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PostPosted: Thu Feb 04, 2021 9:11 pm 
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So I powered the amp up for the first time today, and got a wisp of smoke from the area where the B +2 500R 5W resistor is. I was able to get a reading at B+1 to ground of 473, but B+2, 3,4,5, were dead. The soldered joint at B+2 was not my best work. I tried redoing that solder joint, but still a no-go. Could I have blown the resistor ? or worse ?

Any help greatly appreciated, Thanks, Mike


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PostPosted: Fri Feb 05, 2021 11:30 am 
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mefgames wrote:
So I powered the amp up for the first time today, and got a wisp of smoke from the area where the B +2 500R 5W resistor is. I was able to get a reading at B+1 to ground of 473, but B+2, 3,4,5, were dead. The soldered joint at B+2 was not my best work. I tried redoing that solder joint, but still a no-go. Could I have blown the resistor ? or worse ?

Any help greatly appreciated, Thanks, Mike


If a component was smoking then assume it's dead (it most probably is) and replace it. BUT before you do, make sure you find out why or you'll likely just ruin the replacement too... probably an error in your wiring somewhere.


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PostPosted: Sat Feb 06, 2021 1:10 pm 
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As I mentioned, the solder joint at B +2 was not the best. I had a very hard time getting all 4 connections in the eyelet and consequently I believe there may have been a ground fault at that point. I removed the white 5k 500ohm resistor and found the underneath had a gray scorch discoloration. I have some on order. We no longer have e-parts stores locally. After disconnection at that part of the circuit, I was able to verify I do have correct power to the tube sockets and still have the 473 VDC at B + 1. I will be checking the entire circuit again for ground issues and hope that is my bump in the road. I have built amps before, but know full well my limitations, so I will be proceeding quite cautiously.


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PostPosted: Wed Feb 10, 2021 7:36 pm 
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Update, I replaced the 5WATT 500 OHM resistor that blew during the initial power up. Plugged into my light bulb limiter and turned on the power, then the standby. Light bulb lit up and never dimmed, maybe 2 to 3 seconds, so I shut it down immediately. This time the resistor did not blow, but I was very quick to turn off the standby. Turned power off and discharged the caps, then checked solder joints and probed for ground shorts. Tried again with the same results. Any help out there ???

thanks,
Mike


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PostPosted: Thu Feb 11, 2021 4:16 pm 
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Well, this is embarrassing. I have found the problem and it was not with the amp, it is fully on me. Near the V5 socket , there is a 2 node terminal strip that is used to wire to the B +1 eyelet and resistor that connects to a V5 pin. Because I used a strip that was right grounding instead of left grounding, I wired it exactly as pictured in the layout, and instant ground, DOH !!! After fixing that, I have reconnected the B+ rail components and am getting correct DC voltages to all caps. I know we all make mistakes, but this was a real bonehead move. I shut everything down and am taking a breather before proceeding with the rest of the startup. Thanks to all those who replied with advice. I will keep you posted on my progress, but for right now, I'm just elated I was able to find the problem.

Thanks again, Mike


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PostPosted: Fri Feb 12, 2021 1:38 am 
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Heh... no need to embarrassed... we've all made similar mistakes!

Glad you got it sorted now go enjoy this gem of an amp!


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PostPosted: Sat Feb 13, 2021 2:02 pm 
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Glad to hear it was an easy fix! Like dtp said, we've all been there :D


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