Originally posted by g1
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Laney TT50H No Outout
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That seems kind of high at R43. Caps at either end of it show 400V rating, so be careful. Suggest using variac and not exceeding 400V there. What is the voltage at it's other end? Are all preamp tubes lit up?
What is the DC voltage at either end of the resistor going to the hum pot, R52 ?Originally posted by EnzoI have a sign in my shop that says, "Never think up reasons not to check something."
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Originally posted by g1 View PostThat seems kind of high at R43. Caps at either end of it show 400V rating, so be careful. Suggest using variac and not exceeding 400V there. What is the voltage at it's other end? Are all preamp tubes lit up?
What is the DC voltage at either end of the resistor going to the hum pot, R52 ?
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Originally posted by g1 View PostThat seems kind of high at R43. Caps at either end of it show 400V rating, so be careful. Suggest using variac and not exceeding 400V there. What is the voltage at it's other end? Are all preamp tubes lit up?
What is the DC voltage at either end of the resistor going to the hum pot, R52 ?
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Are you up to full voltage on the variac yet, or still at reduced line voltage?
Measure DC volts at all preamp tubes pins 1 and 6 and post your results.Originally posted by EnzoI have a sign in my shop that says, "Never think up reasons not to check something."
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Originally posted by g1 View PostAre you up to full voltage on the variac yet, or still at reduced line voltage?
Measure DC volts at all preamp tubes pins 1 and 6 and post your results.
v1(#1-262vdc/#6-289vdc)
v2(#1-371vdc/296vdc)
v3(#1-435vdc/241vdc)
v4(#1-373vdc/303vdc)
v5(#1-435vdc/239vdc)
v6(#1-293vdc/282vdc)
R52(0.00vdc/0.00vdc)
Hum balance pot (12vdc/12vdc)
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There are 2 versions of the amp in the schematic package. I may have been looking at the wrong one. Although 8V across R43 seems wrong in any case.
Are C37 and C23 in your amp 400V rated, or 450V ?Originally posted by EnzoI have a sign in my shop that says, "Never think up reasons not to check something."
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Originally posted by g1 View PostThere are 2 versions of the amp in the schematic package. I may have been looking at the wrong one. Although 8V across R43 seems wrong in any case.
Are C37 and C23 in your amp 400V rated, or 450V ?
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Originally posted by ca7922303 View Post
R43(0.453k ohms) resistance
Other than that, if it has the higher voltage rated caps, like the later revision schematic shows, those 435V readings are not a problem. The high voltage at the hum pot is no longer there so I'm sure it is not smoking anymore.
Change that resistor to the proper value and you should be good to do sound test.Originally posted by EnzoI have a sign in my shop that says, "Never think up reasons not to check something."
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Originally posted by g1 View Post
I think that is 470 ohms. It is supposed to be 4.7K ohms. That is why the voltage drop across it is only 8V. So it needs to be changed.
Other than that, if it has the higher voltage rated caps, like the later revision schematic shows, those 435V readings are not a problem. The high voltage at the hum pot is no longer there so I'm sure it is not smoking anymore.
Change that resistor to the proper value and you should be good to do sound test.3 Photos
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