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This is a general list of soldering tips, tricks, and advice that was condensed from several FD Odometer / Speedometer repair posts. It is not exclusive to the FD odometer repair but can be applied to other electronic circuit boards for the FD, FC, and FB/SA22.
Recommended Soldering Tools:
1. Soldering iron, 45W (ensure fine tips are part of the kit)
2. Solder, 60/40 rosin-core, .032" diameter
3. Solder flux (paste or fluid)*
4. Acid brushes (set of 3 is fine)
5. Cotton swabs (use as a substitute for acid brush)
6. Solder wick or solder sucker (or use Item 7)
7. De-soldering Iron, 45W (use as a substitute for solder wick/sucker)
8. Isopropyl Alcohol (any percentage is fine, over 90% is preferred)
* - Specifically use electrical solder flux. Do NOT use flux for (copper) plumbing; it is different!
Soldering Advice:
1. Clean area with alcohol first & then after the solder joint is completed.
2. Apply heat to the solder then let it flow onto the joint.
3. Use solder flux. Solder flux acts like a wick for solder. Solder and flux is like Mary's little lamb... "..and everywhere the flux went, the solder was sure to flow."
4. Never re-use (re-flow) a cold solder joint. De-solder the cold joint and then apply new solder.
5. Electrolytic capacitors are polarized. A stripe on the capacitor indicates the negative lead. The placement of the poles on the cap make a big difference in the circuit. If the polarity on the cap does not match the rest of the circuit, then damage to the cap/board may result or the cap will never operate properly.
6. Typically, replacement caps have a longer Positive lead than the Negative lead. That is another physical reminder to observe the cap’s polarity.
7. Electrolytic caps contain an electrolyte (which is why these old caps leak).
8. Observe the polarity on diodes. In a schematic, a diode looks like this: -->l-- Physically, the diode will have a black line at one end. The black line on the diode corresponds to the schematic symbol. The "arrow" on the schematic points to the negative (-) material and the black line indicates the same (negative material/leg).
9. Examine solder joints for solder bridges (when solder from one joint makes contact (or touches) another solder joint).
10. When a component is desoldered then removed, take a close-in photo of the eyelets (front and back sides). The zoom function on a cell phone’s camera works wonders here.
11. Some component leads require 45* bends to be installed in a circuit board. The best way to do this is to grab a pair of needle nose pliers and bend a lead out 45* near the base of the capacitor. Then slide the pliers down a tad to bend the lead back inwards 45*. Then repeat for each leg. Placement of the inward bend will determine the height of the capacitor. See the photo.
Photo credit goes to Gen2n3, from his post: https://www.rx7club.com/3rd-generati.../#post12165092
12. When soldering components, ensure solder flows to the top of each lead. You should see a small cone shape at the backside AND the front side of each lead's eyelets. If you don't see that then desolder that joint and then reapply new solder.
13. Avoid using too much solder on an eyelet. The expression “the bigger the glob, the better the job” will cause problems. Excessive solder may cause problems later; such as difficult to desolder, create excessive heat, and/or overflow to adjacent contacts may cause short circuits.
14. A 20W soldering iron is too low for this type of project. The 20W iron may not be transferring enough heat or the lower wattage allows for the solder to cool much faster which may cause poor solder joints. A 45W iron will ensure proper heat transfer and keep the solder flowing more than the 20W iron. This would provide better soldering results.
15. If too much heat is applied to the eyelet on a circuit board then the eyelet may lift. This will prevent proper electrical contact of the component to the rest of the board. Alternately, a lifted eyelet may result from remaining solder in the joint (low heat from the solder iron), pulling the component from the board, and/or not using flux to aid in solder removal. A lifted eyelet may look like a simple repair but is complicated with broken solder runs. An at-home repair is ill advised for an amateur. A lifted eyelet repair should be reserved for a skilled solder tech.
16. Inspect the circuit board for possible broken traces (runs). Use a flash light under the board to examine the traces embedded in the circuit board. Dependent upon its location, a trace repair may be possible. See photos for sample trace breaks.
17. If necessary, install jumper wire(s) between broken traces from Item 16. Use a small gauge wire, approx 20AWG to 24AWG in size. Shape the jumper wire around components, never go over them. Tape may be used to hold the wire in place but avoid using it at the ends because it may interfere with the soldering process.
18. Jumper wires are considered components and should therefore be soldered on the component side of the circuit board.
19. After installing a jumper wire, document the repair on a schematic and keep a copy with the car’s records. In the case of the Speedometer circuit board, Body CPU, etc… no schematic exists. Take photos, print them to document the repair and keep a copy with the car’s records.
20. Do additional research on proper solder techniques. Watch YouTube videos and read information from other websites to increase your knowledge. The following links should answer more questions than this quick guide may provide.
Note: This 3.5min video on basic solder techniques did not use flux. However, flux acts like a catalyst for solder to flow through joints. It significantly reduces the time to apply solder.
Cheers,
George
Last edited by Gen2n3; 12-13-17 at 07:45 PM.
Reason: Minor spelling mistakes.
Thank you both for the compliment. I hope this will help the DIY-er gain the confidence to repair electronic projects.
Dale, you are correct! Soldering isn't too hard considering other tasks on the FD. It does require patience, preparation, a steady hand, timing, and FLUX!
I'll be glad to offer more advice or possibly help make solder repairs. PM me or post in the relevant thread (i.e. FD Speedo troubleshooting or logicon threads). If the project is within my skill set then I may be able to help.
Sorry about that , I wanted to put a thumbs up but for whatever reason that appeared .
You did some amazing work on other threads & I have nothing but respect.
An advice that was told to me when soldering is to keep it inside the cabin & use weather-tight connection outside because the soldered joint is succebtable to corrosion.
12-13-17, 02:36 PM
General Soldering Tips-Tricks-Advice
