PT Heat

[RossH]

How warm is acceptable for a PT? I have built a Lite II using a 270FX PT. I am also using a 5AR4 rectifier. The amp sounds awesome. I don't remember it heating up before but last night the volume kept decreasing (I thought it was the amp but it was simply a Small Clone Chorus pedal losing its battery). After being on for about 2 hours and I was looking around I touched the PT and discovered it was quite hot. Too hot for me to clutch it tight around the whole unit and hold tight. Should I be worried?

TIA,
~ Ross

[SteveinTempe]

Can be warm to touch too warm to hold ...the main thing is current
make sure it has some ventilation and you are not exceeding
the amperage rating for the 5 volt TAP
Also check bias perhaps run the power tubes a tad colder
to reduce heat it may be ok Any senoir members want to
take a crack at this..

[zaphod_phil]

Personally, I don't like the idea of the PT runnning that hot. Over time, it's likely that the insulation between the windings will deteriorate, when running that hot. Fairly warm would be OK. You either need to find some way of reducing the power consumption or else get a beefier transformer. As has been suggested already, try biasing your tubes a little colder. Also, if you're running your pilot light of the 6.3V heater supply, try changing it to a neon, you can run directly from mains voltage and connect it to the primary side of the PT. If those tricks don't work, you may need to get a separate 6V transformer for your heaters, or like I said, change your whole PT for something bigger.

[RossH]

Thank you. Maybe it is just pushing too hard. It is a wide open chassis so ventilation isn't a problem. I have a neon light running off the mains right now. I thought that this tranny would be enough. I am running the el84's full bore (~12W) but I only have 2-12AX7's, 2-EL84's, and a 5AR4 running on it. Instead of modifying circuits to accomodate a lacking tranny I would rather just change out the PT. I'll give it a couple more jam sessions and pay more attention to the heat. What is the worse that could happen if it smokes? Does only the PT go or does it take some of its fellow components down along with it?

I appreciate your help, as always.

~ Ross

[SteveinTempe]

I switched my amp from a 5u4 to a 5y3 I like the amp better
the voltages came down there was no loss in power
just extra current being wasted in heat
I think the tubes would last longer if you could eek down to 9 or 10 watts
but again I defer to those with more experience..
I would not change the tranny but I am cheap like that!

[Plexi]

Not much to add, just wanted to agree with what the others posted.
If its that hot,something isn't right. Warm,and fairly hot might be ok.. but one that you can't hold onto,thats a bit much. It may last a while,but may see it fizzle out. Usually when they are like this,thats what happens..they slowly die. I do know that in the fender PT replacements that New Sensor was selling,i quit buying them. They, all would be like this,no matter what amp they were used for. So hot you couldn't touch them. I don't know if they have changed the place they get them from,its been a few years since i bought them. Just thought i'd pass this on. I think Bruce Collins brought up that they changed the manufacture, But since I've been using Heyboers for all the amps,i haven't had any problems.
Now keep in mind that was just the fender replacements..

Some things you may look for, if you have a few strands of wire touching another pin on the tube..it can cause this,and without blowing the fuse.
Look for any stray solder or small piece of wire or just making contact to the pin next to it. You could try it without the tubes in it,see if it gets hot on its own. Some people say hammonds are built like a tank, but about any transformer can go bad,or have problems. Just some seem to have them more than others.
Richie

[Plexi]

woops forgot to add, might try the 5y3 as suggested. The AC15 use them,and they work find,and supply for more tubes than the 18 lite version.

Richie

[Tony]

Perhaps it would be even better to replace the 5AR4 with a Weber Copper Cap and thus eliminating the need for heater current for the 5AR4. The copper cap is a cheap but effective tube rectifier simulator, basically a smart solid state plug-in. People report that the difference between using a copper cap and a real tube is less than differences between various tube brands. I am very pleased with mine, all my vintage amps have one installed now. about it at:

http://www.webervst.com/ccap.html

Best, Tony

[zaphod_phil]

An excellent suggestion! It will provide the response of a vacuum recto, while reducing the PT load and will last virtually forever...