Micca OriGen G2 DAC Problems

The Micca OriGen G2 is a premium DAC, preamp, and headphone amp primarily intended to be connected to a PC.

The Problem & Troubleshooting

My OriGen failed to be recognized by my PC when I powered up my PC after returning from a trip. I attempted to re-installing the driver, swapping USB ports and cables, and tried installing it on my laptop - all to no avail.

Micca's OriGen support tab offered suggestions:

• replace USB cable if power does not turn from red to blue,
• try other drivers using Windows Device Manager.

Another Amazon purchaser mentioned that the through-hole capacitors had swollen in his failed unit. I disassembled mine (great build quality BTW) and desoldered the two caps in question. They looked good and passed ESR tests with flying colors. I recall that the measured capacitance was off, but it didn't concern me (probably higher or within 10 or 20%). Visual inspection of the other components (mostly SMD) revealed nothing of concern. I re-assembled everything and tested again just in case the soldering and handling made any difference. Nope.

If I tear into it again I'll check out the USB data lines, and maybe try powering it via the DC 5V input.

Support from Micca is minimal if not non-existant. Their website is still up but none of the products I spot checked have been available recently on Amazon (their typical outlet).

The Solution

Fortunately my newish PC motherboard has a TOSLINK optical output so I fed that to the OriGen, flipped the input switch, selected the Realtek Digital Output as the audio output on the PC, and moved the 3.5mm analog output cable (feeding my Klipsch powered PC speaker system) back to the OriGen. And there was sound! :-) The LEDs no longer indicate the digital format, and the power LED is red, but I've got great sound again and the convenience of both 1/8" and 1/4" headphone jacks and volume control. It is still powered via USB, now from a powered hub's recharge port.

I can't understate the utility of the vertically oriented volume knob. The DAC is left of my keyboard so I can continue mousing with the right hand ... so convenient! No diverting to click on apps or the Windows tray, or aiming for volume keys on the keyboard. I would have installed it a lot sooner if I had realized how non-distracting it is to my workflow.

Arduino IDE Serial Plotter Syntax and Tips

 Introduction

The Serial Plotter allows you to generate line graphs in realtime as your Arduino program runs. The tool appears under Tools, or Ctrl-Shift-L. You cannot run the Serial Console and the Plotter at the same time, and you need to have the correct serial port selected.

Basic Operation

 In it's simplest form, you could just print data values while in loop() terminal. Separate multiple values with a comma, space, or tab (\t) character. Terminate the line with a newline sequence (\n) or endl if using Streaming. You'll need to maintain the order of the data elements being printed.

Additionally you can print a legend header with the names and colors of the graph lines.

Active Legend / Header

My preferred way to graph is with a header displaying names, colors, and values. In demo 3 of the example, I display the actual values in the legend, then offset the graphs vertically. I added center lines, t, b, and c. The lowest graph is constrained because sometime you have extreme values that would mess up your display because of auto-ranging. Sometime just knowing that a value is "off the charts" is good enough - you can refer to the legend for the actual value.

In short, print "label=<hdr_value>:graph_value\n". label=<hdr_value> will just be a dynamic string in the header, graph_value will be used for plotting. Separate these sequences with a comma, space, or tab, with a single "\n" line termination. In some cases a simple label could be printed once. Printing the labels in a loop allows you to restart the Serial Plotter window and keep your legend.

Sample Plot

References:

See https://dreamonward.com/2020/07/25/arduino-serial-plotter-labels/ and the referenced documentation at https://github.com/arduino/Arduino/blob/ba34eb640e5f6c2f8618debf61022f731c0eab74/build/shared/ArduinoSerialPlotterProtocol.md

The Code, The Code!

Here's some code you can play with:

#include <Streaming.h>

int demo = 3;

void setup() {
  Serial.begin(9600);   // USB "baud" rate doesn't typically matter
  delay(500);           // wait for the Serial port to start up
  switch (demo) {
  case 1:
      // no legend, single value
    break;
  case 2:
    // no legend, multiple values
    break;
  case 3:
    // legend printed in loop with values
    break;
  default:
    break;
  }
}

void loop() {
  // put your main code here, to run repeatedly:
  switch (demo) {
  case 1: demo_1();
    break;
  case 2: demo_2();
    break;
  case 3: demo_3();
    break;
  default:
    break;
  }
  delay(50);
}

int x;
int y=90;

double sine_x, sine_y;

void update_values() {
  sine_x = 1 * sin(float(x)*PI/180);
  sine_y = 1 * sin(float(y)*PI/180);
  x += 2;
  y += 2;
  if (x>=360) x%=360;
  if (y>=360) y%=360;
}

void demo_1() {
  update_values();
  Serial << sine_x << endl;
}

void demo_2() {
  update_values();
  Serial << sine_x << "," << sine_y << endl;
}

void demo_3() {
  update_values();
  Serial <<  "sine(x)=" << sine_x << ":" << sine_x + 1.5
         << " sine(y)=" << sine_y << ":" << sine_y - 1.5
         << " sine(x)=" << sine_x << ":" << constrain(sine_x, -.75, 0.75) - 4.5
         << " t:" <<  1.5
         << " b:" << -1.5
         << " c:" << -4.5
         << endl;
}

Mitsubishi Rear Projection TV Shutdown - X-Ray Protection

Intro

Yes, this is for a late 80's to early 90's big, bulky rear projection set. I had it re-aligned a few years ago and it's (almost) on par with a plasma set. But it started turning off within an hour of startup ... hence my quest to repair it.

On-line Resources

I found the service manual on-line. I'll leave it to you to find a source that isn't a hack-fest. Search for "Mitsubishi Service Manual 48311 pdf" or similar. I list the models that the manual supports at the end.

Also, I found a thread on justanswer.com that suggested this fix.

Blink Codes (page 24)

1. On AC power-up, the front panel LED will blink 3 time if the microprocessor is operational.
   
2. Press the FRONT PANEL!  INPUT + MENU buttons for 5 seconds then watch the LED for the blink code(s). 21 is for X-Ray Protect circuit.

The thread on justanswer.com suggested that capacitor C5A64 was the likely problem. Here's the circuit from page 65:

In short, I checked C5A64, a Nichicon 22µF, 16V electrolytic capacitor. ESR was between 4.7 and 5Ω and the capacitance was within spec. I replaced it with a Panasonic cap with an ESR of 3.0Ω. The set has been running for a couple of hours now so I'm hopeful that I can button it up soon.

Accessing the Circuit Board

The access process is as follows:

1. Unplug the set and give it an hour so so for the capacitors to discharge. It may take more or less time, you be the judge. And just stay away from display tubes and flyback capacitors in general.
   
2. Remove the Phillips head screws around the "Back Board" lower back panel/cover, the I/O panel, and the AC power inlet.
3. On the bottom are 3 boards mounted in a frame that slides back. Most cables are bundled and tied back with "twisty" nylon cable supports. You'll need to free those cables to slide the board frame back. Some leads are too tight and will have to be disconnected to allow the frame more travel. They are the I/O panel connector and one its cable coming through a noise suppressor.
4. There's a long black screw on the rear edge (toward you) of the frame that keeps the frame from moving. Remove it.
5. Lift up on the side latches forward of the flat frame areas labeled "HANDLE", and pull the board frame toward you.

Removing the Board

 The X-Ray circuit is on the right-most Power Board (page 18) as viewed from the rear.

1. Disconnect the 3 flat ribbon connectors by lifting UP on the right-hand side CONNECTOR via the little white tabs on the top. I had to use small channel lock pliers to GENTLY grasp the tabs and GENTLY wiggle some of the connectors loose.
2. There are 4 PH screws that hold the board down; 2 in the center, 2 on the right.
3. There are tabs along the top, bottom, and left edges that need to be sprung back to release the board to pivot to the right, then out.

Capacitor C5A64 is near the edge of the board, center right behind the transformer shield as I recall. Near 20-pin DIP IC5A02. EXACT location and photo PENDING.

Conclusion

I hope this helps someone that want to keep their set in service (despite the lack of HDMI!).

I didn't test many other components, or test reference voltages with the set powered up - the cabling just wasn't long enough for me to access the area easily and what I judged to be safely.

Models Supported by the Referenced Service Manual

V20A Models: VS-50111 VS-60111
V20C Models: WS-48311 WS-55311 WS-65311 WS-55411 WS-65411 WS-73411
V20C+ Models: WS-55411 WS-65411 WS-73411

Ignition Module for John Deere Mower

 The Mower

It's a John Deere F525 front-cut zero-turn mower with a Kawasaki PA540A engine.

Symptoms

It wouldn't restart when hot twice on one mowing session. The engine would turn, but there was no hint of ignition. The mower started and went about 20 feet into the next mow, then died with no sense that it was going to restart.

Troubleshooting

I installed a new spark plug, but still no go. And no spark was visible with a spark tester. The ignition module "IM" (JD p/n AM132770) seemed like the most likely culprit. Unfortunately there's no good bench test for these. I ordered one of the BM11 types from Amazon for under $16.

I tested the IM with a component tester and VOM diode test. It showed p-n junctions in both directions - no shorts or open circuits, so that was inconclusive.

I continued testing, adding a ground jumper from the IM's mounting bolt to make sure there was a good path to ground. I was finally able to get the blower cover off (one pesky mounting hole had to pried loose from inside the cover!). I cleaned the magneto contact points for a good ground and re-gapped the coil when I remounted it. The white wire from the primary winding to the IM had good continuity, both tab contact areas were clean. Starting attempts  showed a weak orange spark with no ignition ... even with  starter fluid.

So I decided to put a scope on it ... because that's what I do (for lack of a better excuse).

The primary is the lower blue trace, 5V/division. The yellow trace is the spark plug lead (with spark plug connected), using an Hantek HT25 10,000:1 clip-on ignition probe, 0.5V/division.

I hadn't done this before, but I see a 10kV negative spike which looks reasonable. I wondered if maybe the magneto was bad. Moments later Amzn pulls up with ignition module in-hand. 10 minutes later it's installed. 

 

I hit the starter and it's a bit rough then a backfire. The second attempt starts normally enough. I back off the choke and we're off to the races. .. she's running strong. I lower the throttle and get a new scope sample.

Here you can see the positive voltage excursions for both the primary and secondary windings are much improved.

Okay, so it's back on with the blower cover, fuel pump, air cleaner, fuel tank, and fender.

It's now been a week since my last mowing attempt. I fire her up, and start to back out of the shed. No go. Forward. No go. Hmm, I reset and release the parking brake. Still no go. Crap - I must have done something to the transmission linkage. But wait ... the transmission is still disengaged from me pushing it into shed. I slide the lever back. Tink - we're back in business and the next couple of hours of mowing are uneventful.

I can't say that this is the most logical troubleshooting session I have ever had. It was easy enough to rule out the interlocks early on. The next time I will check the IM grounding and primary signal before I order the part. The interplay between the IM, coil, spark plug, and HT lead complicates things a bit. But the consensus is to swap out the IM first, assuming wiring and spark plug are in good order. For $15 and change, it's a reasonable approach.

Dura Heat GFA40 Propane Space Heater, PC Board

 History

My previous post outlined disassembly of the heater and my basic troubleshooting steps.

The Board

What follows is a look at the PC board.

So here's the PC board mounted at the top of the base in a plastic holder. Just bend one or both tabs on the ends to remove the board.

Here's the backside, image flipped BigClive style so that the tracks line up with the top side.

This is the schematic I created. But there is something wrong here. Design-wise it looks wrong. It simulates wrong. But I can't find the error. Resistance from the top of ZD1 to D5 is 10.2Ω, i.e., R3. Yet when tested live they are essentially identical at 11.9Vdc and maybe 0.25Vac. The cathode of D5 is connected to relay coil+. I should have measured at the top of D1,D3 - maybe next time

Here's a modified schematic that performs as expected. The only issues I see is that flyback current can be handled by Zener diode ZD1 - D5 is redundant.

So here's what you've got: AC line voltage comes in on the blue connector CN1. L1 goes through the fuse to the full wave bridge (D1-D4) and the motor. The motor returns to the neutral lead.

The neutral flows through 10Ω power resistor R1 and the polystyrene capacitive dropper C1. There appears to be an integrated bleed-off resistor R2 soldered between the capacitor leads. The resistance value us estimated, the capacitance value is a guess from what I could sort-of read on the cap.

As mentioned, D1-D4 form a full-wave bridge, with reference ground at the bottom of D2,4, and DC+ at the top of D1.3. E1 is an electrolytic smoothing capacitor (41µF est). Expect this cap (E1) to dry out and lose capacitance or rupture over time. That will produce more AC ripple and the relay coil will suffer.

Now we take the DC voltage and regulate it to 12Vdc via ZD1. ZD1 was tested separately and passed current at 12V when reverse biased - I don't know the diode model. So D1,3,E1+ source voltage through R3, dropping the voltage to 12V at the cathode of  ZD1. The anode is at reference ground.

That 12Vdc is connected to relay (REL1) coil+, coil- is at reference ground. D5 is the shunt or flyback diode that will pass the current sustained by the relay coil's magnetic field when the heater is unplugged and the  DC voltage falls. Without the diode, the voltage would rise (back EMF) to a potentially destructive level as the the inductive coil does its best to sustain the current flow. Check out  how ignition coils and spark plugs work.

So when the heater is plugged in, the blower is presumed to be running. If power fails or the fuse blows, the thermistor is still hot and generating voltage. The in-series over-temp safety switch hasn't opened yet. So the only thing to prevent the propane gas valve from staying open are the relay contacts which open when the DC voltage collapses. That's the singular purpose of this circuit. If the flame goes out, the thermistor voltage will drop and turn off the gas. If the fan stops or something impedes the flow of air, the over-temp switch will open.

Conclusion

I hope this helps you understand and troubleshoot your propane heater.

Warning: The content above is submitted in the context of a DIY repair. There are likely regulatory factors that affect the design and manufacture of these devices. I don't design or sell these contraptions, so I don't know. I just use them and try to fix them when they break.

If anyone has any insight as to where my original schematic went awry, I'd be interested to hear it.

Dura Heat GFA40 Propane Space Heater

Let's say you have something like one of these, a Dura Heat GFA40 propane space heater:

and you want to repair it.

First you remove the 4 screws that hold the bottom plate of the base in and see this.

and this. You have access to a nice PC board with connectors. That's about where the fun ends because to get to the burner plate to access the thermocouple and over-temperature safety switch, you have to:

1. remove 3 screws to remove the rear screen (easy)
2. remove the motor
• remove the (4) screws that hold the motor base, accessible from within the base. The ones in the 10, 4, and 8 o'clock positions, as viewed from the base, are easy. The one in the 2 o'clock position is behind the switch mechanism. I ended up loosening everything so I could get to that screw straight-on so I could loosen it correctly. That  meant removing the 4 screws that hold on the base,  the 6 screws that fasten to the standoffs between the inner and out tubes, the machine screw and nut that hold the capacitor, the 4 screws (accessible through the label under the knob) that hold the valve to the base, and the valve knob. That make everything loosey-goosey enough that I could loosen the last screw for the motor mount and extract the motor and fan blade.

From there I had good access to the burner plate and could remove the thermocouple, over-temp safety switch, and igniter post as needed.

Now I know I could have just tested between the blue wire (next to the yellow one, not the one to the capacitor) and the bare silver earth wire. First for continuity to confirm the safety switch was closed, then for voltage as I heated the tip of the thermocouple.

But I was sure the themocouple was bad because the heater ignited fine and burned until I released the knob and hence the TC bypass. This was after I repositioned the heater that I had trouble. The first run was perfect - it ignited and ran on the first try. Now I'll get the propane tank and test again with an eye on the relay and the yellow lead to the control valve.

Summary

My takeaway from this exercise is that this unit is not particularly serviceable, due to the singular lack of accessibility to that one motor mount screw. The component layout could have been a little better, but it's generally good, and not a mess of dodgy soldering and wire splices. Virtually all of the screws were the short black sheet metal screws. Exceptions were the machine screw and nut that secures the capacitor, and the small silver screws for the safety switch.

Recap

I spent more time troubleshooting the heater and diagramming the PC board (next post).

When I back-probe CN4 the blue lead shows the thermocouple (TC) generates at around 20mV or more after several seconds. The yellow lead which is connected to the blue TC lead via the relay contacts may only show only 4-5mA. I did not see a matching differential voltage across the leads (?!). The resistance across the pins (with cable disconnected) is consistently 200mΩ. The relay's spec for contact resistance is ≤ 100mΩ. I removed and inspected the spring contacts from the connector housing - both looked good.

I resoldered a number of pins, sometimes removing the old solder, not that any solder joints were looking problematic. The heater is still very sensitive to tapping on the base, or removal of the meter probe from the connector. The relay coil is getting 11.9Vdc. So I suspect the relay could be a little better, but the unit is usable as is, with an occasional tap here and there.

Tacoma Spare Tire Lock

This post is for those that have encountered the spare tire locking mechanism on the first generation (1995-2004) Toyota Tacoma pickup truck. The lock resembles a wheel or lug nut lock that requires an adapter with a special pattern that engages the lock.

Here's what the lock looks like from the back of  my 2001 2.7L extended cab model showing how the spare tire is lowered by a cable:

and here's a closeup of the lock:

Here's the attachment that should be in the bag with your rods used to crank the jack. Mine was buried at the bottom ... I didn't even realize it was in the bag.

The jack crank end hooks through the attachment and snaps into place. Here's a closeup of the end.

Finally I should mention that if your truck has a modified rear-mounted tree detector (a.k.a. bumper) that's jacked up thereby closing the gap where you would normally insert the full crank rod, you can still lower the spare. Just use the last section of the crank rod (the jack end) with an 11mm square female pipe socket and a ratchet, a wrench, or even pliers. I used a "Sunex 214fp 1/2-Inch Drive 7/16-Inch Female Pipe Plug Socket" available from a certain on-line store.

Note: Wonky formatting courtesy of Blogger upgrades.

Harbor Freight Lynxx 40V Pole Saw Gear Grinding Repair

My Harbor Freight 40V Lynxx pole saw started grinding and vibrating badly, making it unusable. I checked the chain drive tension and sprocket which seemed okay, I opted not to go further until I did some research.

I found Slowpoke Slim's "Had to fix my Harbor Freight pole saw today" post on TractorByNet.com which laid out the problem - the two Philips head screws (Owners' Manual parts diagram #24) that hold the support plate (#22) to the motor had backed out. Several other people had the same problem.

Disassembly: Remove the drive cover (#54) by removing the two hex bolts (using provided Allen wrench or T30 bit). Remove the e-washer, "Pressing Plate" (washer), and sprocket (#56 &57). Remove all the T20 torx bolts on both side to separate the clam shell. Leave the Phillips head screw that secures the chain tensioner in place. Make note of the orientation of the support plate, motor, and motor terminals. Remove the two torx bolts that hold the pressing plate (#8) that secures the cable. Lift the motor out while separating the pinion gear from the ring gear.

Repair: I removed the two screws that secure the support plate to motor.  I cleaned them then added two dabs of Loctite, then reinstalled them.

Assembly: Reinsert the pinion gear, and set the support plate into the slots in the clam-shell. Reinstall the cable lock, align the ring gear and bushing and hopefully the clam shell halves will realign and close. Reinstall all of the bolts, sprocket, washer, and e-ring. Reinstall the drive cover. Test, saw, ...

A Peek Inside a Keurig K80

 Here's a quick look at the control board of a Keurig K-Select K80 single cup coffee maker.

This unit has been problematic over the last year or two. It occasionally turns off during the heating cycle, sometimes as many as three times in a single cycle. Fortunately it only turned off once or twice during the brewing cycle - otherwise it would have been gone a lot sooner. We paid about $119 or $129 for it (US$). I replaced it with a Cuisinart SS-10 for $149 - more on that later.

Anyway, here's the K80 control board.

K80 Control Board

It's way better than I expected. Decent layout though with no routed line voltage gap. The quality of the components, most notably the electrolytic caps, is good except for perhaps the relays. There's a flat flex cable connection from the top left to the button & LED interface, and JST connections to the water and temperature sensors, pumps, etc. There's a connection point for serial debugging and a few dedicated test points. Everything was clean, including the tubing (whew!).

As for some of the ICs, there's a Microchip PIC32MX130F064D-I/ML microcontroller, a Fujikura FPN-07PB pressure sensor, a Lite-On MOC3063 opto-isolator triac, and a WeEn BTA316B-600B0 triac. Relays look like Hongfa HF3FD 012-H3F(245)(247).

I didn't find any connection faults to repair so I probably won't delve into this any more.

As for the Cuisinart unit, it heats the water in-line rather than use a tank so it starts brewing almost immediately. We're very happy with the new coffee maker. My past experience with Cuisinart has been exceptional. On the rare occasion when something broke on one of our Cuisinart appliances, their customer service reps have been very accommodating, e.g., "We'll get that out to you right away ... no charge". Can't beat that.

Black & Decker BDFC240 NiCd Charger Repair

 I bought a Black & Decker  Charger to charge the 18V NiCd battery packs that came with a B&D charger and a dismal, minimalist clip-on charger. It came from eBay and seemed to be the real thing. It worked great for a few charge cycles - like maybe as many as six. Then dead, nada, no go.

 Inspection

I opened it up with a T15 security bit and started probing. I traced the continuity of the AC path to the bridge diodes and found AC voltage from terminal Y3 wasn't getting through the common mode choke (located across from Y4). And F1 was open so there was no connection to Y4.

There was a dark spot on one of the choke windings. It appears there was a defect in the winding insulation that caused the choke to short out the 120VAC line input and blow the fuse (fortunately!). There is a clear insulating coating (typically lacquer) on the copper colored winding.

Replacement Parts

I found the fuse on Newark Electronics, Multicomp Pro MST 2A 250V Slow blow, stock #95M6783.

The closest common-mode choke I could find was the Kemet 2A 1µH, Newark #SC-02-10GS.

 Shifting Gears

It seems the choke is not as "in stock" as I was led to believe, so I rewound the toroid myself. I found one wire had a nick in the insulation, the other wire was broken as I unwound it. I had an assortment of solid 22 AWG  PVC wire so I used two strands of that. It was a little thicker than the winding wire so I didn't quite get the 8 turns in, but I think it will do for an hour here and there (I already converted the other battery to lithium).  I soldered the new fuse and rehabbed coil into place and powered 'er up. The red LED came on briefly, and there was roughly 14VDC (as I recall) x 2 on the other side of the bridge diodes.

Conclusion

I inserted the NiCd battery pack and the red LED went to blinking (Charging) until it went solid (Charged) an hour or so later. Battery voltage was checked periodically and it seemed appropriate. I declare it fixed.

Hunter Zephair B3400 Schematic

Switch Wiring for a Hunter 20" Window Fan

I couldn't post (for free) to the Antique Fan Collectors Assoc. forum (www.afcaforum.com) and collaborate on this little rehab project so I'll at least post it here.

I haven't confirmed the position of the switches so "up" and "down are relative to the schematic, and not the physical position of the switches themselves.

The SJn jumpers are a convention I have to use to use with Eagle PCB to effectively allow two names or labels (wire colors) to connect to one node.

L1 and L2 are line and neutral from a 2-wire ungrounded, unpolarized 120V power cord that connects to a standard wall outlet. There are no 240VAC connections here.

The capacitor has two green leads as it is unpolarized and is stuffed into the junction box with the switches.

Note: I've just started to work with this and I'm not matching this to what I would expect to see for motor terminals and windings. Visibility of the switch connections is not great so there may well be errors. EDIT: Correction - the OFF position is on SW2-HIGH/OFF/LOW.

This simplified to this diagram:

which clearly shows the starter capacitor being between line and neutral half of the time which makes no sense to me. I'll correct the schematics when/if I find the error.

Edit: The fan's power cord has been replaced and the fan tested for functionality and ground faults. It is on its way back to the cottage so there will be no further updates.