projects – Faulhorn Engineering Works

Realistic STA-2100D Restore

April 19, 2022April 23, 2022
by Christian Stanton

While cleaning house, my father in-law had a vintage stereo that he didn’t want anymore. I tossed it in the back of the car and took it home. On further research, it turns out it is probably the best stereo that Realistic ever made and a highly collectable.

The main restoration other than cleaning that vintage stereos need is replacement of all the electrolytic capacitors (know as a recap). Electrolytic capacitors eventually leak or degrade their electrolyte.

I purchased a 2100D capacitor kit from ebay vendor hifiaudio-. He also supplied links to both the operations and repair manuals. He supplied a work plan on how to do the re-cap but tdid not include any instructions on the physical layout or disassembly. Most information I found online had full removal of the boards which involves much more rewiring than necessary.

This is a detailed instruction manual on how to rebuild a STA-2100D with minimal rewiring:

Disassembly:

There are good instructions in the repair manual on how to remove the case and expose the bare chassis which I won’t cover here. Thoroughly clean out case by gentle use of a vacuum and compressed air.

Tools:

A quality fine tip soldering iron – I use a Hakko FX-888D
0.32-0.4 mm flux core solder – Everyone has a favorite brand, I use MG or Kester.
Solder wick – NTE – You will use 10+ feet of wick
Flush cutters – Hakko CHP-170
Several sizes of needle nose pliers
#2 Philips Head Screwdriver
Several sizes of straight screwdrivers
A 2mm hex wrench
A good aim able LED light
Electronic Silicone for remounting thermistors
Deoxit D5 Electronic Cleaner
Sprayway Glass Cleaner

You will be working around leaded solder from the board as well as fumes from new solder. Work in a well ventilated area, ideally with a solder fume extractor.

Work Process:

Take plenty of pictures before disconnecting anything!

Have a work area that you can keep undisturbed for the duration of the project.

Work slowly, take breaks… the work is intense and you will make mistakes if tired. Reversed polarity on an electrolytic cap will cause it to explode.

Be methodical:

Remove a single component at a time
Identify the component number and find the replacement component before starting
Note polarity of the PCB marking, the circuit diagram and the component as you are removing
Note polarity of the PCB marking, the circuit diagram and the new component as you are replacing
Catch every snipped wire. If you can’t find it, stop and find it!
Cross things off as you do them
Pay close attention to any broken or unwrapped wires
Confirm the entire board before moving on
Wait until the end to replace tywraps

Layout:

Both the repair manual and the instruction in the recap kit lack any orientation to where boards are found in the chassis. This is a good top down map. Stereo front is down in this picture. When I refer to things front/rear/left/right it’s from this perspective. The numbers here refer to the repair manual PCB references. Note, only the boards needing cap repair are listed and I only describe what is necessary to access them to do the recap. I left as much in-situ as possible without disconnecting wires. The step numbering in the recap kit, does not correspond to the board numbering!

Detailed repair notes:

Rear:

Main Filter Caps
15/16 – Main Amps
18 – Protector & Meter
23 – Relay

Front:

12 – Front End
13 – PreAmp Selector
14 – Tone Amp, Muting, Tape Switch
17 – I/F & Dolby
18 – Power Supply
20 – Speaker Switch – Does not require recap
21 – Mode Switch – Does not require recap
26 – LED Power Switch

Main Filter Caps

The largest caps C1405/C1406 in the chassis are the main filter caps. The ones supplied in the kit are smaller diameter than the originals and required me to CNC machine adapter rings to fit the original mounts. I also tried some 3D-printed adapters, but I felt using bakelite material was going to be more temperature resistant and in the spirit of the vintage amp.

This is the only step where you might need a more powerful solder sucker and iron. Patience and solder wick got it done for me.

15/16 – Main Amps

The Main Amps are easily removed from the chassis to work on.

Take pictures before you remove plugs! Don’t assume my pictures are the same wire colors as yours.

Place the chassis on the right hand side, so both bottom and top are accessible.

From the top: Remove the white pre-amp plug [Yellow Arrow] from the top of the board. For the right amp, remove the screws holding the standoff wires for the antenna lead.

From the bottom: Remove the 4 connections [Yellow Box]. Remove the screw holding the thermistor mount down [Top right in picture above]. Remove the thermistor [Orange arrow] carefully with an hobby knife. Remove the 3 remaining screws [Green arrows]. Note you may have to carefully move wires to get to the screws. Remove the main Amp from the top.

With the Main Amp out of the chassis, remove the 2 screws securing the board to the heatsink bracket. Slide the board up and away from the heatsink brackets and rotate 180 degrees “open” to reveal the solder side of the board.

RECAP the board according to steps in the kit. Replacement is the reverse of removal.

REPEAT for the RIGHT AMP which is a mirror image of the LEFT AMP.

23 Relay PCB

There are only 2 caps near the top of this board and it is possible to do in place.

18 Protector and Meter

You can do this insitu from the top.

Remove the two screws at the top of the board and move the board up and out of the lower slots. Carefully guide the wires (you may have to cut tywraps) and move the board up until fully exposed.

RECAP the board according to steps in the kit. Replacement is the reverse of removal.

This completes the rear section

19 Power Supply

From the bottom: Remove the two screws holding the board brackets to the chassis [Yellow Arrows below]

Remove the ground from the Left Main Amp screw [See Main Amp Bottom Picture, lower right green arrow]. Carefully remove tywraps and guide board out bottom of chassis rotating 90 degrees to expose board.

RECAP the board according to steps in the kit. C721 was missing from the Recap Kit. Replacement is the reverse of removal.

Consider doing board 17 IF + Dolby before replacing board 19.

17 IF + Dolby

From the top: Remove the 6 short screws holding the board to the chassis. Carefully rotate rear edge of board up. Maneuver front edge of board slightly to the rear to clear chassis. You may have to remove tywraps to allow enough movement.

Unsolder the red wire going to terminal 1 near the left rear of the board near the C241 marking (C241 component was missing). Unwrap the yellow terminal 36 and gray terminal 37 wires.

Rotate the board nearly 90 degrees – right side will be freer than left – Stabilize the board as best you can.

RECAP the board according to steps in the kit. C226 was missing from the kit, 47uf 16v. As you maneuver the board back in the chassis, rewrap or solder yellow to terminal 36 and gray to terminal 37 wires. Resolder red wire to terminal 1. Replacement is the reverse of removal.

Check carefully for any broken wire wraps. Reroute wires

14 Tone Amp, Muting, Tape

This board contains most of the knobs and switches.

From the front: Remove the tuner knob with a 2mm hex wrench. Remove all the other knobs and switches. The buttons are attached to the face plate and do not come off. Remove two screws on each side of the face plate. Remove the 3 screws on the bottom of the face plate. Being careful of the tuner indicator, remove the faceplate.

From the front: Remove the hex nuts and washers from the bass-mid-treble potentiometers. Remove the hex nut and washer from the volume knob. Remove the screws from the tape and turnover switches.

With the unit on it’s left side, carefully slide the board back and down until separated from the unit. No wires need to be disconnected.

RECAP the board according to steps in the kit. C1005 is labeled incorrectly in the service manual circuit diagram, it is correct on the board.

Consider doing 13 Preamp, Selector Switch before replacing board. Replacement is the reverse of removal.

13 Preamp, Selector Switch

Turn the unit on its bottom with the left side facing you. Remove the 3 screws securing the metal shield [Yellow Arrows]. Remove the shield.

Unscrew the two screws securing the selector switch to the chassis [Red Arrow]. Unclip the two plastic clips securing the board. Carefully pull the top towards the left to expose the solder side of the board.

Remove the two plugs on the board to relieve pressure.

Guide lower plugs past edge of 14 Tone Amp board. I think I removed one of the plugs to allow further motion.

This is very tight to do this soldering. An angled soldering tip, good lighting and a head mounted magnifier will help. I skipped C310A/B as these were not electrolytic and almost impossible to reach. The polarity on C304A/B is incorrect in the service manual diagram but correct on the board. Negative is top lead.

Replacement is the reverse of removal.

Power Switch

Not part of the recap, but it is common for the power switches to arc and become very unreliable. They are easily replaceable when the unit is open. Remove the two screws from the front panel and pull the switch to the rear until it can be freed.

You can find switches that exactly match but I found a close replacement that I modified. A C&K NE1839EE is almost an exact replacement. You will also need an arc suppressor aka “snubber” because of the large surge current. I used the CDE 504M06QE100. It gets wired across the open contacts.

The only modification on the switch is to transfer the metal bracket from the old to the new. Some work with an hobby knife to widen the slots where the metal bracket fits into the switch were required to make it fit.

The

Cleaning

After double checking everything very carefully and powering on the receiver, I began testing. Most of the issue encountered had do to with corroded potentiometers or switches. Deoxit is the best product to liberally spray into the pots and switches preferably in an orientation to allow flow into the components. Just keep working them until you get a consistent, crackle free reliable, operation. On mine which was fairly clean, it took more than an hour to work out all of the issues. Don’t forget to clean and test the headphone jack.

For cleaning the chassis and faceplate I used canned air, lint free wipes and Sprayway Glass Cleaner.

Calibrating and Testing

By replacing so many components, you have thrown the calibration of various functions off. The service manual has a very good procedure for tuning up the receiver. I followed as many processes as I could without specialized equipment. I was able to use a laptop and an adapter to simulate tape/aux input, a USB recorder cable to test tape output.

CNC

GRBL32, STM32 and other frustrations

November 18, 2020January 6, 2021
by Christian Stanton

I bought a Tom’s Robotics STM32 based CNC board (F13 – 3 axis) [Note: the jury is still out on this product, as I havn’t gotten it to work and Tom hasn’t responded yet] and finally received the MKS Servo57/42a boards (and a spare) that I blew up. I was eager to bench test it.

I physically built out the new controller in a new case that holds all the electronics for my CNC router: the CNC board and the 5v PWM to 0-10v converter for the External Brushless Spindle Controller.

Connecting to the board via the USB port and firing up my choice of CNC controller (bCNC in Python), first issue was the baud rate. By default the F13 is set to 921600 which is not a choice in bCNC. Luckily, Tom forked a copy of bCNC and updated this list of baud rates, so I was able to quickly edit the code.

Connected!

I was able to get bCNC to connect and did a few moves with it without any stepper/servos hooked up. All was looking good until bCNC stopped reporting any status or responding to commands. I was able to repeat this several times after a reset of the STM32.

I immediately suspected communications issues, but swapping cables to known good ones did not resolve it.

Is the baud rate too high? Probably not, but Tom does offer to reduce it to 115200 at ship time. I decided to reflash the STM32 with the lower baud rate. This took a bit of setup as I had the build environment is the STM32CubeIDE and the STM32 requires an ST-Link programmer/adapter. The structure of the source code of grbl32 from Tom took me a bit to figure out. It needed two symlinks for grbl and stm32 inside the cubeide directory. (I’m on a PC, so I simply moved the directories).

After a few hours, I had built and loaded grbl32 to the STM32 board with a default baud rate of 115200. More testing and…. (sad trombone) same issue.

Finally a clue…I eliminated the CNC software issue by just using trusted terminal program (PuTTY) to reproduce the problem without any other software involved. I was able to lock it up. When rebooting the STM32 via the reset button, the serial buffer output: Error: 7 just after the reboot. This is a standard GRBL error for EEPROM read failed. Reset and restored to default values. and indeed all the settings I had modified in my testing (speeds and acceleration) were reset to the defaults.

I have another STM32 on order to eliminate a bad board as the cause.

Update 01/06/2021: Tom very graciously sent me another F13 board+Black Pill which exhibited the same issue. I spent about 3 days trying everything I could think of including annotating code for better logging and poking around in the STM32 debugger. It looks like a timing issue as grbl gets confused about the queue counting method of buffer control…. it at some predictable point for a given file grbl32 fails to respond to the host with an OK and the CNC sender stops and waits to send more commands. Ultimately I needed the machine back up and running so I returned both units to Tom and he gave me a full refund. It is an awesome concept and I feel given my depth of skills I should have been able to make it work, but the truth is that it didn’t.

I went back to a cheap Sainsmart grbl 1.1f board that I had in my parts bin that is working fine and I’m building up around that. I’ll swap that out soon as it doesn’t include all the I/O needed. My real work life has picked up, so progress has slowed…. more to come.

CNC

CNC gets Smart(er) Servos… not

October 22, 2020November 2, 2020
by Christian Stanton

Recently, while milling aluminum on my OX CNC, I had a frustrating number of bad runs because of the stepper motors missing steps. I think this was due to overheating of the 8825 stepper chips on the xPro CNC grbl board. In a fit of pique, I ordered up MKS SERVO57A closed loop stepper boards from AliExpress. These are based on the nano_stepper open source project developed by misfittech. These add a dedicated STM32 controller with to each stepper motor with feedback from a magnet on the shaft. It also provides an optional direct LCD display and menu to setup the servo. It moves the high current driver from the grbl board to the servo board.

The MKS Servo57A
I chose the “A” version because the rated peak amperage is 3A and the steppers are 2.8A. This is set in firmware.
I plan to add a fan/housing to protect the board.
NOTE the handy labeling of the pins on the white connector (doh!).

The feed from the grbl board to the servo board has to now be logic level: STEP, DIRECTION and ENABLE rather than the high current connections directly to the stepper. I had planned this around my memory that I had an xPro CNC v3 which has a breakout connector for logic level STEP, DIR and ENABLE, however when I pulled the board from the CNC, it was a v2 which has no breakout! DOH!

Hack time… The v2 has solder pads used to select which mirror one of the axes (by default Y) to a second stepper motor. This exposes the XYZ(and E not used) axis STEP and DIR. Enable is not directly exposed, but is directly driven from the microcontroller, so I can grab it directly from one of the pins. A bit of delicate soldering of some wire-wrap.

I soldered up a connector board to match the supplied cables for 4 axes (X,Y1,Y2,Z (unused)) and fed power (24v and 5v) and ground. The ENABLE signal is common to all the motors. Some 3D-printed brackets fix the connector board to the xPRO CNC.

The xPro CNC v2 with connector daughter board for the MKS Servo57A.
The solder pads are visible below the connector board.

CAUTIONARY TALE!

After feeling pretty good about the daughterboard for the servos. I reassembled the electronics into the CNC chassis. Hooked up the first y-axis servo and powered up. NOTHING! No display or LED on the servo (there is an OLED that plugs into the SDA connector visible on the top of the board). Perhaps my wiring to that plug is incorrect. Hook the y-axis servo to the z-axis connector. NOTHING! Perhaps the servo is ignoring me. Hook up the second y-axis servo to the y-axis connector. NOTHING! Fall back to testing the z-axis which was to remain a stepper. STEPPER DOESN’T WORK! Start to ring out the supply voltages, 24v is OK. 5v is at 2.25v across the entire xPro board! Check the voltages on the plugboard and they are OK. Check the voltages at the servos and…. CRAP! the cables supplied with the servos swap the pins. 24v was fed into the STEP and ENABLE pins and 5v fed to the DIR pin of the Servos and the xPro board. PZZZZZT!

Tore the whole thing down and tested. Casualties:

Fried the xPro CNC drivers on the MEGA328P for pins 1,2,10,11 (YSTEP, ZSTEP, XDIR, YDIR). They now are shorted partially to ground. I did finally get the 5v supply back on the board, but only the un-buggered x-axis works.
Fried two of the MKS SERVO57A boards. One won’t power up at all and the other won’t accept steps. The third one was not involved in the incident and works fine.

LESSON LEARNED

Bench test everything incrementally including cables!

No hacking around this ugly, I ordered a new CNC controller (Tom’s Robotics F13) which runs GRBL32 (a 1.1f fork) running on a 32 bit ARM Cortex “Blue Pill” controller. Everything is pluggable on this board vs the xPro which was all SMD. I re-ordered 3 more MKS SERVO57A boards (one spare) and a MKS SERVO43A board (for NEMA17). I may switchout the z-axis for NEMA34). Unfortunately this sets me back a few weeks as the servo boards are shipping from AliExpress China.

Tom’s Robotics F13 – Received in three days… now the long wait for the AliExpress parts.

quarinjection

Quarinjection Selecting an ECU

July 1, 2020August 5, 2020
by Christian Stanton

At the beginning of the Quarinjection project, one of the major decisions was what ECU to use. There are only a handful of open-source ECUs that would make the cost feasible for the project. All the proprietary ECUs would cost the entire budget of the project.

RusEFI – Frankenstein, Frankenso, Prometheus, Proteus, Hellen…
These use SMD assembly which leads to a compact, clean board but is difficult to assemble. Based on the stm32f407 ARM development board and running ChibiOS/RT. Code is in C/C++ which is ideal as I have deep experience (not that there is any need to rewrite code).

Megasquirt
The first commercially available (2002) implementation of EFI using a microcontroller. Still sold, but built around on the older 68HC908 processor and the source code is not intended to open source. This has a different audience and there are many PnP versions for different cars. Only assembled boards and are 4-5x the cost of these others.

Speeduino
An interesting project for an open source EFI based on Arduino Mega. Less powerful than the stm32f407 which limits functionality and flexibility, but it should be good enough to work for this application. I’ve been doing quite a bit of Arduino (which is a wrapped C) lately and this is also comfortable.

I spent a few hours thinking about this and ultimately decided that the Speeduino BOM came out a bit cheaper and uses discrete components and the openness of both the platform and the software is attractive. And I already had an Arduino Mega clone in my parts box.

I bought a bare v0.4 board and VR conditioner from ebay (turns out it shipped from Israel) for <$15. It took about 2 months to arrive 🙁 after being lost once. I decided it was never going to arrive and ordered another board from a US supplier and… they both arrived a day apart.

I sourced components from my favorite new (to me) supplier: Mouser Electronics. Occasionally they don’t have something I’m looking for that are peripheral to core electronics (like Diametric magnets) but everything has been easy to find and compare, shipping is instant and customer service is great. Digikey is good also and they are my fallback. I think the BOM, including $14 of extraneous R&D components for my rainy day shelf came to $100.

I don’t know why, perhaps a return to my youth of assembling RadioShack kits, but I find assembling electronics very calming and satisfying. I savored the build of the Speeduino board. Here it is complete with the VR (variable reluctance) driver board for the cam/crank sensors and the stepper motor driver for idle control (which won’t be used in the initial build). I don’t know why some of the resistors spec’d are oversized (the brown blobby things) but I made them fit as well as possible. The Speeduino is just an Arduino ‘hat’ and underneath this board (you can see the pin outline) is an Arduino Mega clone. J5 is a high-amp output which I did not put a connector on yet because I’m not sure I’ll use it.

quarinjection

Quarinjection Throttle Position Sensor

June 4, 2020October 21, 2020
by Christian Stanton

I chose to re-use the current Solex 28/32 PDSIT-4 carburetor rather than purchase a new throttle body. The carbs role to meter and deliver fuel will now be done by the fuel injectors, so the carb only needs to function as a throttle plate and provide the ECU with the throttle position.

I stripped down the existing carb by removing the fuel bowl, automatic choke and venturi and then used epoxy to fill any unneeded fuel or air passages.

Stripped Solex Carb, throttle linkage side. The threaded mounting holes at the top are for the automatic choke which I am reusing for the TPS sensor.

The Throttle Position Sensor (TPS) is a potentiometer that rotates the same ~90 degrees as throttle plate. The position is then read by the ECU. The task is to interface the current throttle movement to the TPS which is normally connected directly to the throttle shaft on the opposite side to the cable/linkage. On the Solex the plate turns the opposite direction to the TPS I have (from a Honda throttle body $10), so it has to mount on the same side as the linkage (or geared to the shaft) . Space is also very limited around the manifold mounted carb.

There are existing threaded mounting holes where the old choke was that I can use to attach the TPS. I designed a mount and lever system that uses the choke lever on the throttle shaft.

The existing throttle lever (lower left) to TPS (top plate) mount and linkage. Only critical detail has been modeled and the bent tabs on the lever are shown flat. The lower bolt intentionally has no spacer to clear the lever.

Assembly installed. Still needs some means of retaining the linkage. The linkage, salvaged from the fuel level float, is 2.5mm, which is again an uncommon size.

Retrospect:

Milling: I was very pleased with the milling now that I have the feeds and speeds dialed in. The dimensions of the holes were slightly small which means I probably have a calibration issue with grbl. I had my doubts about routing a 4.7mm hole with a 3.175mm mill. It works without air clearing but does regrind some chips. I am not doing finishing passes as the double stick mounting tape I’m using can’t take the force after it’s cut free from the sheet.

Design: Version 1 worked as planned and I didn’t have to redesign or recut anything. The full range of motion was just possible with the design, so I should have rotated the lever another 5 degrees counter clockwise. 3003 aluminum is too soft (“tends to be gummy when machined“) for tapping and just kind of smears into a badly formed thread. Next time I’ll use brass or steel press fit inserts. The tapped holes on the carb were metric but done in the 60’s before there were standard sizes, so they are an odd M5x0.75; I retapped these holes to M5x0.80 without losing much integrity. I should have modeled the full throttle lever as it is very close to the lower low-profile bolt for the TPS (there is another lever on the opposite side of the throttle shaft which I may use instead). This is a temporary solution just to get the system to work and then I’ll redesign the entire inefficient intake manifold.

Overall success! On to other components…

quarinjection

Quarinjection Ignition

May 30, 2020July 1, 2020
by Christian Stanton

The ignition coil generates spark and the distributor distributes it to each spark plug. The distributor also varies the timing of the spark based on the speed of the engine (via a set of centrifugal weights) and the load / requested speed of the engine (via the vacuum advance).

The ECU will now control the timing of the ignition, so I only need to generate a spark and get it to the right spark plug. Modern EFI no longer uses the mechanical distributor but individual coils to deliver spark. You can use one coil for each plug or one coil for two plugs (wasted spark).

Neutering the distributor: It made sense to put the coil pack in the same place that the old distributor was located but first I had to eliminate the distributor. It can’t just be removed as the shaft also drives the oil pump.

I cut the distributor housing at the flange and shortened the shaft to sit slightly below the surface of the housing. The lower shaft is supported by an oil pressure bearing. The shaft is thrust downward by the gear geometry and there is an axial bearing surface on the gear. There is a bushing in the top of the distributor housing which I felt was unnecessary now that there is little stress on the shortened shaft.

I’ll fabricate a cover and gasket for flange.

Spark source: I needed a coil that supported 4 cylinders and had a built in igniter. The igniter isolates the high voltage circuit and provides a low voltage interface to the ECU. I chose an ignition pack from 1998-2001 Volkswagen Golf for $15.

I fabricated a mount from sheet steel to locate it near the old distributor location.

Spark delivery: I thought I was going to be able to reuse the ignition wires, but the plugs on the coil are different. The most cost efficient way to replace them was to buy a set of VW/Audi wires ($18) that were compatible with the coil pack and replace the spark plug ends with the correct plug socket ($7). Although there are specialized crimpers, you can get away with some artful work with needle nose pliers. The core is just folded back over the wire.

Ready to be hooked to the ECU!

You can see the top of the distributor flange and shaft just below the coilpack.

quarinjection

Quarinjection Fuel Pump

May 29, 2020July 1, 2020
by Christian Stanton

Modern fuel injection systems run at ~45PSI, much higher than the ~4PSI supplied by the existing mechanical pump. The easiest solution would have been an external pump hooked to the existing fuel line but this wound up more expensive than using a common submerged in-tank pump.

The existing Sonett fuel tank sits directly behind the driver and is an unusual shape for a tank. It is tall and narrow rather than flat.

The tank is ~14″ deep. After a lot of research and cost optimization later… a Chevy 1500/2500/3500 fuel pump from 1997-2000 has the correct size and fuel layout. It is an unregulated pump with a return and vent line with a roll-over valve and correct depth. The supply volume and pressure will work for the regulator and injectors I’m using. As a bonus it includes a fuel level sensor. All for $28! (see below)

The shape of the top of the tank is too narrow to fit the mounting hole for the pump and there is very limited clearance on top of the tank, so I had to recess a flange into the tank.

DO NOT WELD FUEL TANKS! (without knowing exactly what you are doing!). This tank was dry for 15 years and washed out with water based degreaser. If I had any doubt I would have filled the tank with water up to the part I was welding.

Lesson learned: After a bit of ugly MIG welding (and I ground the welds which was a mistake and then re-welded them which was another mistake), The welds were porous and would not seal up. I resorted to a coating POR-15 fuel tank sealer inside and out to seam seal the welds.

Designing the mount: Normally these pumps have a formed flange and a twist lock retaining ring. This is not something that is easily sourced without buying an entire fuel tank. (although I found something close here) I used a design used for other flange mounts with a split internal ring with captured nuts and an external ring to retain the pump. A flat flange seal (below in white) seals the pump to the tank.

Fail/Revise/Repeat: I built a split “C” ring of sheet steel and welded M5 captured nuts to it. The gauge on the steel was too light and the M5 about as small as I could weld with MIG. After installation, I realized that the large flat flange seal would not seal up with the amount of pressure that I could torque the screws to and the gap in the “C” ring left part of the flange unsupported. Lesson learned: A small footprint seal (like an o-ring) works better with low pressure flanges and non-machined surfaces.

I looked at how the original seal worked. It is a sleeve that fits the diameter of the pump with a compressible o-ring-like seal at the top. The pump hat has a second step that provides a small edge for a sealing surface. The seal did not come with the pump, so I had to source one (OEM was cheapest…$13).

I redesigned the inner ring in aluminum and used rivet nuts to provide the threads for the retaining bolts. The inner radius of the ring had to function as the outer sealing surface, so I split the thickness around two of the rivet nuts to provide half rings I could assemble inside the tank. Lesson learned: rivet nuts will distort aluminum! …I had to tediously bend the ring back to round.

New inner mounting ring with split, before rivet nuts

Final Assembly/Retrospect: During the final assembly, I used Permatex Motoseal to seal the inner ring to the tank and the threads (do not use RTV where permanently exposed to fuel!). The existing fuel level float was removed (it was broken anyway) and the one on the new pump altered to reverse the float to clear the inside of the tank. The range for fuel sensor will be reversed but I don’t plan on driving the fuel gauge directly. The original fuel feed at the bottom of the tank was soldered shut.

There was way too much fettling with this assembly! I had to manually correct for sloppy work (or sloppy corrections to good work). The inexpensive pump wound up being more expensive than buying one which included the seal and electrical plug. Ultimately, the design got there and it will work.

**Final Pump Mount (Sealed!)**
Top electrical connections are left:fuel pump and fuel level (combined) and right: tank pressure (for emissions, unused in this application).
Bottom connectors are left: fuel feed, center: vent and right: fuel return.

quarinjection

Quarinjection Basic Requirements

May 28, 2020July 1, 2020
by Christian Stanton

It would be easier to build out the Quarinjection project if I just sourced a bunch of parts designed for the DIY-EFI/Hotrod market. However, one of the challenges of this project was to design robustly on as thin a budget as possible. I sourced off the shelf items designed for high volume production cars which will make the engineering/integration more challenging, but lower the overall cost by allowing me to source from any suitable vehicle and aftermarket manufacturers.

What is needed to run an engine with Electronic Fuel Injection? It’s no different than the 60’s technology that the engine runs on now. You need the proper ratio of fuel and air and a well timed spark.

Existing Engine

Fuel Delivery – Pump: The little V4 has a physical diaphragm fuel pump driven by an eccentric lobe on the camshaft. This sucks gas from from the fuel tank and delivers a few PSI of pressurized fuel to the carburetor.

Fuel Delivery – Carburetor: The V4 has a Solex 28/32 PDSIT-4 carburetor. This regulates the amount of fuel by taking into account the temperature and load on the engine as well as the movement of the accelerator pedal. The carb functions as both ‘sensors’ and the ‘control mechanism’. It is an analog calculator.

Spark Delivery – Generation: The spark is supplied by the ignition coil. It’s similar to transformer (with a trick) to go from 12 volts to 40,000-50,000 volts. The trick is that when you remove the supply voltage from the coil, the magnetic field collapses and generates the high voltage spark.

Spark Delivery – Timing: The V4 has a Bosch distributor which regulates timing of spark based on engine RPM and engine load. It is another analog calculator.

Electronic Fuel Injection

To replace the functions of the existing engine with modern EFI, these are the elements needed:

Fuel Delivery
- Fuel Pump
- Fuel Lines
- Injectors
Spark Delivery
- Ignition
Sensors for engine load, timing and temperature
- Throttle Position Sensor (TPS)
- Manifold Pressure (MAP)
- Crankshaft Position Sensor
- Camshaft Position Sensor
- Inlet Air Temperature (IAT)
- Coolant Temperature (CLT)
An ECU computer to coordinate the sensors and delivery
- Computer Selection

CNC

Router Hacking

May 27, 2020November 2, 2020
by Christian Stanton

In starting the Quarinjection project, I knew that it involved some custom fabrication of brackets, covers, etc. One of my existing skills and resources was a small CNC router that I built a few years ago from an Openbuilds OX design. Ideally I could CNC some aluminum parts. It’s perfectly capable of cutting aluminum, it’s just a trickier material than wood.

The problem: The spindle I have is a 1hp Bosch Colt PR20EVS router. The Colt works well for routing wood but aluminum requires a much lower spindle speeds. The stock Colt router runs 16K-35K RPM. Too high a surface speed (speed of the flute through the material) to cut chips and not just stir weld the aluminum (which I did a lot of trying to get this to work). I needed a maximum minimum(?) speed of around 10K RPM to achieve a surface speed of ~350ft/min with an 1/8″ bit. (The ideal speed for 6061 Aluminum is about 280SFM)

The Colt has a built in speed controller (via a thumb dial at the top) which I figured I could modify to lower the minimum speed without making it unusable. The motor is a 110v AC brushed which have limited torque ranges, so I’d be sacrificing a bit of torque at lower speed.

I measured the speed before taking it apart. (I’m measuring off of the collet nut, but one flat is painted white).

Stock minimum speed was 13K, lower than the spec 16K.
Maximum was also lower than the spec at ~30K.

Surgery!

Hard to see, but the chip on the left is an Atmel U2008B – Low cost AC Phase Controller.
I was never able to identify the other chip, but my guess is some sort of opamp.

Time for a bit of reverse engineering… luckily a simple single sided board which was not buried in potting compound. The core of the speed control is an Atmel U2008B – Low Cost AC Phase Controller. The chip is the one on the left in the picture above. This manages speed via phase shift and provides soft start and some load correction (so as the router gets loaded the RPM stays the same). The large Triac on the heat sink at the top of the board does the load switching.

The Red thumb wheel, a 2.5Kohm rheostat, is in series with a base resistor R7, which measures 2.5Kohm. Setting 1 is 5K=13000RPM, and setting 6 is 2.5K=30000RPM.

The marking on the SMD resistor of 398 threw me for a while (3900MOhm?), but this is a EIA-96 coded resistor sloppily marked 39D=2.49K. These resistors are 0603 sized (6mm x 3mm) which is hard to show just how tiny this is (think grain of pepper sized). Resistor assortments are available and inexpensive ($0.01/ea)

Minimum speed was at 5K total resistance, maximum at 2.5K so an increase in resistance would reduce the overall speed. Replacing R7 with the next stock value of 3.3K (EIA-96 51D) for a total resistance of 6.3K. This should give me a 25% (6.3K/5K) reduction in speed overall or 10,400K RPM minimum (assuming it’s roughly linear). To jump to the next value (5.1K) that I had on hand meant the adjustable range would get too low.

A bit of finicky soldering later…

Speed reduced to 10,300RPM minimum. Maximum is now about 21K RPM.

Success! The router doesn’t seem to be bothered by the change and runs normally at the lower speed. Off to cut aluminum!

Afterthought: I will eventually buy a true CNC spindle for this rather than mucking around with modifying a router, but for $8 I was able to get this to work.

quarinjection

Quarinjection Project

March 31, 2020July 1, 2020
by Christian Stanton

After having an assumed case of Covid-19 early on (in March) and then work projects going on hold, I needed a project I could work on daily to keep me sane.

I was cleaning my tiny shed and re-discovered 2 Ford Taunus/Cologne V4 engines from old SAAB projects. One is a 1.5L from a 1968 Saab 96 and the other is a 1.7L from a 1974 Sonett.

I spent a few evenings getting the 1.5L to run. Dead simple, just 12v to starter and coil and a hose to a fuel supply.

While that amused me for a few hours, I began to think of improvements. Which led me to a something I’ve been itching to do for a while… a full modern electronic fuel injection system.

Research ensued and I determined it was feasible within a certain budget target (~$750). I started with basic principles to reduce cost (although not complexity):

Use an Open source EFI package
Use stock parts, rather than universal or hot rod parts
Minimal “bench” running config
KISS

And away we go…