[Jukebox-list] Fw: Continuing AMi Model C saga

[Jay Hennigan]

From: Dan Gillitzer

> I went back to the guys house tonight. The wires to the cartridge didn't 
> attach to the cartridge pins securely, I got those tight. Still no 
> sound, just the sound from the needle.
> Trick I was told to try is to jump the 2 sockets that the cartridge 
> wires plug in to on the amp and the speaker should hum, and no noise 
> when I did that. Tested the speaker somewhat, by jumping a battery to 
> it, and i did get the faint clicking noise from the speaker. I tried the 
> volume control, first by jumping the 2 wires, then by removing the 2 
> wires (which I was told is the correct way, should go full volume?) from 
> the amp. I did find 3 loose/disconnected wires under the amp, but 
> nothing made it work. The 5U4G tube is not glowing, I "think" this is 
> the power tube, but not sure. It does get hot though. At any rate, I 
> think I'm sure enough that the amp is the problem and the owner and I 
> removed the amp and he'll send it out for restoring. 

The 5U4G is the power supply (rectifier) tube.  It is responsible for 
producing the high voltage that the rest of the amplifier uses.  Its 
glow may be difficult to detect as there is just a ribbon filament 
visible as a pair of flat bands at the top mica insulator and possibly 
near the base of the tube.  The two large black assemblies are the tube 
plates and should not be glowing.  If they're glowing then the tube is 
being overloaded.

In many amplifiers the return for the high voltage is jumpered through 
the speaker plug to ground and there will be no high voltage to the 
circuit if the speaker plug is not inserted.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
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