Bassman help

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lamp
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Bassman help

Post by lamp » Thu Oct 29, 2020 5:56 am

Hoping one of the amp gurus around here can help me. Looking at this photo from a Bassman (supposedly AA864 circuit I’m interested in) can you tell what sort of maintenance work has been done? Are the silver caps replacements? I guess I would expect the big orange ones if they were original?
Just trying to work out what might need doing to it if I get it. Cheers.

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Re: Bassman help

Post by s_mcsleazy » Thu Oct 29, 2020 6:53 am

yeah the silver are replacements. also ask for pictures of under the doghouse. might save you some time/hassle down the line.
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Re: Bassman help

Post by lamp » Thu Oct 29, 2020 7:28 am

Cool, thanks!

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Re: Bassman help

Post by i love sharin foo » Thu Oct 29, 2020 4:35 pm

The cap in the bias circuit has been replaced and also the two resistors across the output tubes. If they've been sone somewhat recently and with appropriate values, it's probably good to go for a while. They are relatively inexpensive and easy to do yourself though, if not. Looks like the polarity switch is still hooked up. I would disable that if it were me also.
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Re: Bassman help

Post by HNB » Thu Oct 29, 2020 4:40 pm

i love sharin foo wrote:
Thu Oct 29, 2020 4:35 pm
The cap in the bias circuit has been replaced and also the two resistors across the output tubes. If they've been sone somewhat recently and with appropriate values, it's probably good to go for a while. They are relatively inexpensive and easy to do yourself though, if not. Looks like the polarity switch is still hooked up. I would disable that if it were me also.
I remember the first time I got shocked touching the metal on an amp with the polarity switched the wrong way. It was not a pleasant sensation. LOL
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Re: Bassman help

Post by i love sharin foo » Thu Oct 29, 2020 4:42 pm

HNB wrote:
Thu Oct 29, 2020 4:40 pm
i love sharin foo wrote:
Thu Oct 29, 2020 4:35 pm
The cap in the bias circuit has been replaced and also the two resistors across the output tubes. If they've been sone somewhat recently and with appropriate values, it's probably good to go for a while. They are relatively inexpensive and easy to do yourself though, if not. Looks like the polarity switch is still hooked up. I would disable that if it were me also.
I remember the first time I got shocked touching the metal on an amp with the polarity switched the wrong way. It was not a pleasant sensation. LOL
Hah! Yeah, it's no fun! My Bandmaster electrocuted me for about a decade before I finally took care of it :D A grounded cord and disconnecting that switch are the first things I do whenever I tear into one!
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Re: Bassman help

Post by lamp » Thu Oct 29, 2020 11:06 pm

Thanks a lot that’s really helpful.

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Re: Bassman help

Post by Sauerkraut » Fri Oct 30, 2020 1:48 am

Looks like all the usually problematic parts have already been taken care of in that one, except for the ground switch/death cap thing.

Here's an Uncle Doug episode with a (silverface, but similar) Bassman in what looks like a very similar condition, in which he changes the ground switch into a negative feedback loop on/off switch, which I think would be a great idea for that amp too.

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Re: Bassman help

Post by lamp » Fri Oct 30, 2020 3:47 am

Thanks for the advice - that looks like a good idea.

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Re: Bassman help

Post by lamp » Sat Oct 31, 2020 1:23 pm

Thanks everyone for your input. 10 years ago I bought a blackface Bassman, it was a 1964 AA864 circuit and it was an AWESOME amp, but unfortunately about 3 years ago I sold it. It was possibly by biggest gear regret ever, but I needed the cash and it wasn't being used much.

Fast forward to this week when I spotted another '64 AA864 Bassman on eBay, hence my question. After chatting a bit with the seller I took the plunge, and got it yesterday. The seller was about 60 miles from me, and I could only realistically make it down to pick it up next Friday, but he offered to drive it up yesterday! Top bloke. His friend had acquired the amp in the early seventies and then passed it onto him when he moved abroad about 30 years ago. Funnily they are both bass players and used it as a bass amp. It's pretty much all original, just the knobs and one jack socket have been replaced. Even the tubes are original! Though that's not a good thing! Switched out the pre-amp tubes and it's nice and quiet...need to do the power tubes and get it re-biased. It's a bit worn, but actually not too bad for a 56 year old amp! Need to spend some time cleaning it up properly. Production stamp puts it at a Nov '64 assembly. Just serviced and recapped in July this year. One of the best things is that it's a proper export version so switchable to 240V and no need for an external transformer.

Got it home, plugged it in and it sounded just as good as I remember my old one sounding. Really happy. Not letting this one go.

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Re: Bassman help

Post by i love sharin foo » Sat Nov 07, 2020 2:06 pm

Glad it all worked out! They are great amps!
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Re: Bassman help

Post by s_mcsleazy » Sat Nov 07, 2020 4:31 pm

oh i forgot to mention. a blackface bassman in the uk is a rare beast. dunno if you already knew that
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Re: Bassman help

Post by lamp » Sun Nov 08, 2020 6:40 am

i love sharin foo wrote:
Sat Nov 07, 2020 2:06 pm
Glad it all worked out! They are great amps!
Thanks!
s_mcsleazy wrote:
Sat Nov 07, 2020 4:31 pm
oh i forgot to mention. a blackface bassman in the uk is a rare beast. dunno if you already knew that
Oh yes, I sure did. Particularly a 240v model that doesn’t need a step down transformer!

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