Resources

The Work Bench

 

Sunday
Sep092012

Desoldering Capacitors with the Hakko 808

Here is a short video that clearly shows how well the Hakko 808 will desolder not only capacitors but IC packages as well.  I think that sulder suckers and solder braid have their place on the bench, but if you value your equipment there's no reason to risk it by overheating solder pads when removing parts.

 

Monday
Aug132012

Marantz Main-out Pre-in  Jacks

Most owners on Marantz equipment are familiar with the Main-in  Pre-out jumpers on the back of their receivers and intergrated ampifiers.  

These little jumpers are often missing from units and I have received "non-working" models which just need to have the jumps put in place.

Something that doesn't come up very often is the fact that there are two different size on jumpers assemblies.  Most models like the Marantz 1060 intergrated amplifier and almost all of the receivers use a jumper with a pin spacing of 15mm center-to-center.  Older models like the model 30, 1200, 1200B use a smaller jumper with a spacing on 10mm center-to-center.

These smaller jumpers are more difficult to find, so when you see them, buy them.

Sunday
Aug122012

Jackson 810 Transistor Tester Gets a Little Maintenance 

I wanted to use my vintage Jackson 810 Transistor Tester on Saturday and when I went to set it up I discovered that one of the input lead sockets was damaged internally. I could not get the test lead to slip in, so I decided to replace the socket.

I searched around and found a Pomona 3760-02 Binding Post that would fit the panel nicely. I removed the old socket and enlarges the hole in the panel with a Unibit and mounted the Pomona binding post.

 

Since I had the 810 opened up, I though it might be a good time to replace the 3 capacitors on its single circuit board. The Jackson 810 was made in 1967 and the board is laid out for axial caps, however there was a single radial cap mounted on the board. During the recap I discovered that the through holes in the board were a smaller diameter than the leads on my new caps.

The original capacitors have a lead diameter of 0.48mm and the new capacitors have a lead diameter of 0.77mm.

I used a set of PCB drills to enlarge the through holes to 0.82mm. I enlarged the holes in a 2 step process, first with a drill just slightly bigger than the original hole, then to the final size. You have to be sure to drill from the solder side of the board to make sure you don't push the copper pad of the board with the drill bit.

The best way I have found to twist the drill bits is to wrap some masking tape around the drill bit shank and just twist it with your fingers. You don't need any really pressure on the bit, just twist it carefully and slowly.

After the 810 was reassembled it was in much better condition and even though it's old, it works well for some applications. One nice feature is its build in signal generator which outputs a 3 volt (rms) sine wave which can be used for signal tracing in circuits.

I scanned a copy of the original Jackson 810 operating manual in the Photo Gallery.

 

Tuesday
Jul032012

Marantz Model 32 Power Supply Project

I've decided that a worthwhile project will be to design a complete standardized rebuild for the relay – rectifier board use in early Marantz amplifiers and integrated amps. This board in various different configurations is used in models 30, 32, 1200, 1200B, 240 and 250's.

The different versions exist to suit the needs of each particular model they are used in. The board in the model 32 amplifier is the simplest version, which makes it a perfect candidate to be used in this trial.

These early boards have antique relays that should be replaced, old capacitors that are almost always bad and a single Tantalum cap which needs to updated before it blows, several high wattage resistors that always show signs of heat stress and 3 transistors that in their original forms don't exist any longer.  The bridge rectifier which often fails will be replaced along with the two diodes and all of the resistors.

The transistors are models SS47 and 2- SPS439 all of these are originally Motorola parts which are no longer available. Substitutes for the SS47 seems to be easy enough, but finding information on the SPS439's is almost impossible. I have been working on choosing proper substitute transistors and I will be testing them in this trial.

Some of the original parts that have been removed.  New replacement parts have been ordered and are on their way. 

Friday
Jun222012

Only Lite Cleaning Required

Sometimes a circuit board will only require light cleaning to make it acceptable and easier to work on. There are many different ideas for cleaning circuit boards, I usually think the simplest method is to brush away the dirt and dust build up with a soft brush.

I remember reading a recommendation that using a shaving brush was a good choice for this type of cleaning. I also remember how expensive shaving brushes were when I went looking for one. One day I was out with my wife and we went into our local Sur la table cooking store for something she needed, while I was looking around I ran across a huge selection of pastry brushes.

Pastry brushes are inexpensive and come in a variety of shapes and sizes and they are perfect for dry cleaning circuit boards. My usual method is to simply use a vacuum and carefully vacuum away the dirt and dust. These brushes also work well for general cleaning of you equipment, their soft bristles won't scratch the finish and can reach into the small recesses of your gear.