Servicing Vintage Electronics
Vintage electronics have their own charm; for some its nostalgia, for some its antique value and for some its just the way they work and perform.
These systems, typically between the 1950’s to the late 1980’s are most the sought-after for their build quality, sound quality and performance. There have been several technological improvements in these systems over time, especially in the department of Signal to Noise Ratio (SNR), thanks to better quality of internal components, wiring layout and PCB (printed circuit board) design.
On receiving these kinds of machines for service or restoration, there are a couple of things to keep in mind and follow, which are mentioned below:
1. Is it worth it?
Now this is a very personal matter. Depending on the kind of restoration required, one has to figure out a budget on the restoration and the amount of work required. Also, the willingness of the customer to spend, incase the job is a commercial one. This matter is subjective to cost of spares, labour hours and time. Being a service engineer as well, I have realised that one kind of slacks off while working on a personal project, while moving much quicker on a commercial one 🙂 Practically speaking it should be a balance of time management, availability of spares and budget.
2. Cleaning up
Upon receiving any equipment, the first thing that one must take into consideration is performing a through cleanup. This is very important, as dust can hide a lot of issues related to PCB and component damage, etc. Having an air blower in the shop is a good thing. Ideally all the dust should be blown off in an open space, rather than at the work bench. This will unnecessarily fill up your work space with dust and if you suffer from an allergy, then God help you. For small tighter spaces like in between components on the PCB, potentiometers and switches, one can use a compressed air can with a fine nozzle for better results. At the end of it all an internally clean unit will enable you to get more accurate test results.
3. Before you plug in
If the unit has been in operation, then it would be quite safe to plugin to the main supply. Though it would be advisable to use an Isolation Transformer (1:1) as a safety precaution, so you are totally isolated from the mains while working on the unit. If the unit hasn’t been operated in a while, its better to plugin through a series lamp between the unit and the Isolation Transformer and then to the mains. This way, if there are any shorts in the power supply unit or high current issues, the series lamp will take on the extra load and save the unit from any further damage. Make sure the mains plug of the unit is in good condition and is making a good connection with the power outlet. A loose plug-socket connection can cause arcing, which can be a bad thing for older equipment.
4. Testing and requirements
All components i.e. capacitors, resistors, ICs (integrated circuits), transistors, diodes, transformers, switches, relays, vacuum tubes, etc. need to tested for their performance. Each component has its own value which should match while testing them out using the necessary tools.
A good quality Multimeter which is capable of measuring capacitance, an ESR (equivalent series resistance) meter, an Oscilloscope, an audio tone generator, and ofcourse a good quality tool kit are the necessary tools required for working on such equipment. ‘Fluke’ and ‘Mastech’ make very decent quality Multimeters. Siemens, Blue and Philips are very good with Oscilloscopes and tone generators. Stanley make excellent tool kits for various applications.
While testing out electronic components, it is quite common to find faulty capacitors, as they are the first of the lot to fail over time. While testing Capacitors, one must ensure that the present value shouldn’t differ from the original value more than +/- 2 to 5 %. Otherwise they must be replaced. Resistors, Transistors, Diodes, Transformers, ICs generally do not fail, unless they have encountered a Short or a Surge in the circuit. The contacts in the relays do wear out over time. They should be tested to check continuity and coil resistance. Vacuum Tubes do wear out over the years and now-a-days, since Tube Electronics are back in the market, procuring them shouldn’t be a challenge. Once you have tested out the components and voltages in the equipment, its a good practice to make a note of components requiring replacement, by making them using a fine tip black marker. This is something which I am very particular of.
Unless one has several decades of experience working on these machines, its a good practice to refer to the Service Manual and Schematics of the unit, which can be a life saver for you. Service Manuals and Schematics for most equipment are available on the internet for free or a download fee.
5. Hunt for spares
There may be a situation where the original component may not be available due to its age, but there are several manufacturers who can supply similar ones of the same or equivalent value. This is very common with capacitors and transistors. Philips, Siemens, National Semiconductors, Toshiba, ELNA components are excellent choice for replacements. From the Indian stable there is Keltron which is ‘okay’. I usually order my spares from Mouser and Project-point. Never faced an issue with the genuineness or quality of spares. Drive-belts, Idler wheels, Pinch Rollers, Tape Heads, Phono Cartridges will need to be imported from a reliable source or manufacturer if available.
6. Soldering etiquette
Soldering is an art which requires precision and patience. Not too much and not too little is the golden rule here. Use a soldering iron between 20 – 40 watts with a good quality silver solder wire, avoid tin solder and make sure to use some flux paste as well. A temperature controlled soldering station with a fine tip and soldering paste is very useful for Surface Mounted Components. While soldering, wait atleast 5 minutes for the iron to heat up or else there may be a possibility of a dry solder. Touch the solder wire to the iron tip and component lead while soldering. Do not let the wet solder bubble up, that can damage the board or cause other issues. Extra leads can be trimmed off and reused for jumpers. I am very happy with the ‘Goot’ soldering iron. There are manufacturers like Stanley, CSI who make good soldering Irons and Stations. From the Indian stable there is Soldron which is quite decent.
7. Testing again and a final cleanup
Once all is ready, power up the unit and let is warm up. Make sure nothing is burning, no unwanted burning smells etc. Check all the voltages at the necessary test points, check for current draw on the power supply unit and if all well, you’re good to go!
Give the unit a clean up, especially the front faceplate. Be gentle of not to scrape off the silk screen print on the faceplate. Always use a microfible cloth with a mild cleaning agent. Avoid harsh chemicals like benzene and acetone on the faceplate. Clean the potentiomenters and swiches with an electonic contact cleaning spray. CRC make decent products for service. Use a silicone grease for all mechanical linkages and gears for smoother performance.
Give a final overall look and if satisfied, don’t forget to smile 🙂