Need help w/ old school HiFonics Pluto

THUMP LUMP

Member
2007-08-10 3:25 am
I have an old Series 7 HiFonics Pluto amp that has went dead on me in storage. When I put power to it, nothing lights up and there is a bit more spark when I touch the ground to my power supply than what would be normal. I have never messed with repairing an amp before but I have replaced components on other things. I know that caps will go bad over time and thought that maybe a cap on the power side of the board may have gone bad just sitting. Here are pics of the board top and bottom.

[IMGDEAD]https://farm5.static.flickr.com/4090/5094180995_673f1cfc8a_b.jpg[/IMGDEAD]

[IMGDEAD]https://farm5.static.flickr.com/4125/5094780810_b4461b85ac_b.jpg[/IMGDEAD]
 
Clamp the transistors to the heatsink and insert a 10 amp fuse in the B+ line feeding the amp. Power up the amp (incl. remote) and post the DC voltage on all 16 pins of the TL594. Place the black meter probe on the amplifier's ground terminal. Place the red meter probe on the point where you need to measure the voltage.The attached image shows the numbering scheme. Copy and paste the following list into your reply.

TL594
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
 

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THUMP LUMP

Member
2007-08-10 3:25 am
First, thanks for the help Perry. I connected it up to my power supply and tried to get readings. I couldn't get anything but I did find that once I powered up the amp, the power supply quit supplying power (zero volts). I disconnected the amp and the supply went back to 13.68v. The 10amp fuse is also intact. I rechecked the supply afterward, to be sure it was working, and it is fine. I thought I had killed my 20 amp power supply. Sorry but I can't get any readings on the IC. Though, the fact that the power supply went to zero, I hope, will tell you something.

Thanks for the help!! I really don't want to toss this fine old amp. It fits in really well with my Cupid and Cyclops HiFonic amps.
 

THUMP LUMP

Member
2007-08-10 3:25 am
I measured the IRFZ44s and found, on the one closest to the corner to measure

Pin 1-2) - 13.9ohm
Pin 1-3) - 13.9ohm
Pin 2-3) - 0.3 ohm

And on the other one next to the one in the corner, with the insulator still on it in the above photo

Pin 1-2) - 0.9ohm
Pin 1-3) - 0.9ohm
Pin 2-3) - 0.3ohm

From a quick look and the data sheet, it mentioned "low resistance" so I am gathering the first one is bad. But only relative to the second as I have no other point of reference. I'm trying to learn!
 

THUMP LUMP

Member
2007-08-10 3:25 am
Thanks for the info about the caps. I have read that an amp this old should have them replaced.

The bands on the resistors are white, brown, black, gold. 91 ohms @5% tolerance, if I read the chart right. They both measure within tolerance. 90.2ohms and 90.4ohms.
 

THUMP LUMP

Member
2007-08-10 3:25 am
OK. I did that and they both are just over 5v. One at 5.12v and the other at 5.11v. I'll shoot and order out tomorrow for the IRFZ44s and the caps. Thanks for all the help!!! And if there is anything else you think I should do or need for this amp before I send in the order, please let me know.

Thanks again!!!
 

THUMP LUMP

Member
2007-08-10 3:25 am
I set the meter to continuity and it didn't show any connection from any one leg to either of the other two on any transistor. I wasn't really looking at the meter for any ohm reading, just listening for the tone to confirm continuity. I never got a continuity tone. Should I look for resistance?
 

THUMP LUMP

Member
2007-08-10 3:25 am
I normally do touch them before and during just to check that I am getting tone. I have come across broken leads in the past and found then out by touching. I went back and used the 3k ohm scale and got flash readings right at first and then the reading went over, but this was only some of the time at random leg tests. Touching the leads using the 3k ohm scale, it read .001.
 
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