Astroid 60 PT Temperature

[passfan]

I am wondering how hot some of your PT's are getting with this amp. Mine is running around 50 deg. C. after around 30 to 45 minutes or so. This is just under the "wow I can't touch it" level of heat. I am using an older woodward-Schumacher running at the spec'ed voltages and calculated out at around 400 ma's. I did load down a 7.2 volt winding to 4.98 volts for my rectifier with a 1 ohm 50 watt power resistor. This was calculated out specifically for the current load of a gz34 and worked nicely. This couldn't be the source of any extra heat in the PT could it ? If I remember correctly most trannies are rated around 85 deg C. or is it 105 deg C. ? The 500pf bypass on V1a rid me of my high freq oscillations but I still have an out of tune artifact with some notes in the middle of the neck that I can't figure out. Anyone experience this ghost note stuff ? Thanks

[passfan]

I think I solved the heat issue. It would appear this PT only drove four octal heaters and is a bit undersized for the 1.5 amp heaters of the el34 OT's. I swapped them out for some STR 6L6GC Sylvanias I had at .9 amps per heater and it cooled down quite a bit. It was enough to take around 1.2 amps off the heater winding. This organ I robbed this PT out of had a seperate filament transformer that could run 10 amps at 6.3 colts. It's just too big and heavy to incorporate into anything transportable.

[M Fowler]

Good thing you realized what the problem may be.

6L6 sounds good right


Mark

[passfan]

Good think you realized what the problem may be.

6L6 sounds good right


Mark

I haven't plugged a humbucker back into it since but it is running cooler. Those big Sylvanias make everything sound good. They are the big bottle, lotsa room to run, ones.