power transformer raven rg 100

[bvh123]

I'm working on a friends amp, It is a raven rg 100, I think it might be the power transformer that is bad. It has very low voltage on the secondary. it has a 68v (ct) . there is five wires on the secondary two blue and a red then yellow then red.
I checked it plugged in and unplugged and the most ac voltage i got on it was 6.00 volts. I can't find a schematic anywhere.
I normally just work on tube amps so I was wanting to make sure  It was the power transformer. I'll appreciate any help

[phatt]

Check continuity on the *Primary winding* first be fore worrying about the Secondary ones.
A high or fluctuating reading means the primary side is likely blown.
Some mains Transfomers have *one shot internal thremo fuse links* which renders tranny unuseable once they trip.
Don't forget the AC cord as well,, all the way from wall plug to internal connections.
I doubt a schematic would be of much help with this sort of problem.
Sorry I can't be of more help. Phil.

[joecool85]

Some mains Transfomers have *one shot internal thremo fuse links* which renders tranny unuseable once they trip.

Bummer, I hadn't ever heard of this.  That would suck 

[bvh123]

the transformer is reading 2.5 m ohms,it also says on the top of the transformer internal fuse 250/5a/130 degrees c.
The power cord was alright. If it is the transformer where is a good place to get a replacement. thanks

[J M Fahey]

Excuse me, but what does:

2.5 m ohms

mean?
2.5 (Meg)ohms or 2.5 (milli)ohms ?
Your internal fuse should be a bimetallic strip, opening at "x" degrees temperature as quoted, but closing again when cold , plus a regular fuse wire, 2x or 3x the regular current needed, which should never trip, provided the regular, external fuse has the rated value.
If somebody replaced it with a grossly over rated one, or "repaired" it with a piece of thick wire or crushed aluminum cigarette paper , yes, the internal one will open killing it for good.
Anyway, that's the "best" thing to happen, considering the alternative of bursting in flames and burning your house ; that's why UL (Underwriter's Labs) mandates such safety devices in every transformer .
A cheap chinese manufacturer would use only a short piece of thin wire.

[joecool85]

Excuse me, but what does:

2.5 m ohms

mean?
2.5 (Meg)ohms or 2.5 (milli)ohms ?
Your internal fuse should be a bimetallic strip, opening at "x" degrees temperature as quoted, but closing again when cold , plus a regular fuse wire, 2x or 3x the regular current needed, which should never trip, provided the regular, external fuse has the rated value.
If somebody replaced it with a grossly over rated one, or "repaired" it with a piece of thick wire or crushed aluminum cigarette paper , yes, the internal one will open killing it for good.
Anyway, that's the "best" thing to happen, considering the alternative of bursting in flames and burning your house ; that's why UL (Underwriter's Labs) mandates such safety devices in every transformer .
A cheap chinese manufacturer would use only a short piece of thin wire.

Very interesting stuff, learn something new every day.

[Enzo]

The internal thermal fuses are not self resetting breakers.  They are a component that looks sorta like a diode.  or maybe a little cap.  Typically they are wedged between the windings - you have to tear the transformer apart to get at it.

[bvh123]

it reads 2.5 meg ohms,is there any place to get a replacement?I e-mailed raven amps with the part # and they never have responded.I hate to try to tear it open.

[J M Fahey]

Yes, then unfortunately it is open.
Please draw a rough sketch of the secondary, the 5 wires baffle me. "Map" which one is connected to which one, and also what they connect to on the power PCB.
Logic says you should have a CT main secondary, maybe red/yellow(CT)/red or blue/yellow/blue.
Probably yellow is CT, red is 34+34V and blue perhaps 15+15V or thereabouts to power the preamp, but I'm only guessing.
One wire (yellow?) must go to ground, and the others to some diodes.
Once you know what you need, getting a *similar* replacement isn´t that difficult.
Probably the power amp is burnt too. Something fried that transformer.
Good luck.

[R.G.]

Looking at the pictures and description of that amp on line, I think it's the successor model to the Rogue combo I scored for $40. The pictures sure imply what I found, and the power transformer nominal voltages look right.

You may be able to replace the transformer with *two* generic transformers; one a 68Vct 2-3A device for the power amp and one a 28? 30Vct? small toroid for the preamp, which is almost certainly a set of opamps. There was plenty of room in the chassis of the Rogue for trickery like this. I'm guessing there may be in that one.

A Really Good trick is to put in a 68Vct toroidal transformer for the main. Much lower hum emission.

[J M Fahey]

Then very probably it is a generic amp, made by some Korean manufacturing giant, and sold in the US under any fancy name that that particular distributor likes.
Please post Raven and Rogue transformers pictures for side-by-side comparison, I also feel they may be the same.
In that case, the working one will provide voltage and pinout information for the dead one.

[bvh123]

I believe you are right on the pinout, the two blue wires are 15 volts.Here is a picture of it. If I've attached it right. thanks for all the help.

[J M Fahey]

OK, you can search for a 34+34 (or easier 32+32 or 30+30) V , 150VA toroid or conventional EI , such as the original one.
What will complicate things a bit is also getting the two 15V windings, although that´s not that unusual.
Google for it; if you don´t find it, I´ll suggest an option, although it´s not as straightforward.
Be ready to repair that power amp, *something* killed that transformer.
Anyway the whole stuff looks quite repairable, much more than the Line 6 posted elsewhere.

[bvh123]

I can't seem to find what I need. is there any places you  would suggest looking for one.I tried searching on google and found a few things but nothing with the 15+15. thanks.

[R.G.]

I can't seem to find what I need. is there any places you  would suggest looking for one.I tried searching on google and found a few things but nothing with the 15+15. thanks.

I didn't think you would find a replacement with the 15V windings. That's why I posted:

You may be able to replace the transformer with *two* generic transformers; one a 68Vct 2-3A device for the power amp and one a 28? 30Vct? small toroid for the preamp, which is almost certainly a set of opamps. There was plenty of room in the chassis of the Rogue for trickery like this. I'm guessing there may be in that one.

You could put in this one for instance:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=237-1326-ND
and bolt it right to the bottom of the chassis. You parallel the primaries with the existing transformer primary, and connect the secondaries where the old transformer's 15v/15v secondaries went. It's another $20, but it's better than junking the amp, right?

Notice that you're contemplating doing things that require messing with rewiring AC power line circuitry. This is major dangerous to yourself and others if you don't already know what you're doing and how to do it safely. Do not try this if you don't already know how to do it right. It's not worth dying for - or having someone else die because you didn't understand something.