| Author |
Message |
    
Virginiak9
| | Posted on Sunday, July 14, 2002 - 9:21 pm: | 
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My power supply has finally gone on my original Galaxy Saturn Turbo base. Loud buzz and then immediately pops the fuse. Sounds like a shorted ic or diode. Any suggestions or help as to where to start would be appreciated.
Thanks in advance. |
Ss8541
| | Posted on Monday, July 15, 2002 - 12:01 am: |
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loud buzz and then fuse blows, hhhmmm, could be the electrolytic filter cap is leaky. this would cause it to not filter out the ac hum, and cause the fuse to blow after the 'load' of being -on- has set in. i'm sure there are other possibilities but this is the 1st to come to mind. |
307
| | Posted on Monday, July 15, 2002 - 6:51 pm: |
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In most cases I have ran into there is a diode bridge on the chassis that shorts one of the internal diodes either on the positive side or negative side. It is a 25 amp bridge and you can get them at Radio Shack. My second thought is the regulators on the back of the heat sink under the small cover. I have seen them die due to stress caused by the massive peak out...
307 |
Honkytonkman593
| | Posted on Monday, July 15, 2002 - 7:36 pm: |
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speaking of galaxy turbos i can get a turbo that someone changed the finals from 2290s to 2879s! is this a possible thing or will it die right out, ive never seen any others like it or heard of anyone doing this so is it possible and what would or could it get out of it? id say its the 25 amp bridge also for the problem, my power supply did that and thats what it ended up to be.....later |
Tech671
| | Posted on Monday, July 15, 2002 - 8:07 pm: |
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2879 changeover usually means they just slapped them in there with no mods to the input transformer, not changing the output transformer completely, and that usually yields more stress on the tfmr, not as loud, and about a 10% gain in power. |
Virginiak9
| | Posted on Monday, July 15, 2002 - 10:42 pm: |
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Thanks for the help everyone.
307, Could you advise the location of the diode bridge inside of the radio. It sounds like that is most likely the problem. I took a quick look around this evening but could not locate it. Thanks again to everyone for the help. |
307
| | Posted on Tuesday, July 16, 2002 - 1:15 pm: |
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It is has been placed in several different locations depending on the year of the radio. The last place I remember it being was in front of the big filter capacitors towards the front of the radio. It was held on to the chassis by a single screw right in the center. It is about 1-1/2 square and has 4 posts on it. I wish I could remember more...Anyone else?
307 |
2600
| | Posted on Thursday, July 18, 2002 - 3:49 pm: |
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The bridge rectifier in the Turbo is under the linear shield cover at the top right (looking from the front) of the rear heat sink. You have to detach the heat sink screws and remove this shield to access it. It tends to blow NOT from excess current draw, but from heat. Without a fan, the heat sink on this radio routinely overheats. Folks will tell you to substitute a 35 Amp or 50 Amp bridge, but melting temperature is still melting temperature regardless of the current rating. Later Turbo and 2990/2995 radios will have a pair of double-diode parts side-by-side in place of the original single bridge. This spreads the heat load on that part of the radio a little better, but beware their bad habit of placing TWO mica insulating washers under these dual-diode parts. One of the two will have a normal layer of heat-sink compound on it, but the second one will be put on DRY, with NO grease. Go figure. Removing the second (DRY) mica insulator and making sure enough compound is in place is a routine 'anti-suicide' measure for this radio. Also, the factory will place this second 'dry' mica under the two big metal power supply regulator transistors at the other end of the heat sink. Likewise removing the dry one, and ensuring an adequate layer of HS compound is another 'anti-suicide' measure. Note that the single-piece (square, 4 lugs) bridge rectifier DOES NOT NEED A MICA WASHER AT ALL. It has internal electrical insulation. The later two-diode 'half-bridge' rectifiers are all-metal, and require the mica sheet (and shoulder washers under the screw heads)so they won't short to the grounded heat sink metal.
73,
2600 |
Virginiak9
| | Posted on Monday, July 22, 2002 - 10:01 pm: |
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Thanks 307 and 2600. Located the rectifier bridge and have a replacement on the way. Hopefully we will have her back up and running again shortly.
Thanks again for everyones help. It's greatly appreciated.
73's from Virginia |
307
| | Posted on Tuesday, July 23, 2002 - 6:40 pm: |
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Let us know!!!
307 |
2600
| | Posted on Wednesday, July 24, 2002 - 12:54 am: |
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Just be sure to put a fan on it. If the heat sink is too hot to touch after talking on it, you are skating on thin ice, and it could fail again. The new version comes with fans. The older ones should have.
73 |
Virginiak9
| | Posted on Friday, July 26, 2002 - 9:12 pm: |
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Hey 2600 & 307, got the parts in today and installed the rectifier bridge with no problems. She lit up and was working perfectly until I went to reattach the heat sink and pulled off 4 jumpers from the power supply board on the opposite end from the rectifier bridge. The jumpers are two orange wires and two black wires which lead back to the + and - sides of the large 35 v vertical capacitors next to the transformer in the chassis. I have 5 possible pins to connect to on the board which are labeled b1, b2, b3, b4 & b5. Any suggestions as to the proper hookup ?
Thanks again !
VirginiaK9 |
307
| | Posted on Saturday, July 27, 2002 - 6:58 pm: |
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Ouch..I can not help , Find someone with a rig like you and ask them to look...OuCh!!!
307 |
2600
| | Posted on Sunday, July 28, 2002 - 11:34 pm: |
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Boy, did you luck out. Got a Turbo right here, came in last week.
B1 and B2: Fat orange wires coming from the + side of the two big black filter capacitors. It doesn't matter which of the two goes on which pin, the two wires are joined together at both ends. They used two wires to increase current-carrying rating without using fatter wire.
---Note--- the MIDDLE five pins B3,4,5,6 and 7 are ALL connected to ground, so the exact pin the four wires below hook to is not critical WITHIN these middle five pins.
B3 and B4: Fat black wires from the - side of the filters.
B5: Fat black wire that disappears below the chassis through a hole in the deck just above the fuse holder.
B6; skinny black (teflon-insulated) wire that leads into the amplifier shield box.
B7: not connected at all on this radio.
B8: Fat orange wire that disappears into the same hole as B5.
B9: Skinny red (teflon) wire leads into the amplifier shield.
The two wires that disappear below the chassis really lead to the radio circuit board. The radio itself (separate from the amplifier) draws no more than 3 amps by itself. These wires look a lot fatter than you would need for 3 Amps. Go figure.......
Take a close look at the "slide-on" contacts on these wires. They are crimped to the wire, and famous for being sloppily done. If the wire "squirms" around loose inside the rear end of the contact, slide the clear insulator sleeve back up the wire and solder the wire to the contact before you slide it back onto the circuit board pin. Just another "unique design feature" from RCI.
73 |
307
| | Posted on Monday, July 29, 2002 - 12:25 pm: |
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2600..You are this weeks "The Man"
307 |
Virginiak9
| | Posted on Monday, July 29, 2002 - 10:14 pm: |
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We are back on the air !!!
2600 you are definitely THE MAN ! She is working like a champ again.
Thanks again to everyone for all of the help. It is GREATLY appreciated and hopefully I can return the favor sometime in the future.
73's to all from Virginia. |
307
| | Posted on Tuesday, July 30, 2002 - 10:24 am: |
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Glad we could help!
307 |
2600
| | Posted on Wednesday, July 31, 2002 - 1:25 am: |
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Congratulations. Job well done, from the sound of it. Just keep an eye (finger) on the heat sink temperature. The turbo is a heck of a package. I've been running one for 5 of 6 years, just 'cause I like it. Couldn't use my radio to trace your wires, though. My power supply ain't stock anymore. Glad I happened to have one here 'stock' to look inside and 'crib' from.
73 |
Dave
| | Posted on Wednesday, September 04, 2002 - 8:08 pm: |
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Has anyone tryed changing the power supply transistors to 2n3771 to run cooler ? I hear it does run cooler. |
2600
| | Posted on Friday, September 06, 2002 - 1:39 am: |
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Nope, the 2N3771 is just one of several parts that are used for this regulator. Reducing the final bias, addressing issues with the extra 'dry' mica insulators and a fan WILL make it run cooler. Skip the fan and it WILL burn up, unless you put the linear in back on standby forever. The AMOUNT of heat these two parts produce is NOT affected by the type number, but by the load the rest of the radio puts onto them, and how well they are installed.
73 |
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