I've had this item for around 5 years now, and today it powered on, tubes lit up, then suddenly the tubes went dark. Tried again to bring it back on, and the same thing. Now the power light is on, but the tubes remain dark after several attempts and nothing pumping to the speakers.
By the way.. I looked through the threads on here and couldn't find anything with this particular issue. So I apologize if I missed something.
I have new tubes on order, but I need to make sure if that's what I'm looking at.
Any advice would be helpful.🙂
The picture attachment is when it was working.. just fyi..
Thanks. -DLNorton
By the way.. I looked through the threads on here and couldn't find anything with this particular issue. So I apologize if I missed something.
I have new tubes on order, but I need to make sure if that's what I'm looking at.
Any advice would be helpful.🙂
The picture attachment is when it was working.. just fyi..
Thanks. -DLNorton
Attachments
Did it come with a manual that has a schematic?
If so, post the schematic, please.
Or at least a very good picture of the insides, taken with good diffused lighting, and no shadows, and no burned out highlights.
That is hard to do. (A single point flash does not qualify, but sometimes a large picture window and open shade or a cloudy day works).
(I am tired of being blindfolded, turned around an indeterminate number of degrees, and being asked to shoot the arrow at the target).
What are the tube types. The outputs look like EL84s. How about the input tube type?
If so, post the schematic, please.
Or at least a very good picture of the insides, taken with good diffused lighting, and no shadows, and no burned out highlights.
That is hard to do. (A single point flash does not qualify, but sometimes a large picture window and open shade or a cloudy day works).
(I am tired of being blindfolded, turned around an indeterminate number of degrees, and being asked to shoot the arrow at the target).
What are the tube types. The outputs look like EL84s. How about the input tube type?
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It's most likely the cheap little switch mode power supply have given it's all. Pretty easy to check for voltages, just use precaution and follow guidelines for high voltage tube amps, just in case.
Or, throw it in the bin and build a better amp from a kit.🙂
jeff
Or, throw it in the bin and build a better amp from a kit.🙂
jeff
Switching supply died. Good point.
The power light is perhaps a neon and series resistor.
That could light from the mains voltage.
The power light is perhaps a neon and series resistor.
That could light from the mains voltage.
I have the same amplifier; search my post on a previous thread to get my (poorly) hand drawn schematic diagram and a list of changes I've made. The filament power supply is 12V and the power tube filaments are wired in series. They're both off if a filament is open, but the preamp tube filament runs at 12V, so it should still glow. If all tube filaments are off, the most common fault is a broken switching controller chip. On my amp it's the TOP250YN type, a cheap $ 2 part. The large electrolytic filter capacitor may also be faulty. The original capacitor is 400V 270uF with snap terminals; a smaller one will be just as good. Supply voltages can be measured by removing the tubes. You should measure 12 V DC between pins 4 and 5 of the preamp tube and 250 V between pin 9 of both power tubes and ground. Be careful to avoid electric shock as dangerous voltages are present on the board. Do not touch the heat sink when the amplifier is on. Do not attempt to repair if you are not comfortable working on tube circuits.
Schematics of unknown origin attached.
Previous posts by PCAN illustrate well a number of things that could / should be design addressed while box is open. Please see links below
My amp of the same type is starting to hum so I guess it it time for an upgrade of capasitors and adding some tape for me as well
Dead mini tube amp APPJ PA0902A
APPJ EL84 SE mini Tube Amp, PA0901A
https://www.diyaudio.com/forums/tubes-valves/250974-miniwatt-n3-2.html#post5157464
Its possible if the output valve has a short the switch mode supply may shut down and the heaters go off. Pull each valve in turn and see if the heaters stay on.
Good evening everyone, I found a used APPJ0901A original amp with Chinese tubes on it. My question is: do I have to change the pinout or modify the pinout to use the ecc83 and el84 tubes ?? Thank you for your answers