Holy Grail moment

[eschertron]

But, the customer wants to play it.

So is he a player, as in professional gigging or scratching the itch by jamming to the radio every night after he gets home from his medical practice? Or may he simply want to play it for the nostalgia, and after spending a few minutes listening to himself through the amp it goes into the collection?

If he really brought it to you before he even plugged it in, sounds to me that he'll understand the argument for making it safe and reliable.

[Steve A.]

I would recommend that the customer have me swap out the speakers and save the originals in the boxes the replacements came in. And recommend that he have me replace the power supply caps while keeping the cap can mounted on the chassis.

Besides that I think it really depends on how the customer will be using it. At home or for gigs. Vintage low gain stuff or will he be boosting it with pedals. I would label all of the tubes with a Sharpie and swap out all of them before plugging in the amp (I don't know if bad components can damage the tubes or vice versa but I would want to play it safe.)

Once you have fired it up you'd want to record all of the important tube voltages and post them here- one of us might notice something a bit off that the rest of us don't. After that you can look for DC leakage on all of the signal caps and whatever tests are done on cathode resistor bypass caps. Save and label any caps you replace.

Getting back to the speakers look into recone options and let the customer decide what he wants to do. If he is looking for vintage-style 12" speakers I really like the Warehouse Guitar Speakers ET65 copies of the classic Celestions at a reasonable price. And now that Musician's Friend is selling the 8 and 16 ohm versions you can get free shipping if you meet the minimum order amount. (WGS's shipping charges always kept me from buying more speakers from them.) They also sell great copies of the Celestion Vintage 30's with all sorts of varients.

I would wait until the amp was running great with new tubes and speakers and then have the customer decide whether to put the old ones back in - I would want him to be present when putting the original tubes back in, starting with the initial preamp tube(s) and following the circuit to the phase inverter. And based on how the tube swapping worked let him decide whether to put the original output tubes back in or save them for whenever he eventually sells the amp. Do the same with the original speakers (you hopefully have a pair of speakers around that you were using for all of the testing) letting him make the final decision on whether to put them back in at the end of the tube tests.

My recommendation of having the customer present during these final tests is based on dealing with customers during my 20+ years as an HVAC service tech and manager. If an original tube or speaker fails they are liable to blame you even if they gave you their okay over the phone. If they are present and giving their okay on reinstalling each of the original tubes and speakers they are less likely to blame you if anything doesn't survive. To be safe I would have my pocket recorder on... just in case something goes sideways.

I would personally recommend that the customer use the amp for awhile with the new tubes and speakers to make sure that everything is working okay if he is at all concerned about the resale value if he eventually sells it. While you can do all sorts of tests on your bench the final test is after the customer has been playing it for awhile.

Steve A.

[Chuck H]

Good call on the tubes I hadn't even considered that.

[Randall]

The customer is going to gig the amp. He's a great guy and all, but I am not going to power this up without him being here to witness it. Not sure I want to recommend pulling the speakers and tubes. I'll bring it up with no power tubes first and take measurements. Go from there.

Anyone know a source for the thin style cap can? 10/10/20 I think?

[Chuck H]

http://music-electronics-forum.com/t35537/

Here's a thread on the matter. The photo's don't come up, but it's still good info.

[Leo_Gnardo]

I'll bring it up with no power tubes first and take measurements. Go from there.

Anyone know a source for the thin style cap can? 10/10/20 I think?

Power up with "pulls" that is good used output & rectifier tubes. Hi voltage could sail way high without the outputs drawing current.

CE has at least one of those skinny cap cans in the catalog. If it's 2-section use a single for the 3rd section.

[Randall]

Well, I brought it up real slow with only rectifier tube, that was not a problem. But with a used set of 6L6s, it freaked out, sounded like gun shots, so new filter caps it is.

[Steve A.]

Well, I brought it up real slow with only rectifier tube, that was not a problem. But with a used set of 6L6s, it freaked out, sounded like gun shots, so new filter caps it is.

I forgot that it was you who started this thread... I'm sure that you have a speaker around to use while testing and servicing the amp (leave the stock speaker but send the output signal to an ext. speaker cabinet.

As for the stock speaker I'd test it first hooked up to a stereo playing appropriate music at reasonable levels to break it in, raising the volume a little bit every hour or so. If you notice anything unusual turn it off and recomend that the customer have it evaluated and repaired at a recone shop if he plans to use it. Or just store it in a box if he ever wants to sell the amp.

[Randall]

I will run some music through the two speakers, but given that this amp looks like it was stored in a cold storage vacuum, I am not particularly worried about them.

[TimmyP1955]

When I was a lad, no one talked about replacing old caps as a matter of course - reforming them was SOP. IIRC this meant bring the unit up on a variac, increasing the voltage until the current starts to go up disproportionately, then back it down to where it was stable and let it set. After x hours, slowly raise the voltage as before. Repeat this dance until the unit is happy at full mains, and powers up & down OK.

[bob p]

Thwarting Entropy?

Thermodynamics tells us that's an endothermic proposition, and eventually it will fail.

[bob p]

Well, I brought it up real slow with only rectifier tube, that was not a problem. But with a used set of 6L6s, it freaked out, sounded like gun shots, so new filter caps it is.

It would be better not to abuse a tube rectifier that way. Why not just use an SS plug-in instead?

[bob p]

And just because someone says they're going to put it in their museum, even that's no guarantee of no foul play. There's a nice brown Vibrolux 1x12 for consignment sale in a local store. I had the pleasure of working on it many years ago. It's been seldom used since than, but all the metalwork has corroded to the point where there's greenish spots on the jack mounting nuts, also a coating of grey-green powder all over the chassis. There's a road case with it, maybe it was clapped in there surrounded by deteriorating foam rubber and whatever icky gas emanated from that over the years. Dam' shame to see the metal and brightwork gone crummy like that.

It's good that you bring that up, Leo -- there really should be a sticky warning about the evils of flight cases because not everyone is aware that they can damage amps if used for long term storage.

Although I'd recommend that Randall's client invest in a flight case for transporting his showroom-minty Supro, he needs to understand that the amp shouldn't be left in the case when it's not being transported.

Flight cases are not designed as permanent storage for amplifiers, they're only designed to protect them from short term damage by baggage handlers. They're built as economically as possible to provide protection from rough handling but that means that they've cut some corners when it comes to cost -- like using cheap open cell foam instead of tuck and roll padding on the inside. Using foam makes them unacceptable as a long term storage solution.

It's interesting that Randall mentioned that the amp looked like it had been stored in a vacuum bag. Storing in a vacuum would be optimal... but that's not what you get with a flight case. Given enough time, foam always decays into that gummy/crumbly mess, and it does release nasty fumes in the process of decaying. You don't want those fumes in a closed box with your precious amplifier or it will end up corroding like Leo described. With black tolex or a chrome chassis it's not so bad, but with tweed or aluminum or untreated steel it's a nightmare!

I have a huge hoarde of gear, so much that I'm currently bringing amps back into rotation that I haven't played for 10-15 years. If you store anything for that long, how it gets stored becomes an important consideration. I've learned by making a few mistakes.

I have flight cases for several pieces of gear, and though my gear gets transported in it, none of my gear is left in a foam-padded case for long-term storage. Everything gets taken out of the flight cases when it gets home where it gets shelved in a climate controlled environment with forced air circulation. Taking things out of their flight cases creates a logistical problem because everything ends up taking up twice as much space as it would otherwise, so the amps end up being stored separately from the cases. If you don't have the room and you absolutely have to store something in a flight case for the long term, I'd recommend putting the amp in a heavy polypro garbage bag with a dessicant pack, and taping it up to make it air tight before putting it into the case. Or better yet, I'd recommend ripping out the foam and replacing it with tuck-and-roll padding. IMO tuck and roll cotton batting is more friendly than the cheap foam that everyone seems to use.

It's a shame when a classic amp like a Brown Vibrolux gets ruined with crusty green oxidation when someone was trying to protect it, just because of that foam. Chances are that amp would have been better off if someone had just stuffed it into a closet. Sigh.

It's surprising that not very many people in the industry worry about the problem caused by deteriorating foam... or if they do worry about it, they're just not talking about it. I haven't heard many people complain about the evils of flight cases, and it's something that you definitely have to consider if you're thinking about real long-term storage (periods of years or more). Maybe we don't hear about this is because with heavy road use the touring professionals change out their cases more often than people like me. They may not own a case long enough to see the foam melt. Or maybe they just get the cases open often enough to spot the foam problem and replace the foam before things get really bad. It sounds like that Brown Vlux was left in the case without anyone looking at it for a LONG time.

I saw a YT video where someone interviewed Brian May at the Queen storage warehouse. They were in a room stacked to the ceiling with flight cases, where all of the Queen gear has been sitting, presumably since the last tour. I can only imagine what's going on with the foam inside of those sealed cases...

[SoulFetish]

Ok lets pretend your a mechanic and someone brings you a pristine old collectable car with original tires and radiator hoses? What are you gonna do? Keep it original or recommend what really should be done?

nosaj

Thats a great question. When dealing with an antique or vintage equipment, almost it's entire value in the market how well it has been maintained in it's original condition. But, whatever the collectable is, certain parts are not considered important to the original condition. Case in point - a 1949 Mercury coup can be sold as stock and original, whether or not it has the original bias ply tires, or it's original oil. In the same way, the vintage value of a 1959 Les Paul does not get depreciated if it doesn't have it's original strings. Electrolytic caps have a relatively short lifespan compared to the rest of the components, and the designers of the amplifier built them with that expectation. Much like the tubes (which is why they are socketed) or an oil filter in a car.
Since this market is driven by what people value and what they are willing to spend, I think it is important to inform the discussion so there is an expectation of what is required maintenance over the life of an amplifier.
Having said that, if the original caps are holding up, there is no harm in leaving them in if the customer wants to keep it that way. Those are my thoughts on it anyway.

[bob p]

Yes -- nobody expects a 49 Mercury to have original bias ply tires. But if you take that Merc to a car show and have it judged for original condition, the judges will start with 1000 points and they'll subtract points for things like radial tires instead of reproduction bias ply tires, and modern radiator hoses instead of period-correct corrugated radiator hoses. Nobody expects an old car to have it's original tires, but the tires have to be period appropriate if you're being judged in an unmodified class.

I have plenty of vintage amps that have 60 year old caps in them. If they continue to function up to spec I'm also inclined to leave them alone. Just like with a car, it's only original once.

https://www.hemmings.com/magazine/hc...s/2960931.html

It's interesting that in the classic car world, unrestored original cars often bring more than full restorations.