Silverface Vibrochamp Issues

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wattsup
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Silverface Vibrochamp Issues

Post by wattsup »

I have an old Silverface Vibrochamp with issues. I got a new set of JJ tubes and when I plug in the new 5Y3 rectifier tube and power up, the first string resistor after the rectifier tube smokes. I figured the resistor probably needed to be replaced anyway so I replaced it with a 1K 5W. on power up, that smokes a little then overheats and blows. I've replaced the 1K again and tried a GZ34 in place of the 5Y3 and it behaves well with it. Put the 5Y3 back in and it fries the 1K. Any advice is much appreciated.
sluckey
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Re: Silverface Vibrochamp Issues

Post by sluckey »

Put your old 6V6 back in. Resistor still smoke?
tubeswell
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Re: Silverface Vibrochamp Issues

Post by tubeswell »

wattsup wrote: Fri Aug 18, 2017 9:42 pm I have an old Silverface Vibrochamp with issues. I got a new set of JJ tubes and when I plug in the new 5Y3 rectifier tube and power up, the first string resistor after the rectifier tube smokes. I figured the resistor probably needed to be replaced anyway so I replaced it with a 1K 5W. on power up, that smokes a little then overheats and blows. I've replaced the 1K again and tried a GZ34 in place of the 5Y3 and it behaves well with it. Put the 5Y3 back in and it fries the 1K. Any advice is much appreciated.
Filter caps need replacing probably. (Shorted caps will cause the supply resistors to fail, because where the cap is shorted, the resistor is going directly to ground and all the B+ voltage is being dropped across it). Have you measured the DC voltages at each high tension supply node?
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pdf64
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Re: Silverface Vibrochamp Issues

Post by pdf64 »

Maybe the 5Y3 has a plate to cathode short and is passing ac?
Is the amp's fuse type correct? Consider using a light bulb limiter until you've resolved this.
wattsup
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Re: Silverface Vibrochamp Issues

Post by wattsup »

sluckey wrote: Fri Aug 18, 2017 10:27 pm Put your old 6V6 back in. Resistor still smoke?
Thanks slucky. Put the old 6V6 in and it behaves. Pulled that one and put a broken in 6V6 with about 40 hours on it from another amp in also. Behaves with that one too. Looks like it may have been a bad 6V6 from the factory? I'll have to find someone local with a tube tester to know for sure. For now everything else checks out and it's playing nice.
wattsup
Posts: 110
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Re: Silverface Vibrochamp Issues

Post by wattsup »

tubeswell wrote: Sat Aug 19, 2017 4:37 pm
wattsup wrote: Fri Aug 18, 2017 9:42 pm I have an old Silverface Vibrochamp with issues. I got a new set of JJ tubes and when I plug in the new 5Y3 rectifier tube and power up, the first string resistor after the rectifier tube smokes. I figured the resistor probably needed to be replaced anyway so I replaced it with a 1K 5W. on power up, that smokes a little then overheats and blows. I've replaced the 1K again and tried a GZ34 in place of the 5Y3 and it behaves well with it. Put the 5Y3 back in and it fries the 1K. Any advice is much appreciated.
Filter caps need replacing probably. (Shorted caps will cause the supply resistors to fail, because where the cap is shorted, the resistor is going directly to ground and all the B+ voltage is being dropped across it). Have you measured the DC voltages at each high tension supply node?
Thanks tubeswell. Have ordered a replacement can cap. This one checks out ok voltage-wise but on power up and intermittently it crackles and hisses so I'm sure it needs to be replaced. Looks like it's as old as the amp.
wattsup
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Re: Silverface Vibrochamp Issues

Post by wattsup »

pdf64 wrote: Sat Aug 19, 2017 5:57 pm Maybe the 5Y3 has a plate to cathode short and is passing ac?
Is the amp's fuse type correct? Consider using a light bulb limiter until you've resolved this.
5Y3 Checks out ok and working like it should. Thanks though. I really need to build one of those!
Stevem
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Re: Silverface Vibrochamp Issues

Post by Stevem »

If the amps fuse is the right value it should pop before any resistors do!
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