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Topic: Bandmaster Reverb power transformer |
Jim Phelps
From:
Mexico City, Mexico
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Posted 19 Nov 2007 9:34 pm |
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| I think mine may be partially shorting. Anyone know what the primary should read in ohms for a good transformer? |
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Jim Phelps
From:
Mexico City, Mexico
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Posted 20 Nov 2007 11:29 pm
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| Ah c'mon guys... bet somebody knows.. Jim Sliff? |
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J Fletcher
From:
London,Ont,Canada
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Posted 21 Nov 2007 5:12 am
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| Don't know what the primary resistance is but, are your secondary voltages too high or too low? |
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Jerry Erickson
From:
Atlanta,IL 61723
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Posted 21 Nov 2007 5:53 am
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| Is this amp the 40 watt,tube rectified model or the "70" watt solid state rectified model? |
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Bill Hatcher
From:
Atlanta Ga. USA
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Posted 21 Nov 2007 10:07 am
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| I have never had to replace a power tformer in a Fender amp. Is it overheating??? |
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Ken Fox
From:
Nashville GA USA
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Posted 25 Nov 2007 9:08 am
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I never trust a DC ohms reading to mean much of anything with a transformer, as the DC resistance of a primary or secondary is so low to start with. For a power transformer I would disconnect the secondary loads and check it with my digital amp meter. I have a wall unit that measures AC amperage, wattage, voltage, etc just for that purpose. I also have several AC impedance meters that I use to check things out with.
If it has shorted primary windings it will have a higher than normal AC current draw and eventually start blowing fuses as well. |
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Vernon Hester
From:
Cayce,SC USA, R.I.P.
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Posted 26 Nov 2007 12:44 am Fender
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When you turn on the amp and that noise starts!!!
Remove the 12AT7 reverb spring driver tube,noise goes away
replace the transformer.You can find them on the internet for about $17.00.
Vern |
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Ken Fox
From:
Nashville GA USA
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Posted 26 Nov 2007 5:53 am
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I had an issue with hum in the reverb and tremolo circuits on a Twin Reverb this week. It was due to broken down insulation in the choke coil. The choke was acting as a 130uf cap to ground with a high ESR (equivalent series resistance). That was loading the DC supplied by the choke and causing a 2 volt ripple in the supply to the reverb and tremolo circuits. I found that with my ESR meter. After taking the choke apart I found one side burned to crisp! Still it was passing current through to the rev, trem and preamp tubes!
The point being that a lot of problems are pretty hard to chase down without a scope, meter and other tools.
You never stated exactly what kind of issues you were having that made you suspect a bad power transformer.
What are you hearing, seeing or feeling that points to the transformer? |
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