Is my O.P. transformer fried

[timwhite76]

Will do, thanks for the tip

[timwhite76]

When you say power up, do you mean while still in standby? Because it does, but I don't want to take it out of standby if I'm not supposed to

[timwhite76]

I haven't taken the chassis off yet, but the power tubes look okay, again I have to take the chassis out of the cabinet. But im not doing that until I know if IM supposed to take it off standby. I flipped it off standby for a split second and it sparked again. I have all the tubes out, and drained the caps

[cbass]

If you aren't already using one already.You really shouldn't power up again without a current limiter.

[timwhite76]

I don't have one. Will radio skank have it? How $? When I power up, does it stay on standby, or fully on? When I have what I need. My gm father probably has one, he restores old tube radios

[timwhite76]

Again, I want to thank every1 for their help. I've been a member of Fenders forum, though have thought of not going back. All the helpful people that were there are gone, replaced with people who seem like they're 15 years old. I work mostly as a luthier & helped countless people, including sending some free surplus parts. This last thread about my amp had me @ my wits end with all the D bags. I said I wasn't coming back. Gthe only reason I'm notis I got 13 Pms from people I've helped and did some free work for. But uou are SO HELPFUL, but almost as important, humble. I. Go on fenderforum only to see if someone is asking a ? I can help with. Others seem to go on to see if they can find ways to insult and talk down to. Glad I came here.
I truely hope there comes a time I can help any of you,. I get a lot of satisfactionwhen I can take a situatuon when someoen thinks they have to toss out a guitar or pedal, then I realize its a simple fix, and they repair their gear. I'm not a truely ultruistic person, because I believein quasi karma, & if I help someone, later down the road it gets repayed. Not necessarily from them, but in some way

[martin manning]

A light bulb current limiter is something you build yourself, basically an incandescent light bulb wired in series with the 120VAC power. If the bulb glows brightly and continuously you have high current draw, possibly a short somewhere. A normal indication is when the bulb glows briefly (while the power supply caps are charging) and then goes dim. Starting with a low-wattage bulb, 40W say, will give you the largest safety margin.

[timwhite76]

How do I hook it up? To the amp? And I still don't know if I'm supposed to turn the amp on in standby mode or not

[martin manning]

Just like the picture above... you have to be logged in to see it. Plug the limiter into the wall and plug the amp into the limiter. Turn the amp on in standby first- so you're looking for high current draw in the primary side of the power supply and in the heater circuit. If that looks good, switch the amp into run mode to check the high-voltage secondary.

[Firestorm]

You put it in series with the amp's power cord: you plug the amp into it. Until you build one, I think you can safely see if the fuse blows with no tubes in. By safely, I mean if a tranny is shot, you won't screw it up any more this way. I'd put a slo-blo fuse in, no tubes, standby switch in the standby position and turn the power on. If the fuse doesn't blow, turn the standby switch to the play position and watch carefully to see where the arcing comes from if the fuse blows.

If the fuse doesn't blow, you've likely got a tube problem. If it does, then it's likely a transformer problem, so you drain your caps and start measuring your OT and your diodes. If that doesn't turn up anything, you can also disconnect all the secondary leads from the PT (CP11, 12, 13, 14, 15, 16) and power up again. If the fuse blows in that situation it's 99.99% a dead PT.

[katopan]

Problem is every time you blow a fuse you're doing more damage. As has already been said if you're PT is shot then nothing lost. But if it's something downstream (OT, power valves, recto, etc) then every time you "test" it by blowing a fuse you're stressing your PT and if you did that enough times you could end up with a shot PT as well as whatever caused the original fault.

[cbass]

I'm no expert.But if I were Tim I would not fire that amp up again untill its hooked up to limiter.
IMO firing up and seeing if the fuse blows is not a very good way to trouble shoot.

IF YOU ARE GOING TO WORK ON AMPS AT ALL YOU NEED A CURRENT LIMITER.

[timwhite76]

Ill make one, in the meantime. The fuse didn't blow, matter of fact, I had it on standby for several minutes. Like I said I threw it off standby for a moment, the spark looks like its coming from the chassis just above the OP T., or the tranny itself. It emits a small amount if light smoke, which worries me. I put the preamp tubes in, turned it on(standby mode), and it turned on. I believe the fuse is fine, but ill have to look again. I'm going to remove the chassis before I try it again so I can really see where the arc is coming from.
IM willing to bet there is a power tube issue, but I don't know what damage it did. Looking at the board, I don't SEE any obvious damage, but obviously I can't see where the sockets and such.
Jesus, do they still make incandescent bulbs anymore? Lol. Btw, I used a slow blow fuse you suggested. IM going to take pics of the board, up close in sections if itmakes it easier for everyone to see, and the top of the chassis when I take it apart. IM going to get the 6L6's that where in there treated. I don't plan on reusing them, but knowing if one is blown, that helps narrow down the issues. Ttyl.
Tim

[timwhite76]

I see how to use the lightbulb limiter new. My laptop is busted, so it was difficult to see on my phone. I'm going to print out all the threads at work so I can have them on hand. 1 benefit of. This;when I'm done, ill have more knowledge about this stuff

[Firestorm]

In this amp, the standby switch is located on one of the HT secondaries, so with the amp in standby mode only the tube filaments, bias supply and the +/- 16V supply for the op amps are getting any juice. Since the fuse didn't blow in that scenario, you are likely looking for an HT problem.

If there's a proper short, you can find it with your DMM. If it's an arc, probably not. Start with the OT: Discharge the caps, pull the connector from CP18, then put the plus lead from your meter on the CP18 connector (where you removed the CT wire) and measure resistance to ground. It should be infinite. If it isn't, check the OT protection diodes. Let us know what you find.

At some point, you'll have to decide how deep you want to get into this thing. If you can't pin down the problem by measuring from the connection points and examining the leads, you may have to pull the PCB from the chassis, which is a PITA. These amps were not designed for serviceability; they were designed for ease of assembly.