Well, no, look at the schematic. The notch on the (schematic) IC is pointing up, and the two lines coming off are on the right side, where pin 40 is clearly labeled at the top right. So, counting down, the two pins are 30/31, and Tony was measuring two pins on the top of the IC with the notch to the left. Maybe Tony was off-by-1, and measuring 31 & 32, or 29 & 30. I think the hamster was alive, but the hamster-wheel bearings are seized! 🤣😆😂 Though he was saying 10 & 11, so that hamster is asleep at the wheel. As for the pulses, maybe it’s just a switching transient as the CPU executes a specific instruction; perhaps the decoupling cap on the CPU is weak, or it needs another in parallel.
So about 10 years ago, I purchased a pallet of surplus test equipment. This was from a repair facility that shut down after the owner died. In the lot were "5" Sencore LC-102. In the end I spent WEEKS trying to fix them, and in the end I used 2 of them for parts to get the other 3 to work. I swore I would never try and repair these again. One came up on eBay about 8 years ago, for $150.00 Not Working. As you know these can sell for well over $1000 so I figured lets get it and try and fix it... Lucky for me after a few parts swap, Microprocessor, the unit came back to life. So after 6 units, 2 had bad processors, that might tell you something. During Covid, I decided after retiring to clean house, so I sold off the parts units. I have been following your videos and your on the right track, but the issue with the LC-102 is they definitely have reliability issues and in my case it was not a single failure of a single part, but rather multiple issues, that is what made it so challenging... BTW, I found a Logic Probe very handy to use.. As well as a Pulse Injector probe. I am sure you have one in your tool chest of equipment. Good Luck, If I had any more parts I could send them to you, but not anymore... Robert
For a case like this, it's useful to see what the CPU does with those pins when the load is removed. If you are not comfortable with bending out the pins on the CPU itself, you can place a 40-pin stamped IC socket on the CPU chip, then bend those two pins out before plugging that socket into the one on the pcb. That way there is no risk of snapping off a pin of the CPU. It looks to me like pin 10 can drive high, but not low. So perhaps the internal N-channel pulldown transistor is toast? Pin 11 did seem to have some activity on it. You need to set your scope to Normal or Single mode to check for short pulses. If the scope triggers, there is a pulse, then you zoom in to examine it. Lucky for you the code is in an EPROM instead of inside the CPU, as it sometimes is. So you can source an 80C39 or 49 to replace it if nec.
That's what I am thinking. I was hoping someone could test theirs to see if this is the case. As a last resort, I will try the socket and the bent pins.
Port pins on MCU's can be configured as input or output. If the pin is set as input, it will just float to whatever level the external circuit is pulling it to. In this case, it seems logical to assume that Pin 10 is set as an output, in which case it should be either high or low (CMOS levels, so close to gnd and 5V) We don't see any low levels so perhaps the internal pulldown transistor is hosed. If so, and you bend out that pin, it may just sit high, as sometimes it will be driven high, and other times its capacitance may hold it high, although the scope will tend to pull it to gnd, especially if you use x1 probe. You can also simply connect a 2K resistor from that pin to ground as a pulldown. In this circuit, that should give you 0.5V when it's not being pulled up, due to the 10K pullup at TR21. Even a 1.5K should be OK for the MCU. Not sure how much current it can source. Anyway, this is just as test to learn more about what's happening.
I suspect you may have discovered the issue by the time you see my comment, but anyway. Reading between the lines and other comments I think you mentioned that the signals look sort of correct, compared with waveform examples you have been sent, if you disconnect pins 30 and 31 from the micro. I would first confirm this by using an old scope with single shot triggering (and ideally storage) which behaves properly with fast transitions, pulses. If the signals are ok measure resistance, diode check between pins 30 and 31 on the socket and ground and 5V and ensure you can see expected diode junctions, resistor values etc. Add a couple of external 10k pullups to the micro pins and recheck the signals, this will mostly confirm if anything is wrong with those pins on the micro I'm sure you have checked and or replaced TR21, lift R92, reconnect pins 30 and 31 and recheck, especially ensuring P13, pin 30 toggles properly to 0V depending on front panel switch activation. Good luck.
Also consider a solder bridge as the problem, not the CPU, closely inspect the board at the parts themselves, traces between the two points, and CPU pins in case of a problem there.
That's what a faulty I/O pin looks like. I think it would be a really good idea to source a CPU and test, as someone else mentioned, an 8049 should work just fine and they're really common. They're pretty much the same chip but the 8049 is specified with internal ROM which can be 'sitched on or off' by logic levels on pins (it can be quite interesting to read out the 'no ROM' versions, they're often failed or cancelled factory programmed parts, I've got some 8032 chips with Intel MCS52 BASIC 1.0 in for instance)
Hi, I enjoyed very much watching this series as I own one of these myself. I have had a plan for many years to recap it, and now I'm surely going to speed up that. I think maybe you do the zero leads calibration wrong. I always hold the switch in the open or in the closed position for the duration of the test, and not just flip it and then release it. Thanks a lot and all the best. 😄
Have you checked on the 6.2V side of R101 to see if the voltage is being lost before or after that resistor? if voltage is there then it could be C22 shorting the input to the op-amp.
6.2 volts is solid. TR40 and TR40 both have a high signal at the gates, which is causing them to turn on. I think the uC is supposed to set these to a low signal, which would provide the proper 1 volt signal on pin 5 of the LM319. This is what I'm not sure of, though. Hopefully, someone else can verify on their unit pins 30 and 31 (I misspoke about pins 10 & 11) of the uC are low instead of high.
Hi Tony, In my experience, most of the I/O pins on these MCUs are protected with internal diodes connected to power and ground. You might want to try removing the MCU and measuring between the suspected pins and pwr/gnd pins using the diode scale. At the very least, you can check to see if the pins are shorted to power or ground compared to the other I/O pins.
Toni - The old adage holds "What is the last thing you did before it stopped working?" You mentioned how fragile this board is. Is it possible you may have damaged a VIA or other trace under the LM319 when you removed it?
I think an 80C49 will work if you can’t find 80C39. The lower 8 bits of the address bus and the 8 bit data bus are multiplexed. That’s what the ALE (address latch enable) and PSEN (program store enable)pins do. That’s what 0:00 that 8 bit 74LS373 transparent latch is for. It goes between the EPROM and uC.In a previous video, the ALE signal looked good, I think it’s 1/6 the clock frequency.
Tony, did you remove the Cornell Dubilier Relay and clean it? I cleaned the one on my unit and used card stock and Deoxit 5 (red can) and it helped with the ranges issue. Give it a shot.
Tony, when looking at CPU lines turn off auto-trigger and set you trigger level to around 2 volts. That way you will see when the line goes low or high. In your video I believe you are just seeing switching transients (those little spikes). If your scope has a preset TTL trigger level you can use that. Regards, David
In some of the clips, I had the trigger set to TTL. When my scope is set to TTL trigger, it will disable the trigger level setting, so if you have a wonky waveform, it won't trigger properly, hence the reason I sometimes went to normal or auto trigger. Sample rate and time base can also affect the display. I love the new digital scopes, but I still like the simplicity of my Tek 2467B ;)
@@xraytonyb I agree with you on the "modern" scopes, I keep a Tektronix 2445B and an HP 1980B in the workshop. My most modern scope is a Tektronix TDS544A. A couple of things that can help when looking at digital signals (besides TTL triggering) are (1) For expected active low signals trigger on the negative slope and for active high trigger on the positive slope. (2) Set the display trigger point to left instead of center - gives a bit more room for observing pulse trains and (3) Use single sweep mode to capture infrequent events. Regards, David
Hi Tony ... I think your trouble, if the MCU ports P13, P14 are OK, it's related to the EPROM causing a bad program running. Did you find the correct BIN file for your device to try a new EPROM ?
I thought about that. The bin file I am using was copied from the old prom. The one I downloaded from online was a newer version. My unit had version 15 and the downloaded one is 17. I might try it, but I don't know what changes were made. It is certainly a possibility. Thanks for the comment!
Tony, sent you an email with those traces. Both look nothing like what is being displayed on your pins. 59hz signal with peak 8V and min -11V on both pins.
There is likely firmware in the 80c39, that's why your replacement doesn't work. I had one of these years ago, CPU died replacing it with an identical non-sencore part did not work. Sencore sent me one NC and it was fixed. I hope they still support it.
It was really hard to tell if that was an actual logic pulse, or just noise. Another viewer sent images of the signals on pins 30 and 31 and they look nothing like this.
Link to my probing with a scope. th-cam.com/video/Wj8pAyBFDG0/w-d-xo.html No way close to the quality of Tony's work. This was done during a thunder storm and I think the first unit was hit with a surge. This unit is the one I keep on the bench. The first unit was the back up unit. Which now with not perform a Short test. UPDATE, The short test problem was a dirty contact on L9. You can remove the relay cover and clean the contacts. This fixed my problem of the Short test presenting a error 4
Thank you so much for this! I have just completed part 5 and will be posting it in the next day or two. If I disconnect pins 30 & 31 (by folding them out of the socket), it will intermittently give the same waveforms as your video shows, but not always. However, if I re-connect the pins, it will never pull the signal low, nor will I get more than that single pulse on pin 30. I think this is telling me that I have a faulty MCU chip. Thanks again!
Though on the schematic, your pins are on the upper right of your cpu, actually on the cpu ic, with the notch at the top, pin 1 is at the upperleft, pin 2 would be the next one down from pin 1, etc.... Therefore, pins 10 and 11 would physically be on the left side of the ic. You might look for 0 ohms from your ic to mosfet gate to verify you are truly testing pins 10 and 11(power off)?
I have the chance to buy an old Sencore LC103 but I don't want to spend so much money on a device that I cannot calibrate by myself. In case you have a copy of the Sensore LC103 calibration software, would you mind sending me a copy? I would be very grateful. Thanks a lot in advance, Mike
Yup it has 2K of ROM in the CPU. And P10-17 have internal 50K pull UP resistors on them. What if you bent the 2 CPU pins out of the socket and scoped them out? (Kind of a last ditch test)
Ill join in on this . Did you check the negative canuter valve to see if the phaso quadralinear valve is in amorphic alignment with the asynchronous dingle hooter
At 8:54 you’re saying pin 10 and 11, but you’re on the wrong side of the chip!
Good catch!
OOPS! Good catch. Try 30 and 31. The wheel was turning, but the hamster was dead :)
Well, no, look at the schematic. The notch on the (schematic) IC is pointing up, and the two lines coming off are on the right side, where pin 40 is clearly labeled at the top right. So, counting down, the two pins are 30/31, and Tony was measuring two pins on the top of the IC with the notch to the left. Maybe Tony was off-by-1, and measuring 31 & 32, or 29 & 30. I think the hamster was alive, but the hamster-wheel bearings are seized! 🤣😆😂 Though he was saying 10 & 11, so that hamster is asleep at the wheel. As for the pulses, maybe it’s just a switching transient as the CPU executes a specific instruction; perhaps the decoupling cap on the CPU is weak, or it needs another in parallel.
Yeap
So about 10 years ago, I purchased a pallet of surplus test equipment. This was from a repair facility that shut down after the owner died. In the lot were "5" Sencore LC-102. In the end I spent WEEKS trying to fix them, and in the end I used 2 of them for parts to get the other 3 to work. I swore I would never try and repair these again. One came up on eBay about 8 years ago, for $150.00 Not Working.
As you know these can sell for well over $1000 so I figured lets get it and try and fix it... Lucky for me after a few parts swap, Microprocessor, the unit came back to life. So after 6 units, 2 had bad processors, that might tell you something.
During Covid, I decided after retiring to clean house, so I sold off the parts units. I have been following your videos and your on the right track, but the issue with the LC-102 is they definitely have reliability issues and in my case it was not a single failure of a single part, but rather multiple issues, that is what made it so challenging...
BTW, I found a Logic Probe very handy to use.. As well as a Pulse Injector probe. I am sure you have one in your tool chest of equipment.
Good Luck, If I had any more parts I could send them to you, but not anymore...
Robert
This was really helpful. Thanks!
Hi Tony. The 6V2 line is generated by a clamping zener diode from the 12V line. The circuit is under IC between R49 and R50 on the main schematic.
Very interesting. I have no answer, but I'm confident that you will get your answer. Nice video. Cheers!
For a case like this, it's useful to see what the CPU does with those pins when the load is removed. If you are not comfortable with bending out the pins on the CPU itself, you can place a 40-pin stamped IC socket on the CPU chip, then bend those two pins out before plugging that socket into the one on the pcb. That way there is no risk of snapping off a pin of the CPU. It looks to me like pin 10 can drive high, but not low. So perhaps the internal N-channel pulldown transistor is toast? Pin 11 did seem to have some activity on it. You need to set your scope to Normal or Single mode to check for short pulses. If the scope triggers, there is a pulse, then you zoom in to examine it. Lucky for you the code is in an EPROM instead of inside the CPU, as it sometimes is. So you can source an 80C39 or 49 to replace it if nec.
That's what I am thinking. I was hoping someone could test theirs to see if this is the case. As a last resort, I will try the socket and the bent pins.
Port pins on MCU's can be configured as input or output. If the pin is set as input, it will just float to whatever level the external circuit is pulling it to. In this case, it seems logical to assume that Pin 10 is set as an output, in which case it should be either high or low (CMOS levels, so close to gnd and 5V) We don't see any low levels so perhaps the internal pulldown transistor is hosed. If so, and you bend out that pin, it may just sit high, as sometimes it will be driven high, and other times its capacitance may hold it high, although the scope will tend to pull it to gnd, especially if you use x1 probe. You can also simply connect a 2K resistor from that pin to ground as a pulldown. In this circuit, that should give you 0.5V when it's not being pulled up, due to the 10K pullup at TR21. Even a 1.5K should be OK for the MCU. Not sure how much current it can source. Anyway, this is just as test to learn more about what's happening.
CR5- 6.2 Zener under IC14 (A/D)
Thank you!!!!!!!!!
I suspect you may have discovered the issue by the time you see my comment, but anyway.
Reading between the lines and other comments I think you mentioned that the signals look sort of correct, compared with waveform examples you have been sent, if you disconnect pins 30 and 31 from the micro. I would first confirm this by using an old scope with single shot triggering (and ideally storage) which behaves properly with fast transitions, pulses.
If the signals are ok measure resistance, diode check between pins 30 and 31 on the socket and ground and 5V and ensure you can see expected diode junctions, resistor values etc.
Add a couple of external 10k pullups to the micro pins and recheck the signals, this will mostly confirm if anything is wrong with those pins on the micro
I'm sure you have checked and or replaced TR21, lift R92, reconnect pins 30 and 31 and recheck, especially ensuring P13, pin 30 toggles properly to 0V depending on front panel switch activation. Good luck.
That scope noise is probably from the parallel circuit that shares that connection to the CPU.
Did someone put in some P-channel MOSFETs in place of the N-channel?
Also consider a solder bridge as the problem, not the CPU, closely inspect the board at the parts themselves, traces between the two points, and CPU pins in case of a problem there.
That's what a faulty I/O pin looks like.
I think it would be a really good idea to source a CPU and test, as someone else mentioned, an 8049 should work just fine and they're really common.
They're pretty much the same chip but the 8049 is specified with internal ROM which can be 'sitched on or off' by logic levels on pins
(it can be quite interesting to read out the 'no ROM' versions, they're often failed or cancelled factory programmed parts, I've got some 8032 chips with Intel MCS52 BASIC 1.0 in for instance)
Hi, I enjoyed very much watching this series as I own one of these myself.
I have had a plan for many years to recap it, and now I'm surely going to speed up that.
I think maybe you do the zero leads calibration wrong. I always hold the switch in the open or in the closed position for the duration of the test, and not just flip it and then release it.
Thanks a lot and all the best.
😄
The IC9 is an EPROM for the MPU (80C39) firmware.
Have you checked on the 6.2V side of R101 to see if the voltage is being lost before or after that resistor? if voltage is there then it could be C22 shorting the input to the op-amp.
6.2 volts is solid. TR40 and TR40 both have a high signal at the gates, which is causing them to turn on. I think the uC is supposed to set these to a low signal, which would provide the proper 1 volt signal on pin 5 of the LM319. This is what I'm not sure of, though. Hopefully, someone else can verify on their unit pins 30 and 31 (I misspoke about pins 10 & 11) of the uC are low instead of high.
Hi Tony, In my experience, most of the I/O pins on these MCUs are protected with internal diodes connected to power and ground. You might want to try removing the MCU and measuring between the suspected pins and pwr/gnd pins using the diode scale. At the very least, you can check to see if the pins are shorted to power or ground compared to the other I/O pins.
Toni - The old adage holds "What is the last thing you did before it stopped working?" You mentioned how fragile this board is. Is it possible you may have damaged a VIA or other trace under the LM319 when you removed it?
Be sure to check out the opening statement I make in part 5, when I post it ;)
I think an 80C49 will work if you can’t find 80C39. The lower 8 bits of the address bus and the 8 bit data bus are multiplexed. That’s what the ALE (address latch enable) and PSEN (program store enable)pins do. That’s what 0:00 that 8 bit 74LS373 transparent latch is for. It goes between the EPROM and uC.In a previous video, the ALE signal looked good, I think it’s 1/6 the clock frequency.
That's what I thought as well. I might have an 80c49 somewhere in the old parts graveyard.
@@xraytonyb Being CMOS, you would think those port pins would be at 5v, not 3.5V?
80c49 might work because PIN7 (EA) is also set to Vcc (high) and fetch only external memory.
@@e42_channel True, we used to do that with 8048’s because they were only 99 cents.
@@mmaranta785 Thats right, output voltage for BUS Signals are low(max 0.45V) and high (min. Vcc-0.8V)
Tony, did you remove the Cornell Dubilier Relay and clean it? I cleaned the one on my unit and used card stock and Deoxit 5 (red can) and it helped with the ranges issue. Give it a shot.
Tony, when looking at CPU lines turn off auto-trigger and set you trigger level to around 2 volts. That way you will see when the line goes low or high. In your video I believe you are just seeing switching transients (those little spikes). If your scope has a preset TTL trigger level you can use that. Regards, David
In some of the clips, I had the trigger set to TTL. When my scope is set to TTL trigger, it will disable the trigger level setting, so if you have a wonky waveform, it won't trigger properly, hence the reason I sometimes went to normal or auto trigger. Sample rate and time base can also affect the display. I love the new digital scopes, but I still like the simplicity of my Tek 2467B ;)
Since both pin 30 & 31 were already in a High, or 1 state, I set my scope to trigger on the downward slope and it seemed to lock in very well.
@@xraytonyb I agree with you on the "modern" scopes, I keep a Tektronix 2445B and an HP 1980B in the workshop. My most modern scope is a Tektronix TDS544A. A couple of things that can help when looking at digital signals (besides TTL triggering) are (1) For expected active low signals trigger on the negative slope and for active high trigger on the positive slope. (2) Set the display trigger point to left instead of center - gives a bit more room for observing pulse trains and (3) Use single sweep mode to capture infrequent events. Regards, David
I would check for short combination between pins 29 to 30 to 31 to 32
Hi Tony ... I think your trouble, if the MCU ports P13, P14 are OK, it's related to the EPROM causing a bad program running. Did you find the correct BIN file for your device to try a new EPROM ?
I thought about that. The bin file I am using was copied from the old prom. The one I downloaded from online was a newer version. My unit had version 15 and the downloaded one is 17. I might try it, but I don't know what changes were made. It is certainly a possibility. Thanks for the comment!
@@xraytonyb You're welcome ! Hope to "see" you soon !
Yo seem to be probing the incorrect pi n 10 on the MCU. Reference notch is on my left.
Tony, sent you an email with those traces. Both look nothing like what is being displayed on your pins. 59hz signal with peak 8V and min -11V on both pins.
There is likely firmware in the 80c39, that's why your replacement doesn't work. I had one of these years ago, CPU died replacing it with an identical non-sencore part did not work. Sencore sent me one NC and it was fixed. I hope they still support it.
From what I understand, the 80C39 does not have internal NV memory, but the 80C49 does. Anything's possible, though.
There is no firmware inside the 8039. Pin 7 is EA which should be a logic high to use external program memory-in the EPROM.
Hi Tony, have you tried reinserting the original EPROM. maybe there was a difference between them.
Rich
I have several proms with two different firmware versions. They all seem to do the same thing. Thanks for the comment!
When you said 'hit capacitor value' there was a low going pulse on the constant high 4.75v on TR40, at about 5:22
It was really hard to tell if that was an actual logic pulse, or just noise. Another viewer sent images of the signals on pins 30 and 31 and they look nothing like this.
Link to my probing with a scope. th-cam.com/video/Wj8pAyBFDG0/w-d-xo.html No way close to the quality of Tony's work. This was done during a thunder storm and I think the first unit was hit with a surge. This unit is the one I keep on the bench. The first unit was the back up unit. Which now with not perform a Short test. UPDATE, The short test problem was a dirty contact on L9. You can remove the relay cover and clean the contacts. This fixed my problem of the Short test presenting a error 4
Thank you so much for this! I have just completed part 5 and will be posting it in the next day or two. If I disconnect pins 30 & 31 (by folding them out of the socket), it will intermittently give the same waveforms as your video shows, but not always. However, if I re-connect the pins, it will never pull the signal low, nor will I get more than that single pulse on pin 30. I think this is telling me that I have a faulty MCU chip. Thanks again!
Pull & test the mosfet’s !
Look at the CPU drive pins also with no transistors fitted .
Though on the schematic, your pins are on the upper right of your cpu, actually on the cpu ic, with the notch at the top, pin 1 is at the upperleft, pin 2 would be the next one down from pin 1, etc.... Therefore, pins 10 and 11 would physically be on the left side of the ic. You might look for 0 ohms from your ic to mosfet gate to verify you are truly testing pins 10 and 11(power off)?
I have the chance to buy an old Sencore LC103 but I don't want to spend so much money on a device that I cannot calibrate by myself. In case you have a copy of the Sensore LC103 calibration software, would you mind sending me a copy? I would be very grateful.
Thanks a lot in advance,
Mike
Yup it has 2K of ROM in the CPU. And P10-17 have internal 50K pull UP resistors on them. What if you bent the 2 CPU pins out of the socket and scoped them out? (Kind of a last ditch test)
I don't think the 80C39 has the 2k ROM. Only the 80C49 has ROM.
I have 10+ ZyMOS P80C39 lying around. Let me know if you have trouble finding a original MCU.
You should be able to get the data sheets for the microprocessor check its on and off status high/low
Hi,are you interested in trying a thermal camera to locate electrical faults efficiently？They can detect temperature of components.
I tried that earlier. Nothing seems to be getting warm.
@@xraytonyb It depends on the temperature range ,resolution and heat sensitivity of the thermal camera.
@@xraytonyb Our thermal camera's resolution: 256x192, temperature range: -20°C to 550°C (-4°F to 1022°F) and heat sensitivity: 50mk
Ill join in on this . Did you check the negative canuter valve to see if the phaso quadralinear valve is in amorphic alignment with the asynchronous dingle hooter
Stupid question - I watched you probe "pin 10" on the top side of the mcu? I think you mean like pin 30 maybe? 10 from the right top size?
Yes, another viewer already caught this! Sorry!
How did you manage to program the new microprocessor?
I think the Toshiba micro is generic as much of the operational firmware is on a separate chip with paper sticker.
The only thing I would say is that I don't have much faith in Sencores' schematics. Experience talking. Good luck.
I certainly have to agree with you there!!! I would also add that their PC board layout is equally the rat's nest. ;)
I think they farmed it out. Looks japanese.