NAD 1967 BF Bassman AB165 rough player

ETMusic777

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In an earlier thread this month, I showed photos of a 1964 AA864 Bassman which I had acquired from Guitar Center online. I've been playing that amp and really enjoying it for the past several weeks. Its one of those amps that you just do not want to stop playing because it feels so good under your fingers.

These days, its tough to find blackface Bassman heads for under $1000. Over this past weekend, a "1966 Bassman" popped up in Orange County listed at $950 but it only had 1 photo which was not very clear. I made note of it but did not want to spend that much right now on another Bassman. The next day, the seller edited his ad to say "the first $500 takes it". So I could not resist that and drove down yesterday to see it in person.

Turns out its actually a 1967 blackface Bassman, based on the chassis stamps, transformers and serial number. Its rough cosmetically and is missing the back panel. The original black tolex has been painted over with a strange grey paint and the grill cloth has been replaced with black. The Fender badge had the black paint removed and is now all grey. Its kind of like an Oakland Raiders motif, lol. Also a couple of the knobs are not original.

Anyway despite the rough appearance, the amp sounds fantastic so I bought it. For $500 I know I probably won't lose money on it.

I will do some cosmetic restoration on it. I am trying to decide if I should just retox it and put a new grill cloth on it to bring it back somewhat to its original appearance, or do something cool with it like a different color tolex and grill to give it a unique appearance. Any thoughts on that?

I started working on it yesterday removing black paint from the handle covers, and also straightening out the small gouge in the back panel which was dented in, and then "folded over" on the top of the chassis for some reason, perhaps to get the chassis to slide in to the slot. I unfolded the dent and straightened it out with a pliers and hammer. You can see the dent at the top of the middle of the back panel. I wonder how that could possibly happen? Maybe the amp was dropped and suffered gash back there.

Positives: The amp is dead quiet and sounds great. It has about 15-20% more gain than the 1964 AA864, however I would not say that its useable gain...just more "fuzzy" and heavy metalish. I did an A/B test using the Normal Channel set on 4/4/4 between the 67 and the 64 and they sound very very similar, however in my opinion the AA864 is just a touch "sweeter" and a touch more responsive to the fingers and playing. That makes sense because it was Leo's circuit not CBS. Now, I am not dissing the AB165 at all. Its a high gain monster and is unbelievable on any standard of tone.

Photos below. Its the black one on the bottom of the 1964 in the main photo. It needs a recap, however someone already did the 3 prong cable, bias cap and one of the caps in the first preamp section and a screen grid resistor. It also has a non original doghouse cover. I plan to go through the entire amp replacing anything that is needed. Its dirty but is a player.
 

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Wally

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Good score. Fwiw, that AA/AB165 schematic is dated to January, 1965. CBS signed the papers in the first week of JAN, 1965. I don’t c9nsider these Bassman amps as well as the AA165 Pro Reverb to be ‘CBS‘ circuits. I reserve that distinction for the circuit changes that came in the summer of 1968…starting in May, 1968. Ommv.
Regardless…..the AC cord needs to be properly installed in the best and safest manner.
congratulations….
 

ETMusic777

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Good score. Fwiw, that AA/AB165 schematic is dated to January, 1965. CBS signed the papers in the first week of JAN, 1965. I don’t c9nsider these Bassman amps as well as the AA165 Pro Reverb to be ‘CBS‘ circuits. I reserve that distinction for the circuit changes that came in the summer of 1968…starting in May, 1968. Ommv.
Regardless…..the AC cord needs to be properly installed in the best and safest manner.
congratulations….

Thanks Wally. I noticed the power cord too. I made that AB165 comment based on some things that I had read in online forums and articles, that stated that AB165 was CBS's first alteration to any of Leo's designs. As you noted it may not be true because that circuit had probably been in the works prior to CBS taking over.

Regarding my A/B comparison between AA864 and AB165 in a cleaner setting, its very very close. I recorded the A/B and to the average person there would be no noticable difference, they sound that similar. Its just as a player, the AA864 has a very very every so slightly more responsive to the touch thing going on. Its difficult to explain to a non guitarist. It could just be between these two amps and maybe a simple change to a resistor or recap could make them equal in that regard.

Quick question for you, if you don't mind: There is a popular mod to the AB165s to make the power section AA864. That may be beyond my capabilities as a tech at this point. Do you recommend that I look in to doing that with this amp? What advantage would there be other than bringing back adjustable bias?
 
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corliss1

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I only "mod" stuff when it's not doing something I want it to do, and there is a known mod that can make it do that thing. I'd get it serviced and ready to go and then see how you like it - you could find it's just fine as is.
 

noname_dragon

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You got a deal.. I think it's in nice shape! Gently wash tolex with dish soap and a stiff brush. You might be able to improve the stain on the front grill if it bothers you. Get basic service by a pro and all good.
 

Wally

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@ETMusic777, +1 with the advice from @corliss1 to put the amp in proper working condition before making any changes. The AB165 has three gain stages in the Normal channel compared to two gain stages as in the AA864 and AA165 Bassman amps. That Normal channel in the AB165 is hotter because of that.
 

ETMusic777

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Well I have my first repair to make. I turned the amp on this morning briefly and then turned it off to make a cup of coffee. When I turned it back on, the switch felt odd and sort of crumbled and is now not stable and the amp does not turn on. I think the power switch just died and will need to be replaced. The fuse is fine, its obviously the switch because I felt it break when I turned it on.

It does not appear to be the original switch anyway, and a replacement original type switch is less than $10. Im guessing when the amp took a fall and damaged the back panel, it took out the original power switch and put this one on, which just failed lol.
 

Wally

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You might as well do all necessary service while repairing the switch. Do all electrolytics, tighten all nuts and screws, clean all tube sockets, clean and lube pots as necessary. Make a voltage chart. Check the bias
Repair the AC cable connections after install new electrolytics..and before firing the amp up.
 

Paul G.

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Thanks Wally. I noticed the power cord too. I made that AB165 comment based on some things that I had read in online forums and articles, that stated that AB165 was CBS's first alteration to any of Leo's designs. As you noted it may not be true because that circuit had probably been in the works prior to CBS taking over.

Regarding my A/B comparison between AA864 and AB165 in a cleaner setting, its very very close. I recorded the A/B and to the average person there would be no noticable difference, they sound that similar. Its just as a player, the AA864 has a very very every so slightly more responsive to the touch thing going on. Its difficult to explain to a non guitarist. It could just be between these two amps and maybe a simple change to a resistor or recap could make them equal in that regard.

Quick question for you, if you don't mind: There is a popular mod to the AB165s to make the power section AA864. That may be beyond my capabilities as a tech at this point. Do you recommend that I look in to doing that with this amp? What advantage would there be other than bringing back adjustable bias?
Converting power section to AA864 is pretty easy, I've done it a few times (including on my personal amp).

fender_bassman_ab165-fenderguru-mods.gif


Is it worth it? Maybe -- see what Wally says below.

@ETMusic777, +1 with the advice from @corliss1 to put the amp in proper working condition before making any changes. The AB165 has three gain stages in the Normal channel compared to two gain stages as in the AA864 and AA165 Bassman amps. That Normal channel in the AB165 is hotter because of that.
I agree that mods should only be done after an amp is absolutely 100% serviced and up to spec. Once it's operating properly, you can evaluate your needs. Once you're in good shape, I'll be glad to help with mod ideas, being one of my favorite amps, I've got tons of experience.
 

Paul G.

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One more thing, when evaluating the amp remember to check the bias. These amps have a bias-balance pot rather than bias level. Very often the actual bias is set really, really, really cold.
 

schmee

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Nice score. Yeah, do the filter cap job and the power cord correct at least. Replace the 470 ohm resistor on the power tube that wasn't done (although the other was done! DUH!) They have a habit of failing in Bassman heads. Although I'm not a big fan of the AB165 Bassman as much as the others, but yeah.... try it before you change.
 

ETMusic777

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Converting power section to AA864 is pretty easy, I've done it a few times (including on my personal amp).

View attachment 989669

Is it worth it? Maybe -- see what Wally says below.


I agree that mods should only be done after an amp is absolutely 100% serviced and up to spec. Once it's operating properly, you can evaluate your needs. Once you're in good shape, I'll be glad to help with mod ideas, being one of my favorite amps, I've got tons of experience.
Thanks for the schematic and tips Paul!
 

Silverface

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Positives: The amp is dead quiet and sounds great.
This was mentioned eaar;ier, but bears repeating:

My position with newly purchased vintage amps is to NOT turn them on at all until I've inspected them. It's what I do if I buy any amp over 20 years old, and what I advise every player to do. The MUST be checked for filter and bias cap age at bare minimum!

And that amp you bought has original filter caps - which could cook off, along with the power transformer, 2-3 seconds after flipping the standby switch on.

You got lucky.

Most players just HAVE to test an amp - and $150 of parts and labor skipped over due to eagerness ends up costing $400 in parts and labor AND significant loss in vintage value.

I've replaced many power transformers that have blown by players not realizing the filter caps were over 4x their service life! They - and the bias cap - have a 15...20 year at the outside, playing it safe - service life.

Many amps DO sound and work great with old, original high voltage caps - but they are time bombs.
 

insearchofspace

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Looking at your other thread I wonder if that amp is also an AA/AB165 that was modded. I read that tech note in it that the 864 mods were done 5/6/22, along with all those other neat-o mods. On my 864 it barely breaks up when cranked to 10, no where near the heavy metal you described it as.
 

ETMusic777

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Looking at your other thread I wonder if that amp is also an AA/AB165 that was modded. I read that tech note in it that the 864 mods were done 5/6/22, along with all those other neat-o mods. On my 864 it barely breaks up when cranked to 10, no where near the heavy metal you described it as.
The amp from the other thread is a true AA864, it has not been modded in to one. I've compared AA864 schematics and layout and they are 100% accurate. The chassis serial number is 1964. Every chassis date stamp and pot code is between August 1964 and December 1964. The back panel is "Fender Electric Instruments" which is 1964. The tube chart has been torn off unfortunately. This amp either shipped in late December, 1964 or Jan 1965 right when CBS took over, which explains why the front panel is "Fender Musical Instruments". Some articles which I have read indicate that the new front panels started shipping in December 64, as the deal was inked and they were anticipating CBS taking over in January 65. Everything is original on this amp, with the exception of the new electrolytic capacitors, bias caps and the OT. The blue caps are all dated 1964. The wiring is cloth and period correct. The only "mod" is the single resister in channel 2 which has been swapped out. Looking at the other AA864 videos on you tube, they all sound like this one with a significant amount of gain when cranked past 5 on the Bass Instrument Channel. Its an AA864, not a later Bassman which has been modded in to one. It is certainly one of the last 864s to leave the Fullerton factory, if not the very last one which is pretty cool.
 
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ETMusic777

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This was mentioned eaar;ier, but bears repeating:

My position with newly purchased vintage amps is to NOT turn them on at all until I've inspected them. It's what I do if I buy any amp over 20 years old, and what I advise every player to do. The MUST be checked for filter and bias cap age at bare minimum!

And that amp you bought has original filter caps - which could cook off, along with the power transformer, 2-3 seconds after flipping the standby switch on.

You got lucky.

Most players just HAVE to test an amp - and $150 of parts and labor skipped over due to eagerness ends up costing $400 in parts and labor AND significant loss in vintage value.

I've replaced many power transformers that have blown by players not realizing the filter caps were over 4x their service life! They - and the bias cap - have a 15...20 year at the outside, playing it safe - service life.

Many amps DO sound and work great with old, original high voltage caps - but they are time bombs.
Regarding the AB165 1967: The previous owner had been using it in it current configuration. I know that the caps need to be replaced. I ordered a new switch and when it comes in I will replace that and the caps. I'm aware of what is happening with that amp.
 

insearchofspace

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The amp from the other thread is a true AA864, it has not been modded in to one. I've compared AA864 schematics and layout and they are 100% accurate. The chassis serial number is 1964. Every chassis date stamp and pot code is between August 1964 and December 1964. The back panel is "Fender Electric Instruments" which is 1964. The tube chart has been torn off unfortunately. This amp either shipped in late December, 1964 or Jan 1965 right when CBS took over, which explains why the front panel is "Fender Musical Instruments". Some articles which I have read indicate that the new front panels started shipping in December 64, as the deal was inked and they were anticipating CBS taking over in January 65. Everything is original on this amp, with the exception of the new electrolytic capacitors, bias caps and the OT. The blue caps are all dated 1964. The wiring is cloth and period correct. The only "mod" is the single resister in channel 2 which has been swapped out. Looking at the other AA864 videos on you tube, they all sound like this one with a significant amount of gain when cranked past 5 on the Bass Instrument Channel. Its an AA864, not a later Bassman which has been modded in to one.
Maybe I'll have to take mine in. The bass channel gets a little hairy, but the normal stays pretty much clean to 10.
 

ETMusic777

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Maybe I'll have to take mine in. The bass channel gets a little hairy, but the normal stays pretty much clean to 10.
That is interesting. Even my 1974 Bassman Ten starts breaking up around 6 and is fully charged at 10. I am running these amps in to a Fryette Powerstation PS100 first, to attenuate and then out to the speakers. That way, I can fully crank them up and enjoy the gain. The AA864 starts breaking around 4 and by 7 is almost full out gain. By 10 its all the way and a bit fuzzy for my tastes. The AA864 loves humbuckers driving it. Have you run hot pups in to yours? Even my Bandmasters start breaking up after 5 on the dial.
 

ETMusic777

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I think this guy is a member here at the forum, here is his AA864.




Another 864


And another


Here is a 1966 AB165, which sounds amazing in the right hands...more massive gain


I will post clips of all of my Bassmen once I get the 67 sorted out and squared away. Love the Bassman!
 
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