HP-8116A Power Fail  - Page 1
Forum section: electronics / testgear

author: hcapela
author_rank: Contributor
timestamp: January 05, 2022, 04:32:07 pm
content: Good year 2022 without the accursed bug.well there everyoneMy HP 8116A OPT01 2124G 003xx has been showing problems in power on for a long time, only after a few attempts and with time it worked, although the DTY duty cycle function was blocked.Now I tried to analyze why, I measured all voltages DC +24v…. at -15V just right, with just a little adjustment at -15V, as for ripple, less than 1mVAC measured with my trusty FLUKE 8060A .I decided to recap the electrolytic capacitors on board A1, A2 and A3 leaving the Conds. electrolytic of power supply from outside since the voltages and ripple had nothing to say.As it replaced the Cond. on board A1 (C254,253), on A2 (C4,10,11) and on A3 (C6,7,8) he was getting more apprehensive, as Cond. retired were good with a certain capacity or superior to the new ones and with an ESR almost equal to the new ones.And as I feared, the recap didn't solve anything, the HP 8116A only started up after several attempts minutes of Power ON and with the DTY blocked, and the most mysterious noise "cri cri" somewhere, which I still thought was the FAN but with it locked the noise was there, but when I press any HP key it disappeared!!!When it ends up working after several attempts and some warm-up time (10 minutes), this HP has the spirit of the valves 😊HP in its multiple functions works in some works well, others are blocked, but it reacts in settings impossible to run with ERROR, it still thinks and controls!!When I received this HP, it came with a damaged internal battery, (error E01) it was removed and replaced with an equivalent in 2016, now sometimes in the first boots again the error E01 appeared, I go back to the beginning but now I know where to check, the battery supplies the U10e U11 two RAM,s on pin 19 the voltage was less than 2VDC recommended.These RAM,s are for saving configuration of the HP when it is turned off, and recalling that configuration when it is turned on.The battery voltage drops quickly within 24 hours, to contradict the consumption I changed the R8 in 2016 to reduce consumption, but in turn lower the voltage, here you can't have a good of both worlds, never ever change the layout of the vintage HP, they knew well what did they do!!.This situation can be resolved if you resort to a 3.6V battery, I think.As for the current status of the HP, it continues after warmup to work erratically, it obeys certain commands and refuses others, the display shows misshapen characters and the output signal does not always respect established valuesI've already analyzed the signals around the CPU!! (1820-2099 = MC6802), to understand this blocking of functions, the D0/7 signals are distorted in relation to the others, defect or shape!!? This erratic functioning is a puzzle.Who might have any information to help?.Well be there to allHernâni Capela

author: MarkL
author_rank: Unknown
timestamp: January 05, 2022, 06:55:18 pm
content: The RAM is also used when the unit is operating, not just for storing the configuration while power is off. Given the issues you're seeing with the battery circuit, I think the first thing to do is verify that when the unit is ON, you are getting near +5V on the RAM Vcc (U10 and U11, pin 18).The buzzing could be a relay being driven with a wrong (random) signal.Does the unit's operation change after it's warmed up? Does the display start losing segments at startup or after a while? Is it always the same segments? One thing you could try is to use freeze spray (or upside-down canned air) to cool off areas or specific components to try to pinpoint what's being sensitive to temperature. It might provide some clues.As far as the DTY button is concerned... The problem is likely related to the other random behavior, but you could try a quick test to see if the button is working. Hold down the DTY button and power on the unit. You should get an "o" on the display, meaning a key is stuck.There may be more than one issue with this unit. I'd recommend not changing out any more components until you've determined they're definitely faulty. "Shot-gun" component replacement often leads to new problems on top of the old.

author: hcapela
author_rank: Contributor
timestamp: January 06, 2022, 01:52:22 am
content: Mr Markl thanks for your feed back.Already after performing the text to EEVblog. I proceeded with a few more actions that I describe here.Step by step:- To solve the issue of error E01 I installed a new 3.6V 2/3AA battery, the values apparently are as they should be 3.57V on Bat. and on U10 and 11 on pin 18 2.67V at rest, , and 4.97VDC in operation.- The buzzing as You said must be some relay somewhere!!-The HP in phase in which it accepts the commands, all 7 segments correctly respect the input values.- The quick key test, as You said, worked correctly, as I expected the DTY key is OK, and symbol "0" appears, I tested several keys and everything OK, the most curious thing is that when you release the key there is the relay somewhere click and it works- The most curious thing, I doubted the MC6802 CPU, and went to my component list and voila!! I had 2 HD46802P, I confirmed by the pinout that they are identical, and electrically/function I was going to see, when inserted both worked with the same behavior as the original.- The HP initially, when it finishes the boot phase, only allows two commands or a few more, from then on it ignores the commands in all the keys, but the output signal that is it remains unchanged !!- The D0-7 data on buffer U2 has the signals identical in output and input and equal to the waveform of the D0.jpg image, in the phase it works and accepts commands, something must be injecting into the D0-7 BUS outside from your time-slot, I guess.Now, and after much insistence on turning the (heating) on and off, the HP seems to say it seems controllable in its multiple functions. But in function (I.BUR) the BUR command does not react. But the DTY command, which in function (NORM) does not work, is accepted in other functions, maintaining the duty cycle value when returning to the (NORM) function. Finally when operating the AMP, OFS , HIL AND LOL values new keyboard lock!!. And back to the situation of two commands on the keyboard and LOCK !!I'm writing this and insisting on the HP handle, and finally when changing the values of HIH and LOL then blocked and more the LEDs blink and turn off, LEDs OFF (blackout)HP is working in E.SWP function in continuous, allow changing values and AMP but I don't dare touch HIH command ☹.I'm already afraid to turn it on and maneuver the HIH and LOLThanks Mr MarklBest RegardsHC

author: syau
author_rank: Frequent Contributor
timestamp: January 06, 2022, 01:55:33 am
content: I have similar experience on one of the 8116A which the leaky battery corroded the reset circuitry causing the unit failed to start when cold. Some trace inside the inter layer of the pcb become open circuit which I end up replaced the whole cpu board from my part unit.

author: MarkL
author_rank: Unknown
timestamp: January 06, 2022, 03:52:03 am
content: So to confirm, are you saying that you are no longer seeing E01?Can you look at U10 and U11 on pin 18 again but this time with your scope (and not with a DVM) with the unit ON and make sure the voltage is completely steady. Sorry, I should have said this in the first place in my previous post.What other equipment besides the HP 1742A do you have that might help?Do you have a digital scope, logic analyzer, or anything capable of doing signature analysis? Much of the 8116A service information from HP relies on signature analysis. Sigrok has a signature decoder. Signature analysis is not strictly necessary, but it can speed up the troubleshooting process by at least ruling out areas which are operating correctly.At the moment, I think there's an issue with the microcontroller RAM or ROM, or the interface circuitry such as one of the address decoders or bus drivers. It's possible on these units to have bad RAM and still pass the power-on RAM self-test (so the lack of an E01 on boot does not necessarily mean the RAM is ok, regardless of what the manual says).The D0 image you're referring to could be fine. It's impossible to tell without setting up the scope to trigger on the control signals to the drivers attached to D0. Sometimes the bits on the databus are floating and you can get long exponential waveforms going high or low. The important interval to look at is when there is supposed to be valid data on the bus.

author: hcapela
author_rank: Contributor
timestamp: January 06, 2022, 05:19:20 am
content: Thank you for your attention.Thanks syau, but I look for more, recover existing one and not look for another card, warranty, compatible version and will it even be the A1 card malfunction?Yes Markl, I will check the voltage values and the RAM signals with the oscilloscope, but they were replaced in 2016 by me (E01), the two UDP444Cs weren't cheap, €28.30 for 8Kbits!.However, I'm more focused on DAC OFFSETs or interface . because if no zero value in HIH or LOL than the device is Inop.Yes, I have other equipment, but not for reading digital data, I'll give you some news.Bem HajaHC

author: hcapela
author_rank: Contributor
timestamp: January 06, 2022, 04:00:42 pm
content: Mr. Markl I re-applied my probe to both RAM,s , voltages are ripple clean, Dx and Ax data are as analyzed on CPU images are identical to “image D0.jpg” “Adress A0.jpg” , .I point out with the new Bat. and recent RAM,s never happened again now E01 boot errorsThe HP816A works fine until you see :-) , as long as we don't use the following functions:- The HIH and LOL commandsmust be frozen(consequential blocking and lack of HP control)- The DTY* command is not accepted in the (NORM) function- BUR command is not accepted*- command accepted in the I.SWP function.To get out of the lock when triggering HIH and LOL there is a lock , the recovery process complicated, blindly force touch the up/down to set the OFS values ​​to 0 zero HIH and LOL , so RAM records the attempt, and the value decreases for every turn on!!.In this time-consuming and confused process, errors of E54, E60, H14, H11 will appear !!??When blocking the HP , when entering values ​​blindly with the keys blocked .The the RAM still registers the last value and when the HP is turned back on it will take the values ​​to null acceptable parameters of HIH and LOLBut I don't know anymore and why.At the stage of this correction of the OFS I was afraid of damaging the ASICBem HajamHCapela

author: MarkL
author_rank: Unknown
timestamp: January 06, 2022, 06:51:55 pm
content: I still think the RAM or surrounding circuitry may be at fault, or at a minimum its proper operation needs to be verified. If a value you set is getting changed every time you turn on the unit, something is corrupting the value either when it's stored or when it's recalled.What does the nCS (pin 8 ) look like?There was someone on the HP-Agilent-Keysight groups.io list who replaced their RAM and the replacement was also faulty, so don't rule out that the RAM is ok. Discussion here:https://groups.io/g/HP-Agilent-Keysight-equipment/message/114858It would also be a good to verify the contents of the ROMs. ROMs have been known to go bad. You can do this without removing them from the circuit by using signature analysis as described in the service manual. And there's lots of other things in there you could verify with signature analysis.You could also try putting the unit in free run and examine the signal integrity on all address and data lines on the CPU and compare them to the signals on the other side of the various bus drivers. You can use your scope's subtract function and put one channel on one side, and the other channel on the other side of the various drivers. The delay will produce small glitches on the trace, but it will immediately identify if a driver is flaky or not reaching proper logic levels. You should probably trigger your scope on the E signal from the processor to synchronize the trace to the bus accesses while you're doing this.And while in free run, you should be able see the address lines incrementing. A0 will have the highest frequency, A1 will be half A0, A2 half of A1, and so on.Another troubleshooting approach would be to pick one of the repeatable symptoms, like a missing segment on the display, and work backwards step-by-step to try to find out why it's not on.EDIT: Fixed a typo.EDIT#2: Additional thought on comparing signals... While the unit is in free-run the processor's databus is isolated. So there's no point in comparing to the signals on the other side of U2. You could, however, do something similar when the unit is not in free-run, but you would have to trigger on the state of U2. It's a more complicated triggering setup (E qualified by U2 pin 1 and pin 19).

author: hcapela
author_rank: Contributor
timestamp: January 06, 2022, 08:56:00 pm
content: It´s work but but on the edge of the blade.HC

author: hcapela
author_rank: Contributor
timestamp: January 06, 2022, 09:38:39 pm
content: MR Markl thanks for your attention.What does the nCS (pin 8 ) look like? -» Near 0V with noise 0,5VppIt would also be a good to verify the contents of the ROMs -» I have in my Lab a programmed EPROM,I never use that at ☹ to verify the checksum for each one, where in manual find that value.The delay will produce small glitches on the trace,-» OK I try thatA1 will be half A0, A2 half of A1, and so on. -» Where / who signal trigger my scope ?Error E54, E60, H14, H11, -» E54 Lin. Swing problem see IC401 , E60 Pulse Transfer Shaper IC 401!! Again!By Manual pag. 8-4 (You have one?) error type Hxx ??Best RegardsBem HajaHC

author: MarkL
author_rank: Unknown
timestamp: January 07, 2022, 12:40:46 am
content: Don't let those errors E54, E60, etc. distract you. Your microcontroller section is sick and it could be (and likely is) reporting garbage to you. Focus on one thing at a time, and pick the simplest and most obvious area that is having trouble.Quote from: hcapela on January 06, 2022, 09:38:39 pmOk, that's very interesting. Let's look at that. It should be switching at TTL voltage levels but it's not.The nCS signal should also be going to U29 pin 8. Do you see the same signal there?nCS should also go to a 1k pullup resistor inside R10 (pin 14). Do you see the same signal there?The other side of the 1k resistor is on R10 pin 3. Do you see +5V on that pin?U29 pin 9 should have the CS signal on it going from 0 to 0.5V or so. What do you see there? If you probe pin 8 and pin 9 at the same time (the base and collector), are the two signals inverted from each other or are they the same?All this is trying to determine if the 1k resistor in R10 is ok in R10, and if the driver transistor in U29 is ok.If R10 (pin 3 to 14) is suspected open, one thing to try is to connect a 1k resistor from +5V to the nCS pin.Also, the service manual schematics have about 50 changes for your serial number. I think I'm taking them into account properly, but if I'm saying something that doesn't match up with your board please say so. A photo of this half of the microprocessor board looking down on it could be helpful.

author: hcapela
author_rank: Contributor
timestamp: January 08, 2022, 02:07:21 pm
content: Good morning MR MarklNow well, stable personal situation.Yes Markl, I followed your instructions and it was not necessary to use the oscilloscope to verify that the path from nRAM SELECT E to nCS was not correct , with DVM I detected that the R18 between + VCC and U29/B NPN pin 8 was unsolder !! !When looking at the photos of the history of the repair of the primitive error E01 and the installation of a new Bat. and when carrying out consumption measurements on the R18 it was unsolder on one side!!Here is the photo of said R18 and the difference mentioned between the layout of different productions over timeBest Regards

author: MarkL
author_rank: Unknown
timestamp: January 08, 2022, 03:11:55 pm
content: Great! Glad you located the problem!Without that 1k pullup on the RAM nCS, I'm actually surprised the unit worked at all. Maybe the bad solder joint was intermittent or contacting just enough to make it work some of the time.It would also explain the temperature sensitivity of the failure. As the board heated up, it would expand and affect the resistance through the bad solder joint.EDIT: And also, if nCS was being not being held high via the 1k pullup when the unit was off, the RAM would be active and not in low-power standby. That would explain the high drain on the battery. I'd recommend un-doing the modification(s) you made to the battery circuit (R8 and anything else).

author: hcapela
author_rank: Contributor
timestamp: January 08, 2022, 04:19:14 pm
content: Hi Markl,Thank you very much, without your tips and your knowledge I would not have reached this result, the bad contact always makes it difficult and consequently makes the diagnosis very difficult, and hence the erratic operation, now I see that the HP never kept correct the last settingswell be there MarklRight now, I expect a sweep error on my HP8558B, work-in-progress that is just by arrangement of rotary switchesBest RgardsH Capela