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Messages - g1

#16
Amplifier Discussion / Re: Savage Amplifier
March 09, 2024, 02:00:19 PM
HT stands for High Tension, the fuse will be in line with the highest B+ supply line.  Usually there is a turn on surge of current so they use slow-blow fuses.  As they are marked S.B., a fast blow will likely not handle the turn on surge.
Check that fuse you took out of the HT spot, if it is really a 0.5A, I don't think it would power up the amp like it did.
#17
Amplifier Discussion / Re: Savage Amplifier
March 08, 2024, 06:56:21 PM
Looks like it's from here:  https://savageamps.com/the-amps
#18
schematic attached.
Disconnect your load.  Check for DC voltage at the output.  Do not connect a load until you get the amp to the point where there is no longer any DC at the output.
#19
Acoustasonic 100 & 150.
#20
Quote from: markorock37 on March 04, 2024, 01:18:36 PMThere is some metal exposed on the back of these newer transistors. I think it will be best to use the insulators.
Thanks for the update.  Yes, you need the insulators.  I was mistaken as far as the datasheet goes.  I found pictures of other transistors with the same package (TO-247) and they are not insulated on the back either.
#21
PR2432 can be Champion 20,40, 100. 
One side of the power amp with extra speaker is shown in a dotted line.  The 2 versions are AC100 and AC150 (mono or stereo).

No offence intended, but if you can't tell whether your unit matches up to this schematic, a different schematic won't get you anywhere.
TDA8950 power module is obsolete, maybe the new unit has a different module.  You would not be able to modify anything in the power amp, so that would not matter.
But just to speculate, the preamp might be the same.
Fender has really tightened up on any of their schematics getting out in public, so we have to work with what we can get.
#22
This is the schematic for a Champion 40.  Not sure which PR, but it has DSP and the output IC is TDA7294.
PR number is 'production release' and does not necessarily mean it uses a different schematic.  Schematics go by model name and revision number.
Check if this schematic matches your unit.  If not, what is the output IC in yours?
#23
When the fuse voltage rating is less than the circuit requires, the possible arcing is more likely after the fuse has blown.
Your probes have a voltage safety rating as well, and that would be lost with any modification of the probes, no matter how high the fuse rating.
#24
Lots of modern electronic equipment has standby circuitry that is always running unless you unplug it from the wall.
#25
The metal tab type has not been made for over 10 years, if you found some they are old stock or possibly fake.
Like Jazz said, you don't need the spacers for the plastic backed type.
Attached datasheet shows both types.
*EDIT TO-247 package does not have the back insulated and requires insulator.


If you do happen to have found some old style metal tab types, you not only need the mica spacers, but also special plastic washers for the screws.
#26
Quote from: Tassieviking on February 26, 2024, 10:31:55 AMI have seen multimeters that physically block the holes when you turn the knob so it is only possible to use the volt probe when volt is selected
I think if you forget you were in current mode, you will likely to forget to turn the knob as well.  So then you would still do damage with the probes, which are acting as a straight piece of wire in current ranges.
My current range require switching ports, and there is a beeper that goes off if I choose any other range while plugged into the 10A port.
Still doesn't help me if I forget to switch range.   :-[

#27
$30 is for a 2-pack, looks like you can't buy them separately.
#28
Plug your guitar into the 'power amp in' jack, is the hum still there?
#29
Quote from: Tassieviking on February 22, 2024, 12:01:47 PMIt is usually a M205 fuse that costs cents, sometimes a ceramic type but still cheap.
My meter uses a regular fuse for the 2A range but has a special fuse for the 10A range (that has it's own probe port).
The special fuse is very expensive due to safety ratings and odd size.
You can find cheap ones from China but I think they are fake as far as the safety ratings go.
Mine is not a Fluke, but this will give you an idea:
https://www.fluke-direct.ca/online/fluke-instruments-replacement-fuses
#30
If the hiss is so loud that the amp in unusable, it is likely a noisy transistor is the cause.
If you understand the signal path, you can try a cap to ground at various points along the path to try to isolate the location.  Something like 0.1 or 0.47uF rated 100V or more should work.
If the cap to ground kills the hiss, you know the source is somewhere ahead of that in the signal path, so you move the cap further toward the input and try again.