jaytee Posted January 26, 2017 Report Share Posted January 26, 2017 (edited) So I just finished my MB-6582 base PCB. I tried it out with the first two SID chips mounted, success! Beautiful. I mount the other six SIDs....nothing. No startup tones, no LCD activity (not even a backlight). Uh oh. I removed half the SIDs (cores 2 and 3 FWIW) and everything seems to work again. Am I correct in thinking this is an issue of current draw? I am using a regulated 12V 1A supply (using Altitude's single supply approach), which I figured for sure would be enough juice (in the thread for the single supply, Altitude mentions only drawing 800mA with eight 6582s and a fan, and I don't even have a fan). Perhaps not? Is there anything else it might be? edit: And if it is just a matter of amperage (looking through old threads, I do see a few people referencing their MB-6582 drawing 1A or slightly more) can anyone suggest a decent power supply? I hate looking for this stuff; I don't want to run my precious gear off the cheapy-cheap switching supplies that are everywhere. Edited January 26, 2017 by jaytee Quote Link to comment Share on other sites More sharing options...
Zam Posted January 27, 2017 Report Share Posted January 27, 2017 Hello jaytee Maybe the first to do is to measure the actual current at your build. As the voltage drop resulting in the inability to power on the unit. What you describe don't automatically come from a underrated PSU... Best Zam Quote Link to comment Share on other sites More sharing options...
jaytee Posted January 27, 2017 Author Report Share Posted January 27, 2017 I will measure current draw later today; I ran out of workbench time yesterday. What other problems might cause this issue? Quote Link to comment Share on other sites More sharing options...
Zam Posted January 27, 2017 Report Share Posted January 27, 2017 Hi As you only talk about add/remove IC and not swapping IC, maybe one of the IC dead and shorting Vcc Vdd? Best Zam Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted January 27, 2017 Report Share Posted January 27, 2017 Me also thinks, it might be a power problem, if you have a display with a bit higher backlight current draw, you will be over 1A/12V... you might want a bit beefier PSU (it is never good to be so close to the limits). To test this, you could measure the 5V line with two and all eight SIDs installed. If the voltage drops then below a certain value (say something like 4.7/4.65V, but is clearly above 0V, which would indicate a short), that is a sign of a power supply overload issue. But as Zam said, it could also be a short somewhere (if your readout above shows something close to 0v). Not necessarily a defective SID, but maybe also a problem on the baseboard, that will only be visible, when a SID is installed. To test this case, install the two working SIDS into all engines (2/3/4) and try to power-on. To test for defective SIDs instead, try the non-tested SIDs in the otherwise working first engine SID sockets. Best regards and have a great weekend! Peter Quote Link to comment Share on other sites More sharing options...
jaytee Posted January 28, 2017 Author Report Share Posted January 28, 2017 Alright, I did some testing. First off, I gave the solder side of my board a thorough once over. Cleaned up questionable joints, got rid of flux splatter and errant blobs of solder, just generally cleaned it all up. I powered it up with four SIDs again—numbers 1,2,7&8—just to be sure that still worked. All good. I measure current draw, it's around 350mA. I stuff one additional SID in slot 3. It works. Try it in slots 4,5&6. It works. Leave it in slot 6. I stuff a sixth SID in slot 3. Everything still works. I stuff a seventh SID in slot 4. Nothing. Try it in slot 5. Nothing. Remove that SID and try the eighth SID in slots 4 and 5. Nothing. I remove the working SID from slot 3 and stuff the eighth SID there instead (so again, back down to six SIDs). It works. So it seems that it's only related to how many SIDs are stuffed, not where they get stuffed or which SIDs I use. Now I'm thinking it really is a matter of current draw. I test the current draw with six SIDs installed (working). About 550mA. I install a seventh SID. Current draw drops to about 360mA and as expected, the MB-6582 doesn't boot. Is my power supply crapping out? This is the one I use. I've been using it with my sammichSID for years. Any ideas? Quote Link to comment Share on other sites More sharing options...
jaytee Posted January 28, 2017 Author Report Share Posted January 28, 2017 I measured voltage on the 5V line with six SIDs installed vs seven SIDs, as @Hawkeye suggested. 4.99V and 2.45V, respectively. Quote Link to comment Share on other sites More sharing options...
Zam Posted January 29, 2017 Report Share Posted January 29, 2017 Hello jaytee Is there a local regulator at the MB6582 for the 5V rail ? because the supply you show is 12V In this case we also have to know the amperage at 12V supply output, not only the 5V rail... For the 5v rail, If I do little math, 4 SID installed is about 90mA per SID, considering all other component and the 70mA/SID (datasheet I just read) I gess it make sense (I don't know this build) Now adding two SID increase to 550mA, which is 200mA more, 100mA per SID, for two SID alone (all other component idle already in the previous measurement) So your already have a problem at this point, not enough to shut down the unit, but supply start failing... Try another PSU, (and use an autotransformer if you can for this kind of trouble shoot) Best Zam Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted January 29, 2017 Report Share Posted January 29, 2017 Zam: I think he is using Altitude's proven 5V switcher approach, that should be fine, and i agree with both of you, maybe the PSU just does not deliver the promised amount of current. I also think, that SID chips may have certain variations in power consumption. Six SIDs and 550ma sounds well within acceptable range for me, that voltage and current drops after installing the seventh SID (oh yeah, a new songtitle :-)) indicates an overload condition either on the 5V switcher or on the initial 12v power supply (and i really think it is the latter!) Suggestion: Replace it for a 12V/2A PSU and check again... Many greets and good luck! Peter Quote Link to comment Share on other sites More sharing options...
jaytee Posted January 29, 2017 Author Report Share Posted January 29, 2017 I don't suppose anyone can suggest a power supply? My head is spinning trying to find one that isn't a cheap piece of junk. OTOH, would a switching supply maybe be ok in this case, since all voltages are getting run through regulators and filtering caps? Quote Link to comment Share on other sites More sharing options...
Zam Posted January 29, 2017 Report Share Posted January 29, 2017 43 minutes ago, jaytee said: OTOH, would a switching supply maybe be ok in this case, since all voltages are getting run through regulators and filtering caps? I don't see any reason a SMPS won't do the job. Best Zam Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted January 30, 2017 Report Share Posted January 30, 2017 No problem with a SMPS, but is it really necessary? It might introduce noise, if the switcher is bad (if you have the specs and have a high switching frequency guaranteed, don't worry about that point!). A simple transformer -> diode rectifier -> smoothing cap array will do the job fine (aka an unregulated power supply), you have two regulators bringing it down afterwards: a 5V high-quality switcher for the digital parts and a 9V linear vreg for the SID opamps (analog part), no need to have an exact, regulated/switched 12V input... Many greets, Peter Quote Link to comment Share on other sites More sharing options...
jaytee Posted January 31, 2017 Author Report Share Posted January 31, 2017 Ok. So I had a cheap wall-wart Amazon Prime'd to my house. Didn't want to spend a lot of money on the off-chance this wasn't my problem....and I'm glad I didn't. Hooked up to a 12V 2A supply, I have the same issue. Up to six SIDS, everything is gravy; once I put a seventh and/or eighth in (no matter which SIDs or which slot) then MIOS fails to boot, LCD backlight doesn't turn on and basically nothing happens. Is my 5V regulator the next thing to check? Is there any way to check it without just ordering a new one? Quote Link to comment Share on other sites More sharing options...
latigid on Posted January 31, 2017 Report Share Posted January 31, 2017 What switching regulator are you using? Quote Link to comment Share on other sites More sharing options...
jaytee Posted January 31, 2017 Author Report Share Posted January 31, 2017 (edited) @latigid on Here is the part. Recom R785.0-1.0. I see now that in the thread about this power setup, various other prefixed regulators (R78C5, R78B5, etc) are offered, but looking over the datasheet, I can't find any reason why this one in particular would be crapping out. Edited January 31, 2017 by jaytee Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted January 31, 2017 Report Share Posted January 31, 2017 Oh! Good you did not order an expensive 12V PSU and sorry for the wrong advice! It seems Zam was right all the time! Did you measure the current previously on the 12V line or on the 5V line? Might it be, that the Recom has to provide > 1A after installing the 7th SID (that should not be the case...)... In other words, are you using a fan or a display, anything that might be power hungry on the 5V line? For testing, could you disconnect the display, install a 7th SID and start it up? Do you get the startup sound? Best regards, Peter Quote Link to comment Share on other sites More sharing options...
latigid on Posted January 31, 2017 Report Share Posted January 31, 2017 Hmm, my one is 1.5A, but if others are using it okay it's a puzzle. It would be good to connect the 5V post-regulator through a multimeter to be sure on the current. You may have a sVreg that's going into overcurrent shutdown too early. Some things clamp at half the rail voltage -- could explain your 2.45V. Another possibility is an inrush current problem. Can you try to sequence the startup with the LCD initially disconnected? Is everything else standard with your build? No ultra bright LEDs or anything fancy? Quote Link to comment Share on other sites More sharing options...
latigid on Posted January 31, 2017 Report Share Posted January 31, 2017 @Hawkeye 1 Quote Link to comment Share on other sites More sharing options...
latigid on Posted January 31, 2017 Report Share Posted January 31, 2017 Also: Quote Max capacitance Load with normal start-up time, no external components 470µF with <1 second start up time + diode protection circuit 6800µF If you have the large caps in there, removing them or adding the flyback/Schottky diode could help. Quote Link to comment Share on other sites More sharing options...
jaytee Posted January 31, 2017 Author Report Share Posted January 31, 2017 @Hawkeye, @latigid on, great minds think alike, eh? Earlier when I was measuring current draw, it was on the 12V line coming directly from the power adapter. With seven SIDs installed and no LCD connected, there is still no startup tone. (This is actually one of the first things I checked last week, but I checked again just now to be sure.) Right now, there is no CS attached, so no weird LEDs or anything else that might be drawing extra current. I suppose the next step is trying to carefully desolder the Vreg and resoldering it with one leg out to measure current? I'll do that now. Quote Link to comment Share on other sites More sharing options...
latigid on Posted January 31, 2017 Report Share Posted January 31, 2017 Just now, jaytee said: I suppose the next step is trying to carefully desolder the Vreg and resoldering it with one leg out to measure current? I'll do that now. Just cut/desolder the flywire connecting the regulator output to the 5V buss. Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted January 31, 2017 Report Share Posted January 31, 2017 @Altitude are you also using the Recom 5V/1A (not the 1.5A) version in your build? My next gut feeling says, that 1000mA might just not be enough for 8 SIDs and 4 PICs... Many greets, Peter Quote Link to comment Share on other sites More sharing options...
jaytee Posted January 31, 2017 Author Report Share Posted January 31, 2017 Hah, duh. Wish I had checked this thread again before firing up the iron. Anyway, pulled the R785.0-1.0 and breadboarded it for easier debugging. Double-checked that it's hooked up correctly by running it in this configuration: same results as before. With my multimeter in series with the 5V line, I measure: 6 SIDs: 710-730mA 7 SIDs: 730-760mA 8 SIDs: 810-840mA I also want to note that I get slightly different behavior when my meter is in series like this. - No matter how many SIDs are stuffed (6, 7, or 8), the LCD acts kinda funny—like the contrast is worse or uneven, maybe the backlight is dimmer and it is not nearly as responsive. - It seems to boot with a 7th SID installed, but still not that 8th one. - A couple times, it seemed to struggle to boot with just six SIDs installed. It would hang on "Launching CS..." or reboot itself. Perhaps this one is down to iffy connections. Between the breadboard and the alligator clips/probes, it wouldn't surprise me if something just lost connection briefly, especially since this happened just a couple of times while testing and retesting and testing a third time to be sure, but figured I should mention it for the same of completion. So anyway, still kinda stumped. Quote Link to comment Share on other sites More sharing options...
jaytee Posted January 31, 2017 Author Report Share Posted January 31, 2017 (edited) 2 hours ago, latigid on said: Also: If you have the large caps in there, removing them or adding the flyback/Schottky diode could help. @latigid on, just saw this, must have missed it while writing my own response. I saw this in the datasheet and thought it might be related, but didn't really understand what it meant. Are you talking about the 2200uF caps? For the flyback diode, is 1N4148 ok? I don't think I have anything else handy. Edit: I do have a 1N4001 power diode here too. Edited January 31, 2017 by jaytee Quote Link to comment Share on other sites More sharing options...
Hawkeye Posted January 31, 2017 Report Share Posted January 31, 2017 Thanks for measuring! 840ma of 1000ma is too close, as there isn`t even the CS installed... subtract 10% error and it will go into shutdown... Upgrade the switcher to 1.5 amps... that is also the spec of the 5v rail of the original C64 PSU... Many greets, Peter 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.