Gibson and Fender schematics

[Willabe]

How about this? Good enough quality?

This is the GA-77 that's like the  6L6GB tweed Fender 5E series amps.

And has the flawed TS that Vox lifted for their top boost circuit.

[Willabe]

I think these schematics may be missing? The links are not working from this build thread I started.

Found in this build thread, 1st post; 

http://el34world.com/Forum/index.php?topic=14835.msg141885#msg141885

Broken/missing links;

http://www.el34world.com/charts/Schematics/files/gibson/GA-77.pdf

http://www.el34world.com/charts/Schematics/files/gibson/GA-70.pdf

[Willabe]

Doug does have it, but, it's named GA-70.

Messed up Gibby amp models. 

The GA-70 is called the Country and Western amp.

There are at least 3 Country and Western amps, 2 with 3 knobs, '56 and a mid '50's with a couple of pre octals. Then there's the later GA-70, with 4 knobs, and is the same amp amp as the GA-77, but without the extra tone control (tweed style single knob tone control) that the GA-77 has.

Doug could you add/rename the GA-70 you have with Country and Western '57-'58? 

The GA-77 is a 5 knob, '57-'61. It was later called the Vanguard, you have the Vanguard schematic. But you don't have the earlier GA-77 5 knob schematic I posted above. (The GA-77 I posted here/above is much cleaner than the Vanguard and Country and Western schematics.)
 
Pic attached, complete with steer head badge! 

[PRR]

> How about this? Good enough quality?
> This is the GA-77 that's like the  6L6GB tweed Fender 5E series amps.

Gibson_ga77_vanguard.pdf - 119 Kb https://el34world.com/charts/Schematics/files/Gibson/Gibson_ga77_vanguard.pdf  --- seems to be the same amp by another draftsman.

What is stunning is how Gibson plagiarized Fender 5F6A so well. 5 years before 5F6A. The only major difference is the driver to the final stage. A minor differences is the misbiasing of the CF.

[Willabe]

Gibson_ga77_vanguard.pdf - 119 Kb https://el34world.com/charts/Schematics/files/Gibson/Gibson_ga77_vanguard.pdf  --- seems to be the same amp by another draftsman.

Yes, the Vanguard is the same amp, they renamed it Vanguard, and changed the covering. (Maybe the chassis face graphics too?)

What is stunning is how Gibson plagiarized Fender 5F6A so well. 5 years before 5F6A.

I was wondering about that too. So I looked when Fender released the tweed E series amps.

In The Soul of Tone, Celebrating 60 Years of Fender Amps, by Mark Wheeler. Chapter 11, he says the very 1st narrow panel tweeds/the E series, were released in the fall of '54, but 1st appeared in the '55 catalog. And he says the 5F6A was made from '58 to '60.

One of them must have got a very early made amp and opened it up? Or spies?    

The only major difference is the driver to the final stage.

The 5F6A had a LTPI, all the F series did. The E series (just before the F series) had the split load, just like this/these Gibby models.

[PRR]

> This is the GA-77 that's like the  6L6GB tweed Fender 5E series amps.[/i]

The attachment to that post has "1953-54" hand-written.

Do we trust this??

Kuehnel and I are discussing Bassman topics and wondering which came first. Hard facts on Gibson history are scarce.

[PRR]

Gib-GA77-2drawings.gif and gibson-ga-77-amplifier-schematic-2.jpg are variants of the same drawing EXCEPT the typed and hand-written note has been moved from above to below the GA-77 schematic.

Which IMHO casts more doubt on the "1953/54" claim, unless someone knows who manipulated these images when.

[kagliostro]

I'm not sure about what are you discussing, so excuse me if I misunderstand your interest

Doug has also this ga 77 schematic (dated 1954)

https://el34world.com/charts/Schematics/files/Gibson/Gibson_ga77_1954.pdf

Franco

[PRR]

I'm not sure about what are you discussing....

There is a Gibson schematic with the same tone control network as the Fender 5F6a Bassman. The question is: which came first? (Who copied who?) I am now thinking that Gibson's documents and dates are a mess which I can not sort out.

FWIW: the plan you linked is from a site which lists these models "similar" to the one in question.

Gibson GA-70 Country-Western Amplifier (dual 12AY7 version) Owners & Schematics
Note: Tube List: 12AY7, 12AY7, 12AX7, 5881, 5881, 5V4 This version only has 2 volume and 1 tone pots. (Dated 1956) ($15)

Gibson GA-70 Country-Western Amplifier (single 12AY7 version) Owners & Schematics
Note: Tube List: 12AY7, 12AX7, 12AU7, 5881, 5881, 5V4 (Dated 1950's) ($15)


Gibson GA-77 (1953 version) Amplifier Schematic
Note: Tube List: 12AY7, 12AX7, 12AU7, 5881, 5881, 5V4 (Dated 1953) ($15)

Gibson GA-77 (1954 version) Amplifier Owners & Schematics
Note: Tube List: 12AX7, 12AX7, 6SL7, 6J5, 6L6, 6L6, 5V4 (Dated 1954) ($15)

Gibson GA-77 (1961 version) Amplifier Schematic
Note: Tube List: 6EU7, 6EU7, 6EU7, 12AU7A, 6L6, 6L6, GZ-34 (Dated 1961) ($15)

Gibson GA-77RET Vanguard Amplifier Owners & Schematics
Note: Two versions. (Dated 1965) ($15)

Gibson GA-77RV Vanguard Amplifier (12AX7version) Schematic
Note: Tube List: 12AX7, 12AX7, 12AU7A, 12AX7, 12AU7A, 6L6, 6L6, GZ-34 (Dated 1961) ($15)

Gibson GA-77RV Vanguard Amplifier (6EU7 version) Schematic
Note: Tube List: 6EU7, 6EU7, 6EU7, 12AU7A, 6L6, 6L6, GZ-34 ($15)

Gibson GA-77RVT Vanguard Amplifier Schematic
Note: Tube List: 6EU7, 7199, 6EU7, 12AU7A, 6EU7, 6EU7, 6L6, 6L6 (Dated 1963) ($15)

Gibson GA-77RVT Vanguard Amplifier Schematic
Note: Tube List: 6EU7, 6EU7, 12AU7, 6EU7, 6EU7, 6FQ7, 6L6, 6L6, OA2 (Dated 1964) ($15)

[kagliostro]

Oh, I understand (Thanks)

Who copied who?

No technical info about, my nose says Leo borrowed from Gibson 

Franco

[sluckey]

It shorts the two opposite phase signals together. If they are equal amplitude then they will totally cancel each other, leaving zero signal applied to the output tubes. If the PI is slightly unbalanced, the switch will not perfectly cancel the signals and you will hear a little bit of signal through the speaker. The more unbalanced, the more you hear. Silvertone 1484 used this mute method also.

[mresistor]

Thanks  Sluckey..   I took down my post because I was trying to figure that out.  I have not seen this before. 

For those reading this I had stated that I failed to see how the standby works.

[acheld]

It shorts the two opposite phase signals together.

How does that switch do that?   From the schematic, it just looks like an OFF-ON-ON setup.   Interesting . . .

[mresistor]

It shorts the two opposite phase signals together.

How does that switch do that?   From the schematic, it just looks like an OFF-ON-ON setup.   Interesting . . .

The Silvertone 1484 makes perfect sense but I agree with acheld this Gibson switch as drawn makes no sense. It's Gibson magic.

[pdf64]

The Gibson has a combined mains and standby switch, 2 separate poles, providing - off, standby, on.

If only Fender had copied that arrangement, instead of coming up with that stupid hot switching HT standby!
Sorry, the bee in my bonnet is a buzzin’ again

[sluckey]

It shorts the two opposite phase signals together.

How does that switch do that?   From the schematic, it just looks like an OFF-ON-ON setup.   Interesting . . .

This is the schematic mresistor didn't understand. My reply was referring to...

    https://el34world.com/charts/Schematics/files/Gibson/Gibson_ga77_vanguard.pdf

Surely you see that the two PI signals are shorted together when in position 2 "STBY"?

[sluckey]

If only Fender had copied that arrangement, instead of coming up with that stupid hot switching HT standby!
Sorry, the bee in my bonnet is a buzzin’ again

Not stupid at all! I actually prefer to kill the B+ in STBY mode. I find it especially useful when an amp is on the bench.

[mresistor]

I was looking at the top one in post 6   - looking at the bottom one now ..   and now I see it...   

[pdf64]

If only Fender had copied that arrangement, instead of coming up with that stupid hot switching HT standby!
Sorry, the bee in my bonnet is a buzzin’ again

Not stupid at all! I actually prefer to kill the B+ in STBY mode. I find it especially useful when an amp is on the bench.

I dont see that it’s valid to conflate a useful service feature with a front panel feature. Particularly one that is liable to unnecessarily cause a key component’s rating to be exceeded every time it’s operated. Speaking of which, how to avoid the rectifier’s peak anode current bring exceeded when it’s being hot switched?

The useful service feature would be equally well served by a suitable HT fusing arrangement. Which would seem to be a beneficial feature all round, with zero drawbacks?

[acheld]

Thanks for clearing that up.  I was looking at the wrong switch.