Vaunted Blue Mallory Caps....

TheAmpNerd

Member
Messages
1,056
..... Third amp this month.

The vaunted blue mallory hot dog caps, taking
a slow death and ruining your tone.

Final couplings...eating your tubes and output trannies.

Pre amp, giving you that weak, thin, chit tone
with the virtual absense of bass in the amp.

Early fender black face amps.

Mine is not to reason why...

...but to keep the amps sounding and working
their best for the professional musician.

i.e., keeping them out of the hands of collectors
who let them rot on shelves like old elephants about to die.

 

phsyconoodler

Member
Messages
4,315
Great poem,but I failed english because I interpreted poems wrong according to the teacher.
Here goes: you like the molded blues,but you take them out of customers amps and save them for yourself?Never had one fail yet,myself.
Or,you think guys who change them claiming they are bad are crooks?
Better yet,you could tell us in plain terms what the hell you are babbling about.
 

Slick51

Colonel Curmudgeon
Gold Supporting Member
Messages
521
Please don't hold back...it'll raise your blood pressure.:rolleyes:

Spike, read this guy into the program...
 

John Phillips

Member
Messages
13,040
I think my approach to this is quite like TheAmpNerd's, maybe a little more towards keeping originality over 'spec', but still by far secondary to safety, reliability and tone (in that order).

Here goes: you like the molded blues,but you take them out of customers amps and save them for yourself?
Not all techs are dishonest, or even care about these old parts. I do not steal old parts for myself, in fact I go out of my way to acquire the correct old parts from other non-vintage-amp sources and provide them to customers (probably below their open-market value too, if as part of a repair job). I think that in many cases they do make a worthwhile difference to preserving the tone and value of the amp, but actually they would be of little use to me personally anyway since I don't own or play vintage amps.

I do use old-production tubes, and I'll often buy them from customers - especially if there's a surviving tube or tubes in a set of power tubes where one has gone out. Preamp tubes I tend not to change at all unless they've failed, at which point they're no use to me either.

I have even been known to buy badly-hacked vintage amps at market value (for the condition), if they've got enough good parts left - transformers especially. It's worth it to be able to do other jobs better... and charge more of course, but that's for doing it right :).

Or,you think guys who change them claiming they are bad are crooks?
No, they may just have different definitions of what constitutes a failed component. Personally I don't change coupling caps unless they are actually leaking DC, or carbon-comp resistors even if they've drifted significantly (probably at least 50% over value, although above about that is a sign of impending failure), or even all electrolytics unless they are showing signs of leakage, but I know that more 'by the book' techs often do. That doesn't make them crooks, it just makes them possibly less sensitive to the tone and market requirements of guitarists.

I also routinely do change parts which if they fail can do major damage or stop the amp working, even if they aren't obviously faulty at all. I don't think that's "crooked" or even unnecessary either. I don't if the amp is a true museum piece that isn't going to be used professionally, or if the owner asks me not to, with full acceptance of the consequences - but even then, there are some things that I will not not do, for safety reasons.

I don't doubt there are a large number of ignorant, incompetent and occasionally dishonest techs out there - in fact, usually the first thing I do when restoring an old amp is to remove all previous repair work, since it's rarely done to the standard I think is right - but you can't necessarily judge a person's motives by their attitude to original parts.

Yes, it's very tough to see a set of great old-production tubes go back out in the amp they came in, when you know the customer doesn't care about them and they'll probably end up in the trash a year or two down the line when someone tells him he needs to change tubes every year or so (whether they're dead or not)... but that's life.
 

FPicker

Member
Messages
298
So.. my tech replaced these two dark blue cylindrical-shaped (or better, now that you've put it that way, hot-dog shaped) capacitors from my blackface deluxe reverb
(paper label affixed to them says: Molded, 1mfd,400vdc made in US Outside Foil)

They weren't failing or anything, he said he always takes these out and he was surprised the prior tech left them in there.

I don't know what he replaced them with.

Was that a bad thing? Why do you suppose he did it?

He didn't keep them, he gave them back to me.

Sorry to hi jack, but this thread reminded me, I've been wondering..
 

TopBooster

Member
Messages
194
So.. my tech replaced these two dark blue cylindrical-shaped (or better, now that you've put it that way, hot-dog shaped) capacitors from my blackface deluxe reverb
(paper label affixed to them says: Molded, 1mfd,400vdc made in US Outside Foil)

They weren't failing or anything, he said he always takes these out and he was surprised the prior tech left them in there.

I don't know what he replaced them with.

Was that a bad thing? Why do you suppose he did it?

He didn't keep them, he gave them back to me.

Sorry to hi jack, but this thread reminded me, I've been wondering..

You meant 0.1uF caps, right? These would most likely be the two coupling caps between the PI and the output tubes. I don't think it's always necessary to change these without question, but I know that I do change both of them in an amp if one exhibits the slightest sign of leakage.
 

FPicker

Member
Messages
298
yeah sorry it's .1

So are those the "vaunted blue mallory caps" that TheAmpNerd is exercised over?

Why WOULD someone want to change them, if they weren't leaking?

Why WOULN'T someone want to change them, if they are old and prone to leak?

Perhaps this is a somewhat murky area, since evidently on my amp one very well-reputed tech in my area (NYC) elected to keep them in, and now, just two years later one other well-reputed tech thought they should be removed, though they were not leaking?
 

sstweed

Gold Supporting Member
Messages
5,088
I know how to pull a cap and test it for leakage, but what are "signs of leakage" that you can see or hear?
 

John Phillips

Member
Messages
13,040
So.. my tech replaced these two dark blue cylindrical-shaped (or better, now that you've put it that way, hot-dog shaped) capacitors from my blackface deluxe reverb
(paper label affixed to them says: Molded, 1mfd,400vdc made in US Outside Foil)

They weren't failing or anything, he said he always takes these out and he was surprised the prior tech left them in there.

I don't know what he replaced them with.

Was that a bad thing? Why do you suppose he did it?

He didn't keep them, he gave them back to me.

Sorry to hi jack, but this thread reminded me, I've been wondering..
I would hope he also returned to you a .047uF 600V cap and the original 2-wire power cord, unless that had been done already. If not, he most certainly should have done it, and fitted a 3-wire cord.

You meant 0.1uF caps, right? These would most likely be the two coupling caps between the PI and the output tubes. I don't think it's always necessary to change these without question, but I know that I do change both of them in an amp if one exhibits the slightest sign of leakage.
So do I, for the same reason - if one fails, it will almost certainly blow the power tube(s) on that side, and could possibly damage the bias circuit and take out the others too. These PI coupling caps are not very critical to tone, and they're under the highest voltage stress of any cap in the amp (nearly the full B+ on one side to the negative bias voltage on the other), so they're the most likely to fail. There's absolutely no advantage to keeping the surviving one even if only one has gone, so change both.

I know how to pull a cap and test it for leakage, but what are "signs of leakage" that you can see or hear?
Blowing or severely redplating power tubes, if those PI coupling caps have gone - or just excessive hum or an oddly high bias current reading, if they're just leaking a bit. In the preamp, you probably won't see an overloaded tube but it can happen too - you'll normally get excessive noise, a very soggy, compressed tone or it will stop working altogether if the tube fries.

Very scratchy volume and tone controls are usually a sign that caps immediately before, either the coupling cap from the previous stage or in the tone stack are leaking, not that the pots are bad or need cleaning. I've come across far too many old amps were the pots have been unnecessarily replaced (usually badly, with lower-grade crap) because a previous tech didn't know enough to check for this...
 

phsyconoodler

Member
Messages
4,315
Ok,now I know what he's talking about.Changing those PI caps to save tubes and transformers and not letting collectors buy up amps and shrink wrap them.
I do apologize for not reading more carefully.I hate poetic rhymes.It's a school thing.
I also don't change stuff that doesn't need changing and definitely don't hoard caps to sell on E-Bay.
I hate collectors.Most of them can't play worth a damn anyway.
 

epluribus

Member
Messages
9,170
Dude, I try hard to keep my personal opinions off this site, but I gotta give you a big +1 on that quote. If I ever see you in a bar, our first couple of rounds are on me.

LOL! I understand where collectors are coming from, and I'm truly thankful for them cuz it means my grandkids'll have nice museums, but IMHO it's sorta like cool old cars: if ya got it, drive it.

--Ray
 

killer blues

Member
Messages
3,093
..... Third amp this month.

The vaunted blue mallory hot dog caps, taking
a slow death and ruining your tone.

Final couplings...eating your tubes and output trannies.

Pre amp, giving you that weak, thin, chit tone
with the virtual absense of bass in the amp.

Early fender black face amps.

Mine is not to reason why...

...but to keep the amps sounding and working
their best for the professional musician.

i.e., keeping them out of the hands of collectors
who let them rot on shelves like old elephants about to die.
The best way to test these caps is with a VTVM and the amp on. VTVM's have an extremely high internal impedence (mine is 18M) which allows very accurate readings of miniscule voltages. With amp on, check for DC voltage on the grids of the preamp tubes. Anything above a very small amount is indicative of a leaky blocking cap. These caps need to be checked at operating voltages for accurate diagnosis. I have not found many of these to be bad
 

TheAmpNerd

Member
Messages
1,056
Great poem,but I failed english because I interpreted poems wrong according to the teacher.
Here goes: you like the molded blues,but you take them out of customers amps and save them for yourself?Never had one fail yet,myself.
Or,you think guys who change them claiming they are bad are crooks?
Better yet,you could tell us in plain terms what the hell you are babbling about.

I throw them away, period. Why reuse old crap.

Re-read what I said they did; they infact performed
or lack there of as described.

Pretty simple really.
 

TheAmpNerd

Member
Messages
1,056
So.. my tech replaced these two dark blue cylindrical-shaped (or better, now that you've put it that way, hot-dog shaped) capacitors from my blackface deluxe reverb
(paper label affixed to them says: Molded, 1mfd,400vdc made in US Outside Foil)

They weren't failing or anything, he said he always takes these out and he was surprised the prior tech left them in there.

I don't know what he replaced them with.

Was that a bad thing? Why do you suppose he did it?

He didn't keep them, he gave them back to me.

Sorry to hi jack, but this thread reminded me, I've been wondering..

The two most recent examples were as follows:

1. 1964 vibroverb.... when the cutstomer was playing he heard
the cap fizz out and lost virtually all bass response in the vibroto
channel. Remedy, replace both mallories with my personal favorites,
resulting in a lot better tone and bass is back too.


2. 1965 SuperReverb. Came in for Pwr tube and socket replacement.
Player also commented about loud and thin tone with no bass
response. Remedy after power tube and socket replacement.
I played the amp and still had poor response. Remedy, replace
the blue caps in the pre amp section with my personal favorites,
resulting in a lot better tone and bass response.

NOTE: In both these cases the amp performed a LOT better too
with the blue mallories gone. Much better tone and harmoinics.

NOTE2: The cap changes really put you out there too. You WILL
hear all your little F**k ups when playing too.

NOTE3: Any one who has been reading my posts long enought knows
that Kind of caps I like best. To avoid San Francisco type flame wars,
I simply use the term my personal favorites and leave it at that.

 

phsyconoodler

Member
Messages
4,315
Quote:
Ok,now I know what he's talking about.Changing those PI caps to save tubes and transformers and not letting collectors buy up amps and shrink wrap them.
I do apologize for not reading more carefully.I hate poetic rhymes.It's a school thing.
I also don't change stuff that doesn't need changing and definitely don't hoard caps to sell on E-Bay.
I hate collectors.Most of them can't play worth a damn anyway.
__________________





Hey ampnerd,
I was simply commenting about your poetry and how lousy I was at it decifering it.I never,ever intended to even SUGGEST you were stealing caps.
I don't know of anyone who does that.
Sorry dude!
 

ChickenLover

Silver Supporting Member
Messages
1,700
When I very first started messing with amps someone told me that the brown turd caps in my BF Bassman were crappy caps and that he liked to replace them with ODs (715P BTW). When I asked him what old Fender caps were 'the good ones' he said the dark blue Mallory (hot dog) caps. Since that time, I saved a number of them (.047uF death caps mostly but also some .1uFs) and put them in my own amps...thinking/expecting them to sound better but they never do. So I never use them anymore. I don't really have a personal favorite, right now I'm using 6PS and 225P ODs but only because those are supposedly the right type for Dumbles and Trainwrecks (my last and current builds).
 

TheAmpNerd

Member
Messages
1,056
Feedback on the last two amps:

Vibroverb never sounded better!
The guy quit using pedals...yeah!


SuperReverb,
Is out on tour and the guy is in love
more with it now than ever.
 




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