Hello,
Having recently (and quite rightly) been advised to start right from the beggining for learning electronics, so there are no vital holes in my knowledge I've started working through th 'Make: electronics' book, which seems good a suits my learning style well.
To accompany this I have just bought an old (about 1985) Pioneer sg550 graphic eq to play with. The reasons I chose this is that, I wanted to try an eq in my system... although unfashionable, I want to decide for my self whether or not they are good or bad. The circuit board lay out is very open and relatively simple, so easy for me to practice soldering on... and the key reason it was cheap, so if I mess it up it doesn't matter to much.
But, assuming I wont destroy it, I would like to improve it. I have a rough plan for this but need some advice.
1. Test all resistors are still at correct value
2. Replace all electrolytic capacitors - Should I be looking to upgrade capacitors? If so which capacitors will most benefit an upgrade... those closest to power source, inputs, or outputs?
3. Resolder all joints
4. Replace input and output sockets
Thats my plan for now, Is there anything I should add, take away or do differently?
I also have a few other ideas to extend the project. The enclosure has loads of space inside, so I could try to design and build a seperate power supply board. And how about discrete op amps... I don't really know anything about these yet, as opposed to a little chip having a circuit board of bits could be fun to build. What do you think?
FYI, I can't get a schematic diagram.
Having recently (and quite rightly) been advised to start right from the beggining for learning electronics, so there are no vital holes in my knowledge I've started working through th 'Make: electronics' book, which seems good a suits my learning style well.
To accompany this I have just bought an old (about 1985) Pioneer sg550 graphic eq to play with. The reasons I chose this is that, I wanted to try an eq in my system... although unfashionable, I want to decide for my self whether or not they are good or bad. The circuit board lay out is very open and relatively simple, so easy for me to practice soldering on... and the key reason it was cheap, so if I mess it up it doesn't matter to much.
But, assuming I wont destroy it, I would like to improve it. I have a rough plan for this but need some advice.
1. Test all resistors are still at correct value
2. Replace all electrolytic capacitors - Should I be looking to upgrade capacitors? If so which capacitors will most benefit an upgrade... those closest to power source, inputs, or outputs?
3. Resolder all joints
4. Replace input and output sockets
Thats my plan for now, Is there anything I should add, take away or do differently?
I also have a few other ideas to extend the project. The enclosure has loads of space inside, so I could try to design and build a seperate power supply board. And how about discrete op amps... I don't really know anything about these yet, as opposed to a little chip having a circuit board of bits could be fun to build. What do you think?
FYI, I can't get a schematic diagram.
I work on lots of broadcast gear, some from the 70s and 80s. You will find that unless resistors were overloaded, they 'drift' hardly at all. Capacitors EXCEPT for electrolytics are likely to be fine and any inductors (coils) are fine too.
The electrolytic caps however may range from nearly perfect to total trash. You can look up capacitor opinions and I think you'll find good things about Elna Silmics. Personally I buy Panasonic FM or FC series caps for longest life and highest ripple current (lowest ESR). The FC caps are sometimes called FC Gold because of the color of the ground band - they have no gold in them.
Has anyone played with organic polymer caps for audio? They have really high ripple currents and are excellent in class D amps and switching power supplies.
I only use gold connectors if BOTH connectors (male and female) are gold to avoid dissimilar metal interactions. IE I have no gold connectors.
Re-soldering the board might help particularly if the connectors , pots and switches solder directly to the board - mechanical stress fatigue cracks. If there are cracks I remove the old solder and use new.
I've been using Multicore solder 60-40 or 63 37 for over 30 years and being a bit nuts, I have 2 Metcal irons. They're very expensive new but can be had on eBay if you shop well. Once you use a Metcal everything else is a soldering tusk. If you can't get a good connection with a Metcal, take up a new hobby.
Tek scopes, Fluke meters, Xcelite screwdrivers, nutdrivers and Allen drives, Klein pliers. Wiha is good stuff too. If you're serious, the good tools will last a long time and be worth the price. An OptiVisor helps if you're doing surface mount or you're just plain old.
G²
The electrolytic caps however may range from nearly perfect to total trash. You can look up capacitor opinions and I think you'll find good things about Elna Silmics. Personally I buy Panasonic FM or FC series caps for longest life and highest ripple current (lowest ESR). The FC caps are sometimes called FC Gold because of the color of the ground band - they have no gold in them.
Has anyone played with organic polymer caps for audio? They have really high ripple currents and are excellent in class D amps and switching power supplies.
I only use gold connectors if BOTH connectors (male and female) are gold to avoid dissimilar metal interactions. IE I have no gold connectors.
Re-soldering the board might help particularly if the connectors , pots and switches solder directly to the board - mechanical stress fatigue cracks. If there are cracks I remove the old solder and use new.
I've been using Multicore solder 60-40 or 63 37 for over 30 years and being a bit nuts, I have 2 Metcal irons. They're very expensive new but can be had on eBay if you shop well. Once you use a Metcal everything else is a soldering tusk. If you can't get a good connection with a Metcal, take up a new hobby.
Tek scopes, Fluke meters, Xcelite screwdrivers, nutdrivers and Allen drives, Klein pliers. Wiha is good stuff too. If you're serious, the good tools will last a long time and be worth the price. An OptiVisor helps if you're doing surface mount or you're just plain old.
G²
I have to admit, I'm quite partial to nice tools. As this is a hobby, it has to be enjoyable and working a nice kit only increases the pleasure of the task.
I can't see a brand on my current electrolytic caps, but I will replace anyway.
Some bits on my list, like checking resistors and resoldering the board are not essential, but I will do anyway to practice my skills.
I can't see a brand on my current electrolytic caps, but I will replace anyway.
Some bits on my list, like checking resistors and resoldering the board are not essential, but I will do anyway to practice my skills.
The old Edsyn Soldapullt (solder sucker) is very effective at removing solder. As long as you don't overheat the board and lift the pads you should be OK. I'm also a big fan of cleaning the flux from the boards. Aerosol can stuff works but is pricy. I use MG Chemicals in a squirt bottle using cotton swabs. Johnson & Johnson have hollow plastic sticks and will hold a little cleaner when you squirt the remover directly into the swab. I rarely shoot directly onto the boards because it doesn't work much better and just wastes it.
Beware that older boards with acid damage from leaky caps can get fragile even with good tools.
Good luck
G²
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