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DIY Workshop » M³ headphone amplifier (part 2) | soundwitty Member Joined: Oct. 28, 2007 |  Message [#160] posted on: 11-25-2008 04:53 PM CST (US).   |  |  Tanks Amb. I may try to build a MilletMax as I've the board and the most difficult to get bits. In the main time I will recheck the whole board for cold joints and short. There is no shirtcut between ig and og and betwen v- and og even if the multimeter start low in resistance to raise slowly as it would go through a capacitor. I've an old low frequency oscilloscope, cumbersome and probably compeletely out of tune. Not sure this will be helpful though. I know that I will have to get a computer based oscilloscope one day or another. Thanks for your support. Cheers. |
| lcp Member Joined: Nov. 12, 2006 | Message [#161] posted on: 12-06-2008 02:38 AM CST (US). | | Amb, It is me again. My balance M3 got problem. |
amb  Headphone Council Joined: Apr. 1, 2004 | Message [#162] posted on: 12-06-2008 03:00 AM CST (US). | | lcp, since it's a balanced M³, you should have two boards. Do both boards have the same problem? What voltage do you measure at the output of the σ11 PSU? And across the "unused pads" (one square, one round) neat Q1G-, next to C8? What's the Vce of Q5-? Also, your TLE2426's voltage split is uneven. Are you measuring these voltages relative to IG? |
| lcp Member Joined: Nov. 12, 2006 | Message [#163] posted on: 12-06-2008 05:18 AM CST (US). | | Amb, yes, both board have same problem. I am using a DC power supply for test in office. I have measured a 30V DC out at suppply for test. I have replaced one TLE for check. It has same result. I have brought my board to office for check. Hence, I cannot check it at the moment. I will check on tue when at office. |
| dualxeon Member Joined: Dec. 8, 2008 | Message [#164] posted on: 12-08-2008 10:42 AM CST (US). | | I have finish M3 Headphone amp Measure Ground Channel the DC voltage across the R5G resistor is 0. Adjust the BIASOPG trimpot do not work. the other R and L channel work OK.
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| amb Headphone Council Joined: Apr. 1, 2004 | Message [#165] posted on: 12-08-2008 03:19 PM CST (US). | | dualxeon, inspect your ground channel carefully and make sure you have all the right parts in the right places and the proper orientations. In particular, is the BIASOPG trimpot is the correct value? Reflow the solder joints of OPAMPG, R5G, R6G, R7G, BIASG, BIASOPG, Q2G, Q3G and Q4G. |
| lcp Member Joined: Nov. 12, 2006 | Message [#166] posted on: 12-08-2008 07:52 PM CST (US). | | Hi Amb, I have just measured the reading as follow, |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#167] posted on: 12-08-2008 10:16 PM CST (US). | | lcp, also measure the output voltage of your power supply. Is it also low? |
| lcp Member Joined: Nov. 12, 2006 | Message [#168] posted on: 12-08-2008 10:49 PM CST (US). | | Yes, The DC power supply will be lower from 30V to around 18V after few second. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#169] posted on: 12-08-2008 11:00 PM CST (US). | | lcp, is this power supply a σ11? Or something else? If not a σ11, what's its output current capability? Do you have the BIAS trimpots all pre-set to minimum as described in the initial setup section of the M³ website? |
| lcp Member Joined: Nov. 12, 2006 | Message [#170] posted on: 12-09-2008 12:34 AM CST (US). | | Bascially, the amp was working normal before it was suddenly no sound when I powered it up on last Friday. I haven't done anything on this amp. As I have mentioned, the top cover was opened for ventilation. I am not sure whether there is electostatic charge as we are at very low humidity in past few day. The power supply is no sigma11 but other supply from local Diyer where the supply is for PPA. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#171] posted on: 12-09-2008 01:02 AM CST (US). | | lcp, it sounds to me like the fault is in the power supply. Its output is sagging severely under some load. To test this, disconnect the M³ board from the power supply, and connect a 80 ohm 10W power resistor to the power supply output. Measure the voltage across that resistor. Does it stay where it should? Or does it sag to a low voltage as well? Note that the resistor will get very hot after a moment, so do this quickly and don't burn yourself. |
| lcp Member Joined: Nov. 12, 2006 | Message [#172] posted on: 12-09-2008 02:40 AM CST (US). | | Amb, thanks for your advice. I will check. In addition to this, I have short the pin of TLE this morning during volt check. Then, the power supply voltage is not dropped from 30V to around 18V and kept stable at 30V. After Q5+/- is replaced, the voltage of power supply drop after few second. |
| jackhsu Member Joined: Dec. 9, 2008 | Message [#173] posted on: 12-09-2008 02:55 AM CST (US). | | AMB, Can this Pulse transformer be used for S11? http://www.mouse...y673-039-5239-0 If so, which chassis will be a better fit, Hammond 1455N160x or 1455N220x? Thank you. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#174] posted on: 12-09-2008 03:09 AM CST (US). | | jackhsu, that transformer has pins on the bottom and is intended for PCB-mounting. You could use it if you have a board to mount it on, otherwise, it's better to get a transformer with wire leads. For less money than that Pulse transformer, you could get a nice Amveco TE62062 toroidal from Digikey. As for which Hammond, it depends on your transformer choice. You should do a little homework and add up the length of the σ11 board and transformer size, and then add clearance for front and rear panel components (LED/switch/IEC/DC jack, whatever else) to see if everything would fit. |
| jackhsu Member Joined: Dec. 9, 2008 | Message [#175] posted on: 12-09-2008 09:13 AM CST (US). | | Thanks a lot, AMB. I will check it out on Digi-Key. |
| dualxeon Member Joined: Dec. 8, 2008 | Message [#176] posted on: 12-10-2008 10:05 AM CST (US). | |
I was check out all right parts in the right place and the proper orientations and is the correct value, reflow all solder joints still do not work. |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#177] posted on: 12-10-2008 01:46 PM CST (US). | | dualxeon, since the ground channel is virtually identical to the other two channels, and your other channels are working, then you could use them as a reference to identify what's different. Use the schematic diagram and see how each part is supposed to be connected to another, and use your DMM to check for connectivity and shorts. Power up the amp and check the voltages relative to IG at various places, and see if you could identify some gross differences between the channels. Be careful with the DMM probes. Try swapping the opamps between channels and see if the problem moves with it. |
| lcp Member Joined: Nov. 12, 2006 | Message [#178] posted on: 12-10-2008 11:31 PM CST (US). | | Amb, Again, I have checked the DC output. There was no DC drop now. After lower the quiescent current to 80mv (previous 120mA) pin 4 is now -15.06V but pin 7 is still 3.98V. It seems Q5 is working normal. Both have Vce at 0.81V |
| amb Headphone Council Joined: Apr. 1, 2004 | Message [#179] posted on: 12-11-2008 03:31 AM CST (US). | | lcp, are you counting the opamp pin numbers the correct way? It's supposed to be:
If you were measuring the voltage of pin 6 (which perhaps you think is pin 7) relative to IG, you'd get about 4V... Attachment: C4452.gif |
odilon_df Member Joined: Oct. 6, 2008 | Message [#180] posted on: 12-11-2008 07:32 AM CST (US). | | Hi guys, Do you see any problem on changing the R5 and R8 values from 100 ohms to 91 ohms ? I have good set of 91 ohms resistors , but I just found trash 100 ohms in Brazil... |
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