Blown Transformer on 2006 Carvin V3

[zboblitt]

I have the original version of the Carvin V3 Head. I believe it's power transformer went out because I measure 5 ohms between hot and return of the IEC when I flip the mains "on" while unplugged. 6A circuit breaker inline tells me I know the transformer should be at a minimum 20 ohms (the circuit breaker flips off within 1 second of turning the amp on). I looked up the V3 schematic and found the transformer to be 15-10714. That's all the information I can find on it. Does anybody know this transformer by another name, who makes it, how to get a replacement, was it proprietary to carvin, any information about it? Thanks.

[Helmholtz]

I believe it's power transformer went out because I measure 5 ohms between hot and return of the IEC when I flip the mains "on" while unplugged. 6A circuit breaker inline tells me I know the transformer should be at a minimum 20 ohms

I think you are mixing up DCR and primary impedance. Such low primary DCR values are not uncommon with PTs.

Does the circuit breaker trip with all secondary wires disconnected?

[zboblitt]

Does the circuit breaker trip with all secondary wires disconnected?

Yeah it still trips even with the secondary wires' connector unplugged from the PCB, so that leaves me to the IEC, power transformer, or circuit breaker. I guess you have a good point that I shouldn't have jumped to the power transformer from the low DCR since this is AC current which will have more resistance from the 'inductor'. Any other troubleshooting tips? Thanks!

[xtian]

You can test transformers using the neon bulb trick:

https://www.premierguitar.com/articl...ormer-tester-1

[glebert]

This appears to be a pretty simple tube PT, no low voltage windings for op amps or anything, no tube rectifier heaters either.



Maybe something like the Edcore XPWR002? https://www.edcorusa.com/xpwr002

[zboblitt]

You can test transformers using the neon bulb trick:

https://www.premierguitar.com/articl...ormer-tester-1

So I don't have a neon bulb; however, I do have a multimeter. Using a 9V battery in the same manner he used the 6V battery, the secondary coil (700V to 120V input) only jumped to 1V each time. The highest I could get it to jump was to 4V. I would expect somewhere in the 60V range for a 7:1 turn transformer using this trick. Thanks for the idea, but I'm still left thinking the transformer is toast. Here are some pictures. Looks a little....liquidy... on the top there.

https://i.imgur.com/2q0eAD5.jpg
https://i.imgur.com/PoM6pCB.jpg

[zboblitt]

Thanks for the tip about edcore. I found this one https://www.tubeampdoctor.com/en/mai...nmQaCyv0E2Pek0 which shows 400mA at 345V and 7.5A at 6.3V. Assuming that website is correct, it looks like edcore does have an option to meet that: https://www.edcorusa.com/xpwr127?fbc...th-iu8XDuPIjcc Not sure how I feel about the 8 week lead time though.

[Helmholtz]

So I don't have a neon bulb; however, I do have a multimeter. Using a 9V battery in the same manner he used the 6V battery, the secondary coil (700V to 120V input) only jumped to 1V each time. The highest I could get it to jump was to 4V. I would expect somewhere in the 60V range for a 7:1 turn transformer using this trick.

You can't replace the neon with a multimeter. The principle is magnetic (self) induction and works similar to a spark coil. Disconnecting the battery interrupts the current and produces a large but short flyback voltage spike that overcomes the ignition voltage of the neon lamp. Other than a neon discharge lamp a meter conducts all the time and thus prevents a large voltage spike. Also meters are much too slow. The neon lamp doesn't conduct below its ignition voltage of 60V to 80V and reacts very fast.

But I agree your PT looks toasted.

There are other methods to test a transformer. Do you have a bulb limiter? Or some other PT that delivers heater voltage?

[zboblitt]

You can't replace the neon with a multimeter. The principle of the test is based on (self) induction. Disconnecting the battery interrupts the current and produces a large but short flyback voltage spike that overcomes the ignition voltage of the neon lamp. Other than a neon discharge lamp a meter conducts all the time and thus prevents a large voltage spike. Also it's too slow. The neon lamp doesn't conduct below its ignition voltage of 60V to 80V and reacts very fast.

But I agree your PT looks toasted.

There are other methods to test a transformer. Do you have a bulb limiter? Or some other PT that delivers heater voltage?

I see your points on a multimeter vs the bulb. I don't have a bulb limiter either, nor other PT unless I pull one out of my Dr Z. I put this PT back in the carvin and turned it on again, just to make sure the problem continued to be repeatable and of course it was. This time I paid attention to the LEDs which always flash on immediately with power. The breaker popper after about 1 second, but during that 1 second, no LEDs turn on, the lamp bulb doesn't turn on, nothing even flickers. I'm fairly confident the PT isn't working at all.

[Prairie Dawg]

I know this is a Zombie thread but I've got the same issue-a fried 15-10714 Carvin power transformer for a V3. There IS a low voltage winding on this transformer that can be seen on the schematic and it is 8VAC. Did anyone have any success in locating a serviceable or new transformer? Any leads on one? The current owners of the Carvin name are not responding. TIA. You may reach me at rwluedemanATmchsiDOTcom.

[glebert]

If you can't find a transformer that can do all the voltages needed can a small transformer be fit in to supply just the missing voltage, like the 8VAC?

[The Dude]

Tube Amp Doctor has one in stock. Since your profile doesn't have your location listed, we have no idea where you are to recommend a vendor.

https://www.tubeampdoctor.com/en/mai...eve-vai-ts-100

[Prairie Dawg]

This appears to be a pretty simple tube PT, no low voltage windings for op amps or anything, no tube rectifier heaters either.

[ATTACH=CONFIG]56712[/ATTACH]

Maybe something like the Edcore XPWR002? https://www.edcorusa.com/xpwr002

I hope this finds you zboblitt.

The Carvin 15-10714C power transformer in the V3 does indeed have a low voltage winding and a low voltage supply, it's there on the schematic-otherwise how would you run the LEDs and the relays?
. The leads are orange and brown on the nine pin plug, goes down to a pair of 1N4007 diodes and 7805 voltage regulators on the main board. I'm in the same boat. Power transformer has no identifying marks so who knows where it came from? Carvin was no help at all.

Sourced a replacement power transformer, think it came from Lenco by way of a third party but the low voltage supply is on the fritz somewhere downstream.

Big power transformer meltdown. Cascading failure.

First, the bias control failed-the wiper went open. The amp did the japanese lantern thing because there's no HT fuse. 6A circuit breaker had failed "on" previously. Result: power transformer cooked itself, all four power tubes roasted.

Now, it's got a mains fuse and a HT fuse ala Marshall and a Marshall 22k bias pot, one of those big ones. Got good steady plate voltage and bias voltage, but nothing's happening on the low voltage rail. Diodes and regulators changed. Sheesh. This amp's a freaking albatross.