TF-130 Power Transformer

['67_Plexi]

OK guys, most of you have read the transcript from the '97 HRM amp that was somewhat reverse engineered. This thing used a Twin Reverb (TF-130) power transformer to power 4 EL34's. I'm a bit puzzled by this choice because of filament supply currents.

Let's take a Twin Reverb with 4x6L6GC's, 4x12AX7's and 2x12AT7's,
the total filament current demand would be approx 5.4A.

Now if we take a HRM EL34 Dumble with 4xEL34 and 3x12AX7 the total filament current demand would be 6.6A.

What is the typical design rating of a Twin Reverb O/P tranny, is it still within limits, how hot would it get ??

[groovtubin]

OK guys, most of you have read the transcript from the '97 HRM amp that was somewhat reverse engineered. This thing used a Twin Reverb (TF-130) power transformer to power 4 EL34's. I'm a bit puzzled by this choice because of filament supply currents.

Let's take a Twin Reverb with 4x6L6GC's, 4x12AX7's and 2x12AT7's,
the total filament current demand would be approx 5.4A.

Now if we take a HRM EL34 Dumble with 4xEL34 and 3x12AX7 the total filament current demand would be 6.6A.

What is the typical design rating of a Twin Reverb O/P tranny, is it still within limits, how hot would it get ??

FWIW, i`m running a 60`s TWIN, and NO overheating SO FAR To be honest, i see the 100 watt ( vs 80) Fender PA POWER trannie used ALOT like the one GIL so GRACIOUSLY showed here at the forum, look up the #`s, I have a SET JUST like that here at the house ANXIOUSLY awaiting their turn! Have built ONE Dumblish amp based on those trannies 3 yrs ago

['67_Plexi]

Thanks for the reply. The amp that Gil posted was running 6L6's, which is what this PT is designed for. According to the common sources Dumble still used this PT in the later EL34 amps. Each EL34 tube takes 1.5A of heater current, whereas a 6L6 only takes 0.6A. This puts about 1.5A more demand on the transformer than a Twin Reverb would. I was asking if anyone knew what the max filament current a Twin Reverb PT could safely supply.

[groovtubin]

Thanks for the reply. The amp that Gil posted was running 6L6's, which is what this PT is designed for. According to the common sources Dumble still used this PT in the later EL34 amps. Each EL34 tube takes 1.5A of heater current, whereas a 6L6 only takes 0.6A. This puts about 1.5A more demand on the transformer than a Twin Reverb would. I was asking if anyone knew what the max filament current a Twin Reverb PT could safely supply.

sorry ta bug in, BUT since HOWARD used EL-34`s w/TWIN tranny(I DO AS WELL IN MY HRM BUILD) i`d SAFELY asume IT CAN AND DOES WORK W/O ILL AFFECTS! You KNOW the MATH, it sure LOOKS like it WON`t handle it, but......the REAL reason he used that TWIN power was to APROXIMATE the sound of a VARIACED MARSHALL.... My B+ is well below 450vdc, Hope this helps even tho i didn`t discuss a twin power transformer current capabilities, willin ta bet tho, that they are WELL over rated from shumacher... otherwise HE WOULD`NT HAVE USED IT!!

[Darkbluemurder]

Thanks for the reply. The amp that Gil posted was running 6L6's, which is what this PT is designed for. According to the common sources Dumble still used this PT in the later EL34 amps. Each EL34 tube takes 1.5A of heater current, whereas a 6L6 only takes 0.6A. This puts about 1.5A more demand on the transformer than a Twin Reverb would. I was asking if anyone knew what the max filament current a Twin Reverb PT could safely supply.

If I am not mistaken a 6L6 takes 0.9A heater current, i.e. 0.6A less than an EL34. Converting a 4 power tube amp from 6L6 to EL34 would therefore place 2.4A more heater current on the PT.

['67_Plexi]

groovtubin, I'm with you on that one mate. I think your theory is correct.
I guess buying a good quality TR transformer is the key. I have sent a message to Mercury Magnetics to get their spin on it and if they can recommend a particular Twin Rev PT that has the current and voltage capabilities for the job at hand.

Incidentally in my last HRM build I used a Weber 100W Marshall transformer, which although looks really well built and produces a pretty close B+, gets pretty damn hot, although the amp hasn't suffered from it (yet).

['67_Plexi]

Darkbluemurder, when you take into account that a Twin Rev has 6 preamp tubes, whereas the Dumble only has three, the filament current differential between the two amps is 1.2A which is approx 20% more.

[Darkbluemurder]

Plexi,

No problem. A preamp tube has 0.3A heater current, so going from 6 tubes to 3 tubes reduces current by 0.9A. But now I understand how you calculated the 1.5A (increase power amp tubes 2.4A less decrease preamp tubes 0.9A).

Cheers DBM

[pazzo63]

Hi,please i 'd like to know if the tf-130 power transformer has the european voltage,if not what is a great replacement with same characteristics for people that are not in USA?THANKS in ADVANCE

['67_Plexi]

The TF130 only has 120V primaries.
These transformers come from Magic Parts, who are a wholesale distributor. They do not stock anything but 120V.

In reality the TF130 just a basic (Blackface spec) Twin Reverb style Power Transformer.
Any good quality BF 100W PT, such as a MM or HB will do the trick.
Both of those Companies will supply PTs with multiple primaries.

[Funkalicousgroove]

From my understanding, New production trannies utilising new materials(pvc/teflon wire) even if built to original specs will actually have higher VA ratings simply by virtue of their components. 22awg cloth cover can handle something like 5A, PVC I think is more like 7 and Teflon doesn't melt with my soldering iron at 700 degrees+. The current rating of a transformer is based on how much current it can produce before it becomes chernobyl inside, but it seems to me that by using wire with a much higher dielectric strength you have more power available than a trannie wound with lacquered cloth wire. Just my $.02, please correct me if i'm wrong here.