Jun 29, 2010

Viewsonic ve710b

Picked up several monitors from a fellow who said they either worked for a few minutes and shut off or took a really long time to turn on, both signs of bad capacitors. Monitors are in excellent physical condition.

First here is the ve710b which is a 17", 1280x1024 max res, very clean looking monitor with a thin bezel, - typical office monitor, would be good for multiple monitor setups.

The first one of these I took apart took me forever as I didnt know how to take it apart, now I can recap one of these in less than 15minutes. You start by prying off the silver plastic covers over the screws that hold the base on (fold it back for easy access).

After removing the base and the front bezel (which clips to the back cover) you can unscrew 4 screws and remove the back cover as well.

Here it is flipped over and the back cover removed, you have to remove the little covers to disconnect the backlights and the lcd, then unscrew the four small screws holding everything to the lcd panel.

Here is everything with the panel removed, of all the ve710b's that I repaired none had problems with the display board so all you have to unscrew is the power board on the right (though you might have to unscrew a couple to get the power cable loose from the video board).

Front side of the power supply, you can see the bad capacitors by their bulged appearance. They were 2x 470uf 16v, 2x 1500uf 10v, 2x 1500uf 16v, and 1x 1000uf 10v.

New Nichicon capacitors installed, the 1000uf 10v was replaced with a 25v capacitor as I was all out of smaller ones.
Because of how many of these ve710b's I repaired I can attest that their were two different power supply versions used in this model, the second uses 4 of the smaller single bulb backlight connectors (manufactured July 05 and after) and in place of 2x 1500uf 10v = 1x 1000uf 10v, 1x 1000uf 10v = 1x 470uf 16v, 1x 1500uf 16v = 1x 470uf 25v - (oddly enough every time I replaced this capacitor with a new one the monitor would not work right even with all new caps everywhere else, so I ended up completely removing the 470uf 25v cap and have yet to have trouble with it missing)

I will get working pictures up when I post on the next monitor = Viewsonic va921b

Jun 22, 2010

1974 CB200T

Here are a few pics of a project I started over 10 years ago and let sit mostly due to lack of knowledge.
I currently have the motor torn down and have been cleaning the cast aluminum.

Cylinders, timing tensioner and pistons

Cylinders Removed, rods visible

Cylinders, cooling fins

Head with intake valves visible

Clutch cover

This motor was originally torn apart because I let the tension mechanism get too loose and it fell apart. I intend on installing new rings, oil seals, checking valves, and all new paint (original motor only had paint on side covers) I will also be cleaning thoroughly and checking for wear (not much as this motor had very few miles).

Jun 21, 2010

Electric Fencer - Southern States model 700

My dad gave me this one to work on and the broken rivets, disconnected wires and missing fuses made it quite evident that someone had attempted to fix it previously.

Upon pulling it apart I noticed this:
Here being the front of the same board
The circled burn mark is under the large thyristor, so something was either jumping across there or it was once a good connection that is now burned and open.

I called my dad (who had several of these yet declined to send me more than one) and he said that the burned area is supposed to be an open and not a connection.

So I wired in some fuses and hooked everything up and you could hear the transformers working and then shut off as things got hot, but never did anything click and work as it is supposed to.

I pulled the large thyristor and the two outside pins are closed in both directions and everything is open to the middle pin in all directions. I believe in a good working thyristor the middle pin is a gate and should be closed to one of the side pins and the two outside pins should act as a diode.
(the thyristor in my fathers fencer (also not working) acts exactly the same) So either both our thyristors are bad or there is some other problem I am overlooking.

Jun 18, 2010

So I'm creating this blog to create a sort of history of the different projects I do.
Hopefully I can get something up soon.