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Hi, I'm in the process of rebuilding from scratch a pair of Dynaco Mark 3's.Every thing is in place except the rust pitted chassis. The chrome plating is shot so not knowing the re-plating process I have opted to paint the chassis. As a house painter I have a nice Mikita grinder which took off the chrome but would not get at the pitting. I'm not a car body man so I'm not familiar with the cost of sand blasting although I have done it a lot and there is a lot of equipment and mess to a simple project like the Dynaco chassis. There is another way to prep for painting and can be found in almost any city or small town. The local(tomb stone maker). I worked for one in 1993. One of my daily duties was to frost the tomb stone.Frosting involved taking the nice shiny granite finish and dulling it in a square so that you could read the dates and inscriptions.The rest of the monument would be shiny but not the frosted area. I would go in a small booth with a (Homer Simpson) suit complete with an air hose. The blast, was not sand but these tiny miniscule ball bearings that were used over and over again,never lost because your in a booth. To do a chassis of a vacuum tube amp would take 10 to 15 minutes to get the chassis ready for priming and never in your lifetime to see rust popping out again once all painted.I would not trust this to a body man as they would have no love for a prized vintage tube gem as most on this post would. You can see the finished product before priming it yourself then painting it or off to the powder coater or body shop. I got layed off back then on Xmas eve, not because of job performance but of small town football rivalries, my employer,my age played for the losing team. He's still in business and I am going back there to ask if I can go back in that booth and get the job done. All monument makers should have a frosting booth and most towns, around Maine anyway seem to have a tomb stone maker.The guy I worked for frequently let artists,stained glass people use the froster for the cost of a Budweiser 12 pack. I hope I didn't bore you but it's an avenue less traveled that maybe one of you might walk.Remember, the timing of the frost job should be noted to get the primer on ASAP. My friend the body man told me to use this spray can, blue,black top called (Permatex Rust Treatment) the pro solution trusted for 90 years which I got at NAPA. Go to your tomb stone guy,say your interested in a Mosoleium, and he might do it for free.Check his work and plan to out live him! Then primetime!...I'm going this week and if all goes well I will have pictures......Mark Korda.
Follow Ups:
The surface treatment you mentioned is fine. Touch base with Jim McShane, during the week, and he will point you at a source of superior automotive finishing products. Use a good self etching primer. The Permatex stuff might be something that converts rust into plastic and that's not bad. Duro "Extend" is another such product.
Hammerite spray on hammer tone finish is reasonably idiot resistant and comes in several colors. The irregular surface produced is ideal, when the substrate is flawed, not mirror smooth, to begin with.
Eli D.
Hi Eli, thanks for writing back. I'll check that out. As a house painter I went out to my car and got the can of primer I use for radiators. It is what you said the other primer was, a rust converter. A substrait you can put right over rust, I want a preventative put on real shiny metal....good eye. I'll re-check primers. The stuff I use on radiator covers that are rusty has lasted over 8 years with nothing popping out, but the rust was laboriously ground off with a Makita grinder. The stuff is Rust Destroyer and is thick red goopy stuff with a logo of a tank on the label. Eli, when it's time to retire don't! Open up a tube teaching school.I'll be the first to enroll if I can get by the entrance exam! I still have the Dyna-PAM tone control project to do.Not to many people know it was you with the answer double checked by VanAlstine because he was a little unsure himself.I'll stop kissin your ass but I'm glad Vintage has ya....Mark K.
sandblasting or bead blasting is cheap and very effective. Motorcycle shops typically have a small both bead blaster. The pitting will remain of course, but i use an automotive zinc chromate primer which goes on fairly thick and wet sand til the surface is smooth. I then follow u with the top coat.
Also very highly recommended is powder coating. Extremely tough and heat resistant, it has great fill properties. I took my most corroded ST-70 chassis to be blasted and powder coated. While the deep pits were visible when viewed from an angle, nothing as visible from three feet away.
uses powder coating on his incredible ST-70 rebuilds. Not only is it durable but you can get a wide variety of colors to choose from. Will has fun building these and isn't afraid to throw some color into a traditionally blase (color-wise) medium.
"Once this was all Black Plasma and Imagination" -Michael McClure
I can't argue with those results. It looks great! It looks like there was more that cosmetic mods done. I have never seen a Coke Bottle EL34, so I am guessing those are 2A3 DH triodes. They look a little to small for 300B's. What is he using for a driver?
Dave
~!
The Mind has No Firewall~ U.S. Army War College.
Don't know the technical aspects of that amp. I've owned a couple of his ST-70's that were standard rebuilds in that the original circuit design was employed, EL-34, GZ34,7199 tubes
used BUT with choice of ultralinear or triode modes. He put one of those cool meters for biasing on the last one (black one in pics).So, the green pic is one he sent me years ago as he explored different ways to build and rebuild various ST-70's. I never heard or had it. He sent me a pic once of his shop where he had many different colored amps done and ready to sell. LOTS of color!
I'd have bought one of his more colorful amps, but WAF was mighty low on that.
Will's even more particular about how they sound/operate than how they look too!
"Once this was all Black Plasma and Imagination"-Michael McClure
Edits: 06/16/15
Those all look like EL34's. There may be a coke bottle EL34. I am just not aware of it. I love the Stereo 70, but I share Eli's concern about the scarcity of 7199's. Of course there are a lot of solutions to this problem out there.
Dave
Couple years ago Will asked if I had some spares for him.
Luckily I did.
I'm sure he's tapped into more since; he has that talent!
I only used EL-34 amps from Will, but he did experiment with other configurations (such as that green amp).
Don't know if he still does, but he still makes HIS ST-70's.
"Once this was all Black Plasma and Imagination" -Michael McClure
Maybe the tubes are Sovtek 6B4Gs. "Uncle" Ned Carlson has a mod for Dyna ST70s that allows for alternate use of EL34 class multi-grid types and, specifically, Sovtek 6B4Gs. NOS 6B4Gs will not survive under the conditions found in a Dyna ST70.
Eli D.
Could be!
Dave
must have squeezed a couple of 2.5v fils trans in there somewhere and really tweaked the circuit. maybe a choke input filter to bring the B+ down?
!
The Mind has No Firewall~ U.S. Army War College.
A 5R4, instead of a 5AR4, will bring the B+ rail voltage down too. At the max. 250 mA. draw, the forward drop in a 5R4 is a whopping 67 V.
Eli D.
Hi Musetap, that was a beautiful paint job by Will Vincent. That yellow is exactly what I'm looking for.I like to name colors where I've seen them before and to me that is Bruce McClaren CanAm sportscar yellow.If you go to Google and put his name in you'll see. That green reminds me of Stewarts Old Fashion Soda flavor Key Lime.Uncle Stu, when you said there were visable pits in your paint job, you didn't mean rust too did you? I can live with the pits but rust reminds me off my broken down Ford Focus. Thanks you guys for giving me a ton of information....Mark Korda
I did a check of available "hammerite" colors. No yellow, but "gold" and "bronze" are available.
FWIW, I think the spray paint will cost less than powder coating.
Eli D.
!
The Mind has No Firewall~ U.S. Army War College.
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