This is the beginning of what is the second phase of a greater project going back several years, that being the initial salvaging of this amplifier after being found stored in a Florida attic for over 40 years. For this effort a complete video series exists where the amplifier was brought to a working order but left in the original patina also retaining the use of less that reliable parts, which have caused unpredictable issues over the years.
As a primary platform for this restoration, I've opted for the stainless steel chassis from dynakitparts.com along with new pots, switches connectors, screws and so-forth. Further work will be the cosmetic restoration of the transformers as well. An unboxing goes into each part and kit specifically. A smaller secondary unboxing comes later in this episode.
The project itself begins with the removal of the output transformers which i've opted to recolour on the ends of the cables on both sides due to fading. At that point it was safe to cut out of circuit. This process includes cable to the rectifier and the power transformer as well as the selenium rectifier, some of which have two colours. Once all cables are clipped, starting with the power transformer, each are removed one by one. Emphasis for the power transformer starts with the connections on the c-clamps. Output transformers are removed in a similar fashion, noting that the red center tap wire goes all the way to the electrolytic capacitor and needs to be pulled back on one side.
With all transformers removed the covers are unscrewed and separated so that they can be sandblasted and painted. All of the inner transformers appear ok. I take the covers to Jason's bug ranch and put the covers into the sand blaster to clean then which also textures the raw metal for good adhesion. The first painting attempt as a high gloss, didn't go well. too many imperfections in the metal, and dust and wind in the shop. A second attempt after a stripping and re-degreasing came out perfect by allowing for a light texture to come through, almost like a leather or knockdown.
Each of the transformers are masked and sanded with a Dremel for rust removal and painted as well, cleaned at intervals with spirits. During this time, custom threaded rod with acorn nuts are made for the restored transformers to replace the old screws. With all of these pieces, the reassembly of the transformers commences. Paying attention to stamp placement, the output transformers are done first, doing the measurements of the studs for the final cut. With that the covers are tightened down.
The power transformer is assembled last, also ensuring that the cover is on in the correct direction. The rod length must account for the new dampeners so no adjustments will be made at this time. Having completed the transformers, this concludes the first video in this project series. #dynaco #st70 #tubeamplifier #antique #restoration
