Toasty PT Opiinons?

[mhuss]

I have a single-ended Champ-style amp with a single 6L6GC that has a Hammond 270BX PT, rated for 50mA on the HV secondary. The amp is consuming right around 50mA, and the PT gets very warm after the amp has been idling for a while (i.e., max dissipation in class A). The exterior get up to about 50-55C (131F) -- very warm, but you can keep your finger on it. Do you think this an acceptable state of affairs, or am I pushing the PT a bit too hard? (I generally choose more leeway, but it was one of those "transformer at hand" situations.)

[Jazz P Bass]

131F is not going to 'melt' anything.

[Chuck H]

Should be fine. The Hammond products I've used (and I've used many) have proven VERY reliable under some occasional (and accidental) adverse conditions. The techs at Hammond will tell you that their product is capable beyond specs. That PT is designed to deliver it's rated voltage at the specified current. It's made with the expectation that is exactly what it will need to do for the life of a device. And that's what you have it doing. Since the amp is class A you shouldn't be taxing with more current even under hard playing conditions. I'd still run the amp through some hard paces for a good amount of time to be sure though. Nobody can treat an amp harder than a no tech guitar player. Dropping it on an outdoor stage in the direct sun in July and leaving on all day without a break for several sets, yada, yada... Maybe keeping and playing it in a crowded room where the only place to put it is backed up to the wall between the radiator and the toaster oven You get the idea. Use it HARD for a good hour and then take it's temp. And just to be sure, let it idle for an hour and re test too. Just in case idling is using MORE current than playing. That happens with some Class A designs.

[Tom Phillips]

My vote is also that 131F is fine.
Tom

[catalin gramada]

Hi. I have some reserve around Hammond products. All PT I used have the same problems which need little maintenance. In order: the coil is rating /the last transformer bought have 1mm space between core and coil!!! It need to be imersed in resin to fix. The scheme used for grounding using one non isolated screw bolt between the bells is not functional. I isolate everything in between and put electrostatic shield to ground and the iron core to ground with separate wire at one feet of the bell.You need also to keep one feet of bells free of paint for good contact but isolated in between to not create a loop in short. Thinking more like two separate cages grounded just in one spot.Of course can choose this point to be one end of the bolt like Hammond done but need more care for isolation and contacts . And btw. don't ever try to tie nothing else. like decoupling caps. heater reference or whatever to this spot.
I wonder by you heating issue. The Hammond I used have less than 10 percent voltage differences in full load spec wich means a well designed tranny in my understanding
Cheers