Peavey Classic 30 II 2018

[Oldmactech]

Getting started on a Dead Peavey Ckassic 30 Chinese 2018 vers.
Im told it has a bad transformer but not sure how to troubleshoot that yet.
No signs of life whatsoever, visible fuses all test good so not one of those EZ ones.
wrestling with trying to get the circuit board out isn’t much fun.

[Oldmactech]

Totally dead, I’m told the OT is bad. Haven’t tested yet.
pain the get the board out. This one looks more like a computer board.
Could use a schematic, Peavey not helping yet.

[The Dude]

I'm not sure about the II, but the classic 30 transformer plugs into the board via a single connector. If it's the same arrangement, you shouldn't need to take the board(s) out to test the transformer. Just unplug it and check secondary voltages at the connector. If nothing there, check primary voltage and for open primary.

[Enzo]

If the tube heaters do not light, and the power light does not come on, I'd start with the primary side. Pull the mains fuse and measure with an ohm meter. With a good fuse in it, pull the power plug from the outlet and measure resistance between the two main prongs of the power plug. The power switch set to ON for this. You are now measuring resistance up through the cord, through the fise and power switch, through any inrush limiting thermistor and the transformer primary. You should see a lowish resistance. I don't know what maybe 200 ohms or something, just not open and not 2 ohms.

If you get an open reading, then might as well test the transformer. Probe with your ohm meter RIGHT AT the primary wires of the transformer. Still get open? If so, the thing is bad. If it measures 50-100-150-200-250 ohms or whatever, then explore the switch, fuse holder, wiring power cord itself

[Enzo]

Hey, hi. Please, can we just have ONE thread about this?

[The Dude]

Yep. I'd start with the primary tests, too. I just went a bit "backwards" to point out that you didn't need to take the board(s) out to test the transformer.

[Oldmactech]

Sorry, for some reason I get an error message when I post a new thread. Unintentional.

[Jon Snell]

If the mains fuse is not blown and the primary reads as open circuit, the transformer has an internal thermal fuse that has probably blown caused by heat. The heat is caused by a bad mains plug/socket/lead/extension lead because transformers don't like dirty/interupted mains.
If the primary reads OK then check the secondary voltages as the transformer may be OK.

[Jon Snell]

Please refer to the first post; https://music-electronics-forum.com/...-classic-30-ii

[Oldmactech]

Haven’t checked continuity yet but I did notice that the power tube sockets have signs of resoldering. Stray flux and globs of solder. One of the preamp tubes has a couple of solder points that have turned black. Everything else looks ok at least visually.

[Enzo]

Wax on...wax off...

Primary side continuity takes a good 15 seconds to test, and you don't have to open the amp.

[Chuck H]

Sorry guys, I gotta let this one go until more things with the new format are put in place. I can't find any "thread tools" avenue that would let me merge the multiple posts that's identifiable on screen or in any way recognizable or similar to the older format. I'm sure tboy will work it out, or not. No great shakes here so NBD.

[Oldmactech]

This is the daughter card between the AC and Output Transformer. Getting no resistance at the AC connecter. 1.2 ohms at the 4 connections and at the red and yellow secondaries.

[The Dude]

"no resistance". Does that mean '0' ohms or infinite resistance? And, where did you measure? Were you right on the IEC connector or are you talking about the spade connectors? If you get nothing at the IEC connector, try right at the transformer primary wires. What do you have for resistance there? Your post needs some clarification on a few things. Also, I notice that there is what looks to be a thermistor (R27) there with possibly a broken leg. I'd check its resistance, too.

[Oldmactech]

testing across AC input (it has a detachable AC cable with male prongs on this card)t 20 ohms scale, shows open. (Older multimeter, displays a solid 1) testing across connected spade lugs Brown, white, blue, black, all 1.2 ohms. same with red and yellow secondaries.
Good catch on R27.thanks.