'68 Bandmaster head

[dymand68]

picked one up last night..pretty clean; $350; the guy i bought it from lives in an apt. and has an 8 month old sleeping; thus I did not crank it when testing it out; he did not have a cab so i brought my 8 ohm 212; i could tell b4 buying it the volume was not overwhelming; upon getting it home and trying it out i quickly discovered that even on 10, the volume was lacking; any ideas? to put in perspective: I have a '68 Pro Reverb, all original that is WAY louder than this; I also have a '72 DR that, when run thru JUST that same 212 cab is way louder than my new BM; the wild card is how loud will the BM be if I run it thru the appropriate 4 ohm load...no way to find out currently
- the other concern...vibe was dead initially then kicked in working normally after about 5 minutes; sadly, it sounds much better than the vibe which was supposedly repaired on my 66 Showman head

[vjf1968]

Originally Posted by dymand68

picked one up last night..pretty clean; $350; the guy i bought it from lives in an apt. and has an 8 month old sleeping; thus I did not crank it when testing it out; he did not have a cab so i brought my 8 ohm 212; i could tell b4 buying it the volume was not overwhelming; upon getting it home and trying it out i quickly discovered that even on 10, the volume was lacking; any ideas? to put in perspective: I have a '68 Pro Reverb, all original that is WAY louder than this; I also have a '72 DR that, when run thru JUST that same 212 cab is way louder than my new BM; the wild card is how loud will the BM be if I run it thru the appropriate 4 ohm load...no way to find out currently
- the other concern...vibe was dead initially then kicked in working normally after about 5 minutes; sadly, it sounds much better than the vibe which was supposedly repaired on my 66 Showman head

Any used amp I would take to a good amp tech. You may have to have some caps replaced and possibly a re-tube and biasing. May cost you another $300+ but would be worth it to get it up and running like it should.

[dymand68]

thanks, yes there are plenty of amp techs in metro ATL area; I guess my primary question is how much difference should be expected when running that 4 ohm BM head into an 8 ohm cab versus the proper 4 ohm load

[DMace]

I used to run my BMR head into an 8ohm cab all the time. It was screaming loud. You probably just need tubes/caps.

[dymand68]

does anyone know if I can test the existing two BM 6L6 power tubes by replacing them with two 6L6 tubes which I know are good and matched? i have a relatively new matched quad of 6L6s in my Showman

[Raybob]

Originally Posted by dymand68

does anyone know if I can test the existing two BM 6L6 power tubes by replacing them with two 6L6 tubes which I know are good and matched? i have a relatively new matched quad of 6L6s in my Showman

You can test if they work or not but you can't tell which pair sounds best unless the bias is adjusted for each set.

Raybob

[T Prior]

seeing that you feel the output volume is low, it is best have an experienced tech look at the amp, first off you need to learn if the DC Power Supply voltages are where they should be or you can change tubes all day long , even bias them , but you will be down on power if the DC voltage is off. Biasing the output tubes is the right thing to do but I doubt you would notice any significant increase in gain by doing this even under the best conditions. Raw DC, filter caps etc....these items need to be verified as OK before you take that amp out to gig. Old tube sockets that are dirty and or loose , plate/grid resistors etc...all this stuff needs to be addressed.

The BM is a great amp, I have a 73 and love it to death, but I also took care of the basics before dragging it to a gig. A full set of filter caps can be purchased for about $70, installing them, well that's another issue. Clean / tighten or replace tube sockets, replace the resistors, be sure the PS is right on, use GOOD tubes ( note I didn't say NEW tubes) and that amp will sing for ya....


Buying vintage is not just kool, but fun. BUT, there are things to consider.

Buying vintage Fender amps, I will say up to 73 is a no brainer. I say up to 73 as this is the approx time line for Master Volume added to the amps. When buying an amp, regardless of what the seller says you really have to consider maintenance, if you do the work you really must allow for around $100, if someone else does the work, more. If the amp does not need work then great but the fact of the matter is, expect it. My opinion, do not expect to take any vintage amp you bought today to a gig tonight. These amps are easy to fix, easy to work on and easy to get to excellent operating performance. They all look great but that doesn't mean they work great, but they can all be made to work great. I referenced MV amps, they are fine as well, just a bit different, also excellent amps.

patience grasshopper


t

[dymand68]

thank you for the input T Prior-
I tried it for a bit longer yesterday with different results.....consistent booming volume (likely the appropriate level) vibrato is smooth and steady..I'm not sure it produces the clarity it should at all times; so yes, a trip to a local experienced Fender amp tech is in order...when i get my money right. I will pull chassis, examine, photo and submit. That may answer some questions...I know it has a new-ish 3 prong so it's been pulled and serviced at some point...I may hit you up for some pointers on checking line voltage level(s). I have some hands on knowledge with high voltage; less with low voltage

[muchxs]

If you're taking the chassis out of the cabinet pull the doghouse off an look at the filter caps. I'd say look but don't touch but you say you have experience with high voltage... you probably know what to keep your fingers out of. Drain the caps. Replacing the electrolytics in the power supply isn't rocket science, if you're short on cash you can spend what you have on parts rather than a bench charge. If the caps look orig you might as well swap 'em out. Let's elaborate further on "short on cash": There are lots of good high voltage electrolytics out there besides the expensive and really no better Sprague Atoms. Even Gerald Weber thinks so, he just came out with his own line of "Kendrick" caps. F&Ts from AES work just fine.

http://www.tubesandmore.com/

While you're in there consider replacing the 70 @ 350s w/ 100 @ 350 or even as high as 220 @ 350. 22 @ 500v should be enough for the other three.

Go down the main circuit board and swap out all the 25/25s. F&T builds a Mallory copy w/ two leads on one end and one lead on the other just like vintage Fender. Go to a 100uf @ 100v in the bias supply.

If you want to be picky about it you can chase after drifted resistors. Drift is actually part of the mojo of a vintage amp, change the part, change the tone. Up to you.

I was looking at a SF Twin yesterday that had been "blackfaced". Not sure what they were thinking but it was pretty random, a Radio Shack carbon film here, some goofy carbon comps obviously salvaged out of something else there. If you think you can make it good as new have at it. Otherwise,

[dymand68]

follow up- finally discovered at least one preamp tube was problematic; will replace entire complement....12AX7s will replace 7025s?

[marshman]

Yeah, 12AX7=7025.