'79 JMP crackling, and question about plate voltage

[psychodave]

It’s nice to see people posting how much F&T caps suck. I learned this about a decade ago. Popped in new caps. Brought up the voltage slowly... did everything right and the amp sounded like shit. Brought it to a friends house and his first words were “what did you do?” Fortunately I numbered the original caps and was able to put them back in and boom! The amp was back to sounding good.

 

[Rick Lee]

I've never had a problem with F&Ts. I've recapped lots of old Marshalls with them and I spend a lot of my spare time thinking about how much I love that tone and when I can get back home to play loud. My tech swears by them too. Though, I guess I'll give ARS a try next time I need to do this job.

 

[Exo-metal]

Take a chopstick, and with the amp on, press on every component( caps, resistors, even switches, jacks, sockets, and pots), and solder joint. I usually find the crackling with this method.

That's not how you play chopsticks lol and ARS are the way to go. Enjoy that 50w, killer amp!

 

[CornNutz]

I like F&T caps for preamp and ARS and LCR for mains and screen. If it’s high gain then I like the clarity that F&T brings to the table but again only in the preamp. If it’s not high gain I do all ARS or LCR. I once recapped an entire 2204 with F&T and it made the amp sound brittle and super bright - it lost the warmth it once had. I do still prefer LCR over ARS, but ARS are easier to get in the states.

Clean the power tube sockets and if that doesn’t resolve the issue, check your plate resistors for heat damage and fading. That will cause the issue as well.

Yeah, F&T caps do not sound right. Especially in any kind of classic amp. ARS, and JJ caps are good for this.

Now that being said they can work, if you're building up a circuit/mod from the ground up. If you find the amp too dark, or loose you can put f&t in some spot to tighten/brighten it up.

 

[Racerxrated]

It’s nice to see people posting how much F&T caps suck. I learned this about a decade ago. Popped in new caps. Brought up the voltage slowly... did everything right and the amp sounded like shit. Brought it to a friends house and his first words were “what did you do?” Fortunately I numbered the original caps and was able to put them back in and boom! The amp was back to sounding good.

Right before I did my first filter cap change a few yrs ago I had just bought an 87 2555. First 100w original, and it just didn’t sound right...had a ‘grainy’ thing going on that I couldn’t dial out. Only change in the circuit was new F&T filter caps. Sold it and in came an 82 2204, again with newer F&T caps. Same grainy gain...hard to describe but I swapped them out for ARS and voila- back to a recognizable Marshall kerrang.
I know F caps aren’t supposed to alter tone but I know what I heard before and after F&T.

 

[harddriver]

It might be a dual can attribute thing. I agree the ARS and indistinguishable from LCR caps. I am running F+T axial caps in the mains and screens of my 68 plexi and F=T dual 50/50uf for 100uf in the PI, and an NOS ERIE 32/32uf in the preamp. The amp sounds like a great Marshall plexi and is not grainy in any way.

In my 69 plexi I used ARS dual 50/50uf in all positions and that amp sounded as good as my 68, so YMMV but I do agree I do like the ARS caps and I feel they are on par with NOS LCR's. I have used the CE dual can 50/50uf caps in the the past and they were ok but I think I like the ARS best for sure.

 

[Rick Lee]

On this thread's suggestions, I just threw a set ARS caps into my 1987xl, which is my #1 amp and I play it at full tilt all the time for many hours a week. I mean, I beat this amp like it owes me money. I fired it up after the cap install, let it get hot, re-biased to about 70%, PV was right at 450, ran it into my Mojotone 4x12 with Scumbacks, used my normal settings, both volumes on 6. It sounds totally different. It doesn't seem nearly as loud as before. I mean, I was able to play without earplugs and it didn't blow me out of the room. Seemed to have way less distortion too. I like it, sounds more vintage to me. There are no funny noises or smells. So I think I did everything right. But it's just not cornea-popping loud like it used to be.

 

[Racerxrated]

On this thread's suggestions, I just threw a set ARS caps into my 1987xl, which is my #1 amp and I play it at full tilt all the time for many hours a week. I mean, I beat this amp like it owes me money. I fired it up after the cap install, let it get hot, re-biased to about 70%, PV was right at 450, ran it into my Mojotone 4x12 with Scumbacks, used my normal settings, both volumes on 6. It sounds totally different. It doesn't seem nearly as loud as before. I mean, I was able to play without earplugs and it didn't blow me out of the room. Seemed to have way less distortion too. I like it, sounds more vintage to me. There are no funny noises or smells. So I think I did everything right. But it's just not cornea-popping loud like it used to be.

Correct me if I'm wrong, but there 'may be' a break in period for new caps. Whenever I've changed them it always made the tone much better due to the older bulging caps not performing like they should, but I had a 2204 that had newer F & T that I swapped for ARS and I liked it better after the change but I can't recall if it was any less 'beastly' so to speak.

 

[Monomyth]

I’m so glad to see everybody agreeing that ars filter caps are the best for tone, I totally agree.

 

[RedPlated]

This thread encouraged me to order more ARS caps and swap out the F&T's I had in my 2204 JCM800. The 50w amps are literally a 20 minute job.

I have two more Marshalls with F&T's that I'll also likely swap out.

 

[Rick Lee]

My F&Ts were maybe 3-4 yrs old and did not need to be replaced. I just felt like trying ARS out.

 

[Rick Lee]

I fired up my '69 1959 clone build with F&Ts just to compare and, man, it sounded so much better.

 

[RedPlated]

On this thread's suggestions, I just threw a set ARS caps into my 1987xl, which is my #1 amp and I play it at full tilt all the time for many hours a week. I mean, I beat this amp like it owes me money. I fired it up after the cap install, let it get hot, re-biased to about 70%, PV was right at 450, ran it into my Mojotone 4x12 with Scumbacks, used my normal settings, both volumes on 6. It sounds totally different. It doesn't seem nearly as loud as before. I mean, I was able to play without earplugs and it didn't blow me out of the room. Seemed to have way less distortion too. I like it, sounds more vintage to me. There are no funny noises or smells. So I think I did everything right. But it's just not cornea-popping loud like it used to be.

This doesn’t sound right unless the cap values were significantly altered, caps are bad or installed incorrectly. Shouldn’t be that drastic.

I just installed ARS in place of F&T in one my amps and the gain is no different that I can tell.

 

[Wizard of Ozz]

On this thread's suggestions, I just threw a set ARS caps into my 1987xl, which is my #1 amp and I play it at full tilt all the time for many hours a week. I mean, I beat this amp like it owes me money. I fired it up after the cap install, let it get hot, re-biased to about 70%, PV was right at 450, ran it into my Mojotone 4x12 with Scumbacks, used my normal settings, both volumes on 6. It sounds totally different. It doesn't seem nearly as loud as before. I mean, I was able to play without earplugs and it didn't blow me out of the room. Seemed to have way less distortion too. I like it, sounds more vintage to me. There are no funny noises or smells. So I think I did everything right. But it's just not cornea-popping loud like it used to be.

Give it some time. I also recommend forming new caps with a variac. Bring the voltage up to 110V slowly. Leave it 20, 50, 80 volts for a few minutes each.

 

[Racerxrated]

I fired up my '69 1959 clone build with F&Ts just to compare and, man, it sounded so much better.

We all hear things differently; maybe F&T are more to your liking? I'd give the ARS amp a little more time but you can always swap the F&T back in.

 

[Rick Lee]

Just fired her up again and gave up after 10 min. F&Ts going back in as soon as the power tubes cool down enough to pull. Gawd, I hate these ARSs. This is my favorite amp and otherwise has the tone of the gods. Lesson learned.

 

[Rick Lee]

And I just put the F&Ts back in. I did discover a cold solder joint on the negative terminal on one of the ARS caps. So I resoldered and fired up. No joy. Still sounded dark and not loud enough. Threw the F&Ts back in and BOOM - that's what I'm talking about. This is my baby and I will stop futzing around with a good thing. She's perfect as is. These ARS caps are either just not for me or they're a lemon batch.

 

[napalmdeath]

My brother dropped his off with a reputable tech. It needs an overhaul! The preamp sockets were loose, and hopefully it'll get sorted out. FWIW, its a '79 2x12 combo with the original speakers!

 

[RedPlated]

Had these laying on my bench so I took a pic. Big difference in size.

 

[SpiderWars]

Caps keep getting smaller for the same ratings. They must be using some sort of 'improved technology' to do that. The F&T caps are smaller than 500v 100x100 can used to be possible to make. So maybe the newer technology doesn't sound as good? I'm about to build a '69 SL and I need to know which caps have the magic. Is there something measurable that one can use to choose?

The cap cans in the King Kong I had were 180uF @ 450v and were tiny compared to the F&T above (just one section tho).