Fender Super Reverb RI heating up

[Richard]

I just bought a Super reverb reissue and noticed that when using the tilt back legs the hot air is trapped and the chassis gets hot, I'm guessing about 140 degrees F next to the pilot lamp. the amp does not get excessively warm in normal operation, only when leaned back. Will this heat damage the circuit boards or transformers? What is a good operating temp for those things?

[Jazz P Bass]

Of coarse you realize that there are a few variables that where left out of your post.
Ambient temperature.
Type of music played.
Volume of amplifer (output wattage)
140 degrees is not all that hot for a (2) 6L6 tube amp in working order.
The circuit boards will not care nor will the transformers.
If it really bothers you, place a fan at the rear of the amp.

[Joe L]

Tube amps run hot. In the '70s my Ampeg V4 running flat out with channels jumped would melt a mixed drink between one song to the next. Your amp will last longer if you put a fan on it, but it won't be the cause of it dying mid set just because of the heat. The tubes will not be bothered by it as much as the electrolytic capacitors and are easier for the end user to change out.

The rule I have is - new set of tubes with me that don't require rebiasing and a spare amp. A new set of capacitors at home unless I'm away for a week in which case I bring them with me.

[andyjazz]

What, you have some kind of intrerchangable capacitor circuit on your amp that doesn't require soldering?

[Justin Thomas]

I'm thinking he just carries a "roadside assistance" tech tool kit for extended times away from home. Caps, tubes, resistors, meter, iron, and anything else not available at the local hardware store (which more and more means a Mega-Mart where my questions are met with "What's that?") go with me too. Doesn't take much room & a hell of a lot easier & cheaper than finding the local amp tech in Wherevertown or Bung-Fu (not a dig at local amp techs, but if I can do it myself, I prefer to). Cheap insurance for cheap/poor starving musician types. Someone else's time costs $$$. My own is free. Hell, just solder some spade connectors on your spare caps. Although, I would almost bet that someone here will now design and implement a full-blown quick-change cap board... Anyone?

Justin

[km6xz]

Capacitors get changed out far more than they need to be but I am sure someone will build a little swappable module for $250 which will be all the rage with the magic dust crowd. Perfectly good 12AX7s and caps are probably the most needlessly replaced items in all of electronics. People tend to replace them as a first resort when a problem is suspected somewhere in the amp, before any diagnosis it done. They usually do not solve the problem of course.

[Enzo]

When I toured, I carried parts and soldering iron. I could do the work on the front edge of the stage or in my hotel room or even in the truck.

When I was a technical rep for a company in another industry, the sales guy would routinely ask me to add some feature to our equipment, and I'd go back to the hotel room, design the thing, and build a circuit on a Radio Shack board and install the next day. In the arcade biz I carried caps and transistors to repair switching power supplies in the field. None of that was really that challenging. A workbench is any flat surface you can find, and hand tools and soldering iron fit in your toolbox. Play a gig in some backwater town and your Hammond B3 Leslie cord breaks a pin, you fix it. Sure are not going to order one.

[Steve Conner]

How about on a table in the bar with a gas soldering iron?

[Enzo]

I did find that when the thinking was flowing slowly, it sometimes helped to dilute it with some alcohol.

[Joe L]

Capacitors get changed out far more than they need to be but I am sure someone will build a little swappable module for $250 which will be all the rage with the magic dust crowd. Perfectly good 12AX7s and caps are probably the most needlessly replaced items in all of electronics. People tend to replace them as a first resort when a problem is suspected somewhere in the amp, before any diagnosis it done. They usually do not solve the problem of course.

Not here! My '77 2203 sitting in the corner has the original caps in it. I've used my Sencore LC77 to check leakage at full rated voltage, value and ESR and they still check fine. I only play it at lower levels so it isn't getting really hot but I do play it every day. My '74 1959 screwed the pooch one night in the mid '70s at a gig when it shorted a cap so I replaced them with paralleled 500v spragues and they were still working when I changed them all out for conventional dual 50/50s in 2001.

And the amp I can think of that a cap job would be simple enough to carry a populated board would be Soldano's SLO. Here is my clone.

[isaac]

The easiest, easiest way to do so, I'd think, would be to have a "spare amp" and then keep a drawer with all the very most popular caps and resistors, and a soldering iron, if you have to fix something. And keep spare tubes for everything. Pretty simple actually, but IDK I have never toured, I have played a gig or two so what do I know. ;-)

[Chuck H]

Hey Stan, I agree about preamp tubes and caps being the most needlessly replaced components. But I do want to qualify power supply filters. I'm a big proponent of changing any filters over ten years old if a repair or procedure offers easy access. What is the sense in waiting??? And there are many new model amps that have seemingly very poor quality filter caps. Evidenced by the failure rate under ten years. That said... It seems like the most common operation is to replace a bunch of film caps!?! this is probably because the filter caps are more difficult, and so they are ignored. It always intrigues me when a fairly new poster mentions changing "All the caps" in an amp. Only to find out that they changed the film caps and NOT the electrolytics!?! Anyway... I just wanted to be clear on my take about your post. Power supply caps over ten years old = go ahead and replace them if you have ANY symptom OR if it's convenient. Film caps? Test and replace as needed only.

[km6xz]

Of the last 43 amps I have repaired, not one was traced to a filter capacitor fault, even in the supply. That is a small sample but that is all I have on the new shop work order program I just finished writing.
There are a number of predictors such as heat but caps lasting 50 years is not unusual at all. The surest way to extend the life of caps, resistors, tubes and transformers is to keep them cool. A well designed ventilation path can extend the life of a stock amp. A fan, with its filters cleaned regularly will greatly increase the working life an amp. Amps with regular mounting position of the power tubes having their bases on the top results in more heat transferred to the base, socket and chassis. In my old shop I had a database where all repair records and histories were stored and it was fun to play with searches to isolate models and see what the mean time between failures were, since new and between repairs. There were probably 50,000 guitar and power amp repairs in the at DB and a bit less for digital tape decks and effects. Without seeing the chassis one could predict whether it has tubes inverted by the decreased time between failures.

[Chuck H]

I humbly differ to your greater experience. Good caps can indeed last a very long time if not overheated and used semi regularly. But there are a lot of amps that don't use good caps, are overheated and left to sit for a year or more between owners. The old Mallory cans and such used in the fifties and sixties seem to last a long time with regular use. The power supply in my scope is still fine after twenty years. But there are a lot of amps that use lesser grade components with less than ideal heat consideration. WRT guitar amps I've seen caps fail under the ten year mark often enough to warrant my statements above I think. Maybe a little twitchy, but no harm can come of it.

[Joe L]

Of the last 43 amps I have repaired, not one was traced to a filter capacitor fault, even in the supply. That is a small sample but that is all I have on the new shop work order program I just finished writing.

Damn! Sure sounds like you and I have traveled a lot of the same roads Stan. Except it seems like I was doing 45 and you were doing 80!

What are you coding in?