Dropcheck Posted September 6 Author Share Posted September 6 3 hours ago, AtariGeezer said: Cool, okay.. Just wanted to make sure you didn't accidentally get +5 and +12 backwards. That would have been a real mess... I looked at Brads site last night and don't see the PAL-A or PAL-B listed anymore. I know I have 4 more PAL-C's (made by @bob1200xl 12 years ago), but will have to locate my 1450XL spare parts box in storage to see if I bought spares of the 2 other PAL Chips. I usually try to buy at least two of most parts for the Atari builds. I also have a spare speech chip in storage too that I was hoping to use in a 2nd build of the 1450xl if any more boards surfaced... Hopefully you do. Jurgen was operating from the PAL equations and the schematic I gave him at the time. So he was doing all he could. I don't know of anyone else who was/is able to convert from PAL to GAL. Surely not that hard, but you have to have not only the knowledge, but the right source info too. Definitely need to get a valid conversion as soon as possible. I have a speech chip clone that supposedly is a drop-in replacement, I just didn't want to install it until I got a booting board first. It was expensive to buy and I didn't want to let the smoke out in the power on test. Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted September 6 Share Posted September 6 (edited) (Deleted) Edited September 6 by kheller2 Not enough coffee. Quote Link to comment Share on other sites More sharing options...
Dropcheck Posted September 6 Author Share Posted September 6 I am going thru each chip one by one to verify the traces for the upteenth time. Currently I am on U8 and R134. On the Atari Schematic I believe R134 is tied to pins 3 & 4 of U8 and the indication is that the other end is tied to GND. However, on the bare board I have I can not verify that. There appears to be no traces going any where from that end of the resistor. That leads me to believe that with a 4 layer board that it might go to GND or a +5V internal layer. But it is not ohming to GND or +5V, which is confusing me. Experience says that it should go to +5V, but I'm hardly the expert. If anyone has a populated board can you ohm out that end and tell me if you are getting either indication? Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted September 6 Share Posted September 6 The silkscreen is covered on a populated board for R and C so I'm not sure if what I'm at is R134. But, pin 3 and 4 are tied together and connected to the top resistor, left side. The right side of that top resister... well.. it isn't going to Vss or Vcc. Hmmm.. It is 2.4M Ohms from the top R right side to Vss or Vcc! The schematics state they go to GND on both the 1400 and 1450 boards. We would need someone with a 1400 board to see where it actually might go, or should go. Have you tired it with another FREDDIE and with the and U35 pulled? I am curious if the PALs are correct. Quote Link to comment Share on other sites More sharing options...
Dropcheck Posted September 7 Author Share Posted September 7 8 hours ago, kheller2 said: The silkscreen is covered on a populated board for R and C so I'm not sure if what I'm at is R134. But, pin 3 and 4 are tied together and connected to the top resistor, left side. The right side of that top resister... well.. it isn't going to Vss or Vcc. Hmmm.. It is 2.4M Ohms from the top R right side to Vss or Vcc! The schematics state they go to GND on both the 1400 and 1450 boards. We would need someone with a 1400 board to see where it actually might go, or should go. Have you tired it with another FREDDIE and with the and U35 pulled? I am curious if the PALs are correct. I unfortunately don't have another loose Freddie to use without robbing from one of my 130XEs. This replacement Freddie is supposed to be pin compatible according to Lotharak's site. R134 should read around 4.7K isolated. I did find another error on my part concerning the ram. R100 was tied to GND in my schematic. Not good. It's the ram refresh signal and I have verified on the bare Atari board it is actually tied to +5V. Easy enough to test by simply lifting the resistor leg going to GND and tying it to +5V instead. That might prevent the Atari from booting. I also found that Q8 is backwards on my schematic. Another rather easy fix, by simply putting a replacement Q8 in backwards. It should only affect the -5V line though, so shouldn't prevent booting or display. I continue checking my schematic against the Atari bare board. No way I could have gotten this far without that loan. Thank you again. 😃 1 Quote Link to comment Share on other sites More sharing options...
AtariGeezer Posted September 7 Share Posted September 7 (edited) 15 hours ago, Dropcheck said: I am going thru each chip one by one to verify the traces for the upteenth time. Currently I am on U8 and R134. On the Atari Schematic I believe R134 is tied to pins 3 & 4 of U8 and the indication is that the other end is tied to GND. However, on the bare board I have I can not verify that. There appears to be no traces going any where from that end of the resistor. That leads me to believe that with a 4 layer board that it might go to GND or a +5V internal layer. But it is not ohming to GND or +5V, which is confusing me. Experience says that it should go to +5V, but I'm hardly the expert. If anyone has a populated board can you ohm out that end and tell me if you are getting either indication? Looking at the schematics for the 1400xl and the 1450xl, R134 is tied to +5v, U8 controls/enables the speech chip... Edited September 7 by AtariGeezer Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted September 7 Share Posted September 7 4 hours ago, AtariGeezer said: Looking at the schematics for the 1400xl and the 1450xl, R134 is tied to +5v, U8 controls/enables the speech chip... That's debatable. The official bareboard doesn't actually show connectivity when Ohmed out. And there is a difference between a solid vs empty triangle. The latter empty being ground, the solid marked +5. Then again some people will argue it depends which way the triangle faces. Compare this to the schematics below where both cases are observed. Quote Link to comment Share on other sites More sharing options...
AtariGeezer Posted September 7 Share Posted September 7 34 minutes ago, kheller2 said: Then again some people will argue it depends which way the triangle faces. That's been my observation working in electronics companies. i.e. USAF, a military radio company and a laser company that builds the machines to burn silicon wafer discs. I tested and repaired lots of electronic modules, not to mention Ham and CB Radios too. Just saying that yes, I have seen many schematics where up was noted as positive voltage and down was ground or negative voltage. 1 Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted September 7 Share Posted September 7 24 minutes ago, AtariGeezer said: That's been my observation working in electronics companies. i.e. USAF, a military radio company and a laser company that builds the machines to burn silicon wafer discs. I tested and repaired lots of electronic modules, not to mention Ham and CB Radios too. Just saying that yes, I have seen many schematics where up was noted as positive voltage and down was ground or negative voltage. I agree. But here we have a case where it is not marked +5 and it’s not filled. And oddly enough not tied to either on a working board. One could search the schematic for another instance and try to verify it against the board, or one could figure out the logic that was trying to be created. Either way, bad schematic engineering! 1 Quote Link to comment Share on other sites More sharing options...
AtariGeezer Posted September 7 Share Posted September 7 I have my 1450xl out today and will check voltages in awhile. Quote Link to comment Share on other sites More sharing options...
Dropcheck Posted September 7 Author Share Posted September 7 3 hours ago, AtariGeezer said: I have my 1450xl out today and will check voltages in awhile. It would definitely help if you are getting a definite +5V or GND reading. This is kinda weird. 🥹 Quote Link to comment Share on other sites More sharing options...
Dropcheck Posted September 7 Author Share Posted September 7 Finishing up on the umpteenth time tracing the PBI schematic against the Atari bare board. Just have one more page to go, the dreaded modem/rf page to verify. This is where I have little confidence I got it right. But so far only the two small, easily fixable schematic errors on the test board have shown up, And the question on R134. Quote Link to comment Share on other sites More sharing options...
AtariGeezer Posted September 8 Share Posted September 8 (edited) Okay, I checked the voltage on U8 and R134 with and without U8 installed. U8 Not Installed: Pin 3-4 0 volts Pin 6 5 volts R134 0 volts on either side U8 Installed: Pin 3-4 1.44 volts Pin 6 0.18 volts R134 1.44 volts on either side I'm not showing any connectivity on R134 going to ground or +5 volts. So it looks like the voltage read on U8 pins 3-4 are floating open... Edited September 8 by AtariGeezer Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted September 8 Share Posted September 8 (edited) 22 minutes ago, AtariGeezer said: Okay, I checked the voltage on U8 and R134 with and without U8 installed. U8 Not Installed: Pin 3-4 0 volts Pin 6 5 volts R134 0 volts on either side U8 Installed: Pin 3-4 1.44 volts Pin 6 0.18 volts R134 1.44 volts on either side I'm not showing any connectivity on R134 going to ground or +5 volts. So it looks like the voltage read on U8 pins 3-4 are floating open... perhaps reading them with the chip in use and not in use etc. Make it talk, make it not talk. never hurts to fix something that was incorrect at manufacture either, like let's say the XE boards that had the Freddie decoupling cap not connected causing silliness for video as well as some upgrades. Edited September 8 by _The Doctor__ Quote Link to comment Share on other sites More sharing options...
AtariGeezer Posted September 8 Share Posted September 8 1 minute ago, _The Doctor__ said: perhaps reading them with the chip in use and not in use etc. Make it talk, make it not talk Yep, thought about that too. Speech is used when entering self test, but the keyboard is a little in the way, but will see... Quote Link to comment Share on other sites More sharing options...
AtariGeezer Posted September 8 Share Posted September 8 (edited) Okay, found the Telecommunicator cart and there isn't any change in voltage when speech is talking or not on pins 5 or 6, weird... Pin 5 4.40 volts Pin 6 0.18 volts Edit: just read that pin 7 (Strobe) on the speech chip is a digital signal and not a constant +5v or ground level... Edit 2: So Pin 6 is not an enable/disable control voltage for the speech chip... Edited September 8 by AtariGeezer 1 Quote Link to comment Share on other sites More sharing options...
Dropcheck Posted September 8 Author Share Posted September 8 Found an Atari schematic error on U35 the modem chip. Atari's schematic shows 3.579 Mhz going to pin 9. NOT. No trace. Instead the clock signal is going to pin 8. Again it seems to be a simple fix on my test board. Just cut the trace on pin 9 and connect the signal to pin 8. Still verifying the modem circuitry. Quote Link to comment Share on other sites More sharing options...
Dropcheck Posted September 8 Author Share Posted September 8 10 hours ago, AtariGeezer said: Okay, found the Telecommunicator cart and there isn't any change in voltage when speech is talking or not on pins 5 or 6, weird... Pin 5 4.40 volts Pin 6 0.18 volts Edit: just read that pin 7 (Strobe) on the speech chip is a digital signal and not a constant +5v or ground level... Edit 2: So Pin 6 is not an enable/disable control voltage for the speech chip... So with no signal per sue on two of the three inputs of that NAND Gate on U8 VOTRAXSTB is always pulled high by RP1pin9 and fed to U32pin7. If I read the schematics correctly. Why not just put feed VOTRAXSTB and the pullup resistor to U32pin7 directly? Quote Link to comment Share on other sites More sharing options...
Dropcheck Posted September 8 Author Share Posted September 8 Okay finished the modem/rf circuitry. I redid both transformers, because the pin numbering didn't make sense to me, so at least on this proto board I don't think I can rationally try testing. However I will make the other quick fixes tonight and try another power on test either tonight or in the morning. Normally you can boot the board w/o having the keyboard connected. I'm assuming this 1450XL should behave the same way. Quote Link to comment Share on other sites More sharing options...
+mytek Posted September 8 Share Posted September 8 19 minutes ago, Dropcheck said: Normally you can boot the board w/o having the keyboard connected. I'm assuming this 1450XL should behave the same way. Since the keyboard is nothing but a matrix of normally open switches, the computer has no way to know if a keyboard is present or not unless a key is pressed (the console keys although not in a matrix are also normally open and undetectable). So in other words your board should work without a keyboard connected same as any other Atari 8-bit computer Quote Link to comment Share on other sites More sharing options...
AtariGeezer Posted September 8 Share Posted September 8 9 hours ago, Dropcheck said: So with no signal per sue on two of the three inputs of that NAND Gate on U8 VOTRAXSTB is always pulled high by RP1pin9 and fed to U32pin7. If I read the schematics correctly. Why not just put feed VOTRAXSTB and the pullup resistor to U32pin7 directly? Going by the specs of the SC-01, after the needed phonemes are loaded, Pin 7 is pulsed high to start the speech output. But if Pin 7 is pulled high constantly without the NAND gate holding it's output in a low state, the speech chip won't see that strobe pulse. It appears that PAL-B's "NOT VOTRAXSTB" signal is inverted by U8... There is a sample schematic in the below PDF showing two Inverters in series to Pin 7 of the SC-01. Votrax_SC-01_Phoneme_Speech_Synthesizer_Data_Sheet_1980.pdf 1 Quote Link to comment Share on other sites More sharing options...
Dropcheck Posted September 9 Author Share Posted September 9 2nd power on test. Some life. The monitor goes from blue default to black with a NTSC logo display. So there is some signal getting through. I tried turning the color pot and it went from NTSC to PAL logo. The CPU gets warm, not much else. I'll start testing for clock signals from the main and secondary sources in the morning. I may have to source a real Freddie chip from a 130XE. I don't want to. Hate desoldering on the XE boards. 😔 The PAL(GAL) chips are still suspect. Not absolutely sure of the Handler chip. Seems I remember there were at least two different versions of that .bin file depending on where you got it from. Quote Link to comment Share on other sites More sharing options...
Dropcheck Posted September 9 Author Share Posted September 9 A question: I am using KM4164B-12 memory from Samsung. It supposedly has page mode. Is that compatible? I just went with the part #. I also have MCM6665AP15 from Motorola in a spare 1200XL motherboard that I could try if necessary. Has anyone actually used the Freddie chip replacement from Lotherick? Quote Link to comment Share on other sites More sharing options...
TZJB Posted September 9 Share Posted September 9 26 minutes ago, Dropcheck said: A question: I am using KM4164B-12 memory from Samsung. It supposedly has page mode. Is that compatible? I just went with the part #. I also have MCM6665AP15 from Motorola in a spare 1200XL motherboard that I could try if necessary. Has anyone actually used the Freddie chip replacement from Lotherick? Samsung KM4164 work fine with Atari computers but tend to be as reliable as Micron from my experience! I personally prefer 41256 chips from other manufacturers such as Hitachi, Mostek, Motorola & Toshiba which are compatible but also allow for easier memory upgrades. I don't know anything about the FREDDIE chip replacement, although I expect it to perform as expected. Quote Link to comment Share on other sites More sharing options...
+DjayBee Posted September 9 Share Posted September 9 30 minutes ago, TZJB said: I expect it to perform as expected. With recent developments this sounds quite ambiguous. 😎 Quote Link to comment Share on other sites More sharing options...
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