NAD: Fender Bantam Bass Amp or WTF did I just buy?!

[hulakatt]

Gotta agree with MrShake here, you're not preserving a pristine tweed Twin here, you're trying to keep a relatively obscure, player grade amp in good playing and working condition. It's a tool, not the Mona Lisa. You keep your tools in good shape and they take care of you. Besides, caps are wear and tear items, like replacing brake pads or tires on a car and CBS was not renowned for using top shelf components either.

[HedonismBot]

His thoughts on vintage amp repairs retrieved from his website: http://www.skipsimmonsamps.com/truthabo ... eamps.html

And just to be clear, he wasn’t pushy or anything. We had a good conversation and he agreed to have a look at it. I actually already arranged to drop off the amp at a local shop and have them deliver it to him (they regularly send him stuff to fix anyway) some time next week. I’d be disappointed, though, if he opened it up and told me that he wouldn’t change anything, which seems likely to me. So yeah, I’m on the fence now cause I’d rather just swap the speaker myself and not drive to Loma Rica for nothing.

[hulakatt]

15" speaker, right? I kinda want a BF Fender that takes a 15" just so I can try out one the Jupiter 15's.

[HedonismBot]

15" speaker, right? I kinda want a BF Fender that takes a 15" just so I can try out one the Jupiter 15's.

Yes, 15

[MrShake]

Ok, first and foremost, please pardon the hot headed nature of my response. Also, just to make sure my cranky tone read right, none of my internet irritation was directed your way, HedonismBot, you're good peopl... er... robot.

Maybe I misunderstood the nature of things, too. An assumption on my part, maybe he just meant "he likes to leave amps unmodded", and that's quirky for a tech, but fine. (I sort of agree for my personal usage amp stable, but that's beside the point.). Like, for whatever reason, if he's insistent on not changing the non-polarized caps and keeping the Bantam Bass tone circuit instead of hypothetically modding it to a tweed Bassman, hey, his prerogative as a businessperson.

But, if he calls you and says he won't fulfill a request to change ALL your electrolytic caps, including filter and bias caps -- because even some half-aware idiot on the internet can see they're 50 years old and risk failing at some point -- he's not worth taking a working amp to, he's into showpieces.

Don't forget that ultimately, you're the paying client and they're the service provider.

But again, that's me jumping to grouchy conclusions. I don't know his work other than what I looked up, but I'd be surprised if he wasn't able to give it a tune-up like that (with reasonable bench time since it's in working order now) if he's at all reputable, and let's give him the benefit of the doubt until you hear back.

I've just seen so many of my hobbies get overrun by self-proclaimed experts and collector fetishists (and I'm NOT casting aspersions at this tech, I'm talking about other situations), who are looking for cred totems instead of colors for their canvas, to mix metaphors, and I get touchy when I jump to that conclusion.

So, sorry about any attitude even adjacent to your kick-ass find. Your new amp is awesome and will sound like a monster through that 15".

If I was two or three years further along in my electronics self-education and on the west coast, I'd recap it myself for a case of cheap beer.

[DeathJag]

HIJACK! Please skip if you wanna talk about the Bantam.

15" speaker, right? I kinda want a BF Fender that takes a 15" just so I can try out one the Jupiter 15's.

I’m converting this ‘72 SFTR, it’s not BF but I could be made to be. Steelaire 4 ohm 275 watt speaker.

[MrShake]

HIJACK! Please skip if you wanna talk about the Bantam.

15" speaker, right? I kinda want a BF Fender that takes a 15" just so I can try out one the Jupiter 15's.

I’m converting this ‘72 SFTR, it’s not BF but I could be made to be. Steelaire 4 ohm 275 watt speaker.

God I love 15" speakers. I added one to my live rig as an extension to my ZT Lunchbox. It sounds HUGE. But I can't imagine how good it sounds with that Fender-y goodness.

Also...

HedonismBot- I re-read your first post. You mention you don't know much about amp electronics. I'm only like 2 lessons ahead of you, but just in case this isn't something you're aware of, here's a very important detail I've only learned in the past few years to help you understand your post-diagnosis conversation with your tech:

There are 2 general types of capacitors in your amp. Electrolytic and non-polarized.

The non-polarized ones look like brown shiny gumdrops and flat orange candy discs, like Necco wafers. Those don't generally go bad and they basically help make the amp sound like it does.

The electrolytic ones are the white and aluminum cans (and the big filter caps in that doghouse underneath the chassis). They have a paste-ish material in them that can dry out over time, and their projected lifespan is definitely less than 50 years. If one fails, they then send the wrong amount of juice to the next part.

Maybe you know all this. But when you talk to him, the only capacitors one would need/want to get changed as routine maintenance are those electrolytic ones. .

You don't need to demand he replace *every single capacitor* in the amp if he tells you only the electrolytics need to be changed (filter caps, bias caps, and the other few small electrolytics are the ones to worry about).

The other candy-looking ones are probably fine, and assuming everything else is working as it should per your playing on it, you shouldn't need them swapped.

Knowledge is power, just hope all of that can help you or someone else, and if any of that sounds wrong to anyone, please correct me.

The link FROM that page on his site went into more detail about some of his repairs, and he seems to pretty clearly delineate between the two types of caps and even says that the electrolytics can be changed without changing the sound of the amp.

If it were my amp, I wouldn't leave any electrolytics in there, just to be safe. They're inexpensive and easy for a tech to change, no sense in not doing it in my opinion.

That said, my Bassman sounded ever so slightly more lively when I got it back.

And based only on something I remembered after somebody's comment on my photos, your amp may likely be set up with the typical '70s Fender "bias balance" setup. Years ago, when I was in exactly your shoes (I'd just gotten my Bassman and needed its first fixup), the tech suggested I have that converted to adjustable bias to make it easier to change tubes and rebias it later on. How much easier it is or better for the amp, I don't know, but I wanted to give you the lead to check out the info for yourself and if it comes up, maybe it's something to consider if it suits your needs. It seems to be a quick and easy mod, but I'm not sure, and might be totally unnecessary for you.

Thanks for humoring all my long posts today.

[hulakatt]

HIJACK! Please skip if you wanna talk about the Bantam.

15" speaker, right? I kinda want a BF Fender that takes a 15" just so I can try out one the Jupiter 15's.

I’m converting this ‘72 SFTR, it’s not BF but I could be made to be. Steelaire 4 ohm 275 watt speaker.

I have deep love for the Vibroverb and Vibrosonic amps. I'm sad that they don't seem to get their dues these days.

[DeathJag]

I have deep love for the Vibroverb and Vibrosonic amps. I'm sad that they don't seem to get their dues these days.

… and the brown Pros!!!!

[HedonismBot]

Thanks for your posts, MrShake. I read them, just haven’t had the time to write a substantial response. I appreciate your input and don’t read your tone as cranky at all.

If I end up choosing this route, I’ll politely insist that he checks all electrolytic caps and replaces all that may need to be replaced in the near future (even if they still work now). I guess there’s a chance that I misunderstood him and he’s not as conservative as I imagine when it comes to replacing electrolytic capacitors specifically. Anyway, I’ll probably have a chat with him again after I replace the speaker.
What made me even more skeptical about taking the amp to Skip, though, is the fact that the previous owner claimed that a friend of his, an amp tech, had a look at the amp recently and determined that nothing needed to be replaced. He told me something like: “just keep using the amp regularly, keep the electrolytes moving around and everything’s going to be a-okay”. I thought that was... an interesting approach to amp maintenance and kept in mind that I’ll have to take it to a different tech some time soon. I feel like Skip, considering his views, may tell me something along these lines as well. But we’ll see, I guess.

[MrShake]

Hey, all good, I just want to help share what little info I have any reasonable confidence in, but always defer to more experienced players, so don't take my word as final.

And I'd not worry, I think Skip will probably be fine and happy to help, especially if you're both eye to eye on terminology and stuff. If he's not being a purist about keeping the original speaker in there, I can't imagine he'd have a problem with 5-10 electrolytic caps for safety and longevity.

That other guy though, it's funny. Like, I vaguely understand that usage prolongs the life of electrolytic caps, and NOT using them leads to quicker deterioration. If an amp sits, caps dry up, so if one's been in storage for years, don't just plug it in and throw it on. A lesson I learned the hard way once. If they get charge through them from time to time, it keeps things getting a workout, to a point, as I understand it

But that other tech's logic seems flawed in a way that's over my head? I feel like his diagnosis is just saying "it seems to be working fine and will probably continue to do so... until it fails"? I'm making more assumptions, but that person doesn't sound like a tech with an eye to *preventative* maintenance.

Somebody pointed out to me that while mine still "worked fine", it was possible some of the less critical ones were already dead and may as well have not been there. Had the bias or filter caps failed... poof. Which is why I'm so keen on sharing anything I've learned about it, because I didn't realize that.

Anyway, don't let Tech #2's weird advice scare you off, I'm sure Skip will probably hear and help you out and if not, it's gonna probably be a straightforward job that wouldn't cost much at any decent shop, though I realize you're in a pickle with local options.

I was playing through a 15" last night, and now all I want in my life is a Bassman 100 through a pair of them.

[JSett]

The difference in changing just the main caps and the smaller bias ones is a matter of literally a few bucks, even for the really nice ones. Not doing all of them at the same time, on an amp this old, is just laziness/counterproductive. It's a 5 minute job for the small ones. Save yourself a future trip and another bench fee and just get someone to do all of them in one hit. All of them will be past their life span by now. I'm only a hobbyist and I can change all the caps in a Silverface amp in less than a half hour.

It's like having 4 totally bald tires on a car and only changing the front two because the wires are showing (and the back two are only a few bucks extra to change at the same time)

[Sauerkraut]

I also know just enough to do maintenance on my own BF Fender, so don't trust my judgment, but... the electrolytic bypass caps in the preamp stages don't get exposed to high voltage. Perhaps that explains the reluctance of some techs to replace these unless absolutely necessary: not much can go wrong with them. Even if they fail, they won't explode. Bypass caps often outlast their expected lifespan without any issues. The caps in the dog house, on the other hand, are exposed to high voltages, which means they can explode if they fail and cause significant damage to other parts of your amp. I believe that's why you'll rarely see original caps in the dog house, and if you do, they're often leaking or bulging.

In this particular case, be aware that those white Mallory caps are known to have a high failure rate. When I look at those pictures, I believe I see some bulging on these two . So if it were my amp, I'd still replace them, even if they pose no real danger to the amp. I'd also replace these bias caps at least every 30 years, because if these fail, you'll end up frying your power tubes and (possibly) your transformer.

[MrShake]

Either way, HB, keep us updated, I know we're all rooting for you! It'll be worth the trouble once you have a bullet-proof tube amp!

[HedonismBot]

Either way, HB, keep us updated, I know we're all rooting for you! It'll be worth the trouble once you have a bullet-proof tube amp!

The guy at the store said they’ll give me a call (within a couple weeks) before they send the next delivery to Skip’s workshop. I should probably talk to them again soon just to make sure they remember. The speaker should be here tomorrow or Friday. I’ll keep you posted.

P.S: Thanks for your responses, everyone. Learning a lot from this thread.