Peavey Classic 30 II 2018

[The Dude]

If I read you right, the primary does not seem open. I'm suspect of that thermistor. It may be open. Also check solder connections on the IEC connector.

[Oldmactech]

R27 has good solder connection on the underside. Reads 9.4 in 200 scale.
Right leg of IEC to blue and white wires reads 1.0 on 200 scale
Left leg reads 9.4 to brown and black wires, and thermistor..
Both the on/off and standby switch read 1.1.

Thank you.

[Helmholtz]

What Ohm reading do you get when you short your meter leads? Maybe 1 Ohm?

[Oldmactech]

I get 1.1 ohms with shorted leads.

[Helmholtz]

I get 1.1 ohms with shorted leads.

That's whatI figured. Means that all your resistances are actually around 1 Ohm lower than the readings because meter+ leads always add 1.1 Ohm.

[Oldmactech]

I get that. Do any of the readings indicate whether the OT is bad, or maybe something else?

[The Dude]

I presume you mean PT? Plug it in and check to see that you get ACV right at the transformer primary wires. That will either eliminate or confirm everything before the PT- power switch, fuse, fuseholder, etc.

[Oldmactech]

Getting 123VAC at the primary wire solder points.
On/off switch is working.

[The Dude]

So you have voltage at the primary. Check the secondary for ACV (disconnected if possible) and see if the transformer is working.

[Oldmactech]

Zero ACV at either of the secondaries. There are two pairs of wires from the secondary. Yellow wires measure 2.0 ohm on the 200 Scale . Red wires reads 34.0 on the 200 scale

[Enzo]

You have primary voltage at the primary, Unplug the amp. At those same primary wires - do they measure open between them?

[garytoosweet]

To be clear when you are measuring voltage at the secondaries, the primary is connected to the amp with amp power/mains ON and secondary leads are disconnected from circuit. Positive lead from your meter to one side Red secondary wire, negative lead to the other Red. Your meter is set to AC voltage.

If you have 120V at the primary and 0V at secondary, it suggests that PT is bad.

The PT is a common point of failure in these amps. There are thermal fuses* just inside the copper shield. Once you verify the PT is bad, you may want to open it up and check them. If one is open you may be able to just replace it to revive the transformer.

If you do need a replacement PT, Edcor makes a compatible one which is a bit beefier than the stock PT. It's a close to drop in replacement except you will need to drill 2 extra holes for bolts and need to extend one of the taps (Red HV tap IIRC) about 6 inches. Since they are made to order, maybe Edcor could send it with longer leads if you ask.

[Oldmactech]

Thanks for the detailed reply.

Yes, I measured the secondaries just as you suggest. I get 122 VAC at the primary connector but
0 VAC at the two red secondary wires.

I have ordered a replacement transformer from a Peavey and will report back when it arrives and I install it. I Will peal the original slightly open and see if the thermistor is something I can tackle.

[Oldmactech]

I pulled the transformer and peeled offa layer of the wrapping and exposed what is probably the thermistor. Tests open. Got the thermistor out- after trying ever angle finally got a quick look at it. Looks to be 134degrees F 1A.
tests Open.

going to look at Mouser and such see if it replaceable.

[Oldmactech]

Here’s the thermistor