1955 Fender Twin Amp Modified Tubes & Sockets???

[plexi50]

I am looking at a Fender Twin Amp 5C8 ??? A lot of questions with this one. It looks to me like someone removed all the Octal tube sockets and put in 9 Pin sockets. Look at the tube chart. I have a bad feeling that my customer may have gotten taken. The amp works good but i have not gone over the amp layout and schematic to confirm this is or was a 5C8 circuit. Look close at the preamp tube sockets larger hole punch out for octal sockets. Whatcha think?

[plexi50]

I need to see if the power and output transformers are original now!

[mresistor]

weird

[plexi50]

weird

[plexi50]

DAH!

[J Fletcher]

 Could be an amp built as Fender was transitioning to the 12AX7 and 12AY7 tubes , from the earlier octals . The sockets look like they have been in there for a long time . That's just an observation after a quick look . Jerry

[dogburn]

I suspect it's an early 5D8 - and they just used the 5C8 tube chart.

[dogburn]

Little bit hard to tell from the photo of the tube chart, but the serial number and written tube numbers look to be in the same ink and same handwriting, which suggests it came that way from the factory.

[plexi50]

THIS IS A PIC FROM ANOTHER WEBSITE. IT LOOKS LIKE IT ALSO HAS 9 PIN PREAMP SOCKETS.1952-3

[sluckey]

I suspect it's an early 5D8 - and they just used the 5C8 tube chart.

I agree. Compare what you have to this layout...

     https://el34world.com/charts/Schematics/files/Fender/Fender_twin_5d8.pdf

[sluckey]

That tube chart date stamp GE was stamped May of 1957.

https://vintagefenderamprepair.com/blogs/information/fender-date-codes

[plexi50]

I suspect it's an early 5D8 - and they just used the 5C8 tube chart.

I agree. Compare what you have to this layout...

     https://el34world.com/charts/Schematics/files/Fender/Fender_twin_5d8.pdf

Yes it follows a 5D8 circuit. I love these old transitional changes they made. Does the value increase? Just curious.

[plexi50]

Closer Up.

[dogburn]

Yep, the close-up makes it more clear that the serial number and tube names were written at the same time with the same implement. And the DE date stamps would be for May, 1954, and from a quick search, the 5D8 models were introduced mid-1954.

I can imagine the conversation:
"Leo, where are the tube charts for the new 5D8 circuit amps?"
"Don't have 'em yet - use the old charts."
"But the tubes are different!"
"Well, cross them out and write in the correct ones!"
 

[dogburn]

And for further evidence, here's another example of the same thing from this page:
https://www.retrofret.com/product.asp?ProductID=10334

[dogburn]

It just took a quick search on "1954 Fender amp tube chart" to find a number of examples. But here's one that is really crazy: a Dumble modified Pro amp that sold for $30,000! And the description claims that Howard Dumble himself was responsible for changing out the preamp tubes! So someone paid big bucks thinking it's a 5C5 and that Dumble did more modifications than he actually did.

https://analogr.com/l/621a77e2-e3ec-4011-bc85-dbab6ea1f36c

[plexi50]

It just took a quick search on "1954 Fender amp tube chart" to find a number of examples. But here's one that is really crazy: a Dumble modified Pro amp that sold for $30,000! And the description claims that Howard Dumble himself was responsible for changing out the preamp tubes! So someone paid big bucks thinking it's a 5C5 and that Dumble did more modifications than he actually did.

https://analogr.com/l/621a77e2-e3ec-4011-bc85-dbab6ea1f36c

Boy that's a crazy price! It had some very poor preamp socket soldering that needed to be re-flowed. 2 Wires were just laying on top of the eyelet board and not soldered anymore. Power tube Cathodes were frail strands of hair! Speaker wires were bad and one not connected at all. +424vdc Plates. +428vdc Screens. Cathode vdc +33.5. Grids are 15K each. Talk about different!

[dogburn]

Looks like the handwriting on your tube chart matches that on the "Dumble" amp, so it might have been assembled by the same Fender employee. I looked closer at the documentation of the $30,000 amp, and the only changes the seller documents is the preamp tube change (which Dumble did not do) and a speaker recone, which was for a non-original Realistic speaker, no less! So as far as I can tell, Dumble did not change that circuit and just fixed the speaker, and the buyer is probably convinced he's got an amp with special Dumble mojo now. That could be one of the worst examples ever of someone being duped into spending big money on an amp because of the mere aura surrounding it.

[plexi50]

That's why i am questioning the transformers wiring color and appearance. I will pull the chassis in the morning and take some last pic's. I can see TRIAD on the power transformer and the OT looks correct using a mirror and light. But i have to pull the chassis and do it right for documentation. To tired right now to balance it with one hand and unscrew the nuts.

[HotBluePlates]

Fender did use cover-plates to go from octal-punched chassis to 9-pin assembly in the early 50s.  This amp looks original to my eyes.

The power transformer wiring could be original as well, and is roughly like some others I've seen.  Especially since you note the PT is a Triad.  If it's also a "6516" like the one below, I'd say that seals the deal.

[plexi50]

I'll pull chassis out in a while. Have to be 100% certain. A picture says a thousand words!

[plexi50]

Lazy Day? On the list of things to get is a small decent mirror. I should go to Goodwill or Walgreens. My body is beat! I just finished putting Lower & Upper ball joints and a water pump in my van over the last week. I'm getting to old to do that kind of work anymore. I have a set of (6) fuel injectors that have been sitting next to me for the past 3 years. I dread having to do them. Only because my back can't take standing and bent over for hours anymore. The will is their. The body isn't!

[sluckey]

I'll pull chassis out in a while. Have to be 100% certain. A picture says a thousand words!

Those eight 100Ks at the input end of the board are shouting "I'm a 5D8". The board for the 5C8 looks nothing like this board.

[shooter]

getting to old to do that kind of work anymore

after 50 years I finally started letting the garage mechanic for the area do the "ugly" stuff, I'll still bend over the hood, but all day eating rust crawling around underneath....John, can I....

[plexi50]

I'll pull chassis out in a while. Have to be 100% certain. A picture says a thousand words!

Those eight 100Ks at the input end of the board are shouting "I'm a 5D8". The board for the 5C8 looks nothing like this board.

Yes those 8 100k resistors speak. It's an early 5D8.

[plexi50]

One last thing. Where does this leave us with the single 5U4 rectifier tube? The schematic shows (2) 5Y3 tubes. The 5C8 show a 5U4GB. Just another type o transitional change? History in the making.

[dogburn]

I'd say very transitional. The date code DE is for May 1954, so very early for the 5D8. Seems that going from the 5C to 5D circuits, Fender was switching most (or all?) of the amps to use 12a*7 tubes from the 6SC7 (and other?) tubes from the earlier designs. And that's why so many models had those tube charts with the old tube codes crossed out and new ones written in by hand. So maybe they were experimenting with rectified tubes to find out what worked best with the new circuits.

[plexi50]

All in all this has been a very fun and learning example of the early changes Fender made.Thanks again for all your input and verifications. What's next? A Fender with Wing's!   

[shooter]

been a very fun and learning example of the early changes

do early Gibson's, plenty of undocumented stuff there 

[plexi50]

Yeah Gibson would be the worst for finding schematics.

[shooter]

ah there's 10 different schematics for every amp, they don't match up but hey....