carvin legacy 2 phase inverter problem

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shane
Posts: 129
Joined: Fri Jan 14, 2005 2:18 pm
Location: birmingham UK

carvin legacy 2 phase inverter problem

Post by shane »

Hi Folks
I got an issue with the LTP phase inverter on a Carvin legacy 2.
when coming off standby the anode voltages are taking ages to settle.
The inverting half anode voltage starts at supply voltage but takes about 30 seconds to get to get to its operating voltage.
The other anode starts at about half the supply and rises upto its operating voltage.
both voltages are about 20V higher than stated in the partial schematic I have but then again so is the supply voltage.

I tried a new valve, same result, all the components appear to measure correct ie resistance values etc but I have only measured them in situ on the board.

The guy whos amp it is has complained it has low output on start up but come to life after a while
also says the boost channel dont bosst but thats another matter :D

anyone got any ideas?

Cheers
Shane
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Stevem
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Joined: Fri Jan 24, 2014 3:01 pm
Location: 1/3rd the way out one of the arms of the Milkyway.

M

Post by Stevem »

Does the amp have EL34s in it and the bias switch is set for 6L6 / 5881?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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shane
Posts: 129
Joined: Fri Jan 14, 2005 2:18 pm
Location: birmingham UK

Re: carvin legacy 2 phase inverter problem

Post by shane »

The amp does have EL34's in but the bias switch is set to EL34.
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TUBEDUDE
Posts: 1665
Joined: Thu Jan 04, 2007 5:23 pm
Location: Mastersville

Re: carvin legacy 2 phase inverter problem

Post by TUBEDUDE »

Is the PI stable afterward, no intermittent gain changes? When the triode is not fully conducting, is the bias voltage on the grid high? Solid connections at the cathode resistor? I'd reflow the socket pins on the board, and the Rk and grid components leads.
Did you mean all the HV voltages are high?
Tube junkie that aspires to become a tri-state bidirectional buss driver.
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Stevem
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Joined: Fri Jan 24, 2014 3:01 pm
Location: 1/3rd the way out one of the arms of the Milkyway.

Re: carvin legacy 2 phase inverter problem

Post by Stevem »

And what is the negative voltage you read on pin 5 of the output tubes?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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shane
Posts: 129
Joined: Fri Jan 14, 2005 2:18 pm
Location: birmingham UK

Re: carvin legacy 2 phase inverter problem

Post by shane »

The voltages do stabilise, will try reflowing pins etc. Negative voltage on output valves is -44v.
Saw something in an old post on another forum where guy had a similar issue on an older legacy and it turned out to be the 10uf feedback cap, which on that model was non polarised but on the legacy 2 is a normal electrolytic. May look at that too.
Going on holiday today for a week so will put it on hold. I'll report back when I get back on it.

Cheers
Shane
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Anger
Posts: 1
Joined: Thu Mar 01, 2018 1:06 pm

Re: carvin legacy 2 phase inverter problem

Post by Anger »

Hi!
Did you solve it?
regards,
Joao
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shane
Posts: 129
Joined: Fri Jan 14, 2005 2:18 pm
Location: birmingham UK

Re: carvin legacy 2 phase inverter problem

Post by shane »

I did but I'm damned if I can remember what I did exactly. I definitely changed that cap so thet could have been the issue. Sorry I can't be more help.
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