Replacement Transformer for Fender FM65R (fits Roc Pro 1000 & Deluxe 112)

[Tone Meister]

Fender FM65R power transformer is failing. Nothing is shorted, but with the secondary disconnected from the amp, the secondary should be producing 31 VAC but only produces ~24 V when cold and voltage output decreases steadily as the amp warms up. Once warm, it does ~3 VAC on one lead (P3) and ~14VAC on the other (P5).

I believe the same transformer also fits the Roc Pro1000 and Deluxe 112 solid state.

Item Number: 0027668000
Manufacturer: Fender
Manufacturer Part No: 0027668000 UPC 717669104191

Out of stock everywhere I've looked so far. Has anyone found a suitable replacement that will bolt in with little or no hassle?

[DrGonz78]

I am nearly 100% that I have that exact transformer in my shop. I have to head off to work right now but later tonight I will dig it out.

[Tone Meister]

That would be most excellent. If you have it you can send me a private message with what you want for it and I will provide my mailing address. Thanks.

[Enzo]

Measure the resistance of that winding, just for kicks.

You plan to replace the transformer? So that puts us into the "what have you got to lose?" condition. Carefully cut the thing open and explore the connections where the winding wires are soldered to the insulated wires that go to the outside world. You might just find a failed solder joint going intermittant, and as it warms up the resistance rises in the joint. You may have to cut into soem fish paper, that thin sheet of cardboard-like stuff, but just do it carefully. If it fixes it, great, tape the innards back up and put the cover back on. If not, well, what did you have to lose?

[Tone Meister]

Measure the resistance of that winding, just for kicks.

You plan to replace the transformer? So that puts us into the "what have you got to lose?" condition. Carefully cut the thing open and explore the connections where the winding wires are soldered to the insulated wires that go to the outside world. You might just find a failed solder joint going intermittant, and as it warms up the resistance rises in the joint. You may have to cut into soem fish paper, that thin sheet of cardboard-like stuff, but just do it carefully. If it fixes it, great, tape the innards back up and put the cover back on. If not, well, what did you have to lose?

I had planned to do just that. I have "repaired" a couple like that in the past.

[J M Fahey]

In any case its ratings are the most common in SS amps: anything with 30+30VAC +/-10% , 2A or higher will do.
As in any transformer found in a 60 to 120W SS amp in the last 40/45 years or so, from Kustom and Standel to Peavey/Acoustic/Crate/Fender/Marshall/Laney/Ampeg/GK/etc.Anything that runs out of +/-40V rails or thereabouts.
So you should have a replacement to cannibalize straight in your junk room, or many around here might.

Even one of mine would fit , pity the distance.

[Tone Meister]

In any case its ratings are the most common in SS amps: anything with 30+30VAC +/-10% , 2A or higher will do.
As in any transformer found in a 60 to 120W SS amp in the last 40/45 years or so, from Kustom and Standel to Peavey/Acoustic/Crate/Fender/Marshall/Laney/Ampeg/GK/etc.Anything that runs out of +/-40V rails or thereabouts.
So you should have a replacement to cannibalize straight in your junk room, or many around here might.

Even one of mine would fit , pity the distance.

Good point Juan, but don't forget that I'm just a hack, so I won't have the spare used parts lying around that a professional tech might have.

[DrGonz78]

Good point Juan, but don't forget that I'm just a hack, so I won't have the spare used parts lying around that a professional tech might have.

I am pretty much a hack that's why I have all these spare parts lying around. Actually a few years back I decided to use this 65r DSP as a parts amp. This amp has fixed many amps over the past few years. Here is a picture of the transformer and I am positive it will work just fine in the Fender 65r amps. Since you might try salvaging that old PT then you may not need it. However, I will give you a great deal on it! Just PM me if you cannot repair that other PT.

[J M Fahey]

It certainly must work, doubly so becase itīs a "65" too, and also a Fender.
Only difference *might* be mounting, this one is through chassis (the other one probably is too) but in any other case, replacing with extra long bolts or adding small iron brackets solves the problem.
Just to triple check, measure secondary voltages, I expect around 30+30VAC or not too far from that.

[52 Bill]

That's the correct transformer, the part number in the photo is the same as the one listed earlier.

[Tone Meister]

Measure the resistance of that winding, just for kicks.

You plan to replace the transformer? So that puts us into the "what have you got to lose?" condition. Carefully cut the thing open and explore the connections where the winding wires are soldered to the insulated wires that go to the outside world. You might just find a failed solder joint going intermittant, and as it warms up the resistance rises in the joint. You may have to cut into soem fish paper, that thin sheet of cardboard-like stuff, but just do it carefully. If it fixes it, great, tape the innards back up and put the cover back on. If not, well, what did you have to lose?

With all leads disconnected, measured 2.0 ohms between the two red secondary leads. Measured 1.0 ohms from the CT to one lead and 1.2 ohms from the CT to the other lead. May have found a suitable used replacement (thanks Juan) from an old Earth SS amp, but I am gonna open this one up to see if I can repair it simply.

[Tone Meister]

OK, carefully opened the insulating layers and visually checked for obvious problems and nothing jumped out at me.

Performed RG's Power Transformer Test Procedure and find the following:

• No continuity from secondary CT to chassis
• Primary resistance measures 4.0 ohms (<1Kohm)
• Both primary leads read open circuit to chassis (>1Mohm)
• With the PT completely disconnected and on the bench, with center tap grounded to transformer body and 120 VAC applied to primary, one secondary measures 5.4 VAC and the other measures 1.8 VAC. However, measuring both secondary wires I get 65.1 VAC which is about what this PT should produce unloaded. After 10 minutes the transformer is not even warm.

NOTE: The secondary voltage has dropped considerably from the above readings after just a few minutes with power to primary, with an unloaded secondary. The wall voltage into the primary remains steady at 120 VAC.

NOTE #2: After 40 minutes under power and with an unloaded secondary the transformer nice and warm to touch. Definitely not hot, but nice and warm. Leads read 1.6 and 2.8 volts, and the winding still reads 65.0 volts end to end.

Time to call the undertaker?

.

[J M Fahey]

1) you definitely lost the CT, since transformer canīt even apply proper voltage to the minuscule load presented by the meter, let alone any real world one.
I suspect dirty center tap enamelled wires, soldered with a cold iron, which just melted tin around them, center tap wire might even have been wound around enamelled wires, but cooling tin ring just grabbed dirty enamelled wires, like a poorly crimped low pressure joint.

Might even have worked for some time, but if left unused in storage for some time, an insulating greenish/brownish copper oxide layer might be separating them now.
Easy to repair if you can scratch copper shiny bright and resolder, but if hidden inside youīd have to unwind to expose, probably beyond the call of duty

I always burn enamel first, sand or blade scratch it shiny and only then solder, Friday afternoon worker might have burnt and soldered .

Or they might be using *self-soldering" enamel, the kind which evaporates with no residue at solder temperatures, but that requites a real hot soldering iron , 60W or higher, to be successful.
We are talking 0.80mm to 1mm diameter wire here, which has some thermal mass and takes , say, 5 to 10 seconds to properly heat and shed insulation ... worker might have been in a hurry.

2) It would be interesting to *load* that end to end 60V something winding, at least with a 1k 2W resistor or something, to check whether it holds voltage or drops miserably.
If soldering failed on one, might as well fail on all 3.

Personally I do not use "hidden solders", I bring all enamel wires out with 5 cm tails at least, tape and insulate main winding, and then burn/scratch/solder/insulate each connection.

Transformers look kind of rough but everything is visible, donīt even use the last "fishpaper" outer foil.
Later will post some pictures .

[Tone Meister]

Everything looks new and all three connections are solid. The solders with this one were also brought out to tails and nicely insulated from the main winding with a closely-fitted cardboard sleeve. I seriously doubt it could have been done any better, so the failure must be deeper than I wanna dig.

Think I may have another PT that'll drop right in, but it's gonna be Friday before I can deal with that.

[J M Fahey]

Weird.
Just curious, what resistance do you read between secondary wires?