• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Boiling sound...

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I just picked up a Bogen DB-130 because it has a few EQ curves for 78's. The power cable was dried out so I replaced it. The fuse it came with was not burned so I figured let me plug it in now and see what happens. It worked fine for about 4-5 minutes. I then began to hear a boiling sound by the power transformer. The audio was not effected, but the boiling sound quickly got me worried. There are also 3 huge electrolytic caps by the transformer and it sounded like the sound was coming from them. I immediately turned off the unit, unplugged the power cord and the RCA jacks. I then felt the transformer to see if it was hot, it was not. Then I felt the three caps and two of them were very hot. I remember reading somewhere that as caps age their membrane can become damaged which would warrant replacement. So I am assuming these caps should be replaced.

Any thoughts on this? Should I bother trying to repair the Bogen or should I look for another tube set-up that has different EQ settings or just go with a modern unit, for eg. SMART phonoe ReMaster. I figured the older tube set-up will give more of a genuine sound.

Any help would be most appreciated.
Ya... very very lucky they didn't explode and release hazardous material there. I don't get how someone can ignore a boiling sound... I mean...nothing is supposed to boil, right?

Any amp that hasn't been run for say ten years must be taken up slowly. Especially with old electrolytics. Use a variac (NOT a light dimmer) or insert a 4.7k 20W resistor between the rectifier and PSU caps while monitoring voltage.

Replace the electrolytics. See if you can find units rated for 105 degrees C. If the original units were Twist-Lock mount, you'll have to do some improvisation in mounting the new ones, but silicone caulk can be your friend.

Use a proper three-wire line cord, returning the green ground wire directly to the Bogen's chassis.
i had the same problem with my bogen cha 33 i got last week.
used a variac worked good than i turned it off came back turned it on right away there was a boiling or poping sound. shortly
after it blew the fuze. bad 400V cap replaced it works great.:mischiev:


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