Geddon Posted August 19, 2012 Report Share Posted August 19, 2012 Hi everyone, im almost finished with my mb6581 build but having a lil problem with sid engine 1. I followed the first steps of the midibox sid v2 manual and created a basic tone (fat pulse). It sounds great on engines 2,3 and 4, but on engine 1 the left channel sounds different. Its hard to explain, but its not as thick a sound. Like maybe an osc or two are missing. Ive swapped sids around and the problem persists so i know they're ok. Im sorry im not able to upload a sample at the moment but is there anything i can do to test the circuit? Do you think it may be a capacitor problem? Ive searched the forums but havent found anything similar. I hope i have given enough info for someone to please help! Thanks, Adam. Quote Link to comment Share on other sites More sharing options...
Geddon Posted August 19, 2012 Author Report Share Posted August 19, 2012 On closer inspection, the audio from the right sid of engine 1 is coming from both speakers. But i dont see any short. Quote Link to comment Share on other sites More sharing options...
Geddon Posted August 19, 2012 Author Report Share Posted August 19, 2012 I have noticed that sid engine 1, left sid does not produce any sound from oscs 2 and 3. Also, the right sid osc 1 outputs to both speakers, while oscs 2 and 3 only output to the right speaker. On all oscs which do not output a sound there is a small pop when a note is played. Dumb question, but maybe i have been swapping wrong sids. Which sid is number one on the board, the far left? Quote Link to comment Share on other sites More sharing options...
Geddon Posted August 19, 2012 Author Report Share Posted August 19, 2012 Sorry, ignore that last question about sid numbers, i was having a 'special' moment :b Quote Link to comment Share on other sites More sharing options...
Geddon Posted August 22, 2012 Author Report Share Posted August 22, 2012 Ok im really struggling with this. I assume it must be a simple problem to resolve, as no one has replied. But i just cant figure it out. Ive been studying the sid datasheet but to no avail. Ive spent almost a year collecting the parts, reading these forums, the construction guides etc. Ive been really careful, methodical, patient with every aspect of the build. There have been many times when i had questions but found it far more educational and fun to find the answers myself. But for this one im stumped. I dont expect to be handed the answer on a plate, but if someone could please just point me in the right direction i would be eternally grateful! Thanks again, Adam. Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted August 22, 2012 Report Share Posted August 22, 2012 (edited) Hi Adam, first of all - congratulations on finishing that MB6582! No worries, the problem will be found ;-) Regarding SID numbering: the rightmost SID (when viewing the baseboard from top) is the first sid, the second-right is the second sid, these two are controlled by SID Engine 1. (Which is active by default when starting the MB6582). Which physical output jack are you testing? The mix output, that adds all outs together (3.5mm jack) or the leftmost (as viewed from the back) 6.3mm SID Engine 1 out? The possible problems are: a) Output circuitry on one channel on SID engine 1 has some problems b) A SID on SID engine 1 is damaged (broken filter or osc) They can be narrowed down by doing these tests: Swap the rightmost two SID chips with each other and see if the problem "wanders" to the other channel? This test is good for testing oscillators and especially filters (which are reported broken quite often). Swap in other SID-pairs from another engine, e.g. swap SIDs 3 and 4 from the right with SIDs 1 and 2? This test is good for testing a complete engine output circuit (left and right channel) with "known good" SIDs. For testing, please use an "init" patch, which uses the "Lead" sound generation model, with no filters turned on at first. Then test the three OSCs by detuning them against each other. Then activate a LP filter on all three OSCs and do a cutoff frequency sweep (all controls in the left-lower section of the MB6582 CS). Many greets and best of luck.. Peter Edited August 22, 2012 by Hawkeye Quote Link to comment Share on other sites More sharing options...
Geddon Posted August 22, 2012 Author Report Share Posted August 22, 2012 Thanks very much for the advice hawkeye. Your cs construction guide has been my trusty reading companion for quite a while! The machine is a beast, i shouldnt complain really because 3 of the four cores are spot-on and sound amazing. Ive been having a lot of fun creating sounds and learning the menus. But i just want it to be perfect! Well, maybe not perfect, i already had to desolder a bad encoder and a couple more are a bit funky but i can live with that for now. After more testing, the problem seems to have changed to something more simple. Sid 1 sounds on both left and right channels, and sid 2 sounds on both channels too. Ive swapped sids over, and also swapped pairs and the problem stays with audio output 1. And the ensemble is definitely not set to mono! Ive tested the pins of the audio out jacks with my multimeter for connectivity and all test consistently so i dont think the problem is there. I cant see any shorts, or bad solder points and i reflowed the solder on a few that looked 'dodgy'. I will keep looking and trying, those sids are worth it. Quote Link to comment Share on other sites More sharing options...
Geddon Posted August 23, 2012 Author Report Share Posted August 23, 2012 I forgot to mention, i have been using the 6.3mm sid 1 output but the effect is the same from the 3.5mm. Another few things i have noticed when using engine 1- Using init. patch on left and right channels and all oscs set to pulse, when using the "detune" function the changes are not smooth like the other engines. It is like steps, where the pitch of osc 3 changes eratically. When i play a note and bend it with the wheel on my keyboard, osc 3 of both channels glitches and changes erratically. The fun continues...:) Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted August 23, 2012 Report Share Posted August 23, 2012 (edited) Interesting! Before continuing, lets make sure the voltages are spot on, while the MB6582 is powered up... Use a digital multimeter in the 0-20volts range and measure SIDs 1+2 from Engine1 from PIN 14 (ground, lower left) to Pins 25 and Pins 28 respectively - the voltages should be around +5V and around +9V or +12V depending on your SID type... If these check out ok... can you pull one of the SIDs (ofc while powered off) on the first engine and see if sounds still appear on both sides? It might not be the output circuit, but some problem on the control circuit for those sids, and that they sometimes/somehow get the same commands from the core (thus the "fake stereo") along with other problems that lead to the symptoms like osc glitches you described... If there is mono output on the engine1 6.3mm output jack after this test, please grab a good hi-res camera and take a few shots of SID engine 1 core (front side and back side), that would be around the rightmost PIC chip and post them here. If there is stereo output on the engine1 6.3mm output jack after this test, please do the same and take a few pictures of the output section (front side and back side), that would be around the sids 1+2 and the section above it and post them here. Many greets! Peter Edited August 23, 2012 by Hawkeye Quote Link to comment Share on other sites More sharing options...
Geddon Posted August 23, 2012 Author Report Share Posted August 23, 2012 Narrowing it down... Pin 28 of sid 1 reads 9v, as opposed to 11.9v of the other sids (all sids are 6581s). Pin 25 reads 5.1v on all sids so thats ok. When i first performed voltage checks during construction everything was a-ok, so does that mean that the problem lies within a component? Maybe within the pic?Sorry im not sure how to edit my posts. If i check for continuity between pin 14 and 28 of sid 1, my meter doesnt beep, but it does with other sids. Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted August 23, 2012 Report Share Posted August 23, 2012 (edited) Have you checked, that the jumper above pin28 of the first sid is set to 12V (not 9V)? Edited August 23, 2012 by Hawkeye Quote Link to comment Share on other sites More sharing options...
Geddon Posted August 23, 2012 Author Report Share Posted August 23, 2012 (edited) Oops, yes i must have moved the jumper recently when i was checking stuff. The shame! Anyway, i put it back to 12v but now pin 28 only reads 3v. In addition, i removed sids one at a time and checked the audio outs. The sound only leaks to both channels when both sids are in. When either left or right sid is in, the audio comes from the correct channel. Only oscillator 3 of sid L is glitchy. With both sids in, if i play just osc 1,2 or 3 of left channel, the audio comes from the left and only osc 3 glitches. If i play just the right channel, sound comes from both channels but the glitches are heard only on the left. Im not able to upload any pictures til tomorrow, my new flat has no broadband yet so ive been using my phone. I will borrow a friends computer tomorrow afternoon. I took pics of the core section like you suggested. Is there something in paeticular to look for? Or just bad soldering/missing components? I will tell you that everything is there, but you cant trust anybody! Sorry for the long post but thanks again. Edited August 23, 2012 by Geddon Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted August 24, 2012 Report Share Posted August 24, 2012 Ok, no problem, there seems to be a power supply problem mixed with some problems on the output circuitry... Unblurred, well-lighted high-def photos of the area above sids 1+2 (front and backside) will hopefully help to solve the mystery. Any other ideas from other MB6582 builders are highly welcome! What makes me wonder a lot is how can there be 3V on SID1 Pin 28, when all the others have 12V - the circuit is quite simple there, so sth. strange is going on ;-) Many greets, Peter Quote Link to comment Share on other sites More sharing options...
Geddon Posted August 24, 2012 Author Report Share Posted August 24, 2012 (edited) OK so I double-checked the voltages again. It seems that sometimes when I power up the machine there is no power-up jingle, and all pin 28s of all sid (but sometimes just sid 1) read 3v. But then if I power-off and on again, the jingle plays and the voltage reads 11.9, even on sid 1. But in both cases, the audio of sid 1 still leaks across channels, and the osc 3 still glitches. Bah! sidsfront.bmpsidsback1.bmpsidsback2.bmpsidsback3.bmpboardback1.bmpboardfront1.bmp Edit- sometimes when modulation matrix, there are no leds lit in meter mode, when usually there would be for that patch. Reset power usually fixes this. I tried my spare c64 power brick, just in case it was that but the problems persist. Im wondering if i should just pull sid 2 and have mono engine 1? I dont want to hog all your time for my machine. Edited August 24, 2012 by Geddon Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted August 24, 2012 Report Share Posted August 24, 2012 (edited) Hi there, apart from a very few solder joints on the backside (sidback1), which do look like "rain drops", not like "eiffel towers" :) i can´t see anything right now - you might want to resolder those and see if it fixes the engine1 output section problem... My other guess would be, that the power supply is at its limits which would explain the low voltage across the board sometimes - can you exchange it? Many old C64-PSUs are overloaded by the power draw of a fully populated MB6582... I´d also recommend to buy or build your own powersupply, to avoid frying those expensive sids, when the old c64 psu goes into berzerk mode :) I hope there will be additional feedback, not only from me :) Many greets, Peter Edited August 24, 2012 by Hawkeye Quote Link to comment Share on other sites More sharing options...
Geddon Posted August 24, 2012 Author Report Share Posted August 24, 2012 Good suggestions, thanks. I have 3 c64 psus so i will give them all a try. I wont report back here until i have checked every possibility! I am still baffled but if i have to have a mono engine 1, well that will maybe have to do (for now!) :) Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.