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Tube amp etiquette

quicksand

quicksand

Active Member
I have an all original Fisher x100c that was my fathers since the late 60’s. I use it maybe twice a week to play an album or two at a time. Am I shortening the life of the amp with all the off and on? Any thoughts or recommendations would be greatly appreciated.

Unfortunately I found this place after firing it up to see if the tubes lit around two years ago… live and learn - the tubes all test good to very good.

Thanks!
 
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You're doing less harm using the thing as it was intended than if it simply sat for extremely long periods of time. The capacitors do fail over time, but it seems the ones that sit and sit are the ones that really seem to go up in smoke in a bad way.
 
There are two methods that I have heard... If it isn't broke don't fix it and the other is to go over the caps and resistors. I suspect the caps would be the first thing to go if anything. I have the schematic but hardly the time or ability to test out every piece. My testing skills are limited to what I picked up during IA in high school 20 years ago.

When I said I listen to one or two albums a week that is in a sitting not twice in the same day; sorry if that wasn't clear.

I guess what I am asking is should the piece be used like any other amp or be saved for those special occasions. I would like for it to last and I haven't found a definitive answer on the internets. I would like to think that I am not doing any harm and tend to agree with gadget73's response.

Thanks!
 
Using it is fine, until that "one" time. It really should be checked over by a competent tech, and here's why. The electrolytic caps that were used in that amp, had a life expectancy of 10 years. I'm fairly sure that unit is solid state rectified which means the caps see a "big" hit of power every time you switch it on. If a cap fails "shorted". it can easily take a transformer with it. Out of spec resistors can drastically shorten tube life. The biggest reason though, is that you will never know what the amp is really supposed to sound like until it's running back at spec. Most people think these old amps sound great just the way they are, but are amazed at how much better they sound when restored. It's not like we're talking a huge pile of money either.:thmbsp:
 
I don't see where you are doing anything wrong. As to the caps...electrolytic caps that are 30 to 40 or more years old are questionable even if they appear to be working fine at the moment. I would make a list of all the electrolytic caps, place an order and replace them when time permits a free day to devote to the project.
Having said that I will now spend the rest of my day recapping my Kenwood KW-30 tube receiver!
 
I would say finding an amp which spent it's life being used a couple times a week would be ideal, not much use but still being used to keep caps fresh. I rotate my gear so it may sit 4 to 8 months then get used almost every day from two to 6 hours at a time and all is well (a Fisher 400 being one of them), though most of my vintage stuff has been restored.
 
For sure, all of the above advice is correct. Most of my equipment is HH Scott. One thing that I have found is that amplifiers work the hardest. Vintage tuners are almost always still working even with the original tubes.

One can somewhat tell how much use an amplifier has had by looking at the lettering around the volume control. Many of my amplifiers were made between 1959 to 1964. If an amp looks almost new, the capacitors and filter capacitors are usually still good. I will routinely replace the coupling capacitors to the output tubes and most of the time, the coupling capacitors and bypass capacitors in the preamp sections. I always replace the Siemens selenium bias bridge. Doesn't matter if it is good or not. I use an ESR meter on the filters and if they look good, I will leave them alone. I bring up the power with a variac, monitor current draw and the temperature of the first filter. If all is well, I may leave it alone.

Is this the right thing to do? Well, that is subject to debate. Since I know what to look for and it is my equipment, that is my choice. However, if someone asks me to restore an amplifier, the filters will be replaced. That way, the amplifier can be a "Daily Driver" if that is what the owner desires.

There is a lot of talk about the line voltage being higher today than it was 50 years ago. It is true. My line voltage (mains) is about 123 volts. Since much of our equipment is rated 117 volts, what to do? Some guys will use a filament transformer and configure it as a small bucking transformer. You can lower the voltage easily that way with no big loss of power or generation of heat.

So, in your case, you may want to listen carefully to the speaker when there is no input. Do you hear hum with the volume all the way down? Yes? You may need filters. Do the filter capacitors get warm? (and it is not caused by sitting between the rectifier and output tubes!) You may need filters. I guess it all depends on what you want to do, and if you want it to stay original (whatever that means!)

Sorry to ramble on, hope it helped...
 
jaymanaa said:
Using it is fine, until that "one" time. It really should be checked over by a competent tech, and here's why. The electrolytic caps that were used in that amp, had a life expectancy of 10 years.
Click to expand...

10 years sounds a little short to me. Where did that number come from? Considering that Scott and Dynaco amps easily played for 25 to 30 years on OEM components, I would think a 20 year lifespan would have been more accurate.
 
ducati_EL34 said:
10 years sounds a little short to me. Where did that number come from? Considering that Scott and Dynaco amps easily played for 25 to 30 years on OEM components, I would think a 20 year lifespan would have been more accurate.
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Sorry as to what it sounds like, its a fact of life. Plus, most of the amps discussed here are WAY more than 10 yrs old. Plus, caps are better today than the electros used back then. If the amp has sat around for years, chances are the electro caps in there are dried out. Sometimes using a variac can bring them back to a functioning state, but you are on borrowed time. I've seen cars fire up that have set for years and years, but that doesnt mean they are ready to go by any means.

Modern caps in a more modern built amp, used regularly are liable to last longer.

But after 10 years, its a good idea to have a tech check it out, see how leaky they are, ripple and so forth. Many times caps die a slow death, sometimes not. Like Jay said, we are not talking a lot of money, and the improvement in performance is substantial.

As to "where did that come from" get a newark catalog and look up caps, many times lifetimes will be listed. Plus, you just heard it from people that know...thats where!

Russellc
 
Russellc said:
But after 10 years, its a good idea to have a tech check it out, see how leaky they are, ripple and so forth. Many times caps die a slow death, sometimes not. Like Jay said, we are not talking a lot of money, and the improvement in performance is substantial.

As to "where did that come from" get a newark catalog and look up caps, many times lifetimes will be listed. Plus, you just heard it from people that know...thats where!

Russellc
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I am not trying to save a buck. I am not comparing the caps of today to yesteryear. I am questioning the "caps are only good for ten years statement".

So you are telling me that if I bought an ST-70 in 1965,and used it regularly, that in 1975 I should have it recapped? right... As for manufacturer's claims, remember, they are trying to sell stuff...
 
Even though my late 60's tube amp looked almost new.
I replaced ALL the electrolytics caps anyway.
Didn't cost much $$$.....and a couple of hours with a soldering iron.
My line voltage runs around 125.....so I use an old Speco variac to drop it down to 117v.

Steve
 
quicksand said:
I have an all original Fisher x100c that was my fathers since the late 60’s. I use it maybe twice a week to play an album or two at a time...
Click to expand...

This is exactly what your amplifier was intended to do. You're making your amplifier very, very happy. And your Dad too, hopefully!:thmbsp:
 
ducati_EL34 said:
I am not trying to save a buck. I am not comparing the caps of today to yesteryear. I am questioning the "caps are only good for ten years statement".

So you are telling me that if I bought an ST-70 in 1965,and used it regularly, that in 1975 I should have it recapped? right... As for manufacturer's claims, remember, they are trying to sell stuff...
Click to expand...

I certainly wouldn't want anyone to change old electrolytics that didn't want to, but I've heard firsthand what amplifiers with deteriorating electrolytics sound like (compared to what the same amps sound like with modern fresh lytics). I can't think of a single manufacturer that advertises more than a 10 year lifespan for Al electrolytic caps. Like I say, they don't have to explode to be bad (or cause bad things).:dunno:
 
ducati_EL34 said:
I am not trying to save a buck. I am not comparing the caps of today to yesteryear. I am questioning the "caps are only good for ten years statement".

So you are telling me that if I bought an ST-70 in 1965,and used it regularly, that in 1975 I should have it recapped? right... As for manufacturer's claims, remember, they are trying to sell stuff...
Click to expand...

Like I said, test them for leakage and the power supply for ripple. I'm not trying to sell anything here, and have nothing to gain. And as for the ST 70 YES...they used puke caps, with the exception of the little domino looking one, never had a bad one myself. That was definately a price point amp, the only thing quality is the iron.

Russellc
 
Russellc said:
Like I said, test them for leakage and the power supply for ripple. I'm not trying to sell anything here, and have nothing to gain. And as for the ST 70 YES...they used puke caps, with the exception of the little domino looking one, never had a bad one myself. That was definately a price point amp, the only thing quality is the iron.

Russellc
Click to expand...

I have already installed a Curcio cap board in my ST-70, along with a new driver board. My question was, would an ST-70 bought new in 1965 and used on a regular basis need new caps in 1975? That would be ten years.
 
Fisherdude said:
This is exactly what your amplifier was intended to do. You're making your amplifier very, very happy. And your Dad too, hopefully!:thmbsp:
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Fisherdude - what is your take on testing out the components - the amp sat for probably 25 years before he gave it to me. I had a friend test the tubes, bias - a few random points he felt important and eveything was as it should be and would leave it as is. Being an electrical engineer and on the side repairman I feel like I can trust him - but everyone has an opinion.
 
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