Keeping a tube amp or preamp original

[straycat23]

I know I'm going to get pilloried on this, but I have to ask. If McIntosh designed an amp back in the 1960's to be safe, why am I hearing that it would need to be "serviced", meaning recapping and retubing, to be safe. If I found one that was absolutely original and was very clean inside, why would that not be safe? I know some of the original power capacitors run hot, or so I read, but didn't McIntosh's design take that into account? I saw a YouTube video with a tech taking an MC 240 apart, that he said looked completely unused, and recapping the power capacitors and rebuilt the bias section, and one other Bumblebee capacitor because of leakage. I'm thinking that he may have destroyed the original unique sound. But I may be wrong and often am.

 

[MACKIE1975]

What would you do with an old (antique) car?

 

[knockbill]

Capacitors and other parts have a usable life... After 40+ years, the parts available for older devices change as technology changes/improves...Tube amps and gear aren't as common as they were when tube was the only gear available, so the replacement parts are made with material that is available now, just like mechanical parts etc...

 

[ic-racer]

Once you replace all the faulty tubes, drifted resistors, corroded tube sockets, scratchy pots, high ESR caps, dead pilot lights, crumbled wire, and re-flow all the solder joints, one might as well go for a new build.

 

[straycat23]

This one, according to the tech, appeared completely original and with very little use. I guess there are those still out there. Why would it be deemed unsafe to use as original? If it were an antique car, I would try to keep it as completely original as possible.

 

[Flhrich]

Things wear, even if it looked good on the outside. Electrolytics, tubes and other components have a life span, so that the repair part. McIntosh used the known "safe" parts at the time, but its 50+ years, since then. We now have 50 years of knowledge that the designer at the time did not. Some items did survive other did not, so we restore. From what I understand putting in new parts and in some instances better parts will not change the sound, as it was designed. When I restored my MC2105, it looked near perfect on the outside. When I took the large main capacitor off, one had leaked out as evident of the large rust spot under the cap. Other capacitors and resistors too, were out of spec, so they got replaced.

Things wear out, due to time or useage.

We were all perfect once too, I wish I could replace a few capacitors and be back to original

 

[savatage1973]

Everything "ages"--some things like a fine wine or whiskey for the better--in most cases for the worst. I know people that have bought NOS/NIB gear/speakers and ended up spending just as much to restore them as a "used" piece. Just because it is "new" or "like new" has no effect on the fact that something is 30-40-50+ years old.

 

[MACKIE1975]

Restoration is a must for anything that old.

 

[isotopesope]

This one, according to the tech, appeared completely original and with very little use. I guess there are those still out there. Why would it be deemed unsafe to use as original? If it were an antique car, I would try to keep it as completely original as possible.

You'd still need to put fresh tires on it to be able to safely drive it on the streets.

 

[62caddy]

This one, according to the tech, appeared completely original and with very little use. I guess there are those still out there. Why would it be deemed unsafe to use as original? If it were an antique car, I would try to keep it as completely original as possible.

Capacitors have a finite life and there's an excellent chance the electrolyte they contain had solidified rendering them useless and even dangerous. This is all the more likely after long periods of disuse. For these reasons there's no getting around replacing these parts. Tube life isn't normally affected by age and originals can still be used if they test well.

There's no reason the amplifier should not perform as it did when new if replacement parts are of the same values and quality of the OEM parts. Leaving the unit untouched is fine for a static display piece - so long as you never plan on using it.

 

[One911Guy]

A few years ago I purchased a 1976 Triumph TR6 - All very original down to the date coded original Michelin Redline tires. First thing I did was replace the tires and the fan belt that were original, and the consumables in order to operate the car safely. Coolant, brake fluid, points, condenser, plugs, etc..... I think it was just smart to do to keep that car running and running safely for it's passengers and the people and property it moved in and around. Does the car perform as well as when it left the factory? Yes, and probably better. (ok, no Triumph jokes from those that know) I love those little British cars.

There is even a joke going in and around the NCRS (National Corvette Restorers Society) - Do the original tires still have the original factory air in them? If not, a 5 point judging deduction.......

 

[c_dk]

Power supply filtering capacitors of the electrolytic type are and have been the standard for practical, reliable, reasonably priced performance.

One of their "flaws" is that the insulator between the aluminum foil is literally a few atom thin layer of non conducting aluminum oxide. This makes for a huge surface area, especially when the aluminum foil is etched to "rough up" the surface, and therefore high capacitance values in rather small packages are available.

However, over time, especially when not in use, the aluminum oxide desolves into the electotrolyte which can and will cause the cap to short out, arc internally, create hydrogen gas and cause all kinds of mischief and grief.

That is why a tech will tell you to use your gear......trailer queens need excersised also as any car restorer will tell you.

When you use a amp the oxide layer will heal itself. Some try to restart the old dead chemical reaction by carefully under controlled conditions applying voltage to them....this is very much hit or miss.

Eventually even this runs out as the chemical reaction runs it's coarse. Eventually the electrolyte dries out.

So even the best parts whether today's or from decades ago have a useful life, Mac and other quality manufacturers often used the best parts available to them. We try to do the same today when we restore a unit.

So, restoration means replacing those parts that have a useful lifespan and then use the unit.

 

[Phototone]

The sound of an amp won't be the same as new with 40-50 year old parts. Only with correctly functioning parts replaced to original values will the amp sound like new, and be safe to use. You don't want to have to replace a Mac transformer because $5.00 worth of parts are bad.

 

[savatage1973]

The sound of an amp won't be the same as new with 40-50 year old parts. Only with correctly functioning parts replaced to original values will the amp sound like new, and be safe to use.

This brings up a couple points that I feel are relevant. I have had the opportunity (at my tech's shop) to listen to and compare two identical receivers--one was "like new" but totally unrestored, and the other had just been totally restored--no modifications, just spec'd back to original. Same source, same speakers, same room. The difference was like night and day, with the restored unit far outperforming the "like new", but just "old" unit--both audibly and measurably.

Now this begs the question--which do YOU like better? If you like that "warm/fuzzy/muddy" sound, and don't know or remember what a particular piece sounded like brand-new, right out of the box in 1974, you might be disappointed, because you might not like the level of clarity and detail when it is brought back to spec. I have run across this experience the most with older Sansui and Marantz owners. IMO--they don't "age" well, and just start to sound "tired" (to me), but their owners don't always appreciate the "improvement" when they are brought back to spec.

There is also (again, to me, at least) a big difference between a "restoration" and a "modification". A "restoration" addresses any issues, and uses parts of identical/equivalent values as originals. "Modification" is exactly that--changing things away from the original design (for better or worse, but it is still not "original"). In automotive circles, these are "hot-rodded", or "resto-mod" vehicles, and depending on the quality of the modifications, and preferences of the owner/buyer, may increase or decrease the value--it can easily go either way.

Safety and reliability is a whole other "can of worms". Some things just don't "age" well. Lots of folks in the midwest learned that (the hard way) about car batteries and tires this week. "It's been running/driving fine since I bought it 5 years ago"--until the temp dropped below zero, and a few inches of snow and ice hit, and their car wouldn't start (or if it did) they were careening all over the place out of control.

 

[SaturationPt]

My 240 was original, very low use, and didn't have the "bumblebee" caps of the earlier MC240s. Slowly brought up to voltage over time ("reforming" capacitors they say), and played very nice. Bias resistors checked well within spec, capacitors that I could test were within spec, rectifiers working well, no hum and all voltages in spec. So why "restore" with new power supply caps and replacing selenium rectifier? Partly safety, hate to see something fail and destroy my transformer, and kept original parts in case my offspring decide to sell it when I'm below the dirt.

I feel much better about using it and walking into another room, don't feel I will need to make a mad dash into the media room to unplug it when a tube red-plates or the selenium rectifier fails, that's all. I don't use it but it's ready to run if I want to, similar to the TR6 example above, ... a minimum amount of maintenance is necessary to prepare it even for parades (had a TR6, miss it).

I do also have some perfect-original '60 & '70s original gear that I haven't touched, it is only for display at this point so no reason to alter it.

It's a choice. If I'm looking to buy I'll pay more for original un-touched gear than I will for "restored" unless it was done by someone well known in the field and documented. In many cases (most) I won't touch owner restored electronics and speakers.

 

[62caddy]

Now this begs the question--which do YOU like better?

Easy. To use as intended - electronically restored hands down; display only - original untouched.

 

[quartersaw]

I know I'm going to get pilloried on this, but I have to ask. If McIntosh designed an amp back in the 1960's to be safe, why am I hearing that it would need to be "serviced", meaning recapping and retubing.....

A bad power supply cap can take out a power transformer.

 

[twiiii]

Nothing lasts for ever. Would you drive a 1933 Duisenberg on original tires, with original points and plugs and wires etc? You are just asking for trouble. Even humans need heart replacement surgery from time to time. Or a new a new Kidney maybe a Hernia operation or a repaired broken bone or two. Get her tuned up now before she has to have major surgery. Its will save you money and guarantee more hours of pleasant listening.

 

[UncleBingo]

The capacitors don't "Run Hot". They get hot because the resistance goes up as the electrolyte fails. Burned the living &^%$ out of my finger learning that one on a Fisher Tube receiver that by all other accounts was "Totally original" and "Works great" and "Doesn't need caps, it works fine".

 

[excabincrew]

is there indication of bad power supply before it take out the transformer. Or do we go by the years it is used?