Fender Transformer Date Codes Question

[vintasonic]

Hi

I am researching what is supposedly a 1968 Silverface Vibrolux Reverb which I am trying to date and have a question about the date codes.  Some of the transformers that I have seen have the format of 606-X-XX, others have the format of 606XXX (I have never seen but have read that some have the year as two digits, ie 606-68xx).  What is the difference in the dashed vs non-dashed codes?  It seems like later (70s) have the 606XXX format and the earlier years are the dashed format.

One of the things that led me down this rabbit hole (again) is that the transformers in this amp are 6067xx and 6066xx but the chassis serial number dates it as 1968.

Anyone have any input on this?  Here are pics of the xfrmrs, I do not have the amp in my possession so I can't check for solder work.

Thanks

[sluckey]

The first X represents the year. You have to guess the decade.

The second and third Xs represent the week of the year.

For example...606724 for a Vibrolux Reverb would be the 24th week of 1967.

I can't tell what the dates are from your pics because one code is in the shadow and the other pic is too blurry. Just guessing that the PT date is 1966 and the 27th or 47th week.

[HotBluePlates]

... Some of the transformers that I have seen have the format of 606-X-XX, others have the format of 606XXX ... What is the difference in the dashed vs non-dashed codes?  It seems like later (70s) have the 606XXX format and the earlier years are the dashed format. ...

I don't think you can infer anything useful from the dashes.

   - I have photos of a 1967 Fender amp with a 1966 power transformer with a dash in the EIA/Date code.

   - The 1964 Deluxe Reverb I used to own had no dashes on the power or output transformers, but the choke had dashes in the date code.  All were 1964 dates, backed up by Fender part-numbers that were used up to the mid-60s but not after 1966 (excluding the possibility of being 1974 or 1984 parts).

   - The 1970 Deluxe Reverb below has no dashes in its date code.

   - I have photos of a 1979 Deluxe Reverb with no dashes in the date code of the power transformer, but dashes in the date codes of the output transformer & choke.

   - A better tell is that early 1960s transformers has a "125P___" part number, while most switch to "022___" part numbers in about 1966.  By 1969 or early 1970s, those 6-digit part numbers started getting a prefix-letter, as with the "F025130" as with the Deluxe Reverb power transformer below made in very early 1969 (open the image to view larger).

I am researching what is supposedly a 1968 Silverface Vibrolux Reverb which I am trying to date ...

Got photos?

Establishing the originality & manufacture date of a vintage amp is all about evaluating "the totality of the evidence."  For a 1960s Fender amp that includes:

   - Transformer date codes
   - Potentiometer date codes
   - Chassis completion date stamp
   - Chassis serial number
   - Faceplate/rear panel
   - Knobs (real blackface are different from silverface or modern knobs)
   - Tube chart date stamp
   - Speaker model, date codes
   - Cabinet date stamp
   - Reverb tank date code
   - Electrolytic cap date codes (if original)
   - Type of electrolytic & coupling caps used (if original)
   - Transformer & chassis wire insulation
   - Cabinet construction details (removable vs rabbeted baffle)
   - Chassis metal (nickel plate vs zinc plate)

[vintasonic]

I don't think you can infer anything useful from the dashes.

Thanks for that and your comparisons to other amps.  I opened up my 66 Bassman (which has a replacement xfrmr from the 70s) and the original xfrmrs had dashes, the replacement did not, so hmmm. I have worked in audio manufacturing environments, often format changes in serial numbers or codes relate to specific time periods, so the inconsistent method of stamping on the cases left me to overthink the situation

Again, this is not on my bench yet, I was trying to help someone via pictures and the anomalies between the serial number and the date codes left me a little suspicious.  Also, the amp in like new condition and didn't sell for max price so I have questions.

Once I have it on the bench I can check for solder work and other tells.  I have worked on many vintage amps and am familiar with ways to check but if someone has been inside it or the amp was repaired somewhere along the way it often takes more detective work

Thanks for your help