audiodon
Addicted Member
Hi,
I've traded with JohnVF. He now has my Spendor BC1s and I now have his Fisher SA-300.
He'd had it worked on and most every cap under the hood had been updated, but the power supply caps were undone. I've included a photo that shows the workmanship, which is good.
Sonically, I used it for a few 10 hour days to get a feel for it and to let it relax in. My experience with tube gear that hasn't been used for a while or a lot is that it takes time to show its true colors. I don't know if it's the heat, or the charges in the caps, or what, but some change occurs.
I was surprised to find that Sprague 715P output caps were pretty good. Not the best, but good.
After initial break-in, I cleaned all the tube sockets, put a Mullard 5AR4 in place of one of the two that was a Brimar, replaced the two 12AU7s with NOS 12BH7s I bought from byoungman1, and started rolling in 12AX7s. I also replaced the one non-XF-4 Mullard EL-34 with an XF-4.
Well right now I'm running Sylvania black plate 12AX7s, which brightened it up a bit. The amp has also sped up on the bass, which was sounding kinda vintage-like, if you know what I mean.
I used it this way for a month, then last night I put it on the bench and replaced the four output coupling caps and a few resistors. Now it has Jensen PIO silver leadout caps purchased used from analog addict. They fit. The space is tight. They're .22uf caps, which tend to be big, and long ones won't work. I also replaced the 1000 ohm resistors to each EL-34 with Kiwame carbon comps.
The difference is pretty dramatic. The amp has a lot more authority. Bass is much more extended and liquid and the highs are also much more extended and smooth.
This one's going to require some cleaning up and it'll get the attention it needs, just not right now. One of the two can caps gets fairly warm and will have to go, but it's not intolerable. I know that the power supply upgrade will add transient response, speed and power.
I also knocked a couple of dents out of the cage and it'll need a rattle-can upgrade.
Has anyone got a service manual? I have a schematic, but I have no procedures to set AC and DC balance. Are there rule-of-thumb guides for how this should be done?
Can someone help? I'm sure there should be a certain value of output load resistor used and a sequence of switching the bias controls as well as target voltages for certain places.
If I have to I'll buy a manual on ebay, but there's none I've found in the AK digital docs forum or in the Yahoo Fishergroup archives, or through some google searching.
Thanks in advance.
I've traded with JohnVF. He now has my Spendor BC1s and I now have his Fisher SA-300.
He'd had it worked on and most every cap under the hood had been updated, but the power supply caps were undone. I've included a photo that shows the workmanship, which is good.
Sonically, I used it for a few 10 hour days to get a feel for it and to let it relax in. My experience with tube gear that hasn't been used for a while or a lot is that it takes time to show its true colors. I don't know if it's the heat, or the charges in the caps, or what, but some change occurs.
I was surprised to find that Sprague 715P output caps were pretty good. Not the best, but good.
After initial break-in, I cleaned all the tube sockets, put a Mullard 5AR4 in place of one of the two that was a Brimar, replaced the two 12AU7s with NOS 12BH7s I bought from byoungman1, and started rolling in 12AX7s. I also replaced the one non-XF-4 Mullard EL-34 with an XF-4.
Well right now I'm running Sylvania black plate 12AX7s, which brightened it up a bit. The amp has also sped up on the bass, which was sounding kinda vintage-like, if you know what I mean.
I used it this way for a month, then last night I put it on the bench and replaced the four output coupling caps and a few resistors. Now it has Jensen PIO silver leadout caps purchased used from analog addict. They fit. The space is tight. They're .22uf caps, which tend to be big, and long ones won't work. I also replaced the 1000 ohm resistors to each EL-34 with Kiwame carbon comps.
The difference is pretty dramatic. The amp has a lot more authority. Bass is much more extended and liquid and the highs are also much more extended and smooth.
This one's going to require some cleaning up and it'll get the attention it needs, just not right now. One of the two can caps gets fairly warm and will have to go, but it's not intolerable. I know that the power supply upgrade will add transient response, speed and power.
I also knocked a couple of dents out of the cage and it'll need a rattle-can upgrade.
Has anyone got a service manual? I have a schematic, but I have no procedures to set AC and DC balance. Are there rule-of-thumb guides for how this should be done?
Can someone help? I'm sure there should be a certain value of output load resistor used and a sequence of switching the bias controls as well as target voltages for certain places.
If I have to I'll buy a manual on ebay, but there's none I've found in the AK digital docs forum or in the Yahoo Fishergroup archives, or through some google searching.
Thanks in advance.
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