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on Sat May 02, 2009 9:28 pm

GP49

Bob Latino wrote:
Clik2media wrote:An interesting "quirk" in chassis bolt configuration. All except one of my Dynaco ST-70 chassis has two screw downs on each side. One amp has a three screw configuration with the center screw being counter-sunk. One thing I noticed is that using the two screw config seems to “pull the sheet metal in, where as the three screw chassis seems to hold the metal straight. Any word on the chassis screw configuration year change
thanks


The changeover from the the two screw tube cage to the three screw tube cage took place in the late '60's. I am not sure of the year but I would say about 1968. About the same time Dynaco changed the color and the label on the tube cage....

Bob[/size]



It has been reported that the change to the three-screw configuration was for Underwriters Laboratory approval on factory wired units. UL wanted allow users to be able to remove the top cage for tube replacement and bias adjustment, without the bottom cover coming off and exposing live wires. The same reason was given for the introduction of the protective grid cover over the circuit board.

on Wed Mar 04, 2009 8:34 am

Bob Latino

Clik2media wrote:An interesting "quirk" in chassis bolt configuration. All except one of my Dynaco ST-70 chassis has two screw downs on each side. One amp has a three screw configuration with the center screw being counter-sunk. One thing I noticed is that using the two screw config seems to “pull the sheet metal in, where as the three screw chassis seems to hold the metal straight. Any word on the chassis screw configuration year change
thanks


The changeover from the the two screw tube cage to the three screw tube cage took place in the late '60's. I am not sure of the year but I would say about 1968. About the same time Dynaco changed the color and the label on the tube cage. The earlier tube cages have a "Dynakit" label and are the "Dynaco brown" color. The later tube cages say "Dynaco" and are darker in color almost black. The word that went around is that Dynaco changed the tube cage color because the earlier brown cages would show a blackish color above the 4 output tubes where the paint on the cage would darken with the continued application of heat - SO - what Dynaco did was change the tube cage to a blackish color. When the paint darkened above the output tubes with heat it was about the SAME color as the cage anyhow and was barely noticeable.

Bob

on Tue Mar 03, 2009 12:51 am

Clik2media

An interesting "quirk" in chassis bolt configuration. All except one of my Dynaco ST-70 chassis has two screw downs on each side. One amp has a three screw configuration with the center screw being counter-sunk. One thing I noticed is that using the two screw config seems to “pull the sheet metal in, where as the three screw chassis seems to hold the metal straight. Any word on the chassis screw configuration year change
thanks

Dynaco lore - Dynaco's product numbering system and year of product introduction - photo on Wed Feb 25, 2009 7:51 pm

Bob Latino

Below is Dynaco's product numbering system and the product's year of introduction through 1977. The Mark II was their first product introduced in 1955 (product code > 1). If you have an original Dynaco Mark II assembly manual the serial number will start with a "1". If you have an original PAM-1 preamp the serial number will start with a "2" etc.

Bob