Snoozr Posted January 11, 2011 Report Share Posted January 11, 2011 Funky in a bad way unfortunately. sammichSID voltages are too high. 9V rail is reading about 10.5V. 5V rail is reading around 8V. 12V rail is fine. I followed the Sid V2 optimized PSU schem at http://www.ucapps.de/mbhp/mbhp_8xsid_c64_psu_optimized.pdf J1 (input plug) fine (fine means I can get 12V across the part). Rocker switch is fine. Bridge rectifier X1 is fine. Large cap C5 is fine as is little C6. After that, something happens. From the schem I assume (maybe) that next up is the little electrolytics C4 and C10 and the little radial caps C3 and C9. However, by the time it gets to these, the voltage has gone weird. Voltage is also wrong at the 7809 and the 7805. Read all the voltage Sid threads but couldn't find any smoking guns yet. I'll give the solder joints of all the above a once-over but in the interim if any ideas crop up, let me know. Thanks. Quote Link to comment Share on other sites More sharing options...
Snoozr Posted January 11, 2011 Author Report Share Posted January 11, 2011 PS - I followed the ucapps schematic because I read somewhere that the sammichSID follows this. Quote Link to comment Share on other sites More sharing options...
nILS Posted January 11, 2011 Report Share Posted January 11, 2011 * Make sure the polarity of C5, C6, C10 and C4 is correct * Make sure the polarity of D4 and D5 is correct * Make sure JP is set correctly If all of those are correct, measure the voltages across C6, J20 and J2 and post the results here. Make sure you've set your meter to DC for measuring after the bridge [and AC before the bridge if your PSU is AC] Quote Link to comment Share on other sites More sharing options...
Snoozr Posted January 11, 2011 Author Report Share Posted January 11, 2011 Thanks Nils. Here are some updates. * Make sure the polarity of C5, C6, C10 and C4 is correct These are all correct polarity except for C6 which appears to be non-polarized (monolithic and no + sign on the board). * Make sure the polarity of D4 and D5 is correct They are both correct. * Make sure JP is set correctly JP is set for 6581. I am using the PS-1251 regulated 12V power supply from All Electronics which was mentioned here on the forum. The output of this is 12VDC as checked on meter. If all of those are correct, measure the voltages across C6, J20 and J2 and post the results here. Make sure you've set your meter to DC for measuring after the bridge [and AC before the bridge if your PSU is AC] The output across C6 is still 12V. The output across J20 is still 10.5V. The output across J2 is still 8V. I checked these voltages with two meters, so these numbers are good. A few other things - I touched up a few solder joints around this part of the board. No obvious bridges or shorts. Also I happened to have labeled the 7809 and the 7805 on the visible side and so I can confirm they are correctly stuffed. I checked the small heatsink for the 7809 and it has no connectivity with the rest of the board. However, the large heatsink is connected to ground. I don't know if this matters or not. It is not connected to any of the 5V, 9V or 12V lines. This is probably not the issue but it's the only thing I can think of. There are four holes for C6, two inner holes and two outer holes. The Build Guide shows the leads of C6 going into the outer holes, and that's what I've done. Some of the solder dribbled over into an inner hole and I am having a hell of a time getting it out. There are a number of other points on the board where this issue crops up. I am actually a passable solderer and have yet to have a soldering issue come up on any of my builds, plus I can see some places on the board such as C7R where the inner hole and outer hole appear to share a common metal border by design. So I assume this isn't an issue because the inner and outer holes are already bridged, but just thought I would mention it. Quote Link to comment Share on other sites More sharing options...
Snoozr Posted January 11, 2011 Author Report Share Posted January 11, 2011 Also, JBP has the 2 shunts as per the 6581 build instructions. Quote Link to comment Share on other sites More sharing options...
Wilba Posted January 11, 2011 Report Share Posted January 11, 2011 A few other things - I touched up a few solder joints around this part of the board. No obvious bridges or shorts. Also I happened to have labeled the 7809 and the 7805 on the visible side and so I can confirm they are correctly stuffed. I checked the small heatsink for the 7809 and it has no connectivity with the rest of the board. However, the large heatsink is connected to ground. I don't know if this matters or not. It is not connected to any of the 5V, 9V or 12V lines. It's OK if the heatsink is electrically connected to ground, this is happening via the screw/nut, and the metal part of TO-220 package positive voltage regulators are connected to the middle (common) pin, which should be at ground. This is probably not the issue but it's the only thing I can think of. There are four holes for C6, two inner holes and two outer holes. The Build Guide shows the leads of C6 going into the outer holes, and that's what I've done. Some of the solder dribbled over into an inner hole and I am having a hell of a time getting it out. There are a number of other points on the board where this issue crops up. I am actually a passable solderer and have yet to have a soldering issue come up on any of my builds, plus I can see some places on the board such as C7R where the inner hole and outer hole appear to share a common metal border by design. So I assume this isn't an issue because the inner and outer holes are already bridged, but just thought I would mention it. The capacitor footprints have two pads/holes for each lead. As you already observed, they're connected, so it doesn't matter if the unused hole is filled with solder. The extra pads/holes are so either 50mil and 100mil lead spacing capacitors can be fitted. As for the voltage problem, I am a bit puzzled... voltage regulators really shouldn't be outputting more voltage than their rating. They can output less, if the input voltage isn't high enough, but more? WTF? :D I'm guessing here, but one way it might appear to be higher is if you're measuring using the black probe on something "lower" than the common pin of the voltage regultator... i.e. I think if you stick a resistor between a voltage regulator common pin and ground, the output will be higher than its rating relative to ground. Can you test the voltages directly between the middle pin and each of the other two pins of the voltage regulators? i.e. the input and output voltages directly at the voltage regulator pins. Maybe this will be different to your other measurements. Quote Link to comment Share on other sites More sharing options...
nILS Posted January 12, 2011 Report Share Posted January 12, 2011 I think if you stick a resistor between a voltage regulator common pin and ground, the output will be higher than its rating relative to ground. A diode will do that. The only thing I can think of at this point is that there's absolutely no load and the vregs don't like that. You can temporarily add a load by using a 1k resistor across J20 or J2 (which will draw 9/5mA). Quote Link to comment Share on other sites More sharing options...
Snoozr Posted January 13, 2011 Author Report Share Posted January 13, 2011 A diode will do that. The only thing I can think of at this point is that there's absolutely no load and the vregs don't like that. You can temporarily add a load by using a 1k resistor across J20 or J2 (which will draw 9/5mA). I had a 470 ohm resistor which I inserted in J2. This dropped the 5V line's voltage to about 7.5V as measured both at J2 (measured across the resistor) and at J4 (sanity check). For the Wilba test, I removed the resistor. I tested the 7805. Ground to "Leg 3" (the one on the right as you look at the board with the power switch away from you) gave 8V. Ground to "Leg 1" is around 8.95V depending on the meter. For the 7809, Ground to "Leg 3" (the one on the right as you look at the board with the power switch away from you) is about 11.85 and around 9.5 on "Leg 1". The whole 9V rail seems to have improved as a result of the insertion of the resistor. I decided to stick the resistor in J20 since J2 (oddly) seemed to clear up the 9V line. Hence, resistor ih 9V might help 5V line. Putting it in and taking it out brought the 5V line closer to 7.1V, a small improvement. I will see if I can scrounge up a bigger resistor and try to keep pushing the voltages back to spec. Quote Link to comment Share on other sites More sharing options...
Snoozr Posted January 13, 2011 Author Report Share Posted January 13, 2011 I have a diode checker on 1 of the meters. I have no idea what the units are. When I put the positive probe on the lead in the direction of current ("output") and the negative probe on the other side ("input"), I get a reading of -458. When I reverse the probes, I get a reading of 770. These numbers are pretty consistent across diodes. Quote Link to comment Share on other sites More sharing options...
philetaylor Posted January 13, 2011 Report Share Posted January 13, 2011 (edited) It is not really possible to test diodes 'in circuit' as other components will affect the result. You should really disconnect one end of the diode for proper results. Once you have done this, select diode test mode and when the diode is forward-biased (+ probe to anode and - probe to cathode), if the diode is working correctly the meter should show you the forward voltage drop (usually about 0.6 - 0.7v). When reverse biased (probes swapped round) the meter should show "open circuit". If you get a reading on the meter in both directions this means that the diode is faulty! Edited January 13, 2011 by philetaylor Quote Link to comment Share on other sites More sharing options...
Snoozr Posted January 13, 2011 Author Report Share Posted January 13, 2011 Thanks Phil. So should I snip out the cathode, the anode or both? Also, based on your description of the right way to do it, the "right" reading of the above two was the 770 one. Of course, the real right way would be to snip out like you said. By the way, I tried putting the 1K resistor in J20 and J2 but this did not help. I also put my finger on there (bridging the pads) as kind of a 1M resistor. No change. Quote Link to comment Share on other sites More sharing options...
philetaylor Posted January 13, 2011 Report Share Posted January 13, 2011 Thanks Phil. So should I snip out the cathode, the anode or both? It doesn't really matter which, once you disconnect one of the leads, other components will not affect the test results. Also, based on your description of the right way to do it, the "right" reading of the above two was the 770 one. Of course, the real right way would be to snip out like you said. It is difficult to say but yes 770mV sounds like a likely forward-bias voltage for a standard silicon diode (germanium diodes have a lower forward-bias voltage of about 300mV) but who knows what effect any other components in the circuit are having on the readings? Cheers Phil Quote Link to comment Share on other sites More sharing options...
Wilba Posted January 14, 2011 Report Share Posted January 14, 2011 BTW sammichSID power supply circuit has nothing to do with "Sid V2 optimized PSU schem". Quote Link to comment Share on other sites More sharing options...
nILS Posted January 14, 2011 Report Share Posted January 14, 2011 Since this isn't really going anywhere, I'd suggest desoldering the vregs and testing them separately. Quote Link to comment Share on other sites More sharing options...
Snoozr Posted January 17, 2011 Author Report Share Posted January 17, 2011 Desoldered and replaced the vregs. 9V rail now gives about 9.03V so that seems fine. 5V rail now gives 6.7V. The new 7805 has 7.5V going into it, i.e., the Pin 1 to Pin 2 reading is 7.5V. The Pin 2 to Pin 3 reading is as before. I will upload some pics in the next post in case that helps. Quote Link to comment Share on other sites More sharing options...
Snoozr Posted January 17, 2011 Author Report Share Posted January 17, 2011 Also when I said "as before" in the above post, I mean 6.7V (from the sentence before). Quote Link to comment Share on other sites More sharing options...
nILS Posted January 17, 2011 Report Share Posted January 17, 2011 Let's see if you can figure it out yourself. No help please. (Sorry janis, I removed your post to allow Snoozr to solve it himself) Quote Link to comment Share on other sites More sharing options...
ilmenator Posted January 17, 2011 Report Share Posted January 17, 2011 Damn, nILS beat me to it... Quote Link to comment Share on other sites More sharing options...
nILS Posted January 17, 2011 Report Share Posted January 17, 2011 Actually janis beat us both to it, while I was looking for a pic ;) Quote Link to comment Share on other sites More sharing options...
Snoozr Posted January 19, 2011 Author Report Share Posted January 19, 2011 (edited) OK-thanks. Edited January 19, 2011 by Snoozr Quote Link to comment Share on other sites More sharing options...
philetaylor Posted January 19, 2011 Report Share Posted January 19, 2011 For those of us that haven't seen your pics, what was the problem??? Cheers Phil Quote Link to comment Share on other sites More sharing options...
nILS Posted January 19, 2011 Report Share Posted January 19, 2011 The pics are still there, but apparently flickr and our forum don't always play nice... Here's the pic again: Quote Link to comment Share on other sites More sharing options...
philetaylor Posted January 19, 2011 Report Share Posted January 19, 2011 Ah yes an easy mistake to make (although not usually when mounted horizontally :) ) Phil Quote Link to comment Share on other sites More sharing options...
Snoozr Posted January 22, 2011 Author Report Share Posted January 22, 2011 Update: sammichSID is all up and running. This guy's a 6581 to go with my MB-6582. Thanks gang - bring on the sammichFM!!! Quote Link to comment Share on other sites More sharing options...
nILS Posted January 22, 2011 Report Share Posted January 22, 2011 Glad you got it working! Next time, stick to the build guide, okay? :thumbsup: 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.