Recent content by Ten Over

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    Elevated artificial heater tap - weird result

    Did you disconnect the real center tap from ground?
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    Just got a 1975 Twin Reverb. Got some questions...

    Straightened-out schematics for 1975.
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    Just got a 1975 Twin Reverb. Got some questions...

    135W UL appeared in the later part of 1977 and continued into 1982. They may have stopped production in 1981, but were still delivering stock into 1982.
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    How to Test Power Tubes with minimal equipment

    Can you post the schematic so that the rest of us can see the bias circuit?
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    How to Test Power Tubes with minimal equipment

    Did you ever find a schematic for this?
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    Remove Ultraliner OT taps - quick glance

    Not that good. You asked for Pentode/Triode and I gave you UL/Triode.
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    Remove Ultraliner OT taps - quick glance

    You could take the Ground switch out and replace it with a UL/Triode switch.
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    Remove Ultraliner OT taps - quick glance

    You need to draw load lines to determine this. The highlights are at the intersection of the 0V grid curve and the class B load line. The plate current is 440mA and the plate voltage is 280V. 500V at idle minus 280V is a change of 220V. These are peak values, so we need to convert these to...
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    Remove Ultraliner OT taps - quick glance

    Whereas my schematic has a different overall appearance, the circuit contained therein is exactly the same as the Fender schematic. The 135W Twin Reverb was remarkable in the consistency from unit to unit and in the adherence to the published schematic. I suppose so since the most that...
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    '68 Bassman, blew Tally light, weird resistors?

    There are advocates for the artificial center tap on the grounds that the resistors will burn-up in the event that a power tube shorts its HT to the heater thereby eliminating the path to ground. Others say that eliminating the path to ground in this manner will result in all of the heaters...
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    '68 Bassman, blew Tally light, weird resistors?

    Then I would think that the real center tap in the picture is taped-off inside that heat shrink. If you really wanted to be certain, you could lift both resistors and then test the resistance from the heaters to ground.
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    '68 Bassman, blew Tally light, weird resistors?

    Now that I have looked at the pictures, I have changed my position. It appears as though this heater winding may have a real center tap connected to ground. If so, go ahead and remove the 100R resistors. To determine whether the heater winding has a real center tap connected to ground or not...
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    '68 Bassman, blew Tally light, weird resistors?

    Tally light? You said that it has 100 Ohm resistors to ground. That constitutes continuity, doesn't it? I'll bet the ohmmeter doesn't read zero Ohms to ground. I see those resistors on the AC568 schematic. The older Bassman's had a center tap on their heater winding. This one uses two 100R...
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    Remove Ultraliner OT taps - quick glance

    Maybe you should try connecting the 6L6GC's in triode mode. That'll drain the testosterone right out of it and give you one of the heaviest 50W amps in town. To try: Disconnect yel/brn wire and tape-off. Disconnect yel/blu wire and tape-off. Connect a jumper between pin 3 and pin 6 on V7...
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    Remove Ultraliner OT taps - quick glance

    I don't understand this, but KT66 will use 1.5A more in heater current than 6L6GC. Will your PT willfully supply this? Also, KT66's will up the maximum power to 157W in this amp. Just by the seat of my pants this doesn't seem to be moving in the right direction.




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