fixing a fender bassman 135. glassman?

Chickenwings

Chickenwings

Alnico 6/8
A friend has given me his bassman 135 to fix (because i own a soldering iron!).
q1:
One of the 470 ohm 1w resistors on the power tubes cooked, so i am putting in 4 new ones at 5w each. I think this is better, but please let me know if its a bad idea.
q2:
One of the two 39ohm .5watt resistors wired between v2 and the hum balance pot also cooked. The dude i buy caps. etc from says he uses 2x 100 ohm for artificial center taps. Is this cool?
q3:
I am also replacing the filter caps because they have some brown rusty looking stain spots on their ends.
Stock values are: 2x220uf285vdc - i am putting in 2x220uf300v. I think this is fine.
3x16uf450vdc caps are being replaced by 3x16uf475vdc. I think this is fine too.
There are two 70uf100v caps that need replacing, but he only has 100uf100v caps - is this okay?

Okay thats everything. Cheers!
http://www.ampwares.com/schematics/bassman_135.pdf
 
Re: fixing a fender bassman 135. glassman?

gibson175 said:
q1:
One of the 470 ohm 1w resistors on the power tubes cooked, so i am putting in 4 new ones at 5w each. I think this is better, but please let me know if its a bad idea.
Click to expand...

That will work fine, I replace with 2W resistors all the time.

gibson175 said:
q2:
One of the two 39ohm .5watt resistors wired between v2 and the hum balance pot also cooked. The dude i buy caps. etc from says he uses 2x 100 ohm for artificial center taps. Is this cool?
Click to expand...

I prefer the 100 ohm resistors over the lower value, either would work though.

gibson175 said:
q3:
I am also replacing the filter caps because they have some brown rusty looking stain spots on their ends.
Stock values are: 2x220uf285vdc - i am putting in 2x220uf300v. I think this is fine.
Click to expand...

Those will work fine. I like using a lower value typically but since that amp has a resistor instead of a choke, the added filtering helps smooth out the ripple a bit more. If you ever go with a choke, I'd switch to 100uF @ 350v caps to make it sound a little less stiff.

gibson175 said:
3x16uf450vdc caps are being replaced by 3x16uf475vdc. I think this is fine too.
Click to expand...

Those will work fine. Resist any temptation to substitute 20uF (or 22uF) in these spots as they will make the amp sound way too stiff. In fact, if you want a warmer tone, try an 8uF @ 450v in the final node (furthest from the 220uF's)...the effect is rather profound.

gibson175 said:
There are two 70uf100v caps that need replacing, but he only has 100uf100v caps - is this okay?
Click to expand...

Those will work fine. If you want your bass response to be a little deeper and warmer, try the 100uF @ 100v as the initial filter for the bias and a 10uF @ 150v as the secondary....a little less profound but a great final touch to get the CBS out of a later SF Fender.

Hope this helps.
 
Re: fixing a fender bassman 135. glassman?

Glad I could help. Let us know what you end up doing and what you think of the tone.
 
Re: fixing a fender bassman 135. glassman?

i have to wait a couple of days for the parts. I am scared the 5w resistors will cause trouble elsewhere if a tube craps out, so i am going with 2w. Tonally, its not really something i am going to mess with. I will leave that to the owner.
 
Re: fixing a fender bassman 135. glassman?

Slight Hijack,But still on topic.:D I had a 135 Twin back in the day. Now these OT's run in Ultra linear mode. The amp was ear bleeding LOUD! (And turning it down was not my favorite option) I was told I could take the UL taps off the OT,And bring it back to just a mere 100watts !! I've never been able to wrap my brain around how a amp runs in UL mode? Anyone care to clue me in?:1:
 
Re: fixing a fender bassman 135. glassman?

One of the two 39ohm .5watt resistors wired between v2 and the hum balance
Click to expand...

I can't find these on the schematic I have, but why not replace the micky mouse hum balance all together with a real bias adjustment?
 
Re: fixing a fender bassman 135. glassman?

Lake Placid Blues said:
I can't find these on the schematic I have, but why not replace the micky mouse hum balance all together with a real bias adjustment?
Click to expand...

I think They are 100ohm on the schematic. also the 16uf caps in the amp are 20uf on the schematic. I think there may have been some revisions in the circuit.
I dont want to put in a bias adjustment because i am doing this as a favour. I am not looking to improve the amp. I just want to get it running and give it back to the owner. He will be happy. I will be relieved and will get back to playing my axe.
 
Re: fixing a fender bassman 135. glassman?

also the 16uf caps in the amp are 20uf on the schematic. I think there may have been some revisions in the circuit.
Click to expand...
I think you'll find 20uf caps haven't been made for a long time.
The closest you'll find to that is a 22uf.:cool2:
 
Re: fixing a fender bassman 135. glassman?

Thanks everyone for their input. Amp is all fixed and recapped. Its a serious piece of amplifaction!
 
Re: fixing a fender bassman 135. glassman?

kmcguitars said:
Slight Hijack,But still on topic.:D I had a 135 Twin back in the day. Now these OT's run in Ultra linear mode. The amp was ear bleeding LOUD! (And turning it down was not my favorite option) I was told I could take the UL taps off the OT,And bring it back to just a mere 100watts !! I've never been able to wrap my brain around how a amp runs in UL mode? Anyone care to clue me in?:1:
Click to expand...

I don't know, but this wikipedia page might be accurate.

http://en.wikipedia.org/wiki/Ultra-Linear

*emphasis on might*
 
You must log in or register to reply here.

Similar threads

D
Just Installed a PATB-1 & PA-STK1n
Replies
7
Views
520
dr_m
D
waltschwarzkopf
Firts build! Some questions and a few ideas in mind
Replies
0
Views
240
waltschwarzkopf
waltschwarzkopf
Wolfshead
25w speaker with a 20W amp?
Replies
7
Views
1K
ItsaBass
ItsaBass
Securb
NHD - Just a basic Fender head
Replies
4
Views
481
Securb
Securb
F
Help with buzzing/humming after switching from actives to passives
Replies
13
Views
1K
Blille
Blille
Back
Top