Vintage Amp: Service or not?

[Pryde]

Hello Folks,

After working on a couple vintage Traynors and falling in love with their tone, I recently purchased a 1972 Traynor YGM-3 for myself

The amp is in pristine condition and ALL original including the filter caps, jan-phillips tubes, etc. For sure I will be changing the 2-prong to a 3-prong power cord for safety reasons but am unsure if I should do other service as well.

Basically the amp is dead quiet, works perfect, and sounds absolutely wonderful as is with its original (Mallory) filter can caps and coupling caps. Should I re-cap it based solely on its age even if its working great?

Also these amps are notorious for putting ~35-38ma on the EL84s with the stock fixed bias. On the other ones I serviced I put in a bias pot and biased new tubes at a more normal 21ma. Should I do that also or just let it be until I re-tube at some point?

The question is: Should I "fix" it if it isn't necessarily broken?

Thanks for your thoughts

[R.G.]

If it ain't broke, fix it until it is.

At the bottom of this is the question of objectives - what do YOU want to do?

You own it. You can do with it what you will, including giving it a Viking funeral by shooting flaming arrows into the boat carrying its body, or enshrining it on a pedestal inside a glass dome to be viewed by awed visitors for the sculpture it is. Or painting it purple.

If YOU want to keep it a museum piece, don't touch it, not even to make it safe to operate. If YOU want to play it as a road amp, fix it so it's reliable. If YOU want to keep it as an investment hoping for a financial reward when you sell it, make your best guess about what condition that rich buyer will want.

Your question will get back responses all the way from Nigel Tuffnel's "Don't touch it. No, don't even look at it!" to "Play it till it breaks." to "Update it so it's most functional." to "... hey, I know some really cool mods; first you drill a hole through the front panel logo...". All of these will be from people with THEIR own opinions of what THEY would do - or what THEY want YOU to do.

I don't have the money nor the patience to keep museum pieces. I'm firmly in the camp of "If it doesn't work reliably, it's only good for looking at." I bolster this opinion of MINE by thinking to myself that if some of the old capacitors suddenly short it could burn out the power transformer and possibly start a fire. But that's ME.

[Pryde]

Thanks R.G.

I appreciate the objective perspective(s) you bring to light. I certainly don't care about "museum" pieces nor as a financial investment necessarily. Based on my local market if I ever did sell the amp it would likely be more attractive if the buyer knows it has a good cap job, biased correctly, and safe/reliable to take to gigs, etc. However, I have no plans to sell it in the foreseeable future.

[Mick Bailey]

Traynors seem to retain their original caps a lot more than other amps. Mine is '73 YBA-1A mark 2 and all of the caps read less than 1 ohm ESR, apart from one bypass cap which reads just under 2 ohm and DC leakage is as low as new caps. No buzz or strange noises at all, but it does have 600v on the plates of the EL34s. If it were a customer's amp I'd be recommending a re-cap. For an amp I was intending to keep myself I'd eventually rebuild the cans and retain the sleeves off the 'stick-o-dynamite' Mallorys, with modern caps inside. For me, I like an old amp to look the way it was built, but most people aren't bothered too much so long as it works reliably and sounds good.

R.G.'s point regarding a shorted cap causing PT damage would be my main concern. An observation I'd make is I get more modern amps with shorted caps than I get older amps with shorted Mallorys. The silver ones fitted to Silverface Fenders seem to be particularly durable. But then again, They're 40 years old and are probably on borrowed time.

What would Dirty Harry say?

"I know what you're thinking, punk. You're thinking "Are these caps forty years old or only five?" Now to tell you the truth I forgot myself in all this excitement. But being this is an 80 microfarad Mallory, the most durable capacitor in the world and will blow your PT clean off, you've gotta ask yourself a question: "Do I feel lucky?" Well, do ya, punk?"

[flyingdutchman]

I'd leave the amp as is, except for those few things some older amps need so they'll be safe and reliable.

The 3-pin mains cord is obvious. The "Ground" switch, if it has one, should be disconnected.
I'd make sure the amp is fused correctly, so a shorted filter cap will not blow out the PT. Sometimes a new fuse holder is in order.

If you don't trust the filter caps, replace them.

A problem I've noticed with vintage fixed bias amps is that often current production power tubes will run a bit hot. Since the power tubes are the parts you'll be replacing most often in regular use anyway, and tubes running hotter than necessary is definitely a reliability issue, an adjustable bias mod might be worthwhile.

So far for my $ 0.02

[Pryde]

Thanks for the replies.

The Mallory filter caps in this one are the big silver cans with the grounds heavily soldered to the chassis and they hang below. The other ones I worked on had the dynamite sticks in them

I am thinking I will probably go ahead and throw some JJ or F&T cans in it while I am doing the power cord and likely a bias pot in there as well. A lot of people complain about the stock marsland speaker but I honestly think this one sounds pretty darn good?

[Pryde]

Well I guess the amp gave its 2 cents on the subject as well.
After playing it for about 45 minutes it started making some hiss noise/popping sounds. Gave it the whack-a-mole test and could get some popping noise as well so either loose joints in there are those old tubes are fussing.

Looks like an overhaul is in order after all

[Randall]

I had a dead stock YBA-3 come in recently with a complaint of "weak sound, replace tubes". I told the customer that the while his old electrolytics measured pretty good on the bench, after bearing down for a while on stage there was every possibilty that one could short and put that enormous transformer at risk. And good luck replacing it. So we re-capped it and did the cord/ground cap. After the usual cleaning, re-tension, etc I fired it up with the original Telefunkens, and it came right to life. Customer was thrilled I didn't sell him new tubes, and reported back that the sounds great.

So sometimes measuring these only tells have the story.

[stokes]

Just my opinion,but any amp with 40 yr old filters should have a cap job.Sure the scientists will tell you about the ESR being fine,but old filters,no matter how well they seem to function,are a ticking time bomb.I'm also a big proponent of a bias mod.I've built a half dozen cathode biased amps and even they have adjustable wire wound resistors on the cathodes.As R.G. already pointed out museum pieces are a different story,although I am not a fan of "collectible" amps,they are meant to be played.In all the years I've been repairing and working on amps,there was only one time I wouldnt mess with an amp.The guy had 5 or six vintage fenders he bought me to go over,re-cap and general service.He had a '57 5F1 Champ that looked like it just came out of the box,not even a hint of oxidation on the face or chassis,the tweed was absolutely flawless.I dont think Fender even has such an impecible piece.I told him if he wanted to play it,I should re-cap it,but really couldnt bring myself to touch it.Told him to sell it as is for some big $$$ to one of those collectors I hate so much and I can build him an exact clone that would sound and look as good for under a grand

[R.G.]

There's one other issue to be considered in finding a pristine old amp. There is some chance that the better it looks, the more fragile the caps are.

Electro caps have a limited self-healing ability that only works when they're polarized at working voltage and not being overheated. Under those conditions, little leaky places can actually re-form and repair themselves. This only works if the leakage in that micro-area doesn't over heat the spot.

What that means is that an amp that's still in its sealed, original factory carton and NEVER used is at a huge risk of the caps simply having decayed due to not being used. So in at least this way, an amp that's almost never used may look great, but the caps may fail quickly *because* it's been so little used.

Ain't Mother Nature perverse?

[Pryde]

I did hear that before that dormant electros often fail.

Well the old Mallory cans are already out. Each one had 4 ground tabs soldered direct to the chassis and were a pain to get out of there. Going to mount some can retainers and put the JJ 50/50 500v in there when they arrive.

[leydenjar]

Replace the e-caps or don't turn it on.

And that's from a being named leyden jar.

[km6xz]

A lot depends on the heat the caps have been subjected to. If run with good ventilation and the tubes on the cool side, those caps will likely outlast any typical rock player or several owners. If the ESR is good, and there is no indication of excess heat, I would leave them in. Caps, old quality models, fail a lot less than the internet "common knowledge" has convinced people. If the caps are changed, new caps are a big question mark and an unknown quantity if boutique style. Those used in industrial, medical and communications, might not have the blessings of the golden ears types, but sure have the attention of those who really care about reliability and stability of the components; the design engineers.
The two times in a component's life where the risk is highest is when brand new and when exceeding their design life or design operating circuit and environmental conditions. All that time in the middle is low risk.

[stokes]

There's one other issue to be considered in finding a pristine old amp. There is some chance that the better it looks, the more fragile the caps are.

Electro caps have a limited self-healing ability that only works when they're polarized at working voltage and not being overheated. Under those conditions, little leaky places can actually re-form and repair themselves. This only works if the leakage in that micro-area doesn't over heat the spot.

What that means is that an amp that's still in its sealed, original factory carton and NEVER used is at a huge risk of the caps simply having decayed due to not being used. So in at least this way, an amp that's almost never used may look great, but the caps may fail quickly *because* it's been so little used.

Ain't Mother Nature perverse?

Pretty much what I told him,R.G.Like I say,I'm not a proponent of leaving an amp orig for collectability,but that amp was so incredibly intact,and this guy is a real good client,I want him to be sure before I take a soldering iron to it,just to have some collector tell him I took a couple grand off the price he might have paid if the caps werent changed.I told him to absolutely not use it,he said he wanted to try it for "5 mins" just to get an idea of how good it may sound.I put it on the variac and bought it up real slow,like 2 days slow,but didnt tell him,and when he took it I stuck to my story and told him not to do it.I knew he would anyway,and he did.I gave him shit for doing it,and he swore he wouldnt do it again.Told him he's on his own if he does.Advised him to put it on ebay for stupid big $$$ and see what bites,and let me build him a dead on copy for much less.Only time in my life I've taken that stance.Of course after thinking on it for this long if he decides to,I'll re-cap it for him.He is not a collector and has a brown deluxe and a brown princeton in very good shape that we serviced and a couple not so pristine tweeds we made playable,but that 5F1 is just too clean.I sent some pics to Gerald Weber and he agreed it was the most pristine example he's ever seen.

[stokes]

A lot depends on the heat the caps have been subjected to. If run with good ventilation and the tubes on the cool side, those caps will likely outlast any typical rock player or several owners. If the ESR is good, and there is no indication of excess heat, I would leave them in. Caps, old quality models, fail a lot less than the internet "common knowledge" has convinced people. If the caps are changed, new caps are a big question mark and an unknown quantity if boutique style. Those used in industrial, medical and communications, might not have the blessings of the golden ears types, but sure have the attention of those who really care about reliability and stability of the components; the design engineers.
The two times in a component's life where the risk is highest is when brand new and when exceeding their design life or design operating circuit and environmental conditions. All that time in the middle is low risk.

Totally disagree with this 100% my friend.Back in the day,the golden era,as you put it,manufacturers like Sprague and Mallory gave them a ten year shelf life.I know,shelf life is a lot different than using them.But in a vintage amp,who knows how many 2 or 3 year stretches that amp sat unused.Some years ago,I made a statement related to Boogie amps,but the same goes for any tube amp,that if a vintage amp has caps more than 10 or 15 yrs old,I'll recap it with Sprague and/or F&T brand and they will notice an improvement in the amps response and particularily in a much tighter bass response or I put the old ones back and they pay nothing.Over the next couple years I got more than 60 takers,all local,as I dont deal with shipping,if you cant bring it to me,I dont take it.Never once had to put the old ones back,every one was impressed,that their seemingly fine sounding amp had improved.I have over a dozen of my own amps,all but 2 built by me and change them every ten years.They all get adequate use as both my sons are active players,gigging 2-3 times a week and the ones they dont use,that are left here at my house,get turned on the 15th of every month,as a matter of routine to keep the caps in shape,but every ten years or so the caps go.