Help me understand my 1954 Fender Pro amp?

[agitprop]

I have a vintage '50s Fender Pro that I bought off a lovely little old lady in San Francisco a few years. She also sold me a beautiful 1966 Gibson ES-175D that I cherish. Yes, it really was a little old lady--she had taught music for 40 years, including private guitar lessons for 25.

I have posted some photos below, and I was hoping that someone smart here could tell me more about this amp. . .

The tube sheet says it is a 5C5 (C3), but the last three 6SC7 tubes are crossed out and replaced with 12AX7, in the same ballpoint pen as the serial number.

The power tubes are Sylvanias and the 12AX7 tubes are all GE. The tube cover for the last tube on the right is an obvious later replacement.

The speaker is a Jensen C15N. I have no idea if it is original. I thought this model didn't come out until the '60s, but I can't find anything online that says so definitively.

The power cable was changed to a 3-prong at some point a long time ago, the old lady told me. She thought something else might have been done to the amp, but she couldn't remember. It was serviced every 5 years or so.

Finally, the little old lady thought that this amp was a 1954 model. Her father had bought it new.

Thanks in advance for any wisdom y'all can offer on this amp--I am truly appreciative!

 

[bluesmain]

Wow! That is a rare beauty!

 

[Jeff Gehring]

4626 is a 1954 serial number for the 5C5. The phenolic parts board with the Orange Drops and new 'lytics and the can cap don't appear to be original--should have a black vulcanized fiberboard eyelet board with individual filter caps.

 

[The Dirty Tube]

The speaker is newer. Ceramic speakers began to take hold in the early 1960's.

The miniature (12AX7's, etc.) tubes are correct. Miniature tubes took the place of the earlier octal style, without any need to alter the circuit. So rather than print new 5C5 charts, Fender just decided to scribble over them.

The caps and three prong are definitely a much more recent addition, my guess is the 1980's or even more recently. And it's a good thing.

Edit: Those look like 6L6GC's in the 6L6G slots. Probably 1970's. Keep them, they're ideal. At 6L6G voltages, a 6L6GC will possibly last a lifetime or beyond.

 

[agitprop]

Thanks so much for the insights, Jeff! Do you see anything that I should fix or change? I have strong soldering skills and am comfortable modding stuff; I just don't know how to spot items that deserve a switch.

4626 is a 1954 serial number for the 5C5. The phenolic parts board with the Orange Drops and new 'lytics and the can cap don't appear to be original--should have a black vulcanized fiberboard eyelet board with individual filter caps.

 

[dex17]

Two of those pre amp tubes are marked on the legend, 12AY7, not 12AX7.

 

[MojoHand]

agitprop,

That amp has been extensively rebuilt. The entire circuit board has been replaced. Fender never used turrets or that type of circuit board material. The electrolytic caps that we can see are all new Sprague Atoms. The coupling caps are modern orange drops, and the amp seems to have a cap can installed for the power filter section. The original 5C5 had four 16uf filter caps installed on the board, which was quite a bit longer than the one we see here. Unfortunately, a hole's been drilled in the chassis to accommodate the cap can.

Finally, the entire layout of the circuit board is different from the original. So it's possible that this isn't even a 5C5 circuit anymore. Back in the day, before Fender amps became collectable, people would sometimes transplant new circuits into old Fender chassis. It's impossible to tell without being able to actually trace the circuit, but the layout looks so different that it makes me wonder.

Ironically, the tube chart is probably original. Fender changed the 5C5 in 1954 to use 12AY7 tubes instead of 6SC7's (a relatively minor modification). Typical of Fender, they were too cheap to print up new tube charts and just scratched out the old values and wrote in the new ones. Later in '54, they introduced the 5D5 Pro which added negative feedback and a new phase inverter design. (And new tube charts!)

 

[hogy]

Yes, all the guts of the amp are new, including jacks and pots. As mentioned before, who knows what circuit it is at this point, it would have to be drawn out.

Hopefully the transformers are original.

Speaker is from 1963.

Those "recycled" tube charts are very common. Leo was a cheapskate, he wouldn't throw anything out. I have seen this many times before.