Fender Studio Bass Club!

[Patrice B]

Just bought a Super Twin from 1975 (however, this one has the line out jack, not present on the owner’s manual linked here?). A bit overpaid but there are not a lot of them in Canada and this one was local. Came with known problems:

- previous owner tech diagnosed problems (but didn’t repaired as requested) in the power supply… and it came with a 1.5k resistor removed and the 6.25 fuse obviously blown!

- the only 1.5 k’s I see on the schematic are G1 (grid) resistors or only one from cathode to ground at V1 1st stage.

- there was some work done in the past in the « doghouse » (pics by seller, didn’t opened it yet): 4 electrolytic replaced but two big ones originals remaining.

- all 6 Mesa 6L6GC STR-440 (Shuguang I think?) tests ok on my old Precision tube tester but it doesn’t mean anything until they are really pushed at their real voltages.



Easter week-end is coming so I’ll have the time to look at it:

- replacing the two remaining old PS caps;
- checking the four diodes, resistors values and cathode bypass caps (750uf@3v);
- voltage checks and, eventually, power on without the 6L6GC’s first.

Pics from seller:

 

[johnk_10]

there should be six 1.5K resistors. one each on pin 5 (control grid) of the output tubes. and the line out is on the schematic. the other 1.5K is on pin 8 (cathode) on V1 (12ax7).

 

[Patrice B]

there should be six 1.5K resistors. one each on pin 5 (control grid) of the output tubes. and the line out is on the schematic. the other 1.5K is on pin 8 (cathode) on V1 (12ax7).
View attachment 5398298

View attachment 5398299

I’ll check it in a few minutes… after I verify how to remove the chassis from the combo without crushing it . Four screws and that’s it I would guess. I also think that a missing control grid resistor would obviously leads to a burnt fuse?

Thanks @johnk_10 for your insight!

 

[johnk_10]

i forget, but it might have some screws on the rear lip at the top of the chassis too.

 

[Patrice B]

Done! Out of the cab and first inspection. The thermal fuse must be inside the power tranny I guess?

 

[Patrice B]

Oh well, all caps are brand new! Now to find the cause of the blowing fuse:

 

[johnk_10]

if you don't have a varaic, i'd pull the output tubes and try powering it up to see if it still blows a fuse.

 

[Patrice B]

Ok, from standby switch to plates: 22 ohms on one side and 20 on the other, I hope it’s right?

 

[Patrice B]

if you don't have a varaic, i'd pull the output tubes and try powering it up to see if it still blows a fuse.

I have a Variac but I think I’ll try it without tubes just temporarily .

 

[Patrice B]

Ok, it’s alive without tubes and the fuse doesn’t blow. At first, I thought it was completely dead … but the pilot lamp is kaput. Checked the fuse, fine, huh! Looking again, filaments are glowing on the 12xx7’s, phew!

 

[Patrice B]

Mmmm! Crusty, you said?

 

[Patrice B]

there should be six 1.5K resistors. one each on pin 5 (control grid) of the output tubes. and the line out is on the schematic. the other 1.5K is on pin 8 (cathode) on V1 (12ax7).
View attachment 5398298

View attachment 5398299

@johnk_10 , where did you find this schematic? There is one floating on the web (TubeStore, schematic heaven, etc…) but it’s almost unreadable, too blurry! Thanks!

 

[johnk_10]

@johnk_10 , where did you find this schematic? There is one floating on the web (TubeStore, schematic heaven, etc…) but it’s almost unreadable, too blurry! Thanks!

i forget where i got it since it's been a long time that i found it.

 

[Feinkevi]

Hi friends! I’m probably going to regret this but my Studio Bass head just went up for sale on marketplace in Grand Rapids, MI. I’m thinking $900. Could arrange meetup or shipping at buyer’s expense for someone from here, so let me know if you’re interested or better yet, talk me out of it!

 

[HarrisonBW]

Here's my 76 studio bas and 76 jazz bass, it has a replacement EV speaker with a silver dust cap not sure the model. I was extremely lucky before covid in my east coast search for vintage gear to find this pair completely rediculously priced low. I had to replace many components in the studio bass but wow what a worth while time of life. The clarity in the high frequency from this amp is absolutely mind blowing. The bass is round and bubbly and with the extra EQ you can do wonderful things on any bass tone. The coolest feature of the studio bass by far has to be the built in line level DI. Makes recording way more fun then just DI into a preamp. I'm not super sure about which gain stage the DI output comes from but I'm sure there are some more knowledgable members. It is not as loud as some people say it is but it may be an illusion because of the amount of headroom the amp has. If anyone sees one of these broken or working please go get it. a wonderful amplifier. The only qualm I have is my 60 cycle hum and unshielded single coils drive me insane with small bits of hum. Still working on my knowledge to get rid of this.

 

[rodl2005]

View attachment 7168765
Here's my 76 studio bas and 76 jazz bass, it has a replacement EV speaker with a silver dust cap not sure the model. I was extremely lucky before covid in my east coast search for vintage gear to find this pair completely rediculously priced low. I had to replace many components in the studio bass but wow what a worth while time of life. The clarity in the high frequency from this amp is absolutely mind blowing. The bass is round and bubbly and with the extra EQ you can do wonderful things on any bass tone. The coolest feature of the studio bass by far has to be the built in line level DI. Makes recording way more fun then just DI into a preamp. I'm not super sure about which gain stage the DI output comes from but I'm sure there are some more knowledgable members. It is not as loud as some people say it is but it may be an illusion because of the amount of headroom the amp has. If anyone sees one of these broken or working please go get it. a wonderful amplifier. The only qualm I have is my 60 cycle hum and unshielded single coils drive me insane with small bits of hum. Still working on my knowledge to get rid of this.

That's the 115 combo? Very nice indeed.
I love a Fender tube amp thru a 115

 

[Patrice B]

That's the 115 combo? Very nice indeed.
I love a Fender tube amp thru a 115

Probably a feather light weight to carry …

My Supertwin was a real boat anchor before the surgery that made it into a head only!

 

[rodl2005]

Probably a feather light weight to carry …

My Supertwin was a real boat anchor before the surgery that made it into a head only!

The type we would've chucked a few bricks in the bottom to stop it toppling over

 

[Rsword]

Hi all,

I've had my Fender Studio Bass since August 2024 and I'm in love with the sound it can produce.
The previous owner bought if from a sound engineer which had already separated the amp from the original cab to create a head and cab solution.
The cabinet has 2x12 speakers but I haven't check which speaker brand it is yet, unfortunately.
I got a 1x15 DIY Musicman style cab with Eminence Kappa 15lfa 8 ohm speaker and I must admit that it's the sound of a 15" speaker that does it for me.

Everything is all great with the amp, the looks, the feel and the sound but I'm struggling with the 2x12 sound and volume wise and the 1x15 cab volume wise.
12" is not the type of sound I want so let's leave this cab and speaker size out of the discussion.

15" speakers are my preferred speakers size due the the sound it creates. I'm a real 15" speakers size type of person, I love that sound. But I'm struggling to get loud enough with my bands guitarist. It's a challenge with both of the cabs played separate. I have not tried the 2 cabs together.

The guitarist plays though an old Gretsch bass amp with 2x12 speakers and a VOXAC30 with 2x12 speakers. Recently the guitarist added a Selmer amp with 2x12 speakers. All amps are combos and from the 60's and there is no more than 2 amps "live" at the same time.

How do I proceed if I want to keep the sound off 15" speaker(s) and still be loud enough to match the guitarist with my Fender Studio bass head?
I'm thinking that a 2x15 cabinet might do it but I have no clue on which cabinet that might be? I've seen recommendations on 151566 fEarful, does anyone of you have experience of this cabinet?

What are your thoughts on this? I'm sure the Fender Studio bass should be loud enough.

Fender Studio Bass

DIY Eminence Kappa 15lfa 8 ohm

Thanks in advance and thank you for this club!

 

[Pontiac Thrasher]

Hi all,

I've had my Fender Studio Bass since August 2024 and I'm in love with the sound it can produce.
The previous owner bought if from a sound engineer which had already separated the amp from the original cab to create a head and cab solution.
The cabinet has 2x12 speakers but I haven't check which speaker brand it is yet, unfortunately.
I got a 1x15 DIY Musicman style cab with Eminence Kappa 15lfa 8 ohm speaker and I must admit that it's the sound of a 15" speaker that does it for me.

Everything is all great with the amp, the looks, the feel and the sound but I'm struggling with the 2x12 sound and volume wise and the 1x15 cab volume wise.
12" is not the type of sound I want so let's leave this cab and speaker size out of the discussion.

15" speakers are my preferred speakers size due the the sound it creates. I'm a real 15" speakers size type of person, I love that sound. But I'm struggling to get loud enough with my bands guitarist. It's a challenge with both of the cabs played separate. I have not tried the 2 cabs together.

The guitarist plays though an old Gretsch bass amp with 2x12 speakers and a VOXAC30 with 2x12 speakers. Recently the guitarist added a Selmer amp with 2x12 speakers. All amps are combos and from the 60's and there is no more than 2 amps "live" at the same time.

How do I proceed if I want to keep the sound off 15" speaker(s) and still be loud enough to match the guitarist with my Fender Studio bass head?
I'm thinking that a 2x15 cabinet might do it but I have no clue on which cabinet that might be? I've seen recommendations on 151566 fEarful, does anyone of you have experience of this cabinet?

What are your thoughts on this? I'm sure the Fender Studio bass should be loud enough.

Fender Studio Bass
View attachment 7232931

DIY Eminence Kappa 15lfa 8 ohm
View attachment 7232934

Thanks in advance and thank you for this club!

I was sorta in that realm myself and the solution at that time was mostly to use stuff I had laying around. Were I you I would IMMEDIATLY order a Broughton HPF/LPF!

If you are still reading this you need to stop and go order the Broughton.

Start there and it will probably save you a lot of money.

: )