I wouldn't buy too many. The 6490s are only used in a few amps. If you're going to stock them, stock the 91. It's used in more amps and can replace the 6490 (but the 6490 can't replace the 6491 in most amps).
Good info, thank you! I'll only need to service these arts I am keeping for myself so 10 should do me for now and the future.
That popping issue sounds like what one of my previous a600's did when the ceramic board in the middle was acting up. I resoldered the transistors on it and the popping stopped. Did you get yours going correctly?
When I get the 6490 we'll know. My amp has been modified for some reason and those boards have resistor jumpers on the transistors.
PPI A600 Hi-Res - Amp Guts
You can also see the jumped out chip between the two cards
PPI A600 Hi-Res - Amp Guts
Not sure what they were doing.
PPI A600 Hi-Res - Amp Guts
You can also see the jumped out chip between the two cards
PPI A600 Hi-Res - Amp Guts
Not sure what they were doing.
You can buy those boards for like $30 each shipped pulled off new amps on fleabay. I was thinking of buying four for backup in case the ones in my a600.2's had issues.
Perry I bought the G 2N6490G ON Semiconductor Bipolar Transistors
That look ok? I don't actually know what RoHS is, but I know it was that or the cheap 61 cent transistors and I figured I'd spend a little more and get these.
That look ok? I don't actually know what RoHS is, but I know it was that or the cheap 61 cent transistors and I figured I'd spend a little more and get these.
RoHS means that they don't have lead or other materials considered to be hazardous. They typically function the same as the non-RoHS parts.
Restriction of Hazardous Substances Directive - Wikipedia, the free encyclopedia
Restriction of Hazardous Substances Directive - Wikipedia, the free encyclopedia
Meter set to diode check, black probe on leg 1:
Leg 1-2 and leg 1-3, ~0.6v
All other probe/leg combinations should read open.
Leg 1-2 and leg 1-3, ~0.6v
All other probe/leg combinations should read open.
it's the transistor that was excessively hot Q33. same feed line as 34, 35, and 36 so should either be all hot or all not. It isn't a matter of the heat sink, it gets hot FAST, smoking hot.
Check again but this time, set the meter to ohms to look for leakage. If it shows no leakage, it may simply have a lower threshold voltage than the other, parallel transistors so all of the bias current is passing through the one transistor instead of 4.
Replacing it eliminated both my pop and the overheating. Worked fine for a minute but just shut off with a hissing noise so gotta open it back up and see.
Something in the amp at the power supply is now shrilling at me (hissing scratching sound at the components). and it is not making music anymore from either channel. It idled fine for about a minute then this. UHG......
I guess the power supply is being drawn on heavily so it is shrilling. I'm about over this amp. Only thing I noticed were the ceramic cards were the only things warm in the amp when it started shrilling. (And I am no talking about at speakers I am talking in the amp)
Something in the amp at the power supply is now shrilling at me (hissing scratching sound at the components). and it is not making music anymore from either channel. It idled fine for about a minute then this. UHG......
I guess the power supply is being drawn on heavily so it is shrilling. I'm about over this amp. Only thing I noticed were the ceramic cards were the only things warm in the amp when it started shrilling. (And I am no talking about at speakers I am talking in the amp)
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I've observed Q1, which is used as the voltage regulator on the OTHER channel is arching when I connect the turn on lead to the amp and that appears to be the area of my squeal/hiss as well. I don't know why the other channel voltage regulator would go out, but it tests well?!?! Could something be drawing in the amp so hard it is arching the legs of Q1 which is a 2n6487?
I replaced all 5 of the transistors in the bad channel Q32 through Q37 and it did not help.
PS- it does this with NO LOAD.
I replaced all 5 of the transistors in the bad channel Q32 through Q37 and it did not help.
PS- it does this with NO LOAD.
There are 8 output transistors and 2 driver transistor on the heatsink for each channel. The drivers are the two in the center. The drivers are typically rated for higher voltage. It's likely that the driver voltage (from the two 33 ohm resistors near the inductor) is too high for the 2N6490s you're using (assuming that you installed one in the driver location).
The voltage regulators supply regulated voltage for the op-amps which feed both channels. There isn't a regulator for each channel.
Arcing? From where to where? Bad insulator? Broken terminal?
The voltage regulators supply regulated voltage for the op-amps which feed both channels. There isn't a regulator for each channel.
Arcing? From where to where? Bad insulator? Broken terminal?
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