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Old 3rd December 2007, 02:44 PM   #1
OMNIFEX is offline OMNIFEX  Jamaica
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Red face Finding The Root Of The Problem

I have this very old Bogen Tube Receiver that has a major problem. The output transfomer smells like it's burning and gives off sparks upon powering up.

The receiver works for around 20 minutes (When it is not burning/sparking) and starts to sound chopped up as if the power supply is dying.

Oh, and high frequency static (As if it is missing it's ground connection) is happening as well.

I'm guessing the Caps are bad, but would like a second (third, forth, 99th ) opinion on whats happening here.

The Power tubes are 6X4 and, EZ80. The Caps are Aerovox AFH 3-49-10 (Could that be the production date?) 30 MFD 475V. In addition to a smaller 0-536 Capacitor. Numbers are as follows: 30 MFD 350 W.V. 20 MFD 350 W.V 10 MFD 350 W.V

Power Amplifier Tubes are two 6BQ5/EL 84, and one 12 AX7/ECC83 for the pre-amp.
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Old 3rd December 2007, 04:52 PM   #2
kevinkr is offline kevinkr  United States
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Output transformer or power transformer? In any event from your description this unit sounds hazardous in the extreme and should not be powered up.

The capacitors undoubtedly need to be replaced, but it sounds like a transformer may also be defective.

Do you have any tools, experience and test equipment or access to someone who does?

To sum up this unit needs a thorough going over and should not be powered up again until these issues have been resolved. This receiver represents a possible fire and electrocution hazard.
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
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Old 3rd December 2007, 05:26 PM   #3
OMNIFEX is offline OMNIFEX  Jamaica
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I'm talking about the Output Transformer. Once I pull out the rectifier (EZ80) the problem cease so, it is the caps that need replacing. I must add that this was a hand-me-down and there seems to be some sort of spilage around the caps (Residue is apparent) that dried up I would decades ago.

I've been toying around tube gear since my preteens so I have no quims working on tube gear. What I would like is a source to get some replacement caps.

The output transformer is not an issue for I will more than likely use this as a preamp. So I'll just get some resistors to raise the output impedance.
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