...
sauce Posted January 22, 2013 Share Posted January 22, 2013 I found another thing very strange.When I mute mic, the voltage is 26V on pins 1, 2 and 3 on the LF353 with the NE5534. No problem with the TL081CP the voltage stay VCC/2 (13.6V). Do you think my 2 NE5534 are broken ? Audio is already terminated with a 2k2 resistor. Link to comment Share on other sites More sharing options...
Brian Posted January 23, 2013 Share Posted January 23, 2013 When I mute mic, the voltage is 26V on pins 1, 2 and 3 on the LF353 with the NE5534....Do you think my 2 NE5534 are broken ?Which is what I might expect. The mute switch connects the +ve input to the output. If the output was stuck high then the +ve would go high. There are what amounts to diodes between the +ve and -ve input so the -ve input wpould get dragged high as well. So yes, I think the 5534's are not happy. Do you have access to a 'scope at all? Link to comment Share on other sites More sharing options...
sauce Posted January 23, 2013 Share Posted January 23, 2013 No I don't have any 'scope at home.I tested my NE5534's on a breadboard as votlage follower with a voltage divider of 2x47k and a 22V power supply. The output voltages were 14.5V and 13.2V. It's quite high, isn't it ? Another question with clear-com.I removed all opamp and I just test voltages.Is it normal that VCC/2=12.5V and VCC=27.8V or it just because there is no charge for divider ? Link to comment Share on other sites More sharing options...
Brian Posted January 23, 2013 Share Posted January 23, 2013 Is it normal that VCC/2=12.5V and VCC=27.8V or it just because there is no charge for divider ?No, that is odd. If you have a simple resistor divider where the two resistors are the same value then the mid point of them must be at 1/2Vcc. Your measurements would indicate that R18, which should be 220k, is actually 270k. Link to comment Share on other sites More sharing options...
sauce Posted January 23, 2013 Share Posted January 23, 2013 But I did the same test on my breadboard (divider voltage with 2x220k) with a 22V power supply and I only have VCC/2 = 9.9V.Without any charge maybe it's normal to have less than VCC/2 ? Link to comment Share on other sites More sharing options...
Brian Posted January 23, 2013 Share Posted January 23, 2013 Consider this circuits... ...the voltage at the junction of R1 and R2 will be 11v once the capacitor has charged, which will take around 3 seconds. With no capacitor it will be 11v instantly. If it isn't 11v then something is wrong. [E2A]One question, what meter are you using to measure the voltage with? Link to comment Share on other sites More sharing options...
sauce Posted January 23, 2013 Share Posted January 23, 2013 I use this one : http://www.amazon.co.uk/Compact-Digital-Multitester-With-Diode/dp/B000L0RINQ/ref=sr_1_1?ie=UTF8&qid=1358954380&sr=8-1 The circuit is exactly the same I use with my breadboard without capacitor. Link to comment Share on other sites More sharing options...
Brian Posted January 23, 2013 Share Posted January 23, 2013 Aha, mystery solved. Getting a reading of 9.9v, instead of 11v, with that meter is correct. Can you guess why? Link to comment Share on other sites More sharing options...
alistermorton Posted January 23, 2013 Share Posted January 23, 2013 Aha, mystery solved. Getting a reading of 9.9v, instead of 11v, with that meter is correct. Can you guess why? 10% error http://www.blue-room.org.uk/public/style_emoticons/default/rolleyes.gif Link to comment Share on other sites More sharing options...
Brian Posted January 23, 2013 Share Posted January 23, 2013 10% error http://www.blue-room.org.uk/public/style_emoticons/default/rolleyes.gif No. Meter spec...± 0.8% ± 5 Digits So 11v could read between 10.86v and 11.14v Link to comment Share on other sites More sharing options...
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