Feder Bassman 50

[CJ]

not a bad sounnding silver back, er, silverface, the silverback is a gorilla, not a guitar amp

not all Bassman 50's have a master volume, this one does

 

[CJ]

circuit,  please

some people bag on the  inverter  with 47K resistors, i can not  hear any difference, and it might be more stable,

this has a bias adj that some folks bag on, but it seems cool to be able to balance tubes for matching/hum reduction,

all that is needed to set quiescent current is a simple trial and error of an easy to get to 15k resistor from the pot to ground,

resistor circled in red

no midrange controls,  but a cool Deep switch,

 

[CJ]

chassis shot,  this amp had a 12AT7  that shorted from plate to heater somnotrehow,  never seen that before, took out the heater pot in a blaze of glory,

note wire wrapped cable assy to prevent oscillation,

somebody did an orange drop changeout,

 

[CJ]

only cheap thing on the amp is the pwr tube sockets

we can get 5 ceramic sockets for ten bucks on evilbay and they are pertty darn nice,

had to take 0.015" outof the socket holes with a round file,  bolt circle is the same,

close up of wiring harness trick,

 

[CJ]

sockets obviously

 

[Gene Pink]

had to take 0.015" outof the socket holes with a round file,  bolt circle is the same,

close up of wiring harness trick,

Wire wrap trick is grounded to chassis at both ends?

Have you considered one of these? Faster and cleaner than rat tail filing:

http://www.irwin.com/tools/drill-bits/titanium-fractional-hole-enlarging

Or with coarser steps and much cheaper:

http://www.harborfreight.com/2-piece-titanium-nitride-coated-high-speed-steel-step-drills-96275.html

Gene

PS: Thanks for all your great fix / rebuild pictorials, especially the transformer rewinds. I am learning a lot.

 

[alexc]

Bassman 50 silverface  - hard to beat when they're in good trim.

I like the Master Volume model - in fact never heard a proper bassman that didn't impress me.

Never goes out of style. Not too loud (or soft), easy on the tubes, easy to use, and mostly bullet proof.

Does need a fixing every 35 years or so!

Glad to see another one's innards  - she'll be a happy camper after you've 'done your thing' CJ 

 

[mjrippe]

we can get 5 ceramic sockets for ten bucks on evilbay and they are pertty darn nice

Hey CJ, are those Chinese made sockets or NOS?  I have bought some ceramic sockets from China that start to fail after very few insertions.  Would be nice to find a source for good ones.  Bought some NOS Amphenol octal sockets recently for a Princeton and they worked great after enlarging the chassis hole just a tad.

 

[beatnik]

i like belton sockets

the material they made of seems could be quite reliable over the years

 

[CJ]

here is the socket link, no country specified,

http://www.ebay.com/itm/321611186265?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

we used the stock retainers with the sockets so hopefully they will be ok, they do get loose if you plug the tubes in a lot, so we made sure everything was ok and therefore only plugged them in once,

you can retension with a dental pick,

some of the JJ tubes have slightly larger pins which can screw up sockets,

will look into the Belton sockets, thanks!

some of the Blues Jr preamp sockets are really tight and seem to stay that way, pc mount, they hang upside down with no shields so i guess they wanted them tight,  wish i knew who makes those,

 

[mjrippe]

Thanks CJ, those look good.  The Chinese ones were unglazed ceramic with gold colored sockets.  Re-tensioning was almost useless because the metal was so thin.

 

[Whoops]

i like belton sockets

the material they made of seems could be quite reliable over the years

+1 on Belton Micalex sockets

https://www.banzaimusic.com/Micalex-Socket-Octal-Saddle.html

https://www.banzaimusic.com/Micalex-Socket-Noval-PC-Mount-shielded-base.html