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Post subject: Power issues with 65 Twin Reissue.
Posted: Fri Jan 02, 2015 7:11 pm
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Greetings and let's start by saying thank you for any positive help you can provide.

I bought a Fender Twin Reverb a couple of years ago from Sweetwater. I am trying to figure out what could be wrong with it. I have already checked everything visually with a lighted magnifying glass and nothing on the board appears scorched, no bulging capacitors, no burnt resistors, and both fuses have not been blown. I was testing a pedal when suddenly the power was lost to the entire unit. I wasn't stressing the amp at all, and there is no filament power to both channels. A discussion on what could possibly be wrong with it would be appreciated.

Thanks,
Moby

In addition the front light was not on after the power issue either. The outlet is good and the pedal I was testing was lit up off the same power conditioner. I also tested straight into the wall as well so it's not anything to do with apartment power.


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Post subject: Re: Power issues with 65 Twin Reissue.
Posted: Fri Jan 02, 2015 11:35 pm
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Hi mobytheminnow,

First, check the main fuse with a meter, because visual is not always an indication of a good fuse. Odds are that the main fuse has blown, but if not, the following checks are in order.

Remove the output tubes, as a faulty output tube can cause a blown fuse.

If you have no power light, no heater supply, the first place to check would be the primary of the power transformer (PT). If you have a meter, check for approximately 120 volts from the electrical plug, then for 120 volts into the primary of the PT. There is a fuse and a thermistor on the primary of the PT.

If there is voltage from the electrical plug, and no voltage at the OT primary, and if the the fuse is good, then my guess would be the thermistor is bad.

So, check voltage at the black and white wires coming into the amp. If you have approx 120 volts, go to next step.
Next check voltage at CP1 to CP2, no voltage there means that the fuse is blown. If you have approx 120 volts there, go to next step
Next check voltage at CP3 to CP4. If no voltage there, the thermistor is bad.

If the above steps show voltage for all tests, then check the voltages of the secondary of the transformer.

_________________
---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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Post subject: Re: Power issues with 65 Twin Reissue.
Posted: Sat Jan 03, 2015 2:04 am
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+1 Shimmilou


mobytheminnow , be sure to put a fuse with the right specs ,( look on chassis , not on fuse ) sometimes fuse in the amp is not the right one ( if amp was a second hand ) and a overpower fuse may burn the Power Transformer .


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Post subject: Re: Power issues with 65 Twin Reissue.
Posted: Sat Jan 03, 2015 7:33 am
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Amp was bought brand new, Thanks.



stratele52 wrote:
+1 Shimmilou


mobytheminnow , be sure to put a fuse with the right specs ,( look on chassis , not on fuse ) sometimes fuse in the amp is not the right one ( if amp was a second hand ) and a overpower fuse may burn the Power Transformer .


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Post subject: Re: Power issues with 65 Twin Reissue.
Posted: Mon Jan 05, 2015 8:12 pm
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Took it apart. Checked everything out. Put a fast blow fuse in it from Radio Shack just for testing. The tubes light up now, and I'm waiting on an Amazon shipment of Slo Blo fuses to finish testing.

Thanks everyone, and that fuse didn't look bad, I even looked at it with a loupe and didn't see anything.


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Post subject: Re: Power issues with 65 Twin Reissue.
Posted: Mon Jan 05, 2015 8:18 pm
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Original fuse popped. Prolly at one end or the other of the fuse. That is why you can't see the break.

Keep a few proper fuses with the amp, at all times. It's not unusual for tube amps to pop fuses. Esp at cold startups, where current draw can be the highest.


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