Vox AC15cc1 240v Power Transformer replacement

[Guitar fool]

Hi all,
I picked up a cheap Vox AC15cc1 last night with a blown power transformer. (blows power fuse instantly when power is switched on and all other fuses and tubes removed.)

I thought it would be a simple fix but there doesn't seem to be any transformers available here in Australia. Does anyone know of a 240v replacement that will work and not cost twice what the amp is worth?

Also I can't find and specs for it. It has three secondary coils. I don't mind if the tremolo and reverb don't work but that still leaves two secondary windings that I don't have specs for.

Any help would be appreciated.

[mozz]

Have you measured any primary or secondary windings? You may have to take it out of circuit to actually test it.

[Guitar fool]

Thanks mozz, I just measured it now. I took one lead off each coil and it reads the following.
Red/Black (primary) 6.5 ohms
Purple 119 ohms
Pink 0 ohms
Brown 3.8 ohms

If my understanding is correct then primary is low, purple is too high, pink is shorted out and brown is ok.

[Jazz P Bass]

https://www.tubeampdoctor.com/produc...qv3nnYGbFQjYc3

[J M Fahey]

cheap Vox AC15cc1 last night with a blown power transformer. (blows power fuse instantly when power is switched on and all other fuses and tubes removed.)

Need further testing.
Label all secondary wires, as backup take a couple pictures, cut all secondary wires from where they are soldered today, for now tape all ends for safety and connect primary to mains ... does fuse still blow?

Also I can't find and specs for it. It has three secondary coils. I don't mind if the tremolo and reverb don't work but that still leaves two secondary windings that I don't have specs for.

1) post the schematic
2) draw a "map" showing all transformer wires.

I took one lead off each coil and it reads the following.
Red/Black (primary) 6.5 ohms
Purple 119 ohms
Pink 0 ohms
Brown 3.8 ohms

If my understanding is correct then primary is low, purple is too high, pink is shorted out and brown is ok.

No, different windings will shown different resistance values as needed.
Please show in the wire map resistance from which to which wire.
Besides you mention "one" wire but we don´t know where the other probe sits.

It has three secondary coils. I don't mind if the tremolo and reverb don't work but that still leaves two secondary windings that I don't have specs for.

It needs all 3 windings, but please answer the questions above for a better answer.

[Guitar fool]

Thanks for the help!
Here is the schematic http://www.guitarnewsdaily.com/wp-co...matic_only.pdf
This is a basic drawing of the transformer. I disconnected everything and measured the resistances again as shown. I also measured the resistance between each wire and all the others and they were all OL except for the grey wire ( standby ) and the purple wires.
https://photos.app.goo.gl/Kg92t21aRVVeFPyq9

Need further testing.
Label all secondary wires, as backup take a couple pictures, cut all secondary wires from where they are soldered today, for now tape all ends for safety and connect primary to mains ... does fuse still blow?

No it didn't, just gave a nice transformer hum. Should I reconnect each secondary until it blows?

[g1]

You could do it that way, or you could build a lamp limiter and connect them one at a time til the lamp glows bright. That way you can save fuses, and save the amp from further damage.

[Guitar fool]

I'll have to make one g1.
I connected the purple wires back up to TT5 and TT6 and the fuse blew. I have disconnected R71 and TT7 as well as C132 and C33 and it still blew. I am now using T500 fuses instead of T800 as they are the only ones I have. I don't know if that should be an issue but I will get some T800 fuses soon. I am not sure what could be the problem, there is only two diodes that I will replace and two resistors that measure ok. Am I missing something obvious?

[SoulFetish]

I'll have to make one g1.
I connected the purple wires back up to TT5 and TT6 and the fuse blew. I have disconnected R71 and TT7 as well as C132 and C33 and it still blew. I am now using T500 fuses instead of T800 as they are the only ones I have. I don't know if that should be an issue but I will get some T800 fuses soon. I am not sure what could be the problem, there is only two diodes that I will replace and two resistors that measure ok. Am I missing something obvious?

I would guess one or both D5/D6 rectifiers failed. If the the those two legs of the secondary winding shorted, that would almost certainly draw 4-4.5A (maybe more?) over-current in that winding alone and blow the mains fuse. What did you say the listed fuse value the mains fuse is supposed to be rate at?

[Guitar fool]

I replaced the rectifier diodes D6/D5 and the fuse doesn't blow any more. I put everything back together and there is no sound!!!!
Fuses are good, tubes are all glowing, everything looks like it should but not a sound. No pops or anything.

Edit: HT fuse blown.

[g1]

So maybe multiple problems? Something downstream that blew one or both of those diodes?
Lift the OT connection and those caps and resistors and try again.
All other connections hooked up.

[Guitar fool]

Thanks g1. I replaced the blown fuse late last night and it is all working now. I am not sure when the HT fuse blew, it was fine when I first checked it, must have blown somehow when I was testing the other fuse. Anyway it is working now. Thank you all so much for the help. It's great to be able to finally hear the amp.