Heindenhain QC300 Quadra Check HELPPP!!! - Page 1
Forum section: electronics / repair

author: IngIgn2689
author_rank: Newbie
timestamp: November 07, 2023, 03:26:55 pm
content: Good morning,I have a Heindenhain QC300 device which does not turn on when powered with 120vac. SOMETIMES it turns on when I touch the terminals of the capacitor indicated in the image with the tips of the multimeter or also when I touch the terminals of the oscillation crystal also indicated in the image with the tips of the multimeter.Tests carried out.The entire circuit of the source was reviewed, measuring capacitors uf and esr values, diodes and the TOP245, the oscillation frequency of the TOP, 60 KHz, was reviewed.A 47 uf electrolytic capacitor was replaced.The 12v, 5v and 17v output sources were checked as well as 3.3v and 2.5v. All the components of the source were re-soldered.The oscillation crystals of the other ICs work well, tested on an oscilloscope.The glass that I mentioned above was changed and the IC is a 1670e.This IC is responsible for starting the LCD and communicating with the external eprom memories. These memories and the IC are backed up with a 3.3 volt battery that is in good condition.It is important to note that when it is turned on everything works properly but if it is turned off it does not turn on again until some of the two components are touched. and like I said SOMETIMES.Thanks for the help what any idea may be.

author: Swake
author_rank: Frequent Contributor
timestamp: November 07, 2023, 08:26:05 pm
content: Heidenhainnot HeindenhainQuoteOk it is an SMPS, but are you sure it does not need 230V or 240V?QuoteCould you be more precise please? You mean the probes of a multimeter? What range is the multimeter in (V; A; Ohm; ...)? What multimeter exactly? One probe on one terminal and the other probe on the other terminal of the cap or in a different way?QuoteWhat glass? What is that chip "1670e" exactly, I could not find a datasheet?QuoteWill it start after a considerable amount of time? Let's say several hours or even a day?Nothing that turns hot?Have you checked for ripple on the power supplies?

author: IngIgn2689
author_rank: Newbie
timestamp: November 08, 2023, 03:37:00 am
content: Hi thanks for replayQuoteOk it is an SMPS, but are you sure it does not need 230V or 240V?Yes It´s an SMPS 120VAC in Costa Rica we work with 120vacQuoteCould you be more precise please? You mean the probes of a multimeter? What range is the multimeter in (V; A; Ohm; ...)? What multimeter exactly? One probe on one terminal and the other probe on the other terminal of the cap or in a different way?Ok, perfect, Fluke 289 or Fluke scope 192B, in Voltaje. Both components with one probe in one terminal and the other in the other terminal.Important. When the PS works if I touch the error amplifier optocopler the PS stop. Also when I put the probes in S and D of TOP245 and touch the crystal works fine.QuoteWhat glass? What is that chip "1670e" exactly, I could not find a datasheet?DS1670 Portable System Controller it´s the IC that I mencionedthis IC works with crystal oscillator of 32768 KHz of 6 pF.... Sorry "Glass" bad traduction of Google.QuoteWill it start after a considerable amount of time? Let's say several hours or even a day?Nothing that turns hot?I will check with Thermal camera but when doesn´t Work also looks fine. But I didn´t check with the equipment works.Have you checked for ripple on the power supplies?No, I will check and tell u.I think that this issue is a problem of capacitance some capacitor is bad I thnik.....

author: Swake
author_rank: Frequent Contributor
timestamp: November 08, 2023, 07:45:28 am
content: QuoteThis is a typical frequency for a clock.The DS1670 has microprocessor monitor circuitry (pins 13 and 20). The handling of touching some components is probably interfering with the monitoring on that chip and generating a reset. I suggest you monitor the signals around it to see if these behave as described/expected in the datasheet. Cost of one is 11$ at digikey, that is an expensive chip...Pin 13:Code:Active-Low Reset. The RST pin functions as a microprocessor reset signal.This pin is driven low 1) when VCC is outside of nominal limits;2) when the watchdog timer has timed out;3) during the power up reset period;4) in response to a pushbutton reset.The RST pin also functions as a pushbutton reset input. When the RST pin is driven low, the signal is debounced and timed such that a RST signal of at least 250ms is generated. This pin has an open-drain output with an internal 47kOhm pullup resistor.Pin 20:Code:Active-Low Strobe Input. The strobe input pin is used with the watchdog timer. If the ST pin is not driven low within the watchdog time period, the RST pin is driven low.Another thing in this chip is that it is capable of switching power sources (to maintain clock and settings memory I think). There might be an issue around the battery. Not charging or bad contact or corrosion maybe, and when you touch the board it all of a sudden works just long enough for the thing to reset and start.Code:POWER-UP/POWER-DOWN CONSIDERATIONSThe DS1670 was designed to operate with a power supply of 3.3V. When 3.3V are applied within nominal limits, the device becomes fully accessible after tRPU (250ms typical). Before tRPU elapses, allinputs are disabled. When VCC drops below 2.88V (typical), the RST pin is driven low. When VCC drops below the lower of 2.7V (typical) or the battery voltage, the device is switched over to the backup powersupply. During power-up, when VCC returns to an in-tolerance condition, the RST pin is kept in the active state for 250ms (typical) to allow the power supply and microprocessor to stabilize.It indeed sounds like some capacitor issue or a bad solder joint. Something that is sensitive during start-up but not anymore after that.