Solder flux "crust"

[SonicProvocateur]

So my Mark III is pretty much an ugly mess of flux. Matter of fact sometimes I call it the "Rusty Dragon"...

That aside, is all the extra flux hurting the amps tone? Most days I can't get it dialed in on the lead for a super sweet liquid sound, and it's more recto-ish. Sometimes I think it may just need a cap job, but sometimes I think it's all that messy flux. Is it safe to try and clean? The amp functions fine otherwise.

 

[>Photi G<]

A cap job is probably the culprit. When the board was soldered at the factory, flux was only applied to the off-board connection wires/larger components. Everything else should have been machine wave soldered. Any flux within the connections should have burned off before the solder cooled, and the rusty residue is just on the surface. If you ask me, worrying if that affects your tone is the equivalent of asking if the amp would sound better with all solid-core connections, and a heavier gauge power cord. It's not worth worrying about.

 

[SonicProvocateur]

Right on, I still had a feeling that it might be that. Also, is anyone else running upgraded screen grid resistors? I'm using some Xicon 5w and I love the power handling (Unreal! I can push it higher and higher without sqealing or noise!), but ever since I put them in the tone hasn't been exactly what it used to be (not quite as liquid, but definitely more articulate). Think it would be a good idea to go back to whatever was stock?

 

[gts]

I don't think the screen grid resistors are affecting your tone.
If my thinking is correct they are a protective measure.
And are there to protect other components should a power tube blow (or not blow when it should).

Those currently made are better than the old style originally put in the Mark amps.
Fwiw even Mike B told me this but he said everybody wants to see those old brown one in there even though they are not as good.

But back on point. I don't think the SGR's are having any affect on your tone.

 

[>Photi G<]

Yes, that is true that the old Carbon Comp SGRs are inferior than the Xicons you just installed, and it is true that they sound different. The reason is because they are inferior. Carbon comp resistors tend to fluctuate in resistance in high voltage applications, i.e., in an SGR position. That generally causes a sound difference that people like, usually in the form of sag or swirl. The Xicon resistors are very precise and non-wavering, which makes the sound just a little bit stiffer.

 

[SonicProvocateur]

Thanks for the input guys! I double checked an my Xicons are 500ohm, not 420 - I wonder how much tone difference that's making. Also, when I pulled the chassis, I noticed 2 things.

1) My power caps look older maybe? I dunno:

And my orange drops look pretty haggard. You guys be the judge:

Additional pics:

Thoughts?

To me the 30uf Spragues look newer than the 220 caps. But they may all need a changeout.

 

[>Photi G<]

Unless the Orange Drops are physically damaged, they'll last the lifetime of the amp. The 220's and the 30uF spragues are the same age, just a different color. They should be replaced every 20 years or so. These look original, so now would be a good time to swap them for a fresh set. The low voltage electrolytics should be checked out too. It wouldn't hurt.

 

[SonicProvocateur]

Unless the Orange Drops are physically damaged, they'll last the lifetime of the amp.

So I shouldn't be too concerned about the 715's wrinkled appearance, then? I guess it's the heat from the uncooled 60 watt? I suppose when I send it in, i'll mention the PSU/Filter caps and the Nichicon as my concerns for the recap along with whatever other else needs to be redone. Maybe an LDR or something... I may have them remove my bias mod too... Thanks a ton, guys!

 

[>Photi G<]

Unless the Orange Drops are physically damaged, they'll last the lifetime of the amp.

So I shouldn't be too concerned about the 715's wrinkled appearance, then? I guess it's the heat from the uncooled 60 watt? I suppose when I send it in, i'll mention the PSU/Filter caps and the Nichicon as my concerns for the recap along with whatever other else needs to be redone. Maybe an LDR or something... I may have them remove my bias mod too... Thanks a ton, guys!

Nope. AFAIK, the wrinkles are from the factory when the unfinished caps are dipped in the orange coating to seal them up. Good deal man! Your amp is pretty clean for the most part, so I'd just expect the blue caps/low voltage caps/bias mod to be dealt with, and you'll have a new amp!