Doing some Bassman 10 service....

[lowbrow]

Couple months ago I stumbled on this `75 Silverface Fender Bassman Ten amp in a pawnshop. These where originally available as a 4X10 combo, looked like this...

 

...but someone had removed the amp and installed it in a oversized cheap ass head box from a low end Crate or something. Heavy as hell as it was particle board. I bought a new custom made headbox off ebay which weighs about 1/4 what the old one did:

 

 

It took a new fuse and fuse holder to get it working when I got home. It's far from original, but the only major change circuit wise was a new output transformer. The originals where whimpy and 4 ohm, this one is much larger and 8 ohm, which is nice.

 

[lowbrow]

I was surprised, but after 33 years the filter caps and everything else still works fine...amp is loud, sounds great and has no hum. Still, I worried about the caps in the power section and decided to replace them. Since everything in the tone section still works, I'm leaving it alone for now.

 

Here's a shot of the old filter caps...

 

 

Here is the small board on top of the amp (under the pan) after everything's removed:

 

 

If you look close, you can see I'm replacing some of the resistors as well. The old +/- 10% carbon comps are being replaced by +/- 5% metal film.

 

Here are the new Spraque Atoms installed:

 

 

And next to the components I removed:

 

[Burningleaves]

Cool!

 

 

I had one of those amps ages ago. It was a fun for guitar and bass.

[lowbrow]

I decided to replace the caps in the bias section as well, but I wish I had looked at the values before I ordered. I went off the schematic, which (unsurprisingly) is different from what was actually installed in the amp. The originals (the white cylinder below) are 80mF 70 volt caps. I had ordered 50mF 100 Volts caps (the schematic calls for 50mF 70 Volts, but I couldn't find those on Mouser). Dunno if I will/should change them for higher value caps...anyone have an opinion? Here are the new ones installed (they're the black cylinders:

 

 

 

Next up are new metal film +/- 5% 470 ohm 1 watt screen grid resistors and I may be rewiring the power cord to take out the death cap and polarity switch. The polarity switch as a middle "off" position, so I'm in no huge hurry to do it....but it's probably a good idea anyway.

[lowbrow]

Bump to say the screen grid resistors are installed and I've been playing the amp for the last half hour. It may be a little quieter on idle than before, but it was pretty quiet before, so it's hard to say. It performs just fine and still sounds kick ass. I'm going to recheck the bias here in a bit, but I'd have to say at this point the 50mF 100 Volts caps seem to be just fine. I was playing on Doctor Morbius' DRRI for a bit tonight and I'm happy to report the amp is as quiet perhaps actually more so on idle.

 

Maybe more pics tomorrow....

[Doctor Morbius]

That's a pretty sweet amp. Looks like you're doing a pretty good job on upgrading the components. I have a fear of getting zapped by caps so I've not done anything like that.

 

Maybe you should gig with that Saturday instead of the Piggy.

 

When talking about quiet amps, you have to keep in mind that the wiring in my home is ancient and I pick up all kinds of noise from attic fans and other miscellaneous BS. Yes, the attic fans run in the middle of winter. Have no effing idea why.

[lowbrow]

I thought about that after I posted.....

 

Been using my nit winter cap to swap V1 tubes on the fly:D No better substitute in the tone test than immediate comparisons! And yes, even I can hear the differences!

[Doctor Morbius]

Do those tubes I gave you work?

 

...Or are they

 

[lowbrow]

Work like a charm. Sent you a PM.

[mrbrown49]

Lookin great lowbrow. Would mind explaining your tube test a bit? What are you trying, and what do/don't you like.

[EllenGtrGrl]

 

I decided to replace the caps in the bias section as well, but I wish I had looked at the values before I ordered. I went off the schematic, which (unsurprisingly) is different from what was actually installed in the amp. The originals (the white cylinder below) are 80mF 70 volt caps. I had ordered 50mF 100 Volts caps (the schematic calls for 50mF 70 Volts, but I couldn't find those on Mouser). Dunno if I will/should change them for higher value caps...anyone have an opinion? Here are the new ones installed (they're the black cylinders: Next up are new metal film +/- 5% 470 ohm 1 watt screen grid resistors and I may be rewiring the power cord to take out the death cap and polarity switch. The polarity switch as a middle "off" position, so I'm in no huge hurry to do it....but it's probably a good idea anyway.

 

 

You should be fine Lowbrow. The main thing to remember, is to get caps rated at the same or a higher voltage than the caps you're replacing. With regards to the values for caps (or resistors for that matter), you can get away with a deviation of as much as 20% from the values the amp originally came with. You might have to anyway, out of necessity, since you may not be able to find a cap in the value you're looking for.

[NotDead]

The bassman 10 is on my "get it if I see it" amp list. Not really well known, but a sweet amp in its own right.

[lowbrow]

 

Lookin great lowbrow. Would mind explaining your tube test a bit? What are you trying, and what do/don't you like.

 

 

I was swapping different tubes in & out of V1, or the first pre-amp tube position (a 12AX7). I wanted to get an idea what different tubes sounded like, as V1 has a major impact on tone, and in this amp in particular since there are only two pre-amp tubes, a phase inverter and two output tubes.

 

Tubes get very very hot, as most here know, so touching them bare handed is out of the question. Normally, I'd play it for a while, power down, let them cool then switch out tubes, power back up and play again. Easy to lose the reference of the sound in your head with all that lag time (at least for me).

 

Pulling and inserting pre-amp tubes while the amp is up and running doesn't, to my knowledge, risk any damage...so I used my knit cap like a oven mit so I could pull V1 and insert a different tube and hear the almost immediate effect it had on tone.

 

I was a bit surprised by the results. The amp is currently outfitted with all new JJs. Two JJ / Tesla ECC83s / 12AX7, one JJ / Tesla ECC81 / 12AT and two JJ / Tesla 6L6GCs. I only took the time to try two other tubes in V1.

 

The first was a Sovtek 12AX7WA. This was slightly darker voiced then the JJ with more gain (louder) and more distortion. It's harmonics and general feel was sharper and more aggressive than the JJ.

 

The second I tried was a Hammond branded Mullard 12AX7 from sometime in the 60's. It appears to be from the Blackburn plant. I've never had the opportunity to play a vintage 12AX7 and wondered if there really was something to the hype.

 

There most definitely is.

 

While the JJs are somewhat bright, and the Sovteks are somewhat dark, the Mullard fell in between the two in voicing. Gain wise, it was about the same as the JJ and distortion levels where in between the two as well. Where it excelled, and there was an absolutely obvious difference, was the quality of the tone. Much smoother and richer in harmonic content then the other two. I was a bit taken aback at how much difference it really made. The depth of tone was palitable.

 

So...I removed the Mullard, stored it away in a tube box and am going to hold onto it. We've booked and paid for some recording time early next year. I'm going to make sure what ever amp I use has this tube in V1 when we start laying down tracks.

[lowbrow]

OK...last post. I took a couple pictures as I worked last night and after I'd had some time playing and trying tubes I decided to try to get the head fitted into it's new home. It took a lot less time than I thought it might and I'm very happy with the results. The quality of the cab is very good and I like the overall package now that it's together. Much lighter too. I wish I coul find a Fender badge for reasonable money, but every place seems to want $35 to $50 bucks for them. Not feeling that vane right now...

 

This is the underside of one of the 6L6GC output tube sockets. That big resistor is the screen grid resistor. One of them had gotten hot at some point and they both appeared to have seen better days, so I wanted to swap them out.

 

Here is the new metal film resistors installed.

 

 

 

And here is a very poor photo (shot inside at night) of the finished head.

 

[EllenGtrGrl]

Could somebody educate me? What is the difference between a Bassman, and a Bassman 10? Before this thread, I had never even heard of a Bassman 10 head! I'm curious - especially since I bought blackface (1965 or 66) Bassman head yesterday.

[NotDead]

 

Could somebody educate me? What is the difference between a Bassman, and a Bassman 10? Before this thread, I had never even heard of a Bassman 10 head! I'm curious - especially since I bought blackface (1965 or 66) Bassman head yesterday.

 

 

Bassman 10 is a whole different amp from your '54 bassman(4x10) and your '74 bassman(head/2x15)

[Doctor Morbius]

... The second I tried was a Hammond branded Mullard 12AX7 from sometime in the 60's. It appears to be from the Blackburn plant. I've never had the opportunity to play a vintage 12AX7 and wondered if there really was something to the hype. There most definitely is...

The documentation I found on that old Hammond organ places it around 1965.

 

I wish I would have tried that tube in my DRRI.

 

The new cabinet looks great.

[mrbrown49]

This is a great thread lowbrow! Thanks for the tube info. That's exactly what I found when I was testing the JJs and Sovtek WAs. I've tried the WBs too. They sound very similar to the WAs, but sound a bit smoother and fatter for some reason. The WB also had a little less harshness compared to the WA. I've never had the opportunity to test an old mullard though!

[Tone Eee]

Excellent post on my favorite amp!

 

I've been gigging and practicing with my Bassman 10 for over a decade (sporadically) and I haven't had to do any service at all to it.

Still has the RCA 6L6's and sounds great.

 

Rock on!

[RUExp?]

Congratulations on that. It looks great.

 

I recently got a Fender Bandmaster Reverb head.

[docjeffrey]

Cool amp. Be forewarned.

 

I replaced all of the caps and resistors on my SF Vibro Champ last summer and followed the Blackface circuit design. It sounded amazing. Then the power transformer blew. I was told that this is not uncommon after a cap job.

 

Anyway, I haven't replaced the power amp yet. There are too many choices, so I'm gonna talk to my electronics-genius cousin when I see him next week in LA.

[ballhawk]

Boy I wish I knew enough to attempt this kind of thing. I have an old silverface head (probably early 70's but not sure) that crapped out a few years ago and has been sitting in my basement ever since. All I've ever done electronically is simple wiring and soldering so even if I did diagnose the problem I'm not sure I'd attempt to fix it without electrocuting myself. Unfortunately I can't afford to pay someone else to do it at this time. I suppose I could search the net or look at some books on tube amps so if anyone has a direction to point me feel free to chime in.

[lowbrow]

 

Could somebody educate me? What is the difference between a Bassman, and a Bassman 10? Before this thread, I had never even heard of a Bassman 10 head! I'm curious - especially since I bought blackface (1965 or 66) Bassman head yesterday.

 

 

Once CBS took over Fender, lots of different Bassman models where done, some for very short periods. Bassman, Bassman 10, Bassman 50, Bassman 75, Bassman 100.

 

Most of them had master volumes (pre phase inverter) and some of them had completely different tone circuits compared to earlier Bassmans. Adding to the confusion is the fact that many of the models listed above changed in `76 or so to ultralinear output transformers. Some think that's a terrible thing, others (Billy Zoom from X for example) do not.

 

Now...the Bassman 10 gets dirtier faster than other standard Bassman type amps I've played...especially with the channels jumped. Tone wise...it sounds good to me, but I should leave comparisons to someone else. I do love the way it takes pedals.

 

If you just got a Blackface Bassman than you just got a stellar amp! Congrats!

 

 

I've tried the WBs too. They sound very similar to the WAs, but sound a bit smoother and fatter for some reason. The WB also had a little less harshness compared to the WA.

 

 

Thanks for that tidbit MrBrown, I shall get my hands on some WBs to give them a try. I want to try some TungSols in a couple of my amps...I put some in my MIG50 and it's waaayyyy darker than it used to be. Don't like that...but I have some amps that would benefit from darker preamp tubes...

 

Thanks for the comments everyone. Truth is I didn't know much about the Bassman 10. I ran across this one in a pawnshop for $175 and figured it must be around 50 watts. Being a silverface Fender at that power and price I brought it home. Once it was up and running and I had played her a bit...well, I knew I lucked out big time. I've since read a lot on them and they do seem to have quite the cult following....

[mrbrown49]

 

Thanks for that tidbit MrBrown, I shall get my hands on some WBs to give them a try. I want to try some TungSols in a couple of my amps...I put some in my MIG50 and it's waaayyyy darker than it used to be. Don't like that...but I have some amps that would benefit from darker preamp tubes...

 

 

I've tried the tung sols, and actually was just using those for a while. They sounded great, I actually like them more than the sovteks. Unfortunately I've had reliability issues with them. I ordered a couple sets and they sounded great for a while. One blew, which I didn't mind, I got alot of mileage out of it, but 2 of the three replacements I had sounded terrible. I asked my tech what was going on so he tested the tubes and they measured way out of spec. He said he's had trouble with them as well lately and recommended the WBs as a reliable alternative. I'm happy with the WBs at this point.

[EllenGtrGrl]

Once CBS took over Fender, lots of different Bassman models where done, some for very short periods. Bassman, Bassman 10, Bassman 50, Bassman 75, Bassman 100. Most of them had master volumes (pre phase inverter) and some of them had completely different tone circuits compared to earlier Bassmans. Adding to the confusion is the fact that many of the models listed above changed in `76 or so to ultralinear output transformers. Some think that's a terrible thing, others (Billy Zoom from X for example) do not. Now...the Bassman 10 gets dirtier faster than other standard Bassman type amps I've played...especially with the channels jumped. Tone wise...it sounds good to me, but I should leave comparisons to someone else. I do love the way it takes pedals. If you just got a Blackface Bassman than you just got a stellar amp! Congrats! Thanks for that tidbit MrBrown, I shall get my hands on some WBs to give them a try. I want to try some TungSols in a couple of my amps...I put some in my MIG50 and it's waaayyyy darker than it used to be. Don't like that...but I have some amps that would benefit from darker preamp tubes... Thanks for the comments everyone. Truth is I didn't know much about the Bassman 10. I ran across this one in a pawnshop for $175 and figured it must be around 50 watts. Being a silverface Fender at that power and price I brought it home. Once it was up and running and I had played her a bit...well, I knew I lucked out big time. I've since read a lot on them and they do seem to have quite the cult following....

 

Thanks for the info Lowbrow. I get the impression that the Bassman 10, besides its master volume, is in a 4x10 combo format ala the Super Reverb.

 

Yep, I done bought me a blackface (1965-67) Bassman head on Tuesday, from Cream City/Warp Drive Music. At the suggestion of some of the Doom Roomers (my Crate GXT-100 is not cutting it, and I wonder if it's even worth it to repair it, considering it's a mediocre amp), I went looking for a Bassman as a good lower cost head (since I can't really afford a VHT or an Orange head at the present time, and won't be able to for some time to come), at the local (Milwuakee area) music stores. Nobody had any. At my last stop (Cream City/ Warp Drive Music), a salesman asked me if I was looking for something. I said yes, a Fender Bassman head (I didn't see any on the sales floor). He told me that he'd go see if they possibly had any in the back room. 5 minutes later he came out with a blackface Bassman head!

 

I tried it out with a Ric 620, into a Carvin 4x12 bottom. The Bassman sounded good clean, and started to break up nicely above 5 volumewise. It sounded even better with the channels jumpered. I put a Dano overdrive on it, and it sounded great. Cream City/ Warp Drive Music wanted $600 for the Bassman, but the guy had told me before I started playing, that the price was negotiable. I figured that it might need a re-cap (although I didn't hear any AC hum), so I said I'd take it for $450. The offer was accepted (after all, considering that the amp was in the back, and not on the salesroom floor, it probably wasn't a mover saleswise). I told the salesman I'd let him know for sure this week. Unfortunately I had an unexpected bill come up on Monday that prevented me from buying the amp outright, so I asked if I could put it on layaway. I was told I could. So, I put the blackface bassman on layaway for $150 on Tuesday night.

 

Bassmans sound great cranked up (the Marshall JCM45 is supposed to be based upon the Bassman head circuit), but I've very seldom (even when gigging) been able to run a 50 watt amp full throttle. I could add a master volume to it, but I'm hesitant to mod a blackface fender amp (even if the mod is easy to reverse), due to their classic status. More than likely what I will do, is get an attenuator (preferrably a THD Hotplate), as funds allow.