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OK, so pull the two red wires off the board and measure resistance between them as you hold them in your hand. Then one way or another we can move along to the next step. If F4 is not in series with the winding, we really ought to determine where it is wired in, but first things first. Measure.
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Education is what you're left with after you have forgotten what you have learned. -
I posted earlier the resistance between sp1&sp2 was OLComment
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Unless I am missing something, again that sounds to me like you measured between where something was connected, but does it read the same when read right on the wires hanging in free air, not connected at all?
Yes, it does sound like an open transformer, but we must be sure.Education is what you're left with after you have forgotten what you have learned.Comment
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If I am reading the schematic correctly, F4 is IN SERIES with the HT winding.
If F4 is OPEN then you will not get a reading across SP1 & SP2.
Please replace the fuse & try again.Comment
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This^^^^
That is why I keep yapping about the wires instead of the test points.Education is what you're left with after you have forgotten what you have learned.Comment
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Enzo,yes, I did what u said to do in ur earlier post. I pulled the sp1&sp2 & measured OL between them hanging freely in the air which is why I asked if that indicates the PT is open or Will replacing F4 fix the problem?Comment
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Ok but reread this From JazzOriginally posted by Perkinsman View Post
If I am reading the schematic correctly, F4 is IN SERIES with the HT winding.
If F4 is OPEN then you will not get a reading across SP1 & SP2.
Please replace the fuse & try again.
nosajsoldering stuff that's broken, breaking stuff that works, Yeah!Comment
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Saw that but even if sp1 & sp2 are pulled from the terminals & measured?Comment
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Do SP1 and SP2 come directly off the transformer? We can only guess with no picturesOriginally posted by Perkinsman View Post
If the above is true then you may have blown one in the transformer and I'd suggest replacing it since it's not your amp.
nosajsoldering stuff that's broken, breaking stuff that works, Yeah!Comment
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Excellent point. The schematic is lacking and all we know is there are 2 wires there. I hadn't even considered that they may not be direct to the transformer.Originally posted by nosaj View PostOriginally posted by Enzo
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On some of the Blackstar amps the HT fuse is in a link cable that can appear to be coming directly off the PT. Looking at picture of this amp there's a HT fuseholder on the back panel. Without me reading the entire thread again - is the HT fuse on the good? Did you look where the wires from the fuseholder run from/to, and Is the fuse seated correctly and making contact? A schematic is one thing, but you have to take it as a rough guide and make a diagnosis based on what's in front of you. The simplest and most likely scenario as previously outlined is the tube broke, the amp was powered up and the HT fuse blew. A PT failure is way down on my list of failures, especially if the HT and other secondaries are fused.Comment
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I’m glad nosaj made me double check because there’s a third red wire from sp2 to sp14 & I mistakenly measured for the OL reading....when I detangled the three red wires and measured the two from the PT I got 52 ohms! I’m running to the store for the F4 fuse & will report back.Comment
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Praised the lord...
I think I see my confusion. TO ME, the terms "SP1 and SP2" refer specifically to the POSTS on the circuit board. I THINK Perk uses "SP1, SP2" to refer to the wires themselves. SO in my mind I cannot remove SP1 and SP2 from the board, but I CAN remove the wires from SP1 and SP2. Now that we read the actual wires, we get a very good looking 52 ohms.Education is what you're left with after you have forgotten what you have learned.Comment
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Ok, so I put in a new slow blow F2 fuse & she powered right up. This just goes to show to check the fundamentals like we did when we were kids. The first thing I would have checked was the fuses but these days it’s easier to scour the Internet for a schematic & a new transformer. I was able to bias at TP 10 for 50mV but not sure how to use the “balance” pot to adjust yet. I can’t thank you guys enough for your patience & doggedness. I love this hobby!Comment
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