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Comes in as "everything works fine, just hasn't been serviced in 20 years". Once I got the darn heavy thing opened, I found everything covered in a layer of thick dust, including the 6 Sylvania 6550As. I checked the bias points on the panel, and got 75mV on one side and 24mV on the other. (Disclaimer, I understand this is voltage representing cathode current). Sounded like a tube or two wasn't conducting, maybe. Then I set something on the cab and the speaker went "thunk", so I tapped around to see what it might be. Tap, tap, SPARKS! And a blown up 10A power fuse, broke it right open. One of the 6550s shorted.
Great, it was "working fine" until it came to me, now it needs tubes. The side that read 24mV before now reads 15mV, so it looks like another tube on that side is also bad, but this is where I cease further probing until I talk to the owner. My policy with big amps like the SVT with their 725 plate volts, with modern day manufacturing in mind, is that I do not sell power tubes for them. A 6 pack of 6550A from TAD is about $275. There are other online vendors that sell them for less, but I'm not sure I trust them. TAD at least has a good rep for testing and matching their "premium" sets. If sell them to my customer, and one blows up next month, he is going to be looking at me to make that right, and at those prices I can't afford that. So, I require the customer to purchase them himself from the vendor of his choosing, thus seeing the price, and I will install and bias when he gets them to me.
Well, I just spoke to him, and no worries. He was happy to buy his own tubes, and said "that's cheap" when I quoted him a price. He said the last time it was done 20 years ago they charged him $600, but that was with NOS Sylvanias. When I mentioned it also might be time for a cap job, he said "do it", before I even gave him a price. "anything you thinks needs done, do it. I will pay cash. So there you have it, quite a repair bill. Now I have to go put the cap parts list together and source it, the part I don't get paid for.
Great, it was "working fine" until it came to me, now it needs tubes. The side that read 24mV before now reads 15mV, so it looks like another tube on that side is also bad, but this is where I cease further probing until I talk to the owner. My policy with big amps like the SVT with their 725 plate volts, with modern day manufacturing in mind, is that I do not sell power tubes for them. A 6 pack of 6550A from TAD is about $275. There are other online vendors that sell them for less, but I'm not sure I trust them. TAD at least has a good rep for testing and matching their "premium" sets. If sell them to my customer, and one blows up next month, he is going to be looking at me to make that right, and at those prices I can't afford that. So, I require the customer to purchase them himself from the vendor of his choosing, thus seeing the price, and I will install and bias when he gets them to me.
Well, I just spoke to him, and no worries. He was happy to buy his own tubes, and said "that's cheap" when I quoted him a price. He said the last time it was done 20 years ago they charged him $600, but that was with NOS Sylvanias. When I mentioned it also might be time for a cap job, he said "do it", before I even gave him a price. "anything you thinks needs done, do it. I will pay cash. So there you have it, quite a repair bill. Now I have to go put the cap parts list together and source it, the part I don't get paid for.
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