Original 1958 Champ - What do I do

[Jack Hester]

Personally, I would leave it just the way it is.

I agree.

I have an original '51 Champion 600. Brought it up on a lamp limiter and let it soak on each wattage. Hand-traced the switch-side of the ungrounded cord, and marked it. That side always goes in the 'hot' side of the receptacle. Subtle hum, almost too low to hear. Great sounding little amp.

Jack

[Rhodesplyr]

After using one for several years, I've gotten pretty good at spotting failing electrolytics with an Anatek ESR meter. It's not perfect, but it's helped me identify many capacitors failing via the drying-out mode. It won't catch shorts, but it is what it is.

As far as a '58 Champ is concerned, it's the very definition of "not much to it." It should be fairly easy for an experienced tech to check it out, but, from a liability standpoint, most techs will insist on installing a three-wire cord and removing the "death cap." Jack Hester's very careful treatment of his two-wire cord is, in itself, an argument for why one might want to replace it. You may be trusting your life to the winding insulation of a 55 year old power transformer or a radio suppression cap (death cap). You are directly connected to the amp's chassis through the strings on your guitar. Do you value a solder joint or an original power cord more than the chance of electric shock? You might have to sign a waiver for a tech to look at the amp and not replace the cord.

There are two signal path caps in this amp that should be checked and monitored over time for DC current leakage, both 0.02uF. If you catch the leakage early, it can save you a tube replacement.

I had a customer come in with a 1958 Harvard with completely failed Astron signal coupling capacitors. One measured a dead short. Even then, he went into such a state of neurosis about the idea of replacing them that I simply handed the amp back to him. Not worth it. Life's too short for that much hand-wringing over such things.

[Gtr_tech]

I'd be more concerned with leakage than ESR. Leakage is what makes them heat up and eventually spew their guts all over.

The guy with the Harvard is a cork sniffer who would rather put the amp in a display case than have it operate properly. I'da done the same thing....sent him elsewhere for them to tell him the same story. I have quite a few NOS Astron caps that can't be used because of off the scale leakage.

[soundmasterg]

Just had a 1960 Pro in here with bad Astrons. Every single one of them was leaking more than 0.3V and the amp had an oscillation in the bass notes when it was dimed and the bass was up. It also had a two wire power cord and the death cap still. I replaced the power cord to a 3 wire and replaced all of the Astrons and the amp sounds much better. The Astrons went in a baggie that I gave the customer, and the customer is very happy. The electrolytics in the map had already been changed previously. That said, on your amp I would at least change the power cord over to a 3 wire for safety. You could also measure the coupling caps for leakage, and measure the electrolytics for leakage and ESR. If you can't do that, or don't have the equipment to do that, then you might be able to find a local tech who could check it out for you. If the caps check out as bad, or on their way to failure, then you at least know and can replace them if you choose.

Greg

[Leo_Gnardo]

AI've gotten pretty good at spotting failing electrolytics with an Anatek ESR meter. It's not perfect, but it's helped me identify many capacitors failing via the drying-out mode. It won't catch shorts, but it is what it is.

Shorts, that's what an ohm meter's for. Also could monitor the AC current and if it's suspiciously high, suspect the ancient filter caps. Also, leaky ones warm up beyond the ambient temp of the amp after a few minutes of operation. Found lots of failing can caps as well as individuals by hand touching & checking them for "fever." Recently got a laser infrared thermometer only @ $30, and that's become a handy failure analysis tool in the workshop. Keeps my hands out of the shock zone.

I'll have to revive my old Heathkit ESR meter & try your technique too. Doubtless its own filter caps need replacing.

[Rhodesplyr]

Shorts, that's what an ohm meter's for.

Unless it's a fairly complete short, capacitor leakage often won't register with the tiny voltages an Ohmmeter applies, but I assume, considering your evident experience, that you know this. Capacitor heating is, of course, a bad thing in many ways. If, for example, a first-stage filter cap develops high ESR, then the ripple heats the cap across that resistance, and the failure modes snowball from there.

[Leo_Gnardo]

Unless it's a fairly complete short, capacitor leakage often won't register with the tiny voltages an Ohmmeter applies, but I assume, considering your evident experience, that you know this. Capacitor heating is, of course, a bad thing in many ways. If, for example, a first-stage filter cap develops high ESR, then the ripple heats the cap across that resistance, and the failure modes snowball from there.

Call it a dummy test but I always ohm check those filter caps after first making sure they aren't storing any voltage, or showing the usual signs that say "change me!". What the heck, it might take all of 10 seconds. Sometimes I snag one that way. Then it's on to the usual bring it up slow on the Variac while monitoring voltage, hum, excess current draw and of course emission of smoke and spuzz (the scientific name of that crud leaking out of bad caps.) When in doubt, change it out. OTOH I've found amps with working filters made in the early 50's ! 60 years on the job and still working. Well so am I. Ain't that a miracle.

FWIW in old Fenders 60's 70's I find the second stage cap often fails. In many amps the first filter is 2 caps in series, and they are rated for well over the voltage they'll be seeing. That poor second stage cap has to put up with nearly 500V all by itself and many I see are on their last legs or beyond.

Amp collectors get the "change as little as possible" treatment. Musicians who take their prize gear out and play whether in public or studio or both, I tend to change old caps so they have a shot at 1) retaining their jobs without embarassment due to malfunctioning amps and B) not subjecting their audience, bandmates, crew etc. to a cloud of capacitor vapor. As a side note any amps with selenium rectifiers get those changed out to silicon. Cap smoke stinks. Selenium vapor is downright bad for you.

[soundmasterg]

I had a Sunn 200S years ago that could only manage 360v B+. It was stable and would happily work at that level for a long time....but the electrolytics were bad and replacing them made a much better working and sounding amp. Amazing how long some of those old caps will hang on and still function, even though they are working way out of tolerances and specs though!

Greg

[Rhodesplyr]

You were lucky to have a sane customer. I had a guy bring in a 1958 Harvard, and all the Astrons had major leakage of at least 10V. One measured a complete short. When I told him they needed to be replaced, he practically had a nervous breakdown over the idea of replacing the fabled Astrons and how I was going to ruin the value of his amp, so I just handed it back to him, no charge, and never dealt with him again. Good riddance :-)

He even called after he'd left with the amp to confirm that I hadn't removed anything from it!!

[teletwanger48]

My daddy explained to me when I was just a young boy that there are some follks you don't want to sell anything to... this guy sounds like one of those..