monokinetic Posted November 1, 2007 Report Share Posted November 1, 2007 Hello all,well after a few evenings of staring at the OPL3 circuit board I'm a bit stuck.Current setup is a CORE v2, OPL3 and duggle's AC wallwart to +/- 12v +5v PSU.Testing the OPL3 according to ucapps.de I ran without the TL074 first of all. +/-12V all seemed fine. PSU ran for 30 minutes without melting the house down so I unplugged and installed the TL074s. With all 3 plugged in the +12v line dropped to +0.74v. Worrying, so I pulled the power. Through a process of trial and error I have come to the conclusion that this only happen with IC3 plugged in, if I leave it out the board runs without problems. So I have traced every line from IC3, the positive and negative lines plus everything going to the YAC chip. All connectivity seems fine, no obvious shorts. I decided to risk running without IC3 and plugging in audio outs 3 and 4 (which run from the other YAC and TL074 combination) and I either get nothing from the audio outs or loads of static. Yes I'm 100 percent sure that MIOS is uploaded and the FMtesttone app as well.After reading this thread:http://www.midibox.org/forum/index.php?action=post;quote=75407;topic=9997.0;num_replies=9;sesc=aa4be4696de2bbaaf6667995a59e2bcbI noticed that TK suggested reading the voltage at the following pins, I have listed my results:IC3, O4 = -0.84vIC3, O3 = -0.82vIC5, O4 = +2.52IC5, O3 = +2.52Now the million euro question, any ideas what is going on here!?TIADave mK Quote Link to comment Share on other sites More sharing options...
TK. Posted November 2, 2007 Report Share Posted November 2, 2007 Hi Dave,the voltages at IC5 outputs seem to be ok, a positive offset between 2V..4V has to be expected. I would propose to check this first with removed IC3.You could connect the audio input of your mixer/soundcard to the IC5 outputs w/o much risks - you should hear a silent, but noticable sinewave (with the testtone app). If you don't hear it, we have to search for another debugging approach.Best Regards, Thorsten. Quote Link to comment Share on other sites More sharing options...
monokinetic Posted November 4, 2007 Author Report Share Posted November 4, 2007 Hi Thorsten,As always thanks for taking the time to reply, I really appreciate it.I have spent some time over the weekend to try and narrow down what is causing this. I followed your suggestion of removing IC3 and testing audio outs 3 and 4. When I switch on there is no sound for approx 5 seconds, then there is a faint sound. I generated a 1khz test tone in software to compare with what I hear, it is pretty close but very very quiet. I tried to upload the MBFM1.1a app. after this, but it seems to output the same sound. I would guess that if everything was OK I would be able to upload the app and send MIDI to trigger some other sound? (by the way I have no bankstick attached at the moment, does the FM boot up with some initial sound or not?)Some other findings:one of the capacitors close to IC3 had got twisted and the legs were touching. I replaced it but no change.IC3 and IC5 both get rather hot after 2 minutes of running. Even with only one or the other plugged in, still they get very hot.Approx 1 time in 5, I switch on and when I measure the +12v line there is -0.74. I reset the power a few times and it comes back to +12v!I have tried another crystal oscillator this evening, no change.Oh yes and 1 question to clarify: When I measure the voltage on IC3 or IC5 pins O3 and O4 I have the negative sensor of my multimeter connected to the common ground point (as marked on Duggle's PSU schematic). That's correct isn't it?Tomorrow I'm planning on buying some other TL074's to eliminate them from the equation. Any other suggestions?BestDave mK Quote Link to comment Share on other sites More sharing options...
TK. Posted November 4, 2007 Report Share Posted November 4, 2007 Hi Dave,yes, the MBFM application doesn't output the 1kHz tone, instead you should be able to trigger an epiano sound, which is located in internal EEPROM (so, it should even work w/o BankStick).Hope that you've used "Smart" mode during the application upload - just to ensure that it was really uploaded.Approx 1 time in 5, I switch on and when I measure the +12v line there is -0.74. I reset the power a few times and it comes back to +12v!could be related to the voltage regulator - is the 7812 getting hot?Oh yes and 1 question to clarify: When I measure the voltage on IC3 or IC5 pins O3 and O4 I have the negative sensor of my multimeter connected to the common ground point (as marked on Duggle's PSU schematic). That's correct isn't it?yes, it isBest Regards, Thorsten. Quote Link to comment Share on other sites More sharing options...
monokinetic Posted November 4, 2007 Author Report Share Posted November 4, 2007 yes, the MBFM application doesn't output the 1kHz tone, instead you should be able to trigger an epiano sound, which is located in internal EEPROM (so, it should even work w/o BankStick).OK then something is quite wrong because I cant trigger anything over MIDI. I just get a low buzz, regardless of the app on the PIC. Hope that you've used "Smart" mode during the application upload - just to ensure that it was really uploaded.Of course smart mode is on when I'm uploading to the core :)I double checked the core functionality this evening using the interconnection app, each pin is going fine from the core to the OPL3 connectors.yes quite hot, and the IC3 and IC5 TL074s. The other TL074 seems fine. I tried swapping all TL074s around to be sure it's not chip related. I will still buy some more tomorrow to be double sure....yes, it isOK, just checking. Some more silly questions:I don't have things in a metal box at the moment, just on my work bench. I've not done much with things that make sound with AC based PSU's before. Would that make a difference?Plus, something that seems weird to me is that Duggles schematic and the original say that the non-live pin, where the AC comes in to the part which makes the DC power, is also where audio ground connects. That is correct isn't it?BestDave mK Quote Link to comment Share on other sites More sharing options...
monokinetic Posted November 6, 2007 Author Report Share Posted November 6, 2007 A further update and some more questions:I realised that I had got confused when taking measurements at OP4 and OP3, I was measuring on the wrong pins, sorry for the wrong info. Currently I measure:With IC3 and IC5 inserted: OP3 and OP4IC3= -10.77 -1.04 IC5= -5.23 +5.72Which I would guess is quite wrong!Without IC3 and IC5: OP3 and OP4IC3= -0.02 -0.0 IC5= -0.17 -0.33I haven't had time to get some new TL074s yet. I'm guessing that IC5 has some problems because of the negative voltages on the pins even when there is no chip plugged in. Any ideas?My current questions:is there anyway to test if the crystal is working correctly?is it ok to measure voltages on the YMF262 and the YAC512 chip pins?what are the expected voltages at the OP3 and OP4 pins?TIA for any suggestions...Dave mK Quote Link to comment Share on other sites More sharing options...
TK. Posted November 6, 2007 Report Share Posted November 6, 2007 Yes, it really looks like something is wrong with IC3, or around IC3 (open connection, or short)It isn't possible to check the crystal without a scope. It could make sense to measure voltages around the OPL3 and DAC chip, but since these are mostly digital waveforms, you won't read any meaningful values, it can only give (an expert) a hint, if for example a connection is available between one pin to another.Sorry, I can also not say exactly the expected voltages for the OPs without opening my case. Is there anybody who has an opened case and could do the measurements?Best Regards, Thorsten. Quote Link to comment Share on other sites More sharing options...
monokinetic Posted November 7, 2007 Author Report Share Posted November 7, 2007 I stumbled accross some web images of someone who has built a OPL3 successfully: It looks like his board has quite a lot of tantulum caps (I'm guessing they are tantalums).I have used all ceramic caps for the non-polarised caps.I just double checked the reichelt orderlist and realised that in fact the 9 x 100nF caps are VIELSCHICHTKONDENSATOR. My German is not very good I'm afraid. Can anyone tell me exactly what this type of cap is please?In the meantime I will buy some tantulum's and experiment to see if it makes a difference.D Quote Link to comment Share on other sites More sharing options...
TK. Posted November 7, 2007 Report Share Posted November 7, 2007 It's very unlikely that the caps are causing such an issue. In order to see a picture of "VIELSCHICHTKONDENSATOR", visit www.reichelt.de and type this keyword into the search mask - they are looking similar to tantulum capsI'm using the same caps - but as mentioned before: the cap type doesn't matter here, they don't have essential functions.Best Regards, Thorsten. Quote Link to comment Share on other sites More sharing options...
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