Defender CT PS. Really need some help here.

vintagegamer

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I have a Defender CT with its original PS and it's really tired. I really wanted to go the route of using a switcher to be more reliable, but most people here swear on rebuilding the original so I have tried that first and failed. Here are the symptoms prior to rebuild:

1. lighting on the CT lights, goes out after approx 5 min (this is bc the 2A SB fuse at location F5 burns up)
2. the game powers up but after about 20 min goes into a repeating rug pattern (mainly because the 1A SB fuse at location F4 burns up)

I bought the Bob Roberts rebuild kit which included all replacement caps, a replacement part for the heatsink (transistor?), and 2 replacement IC's and sockets for them. I swapped all of those parts out and the issues described at the points above persist.

I have reflowed all of the solder at the header pins. The +5 light also tends to go off unless I put my hand under the board in the midsection of the PS and push it up a little, then what ever connection is broken connects and the +5 light comes on. I can't find any broken traces or damage on the board in that area.

Please tell me what I need to do next. I love this damn CT until the fuses burn up. :(
 
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I have a Defender CT with its original PS and it's really tired. I really wanted to go the route of using a switcher to be more reliable, but most people here swear on rebuilding the original so I have tried that first and failed. Here are the symptoms prior to rebuild:

1. lighting on the CT lights, goes out after approx 5 min (this is bc the 2A SB fuse at location F5 burns up)

Fuse F5 is a 5ASB fuse according to the schematics.

2. the game powers up but after about 20 min goes into a repeating rug pattern (mainly because the 1A SB fuse at location F4 burns up)

The most common reason for this is a bad BR2. If you have the schematics check the voltages at the test points against the voltages on the schematics. If you need the schematics, you can download them in PDF form from arcarc.xmission.com.

I bought the Bob Roberts rebuild kit which included all replacement caps, a replacement part for the heatsink (transistor?), and 2 replacement IC's and sockets for them. I swapped all of those parts out and the issues described at the points above persist.

I have reflowed all of the solder at the header pins. The +5 light also tends to go off unless I put my hand under the board in the midsection of the PS and push it up a little, then what ever connection is broken connects and the +5 light comes on. I can't find any broken traces or damage on the board in that area.

Try resoldering the leads on the top of BR1. The holes are supposed to be plated through, but they are frequently damaged. Soldering the top of the pads as well as the bottom frequently fixes this problem.

Please tell me what I need to do next. I love this damn CT until the fuses burn up. :(


ken
 
Fuse F5 is a 5ASB fuse according to the schematics.



The most common reason for this is a bad BR2. If you have the schematics check the voltages at the test points against the voltages on the schematics. If you need the schematics, you can download them in PDF form from arcarc.xmission.com.



Try resoldering the leads on the top of BR1. The holes are supposed to be plated through, but they are frequently damaged. Soldering the top of the pads as well as the bottom frequently fixes this problem.




ken

question about the plated through holes... is it possible to run jumper wire through the hole and solder it to both sides to get the same effect? if it's burned up I mean.
 
F5 is a 5ASB
F4 is a 1ASB (Correction: BR3 is in circuit with F4 not BR2)

R15 should NOT be present at all, and there should be a zero ohm resistor at W1

You are putting a 2ASB(F5) fuse in a location that requires a 5ASB(F5) fuse. When that 2ASB(F5) fuse blows, it causes the 1ASB(F4) fuse to blow.

In short, put in the correct fuses and make sure the board is jumpered for a CT not an UR. (i.e. no resistor at R15 and a zero ohm resistor at W1)
Dok
 
If I remember correctly I got the fuse sizes out of the schematic in the Defender CT manual. I will look again tonight and advise.
 
Try resoldering the leads on the top of BR1. The holes are supposed to be plated through, but they are frequently damaged. Soldering the top of the pads as well as the bottom frequently fixes this problem.

THIS!!!
I can't tell you how many times I've fixed these power supplies for my customers by doing this (that is, after they rebuild it theirself....and it still wasn't working).

Edward
 
Since I can't work on this until tonite and don't have a schematic in frt of me at the moment (I'M IN THE DAHHHHHHHHHHHK HERRRRRRRRRRRRE-Scent of a Woman), is BR1 actually the bridge rectifier (thus the br) shown in the pic that I attached with the yellow circle? And if it *is*, I'm a bit confused as to how you can solder the top leads? Is there enough gap there between the square part and the board itself to get the iron into?

PS: the pic is not *my* PS, just a pic I grabbed from the interWebs........ :D

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question about the plated through holes... is it possible to run jumper wire through the hole and solder it to both sides to get the same effect? if it's burned up I mean.

You can if the pad is big enough. Basically you will need to drill a new hole and then just fit a bare wire through the hole and solder both sides. Then clip the excess wire off.

If I remember correctly I got the fuse sizes out of the schematic in the Defender CT manual. I will look again tonight and advise.

Check the fuse sizes in the Stargate manual (the early one that still uses the Defender PS board). The Defender manuals are full of typos.

Also be aware that the numbering for the fuses is not completely sequential (F5 comes before F4). In order from top to bottom:

F1 = 7ASB
F2 = 7ASB
F3 = 4ASB
F5 = 5ASB
F4 = 1ASB

ken

PS: Dok you were right. I typed BR2 when I meant to type BR3. I think it's time to take my fingers in for their 50,000 word checkup. ;)
 
Since I can't work on this until tonite and don't have a schematic in frt of me at the moment (I'M IN THE DAHHHHHHHHHHHK HERRRRRRRRRRRRE-Scent of a Woman), is BR1 actually the bridge rectifier (thus the br) shown in the pic that I attached with the yellow circle? And if it *is*, I'm a bit confused as to how you can solder the top leads? Is there enough gap there between the square part and the board itself to get the iron into?

PS: the pic is not *my* PS, just a pic I grabbed from the interWebs........ :D

Yep. That is the one. It should be slightly raised (usually it is about 1/2") off the circuit board. If it has been mounted flush that is not good. It will overheat and if it is in the metal case (like the one in the picture) it may also create a short if it contacts the top pads.

ken
 
Thank you VERY MUCH for all of the help and input to everyone! I will check all this stuff out tonight! Woot!
 
Ken, I knew where you were going with it. You also reminded me that on the CT's the -5vdc (F4) fuse is tied to the F5 fuse.
 
Since I can't work on this until tonite and don't have a schematic in frt of me at the moment (I'M IN THE DAHHHHHHHHHHHK HERRRRRRRRRRRRE-Scent of a Woman), is BR1 actually the bridge rectifier (thus the br) shown in the pic that I attached with the yellow circle? And if it *is*, I'm a bit confused as to how you can solder the top leads? Is there enough gap there between the square part and the board itself to get the iron into?

They were mounted very low from the factory (and difficult to get under). If it's been replaced (by anyone with common sense;)), it should be mounted much higher (as Ken stated). The more it can ventilate, the better.

Edward
 
Well, it looks like the PS will be going to Dokert's house. :( I swapped out the fuses at F4 and F5, and also checked the bridge rectifier to possibly solder the top leads if I could. If a perfect bridge rectifier is mounted about .5" over the board all of the way around, consider mine a total crap job (I didn't put it on there). It's mounted on a 45 degree angle with 2 of the tabs being close to the board and 2 up in the air.

I checked all of the solder on the bottom, and thought I'd be good to go. I put the PS back in place and upon power up I now get 3 LED's lit on the PS, but I also get the 4 LED's of death lit on the ROM board. I checked voltages at the ROM board and the main PCB and all that should be getting +5, -v, and 12V are getting them as they should (at least as best I can tell).

What sucks is initially I was able to get the game working, I just had no CP lights. Now I have CP and coin lights, and no working game. I think this was Williams' way of making sure average laypeople didn't try to continue maintaining these games on their own. :( I am so bummed right now.
 
Don't give up. One of the most common fixes is to carefully take the ROM ribbon connector off and recrimp it (the MPU board side). Because the !#$%$% male connector is missing the cams to pry the female side loose, everybody just grabs the ribbon and pulls. This will cause the wires to come loose in the connector.

I pop the connectors by using a small flat bladed screwdriver on the small edge of the connector between the plastic tabs on the male connector and dig a corner of the screwdriver (you could use an icepick to do the same thing, I just usually have a small screwdriver) and lift up the connector a little. Repeat on the other side until the connector is loose. You are not using the screwdriver to wedge in and pry, just dig a corner into the connector and lift.

Once you have it free go clamp it into a vice, gently. You don't want to press it too hard, just enough to squeeze the wires back down onto the IDC blades. There is a good description of the process here: http://www.arcadesolution.com/ribbon.html

You can also check for the correct voltages at the 4 corners of one of the RAM chips. You should get -5, +5, +12 and ground at pins 1,8,9 and 16, IIRC.

ken
 
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