Loading ...
Sorry, an error occurred while loading the content.

[Altair Computer Club] Re: Since you said it was ok to post Sol-20 questions...

Expand Messages
  • deramp5113
    Good! That result helps isolate the problem. Drawing just .5 amps, the power resistor won t trigger fold back protection, so since the output still drops to
    Message 1 of 32 , Feb 10, 2013
    • 0 Attachment
      Good! That result helps isolate the problem. Drawing just .5 amps, the power resistor won't trigger fold back protection, so since the output still drops to 3.77v, then you are right, there is a problem in the regulation circuit, not excessive current draw.

      Next, I'd measure voltage at the base of q2 (or pin 1 of u2) and at the base of q1 (or junction of r3 and r4) while the 10 ohm load is connected. This will help determine if there is a transistor problem or an op-amp circuit problem.

      Mike

      --- In altaircomputerclub@yahoogroups.com, corey986 wrote:
      >
      >
      >
      > Bob,
      >
      > Well the resistor says 10 ohms 10W so I hooked it up using a spare molex connector to the +5 and ground as load for the supply. When I measured it between the power resistor I got 3.77/3.78 volts. So it looks like it's something in the powersupply's regulation circuit which now means I have to take the whole thing out of the metal case (the only part of the case I didn't disassemble yet).
      >
      > Any idea on where I should start for my troubleshooting of the power supply? You've been very helpful and I really want to get this Sol running at some point so that when the weather is nicer I can work on the cosmetics of a running machine.
      >
      > Thanks,
      > Corey
      >
      > --- In altaircomputerclub@yahoogroups.com, "deramp5113" wrote:
      > >
      > > Since the filter capacitor is staying at 6.22 volts, the current is limited to a bit over 1 amp with an output voltage of 3.77 volts, and we know the +/-12v supplies are good, it does sound like the fold back protection circuit (r6, r8, q3, 1/2 of u2) is active. This circuit drops current along with voltage down to about 1 amp for a dead short on the output.
      > >
      > > Recheck the specs of the power resistor you have: Is it 10 ohms at 10 watts? "uf" and "amps" are not resistor ratings. If it is 10 ohms and 10 watts, then we can connect the resistor as the only load and verify we have five volts out. A 10 ohm resistor will draw 1/2 amp from the 5 volt supply. Do you have any more power resistors?
      > >
      > > --- In altaircomputerclub@yahoogroups.com, Bob Grieb wrote:
      > > >
      > > > Corey,
      > > >
      > > >    The schematic I have says 5V 3A for the Sol-20 power supply.  If the supply can really
      > > > put out 5V at 3 Amps, and you are only measuring 1.12 amps (112mV/0.1 ohms)  and
      > > > getting only 3.77 volts, then that seems to indicate a power supply issue.  If the supply can
      > > > really deliver 3A at 5 volts, then it seems to me you should see 5V at just 1 amp, even if the main
      > > > bd does have a problem.
      > > >
      > > >      Bob
      > > >
      > > >
      > > >
      > > >
      > > > ________________________________
      > > > From: corey986
      > > > To: altaircomputerclub@yahoogroups.com
      > > > Sent: Sunday, February 10, 2013 2:01 PM
      > > > Subject: [Altair Computer Club] Re: Since you said it was ok to post Sol-20 questions...
      > > >
      > > >
      > > >  
      > > > I measured X2 from the plus terminal of the 18,000uf cap to the ground wire to the board. It read 6.22 volts. I also double checked the power at the board which is exactly 3.77 volts.
      > > >
      > > > So what does that seem to indicate? Should I try hooking up a 10uf 10amp resistor to the +5 to see if there is a drop on the powersupply (using it instead of the motherboard as a draw? I have a spare that's why I ask)
      > > >
      > > > Thanks for all the help,
      > > > Corey
      > > >
      > > > --- In altaircomputerclub@yahoogroups.com, "deramp5113" wrote:
      > > > >
      > > > > Unfortunately, a 112.6mv drop can occur for two reasons: The main board is drawing 1 amp (which would indicate the main board is probably not the cause of the voltage problem), or the regulator is in foldback protection (indicating the main board probably is the cause of the voltage problem). Most likely it's the latter, but let's prove it.
      > > > >
      > > >
      > > > > With the main board connected, measure the voltage at the output of the rectifier bridge (one side of R5, or the collector of either Q1 or Q2, or on pin X2 on the regulator board connector, or on the plus terminal of C8, the big 18,000uf filter cap). Measure this bridge voltage and double check that the final output voltage is still around 3.7 volts like you measured previously.
      > > > >
      > > > > Mike
      > > > >
      > > > >
      > > > > --- In altaircomputerclub@yahoogroups.com, corey986 wrote:
      > > > > >
      > > > > > Well I checked for hot chips... nothing stands out...
      > > > > >
      > > > > > I checked R1 on the regulator board for voltage drop with my digital meter...
      > > > > >
      > > > > > With board connected 112.6mv
      > > > > >
      > > > > > With board not connected 2.3mv
      > > > > >
      > > > > > Does that tell you anything? Does the powersupply sound good?
      > > > > >
      > > > > > Thanks,
      > > > > > Corey
      > > > > >
      > > > > > --- In altaircomputerclub@yahoogroups.com, "deramp5113" wrote:
      > > > > > >
      > > > > > > Corey,
      > > > > > >
      > > > > > > Before removing all the chips, it may be worth making a quick determination if the problem seems to be in the power supply or if it is simply the main board drawing to much current. With everything connected, measure the voltage drop across the big current sense resistor on the regulator board (R1). What do you measure?
      > > > > > >
      > > > > > > Mike
      > > > > > >
      > > > > > >
      > > > > > > --- In altaircomputerclub@yahoogroups.com, corey986 wrote:
      > > > > > > >
      > > > > > > >
      > > > > > > >
      > > > > > > >
      > > > > > > > OK, I went over the document you uploaded and made sure all the Rev 'd' changes were done.
      > > > > > > >
      > > > > > > > I'm actually glad I did remove whatever the person did before and redid the ground modification for the bus drivers and also the DMA interrupt unscramble. I redid them cleaner and neater and used the recommended size wires. All the mods previously, except an upgrade to the cassette switch relays to bigger ones, were done with pretty thick wire contrary to the recommendations for signal wires to be between #30 and #26.
      > > > > > > >
      > > > > > > > There were a few modifications not done, like the clock timing. They are done now.
      > > > > > > >
      > > > > > > > Now when I power on and don't get any video at all. Before I got an out of sync line which could have been related to the messed up clock that the mod was supposed to fix.
      > > > > > > >
      > > > > > > > So I'm actually looking at this as progress.
      > > > > > > >
      > > > > > > > I think the reason it's not working is that the voltage is 3.75 volts not 5v when the supply is plugged in, but it's fine when I test the supply on its own.
      > > > > > > >
      > > > > > > > So next up, remove all the chips into a giant piece of antistatic foam and check the unstuffed board for problems. I have a feeling its old tantalum caps. Just a feeling, but Processor Tech used them on everything and maybe I have to replace them all. I always do that now on Processor Tech cards since I had one with a bad cap cause me a ton a problems. There are just a lot on a Sol 20 compared to a 3P+S. Hopefully that's it and its not a TTL issue as that will take time to sort out with a scope.
      > > > > > > >
      > > > > > > > I'll keep everyone posted and if anyone has more ideas for me to try I am completely open...
      > > > > > > >
      > > > > > > > Cheers,
      > > > > > > > Corey
      > > > > > > >
      > > > > > > > --- In altaircomputerclub@yahoogroups.com, "mfeberhard" wrote:
      > > > > > > > >
      > > > > > > > > Hi Corey,
      > > > > > > > >
      > > > > > > > > I've restored a couple Sol-20s - I'm even running PTDOS on a Helios II drive :-) (Does anyone else have PTDOS running?)
      > > > > > > > >
      > > > > > > > > I have found that the checkout procedure in the Sol-20 assembly manual is an excellent step-by-step guide for bringing up a Sol-20. It gives you waveforms, theory of the circuit designs, etc. I would strongly recommend starting there - walk through the bring-up procedure as though you had just assembled the Sol-20 from a kit.
      > > > > > > > >
      > > > > > > > > Processor Technology published a fairly long series of ECNs for the Sol-20 - and it is possible that some of the cuts and jumps you found were actually errata from Processor Technology. I just created a folder in the "Files" section of this website, called 'processor Technology.' In it is a scan of the ECNs issued by PT that bring a Sol-20 up to Rev E. Take a look...
      > > > > > > > >
      > > > > > > > > -Martin
      > > > > > > > >
      > > > > > > > > --- In altaircomputerclub@yahoogroups.com, corey986 wrote:
      > > > > > > > > >
      > > > > > > > > > So I took the whole machine apart. Removed the motherboard and the power supply.
      > > > > > > > > >
      > > > > > > > > > I removed all the non standard hacks (i.e. left the stuff that the manual said should be there for the Rev D because they got a couple of the S100 lines mixed up).
      > > > > > > > > >
      > > > > > > > > > I repaired all the cut traces (except for the Rev D stuff in the manual) and also replaced the missing R14 1500 ohm resistor and removed an attached 1500 ohm resistor that was put in parallel to R134, 330 ohm (part of the clock timer).
      > > > > > > > > >
      > > > > > > > > > I did not replace the missing R23 yet, according to the docs it's for the current loop interface which I'm not using right now.
      > > > > > > > > >
      > > > > > > > > > I did remove the "Graphic Plus" daughterboard and put the MM6574 and 74166 back in.
      > > > > > > > > >
      > > > > > > > > > Before I started all this I got only two bars across the screen when I hook up the video and the power supply (regulated part) is 3.7 volts when hooked up and 4.8 to 4.9 when not hooked up. the -12 and 12 are dead on...
      > > > > > > > > >
      > > > > > > > > > Now after the cleanup, I get a fast wavy vertical slanted line and voltage is still the same when hooked up, 3.7 volts.
      > > > > > > > > >
      > > > > > > > > > Where should I start?
      > > > > > > > > >
      > > > > > > > > > I was thinking about removing all the chips from the board and putting them in antistatic, then checking the voltage. If the voltage is still bad, then change all the tantalum caps on the motherboard.
      > > > > > > > > >
      > > > > > > > > > Is there any way to test the power supply other than putting a meter on it. I think I have a couple of 10 watt ceramic 10 ohm resistors that I bought to convert an ATX powersupply to a bench supply so is it a good idea to hook them up to a linear supply and test the voltage on the 5v.
      > > > > > > > > >
      > > > > > > > > > I figure after I get the voltage working, the best approach is to follow the manual and bring it up like I was building it. Am I wrong on this, is there a better way?
      > > > > > > > > >
      > > > > > > > > > Any advise will help.
      > > > > > > > > >
      > > > > > > > > > Also if I don't have a ram card in (since the backplane is removed), the ram on the motherboard should be enough to test, correct?
      > > > > > > > > >
      > > > > > > > > > Also is there any way to test the Personality Module outside the system?
      > > > > > > > > >
      > > > > > > > > > Thanks,
      > > > > > > > > > Corey
      > > > > > > > > >
      > > > > > > > >
      > > > > > > >
      > > > > > >
      > > > > >
      > > > >
      > > >
      > >
      >
    • deramp5113
      Nothing more satisfying than making some progress! Mike
      Message 32 of 32 , Feb 24, 2013
      • 0 Attachment
        Nothing more satisfying than making some progress!

        Mike

        --- In altaircomputerclub@yahoogroups.com, corey986 <no_reply@...> wrote:
        >
        > So I got a replacement 18000uf cap for about $8 plus shipping. Since there was a $15 minimum I also got a couple of exact replacement Apple II keyboard lamps I found while trying to get to $15 bucks.
        >
        > Anyway. The supply now makes a little over 5V and I plugged my personality module in and hooked my board up and I have perfect video and got a solos prompt.
        >
        > Can't do anymore testing till I rebuild my keyboard in a week or so, I have a couple of other small favor restoration/build projects to do first but this is awesome because now I'm up to the planned part of the Sol restoration, the keyboard and cosmetic cleanup for the case and motherboard.
        >
        > Thanks everyone who helped!!!
        >
        > Cheers,
        > Corey
        >
      Your message has been successfully submitted and would be delivered to recipients shortly.