I'm looking for information that will allow me to specifically establish date ranges for plexis and early metalface plexis by internal construction details, starting with the board types. I'm rebuilding what I now believe to be a late '68 or early '69 100 watt Plexi, and I can't be more specific than that because I never got the original back panel with serial number nor is the serial number documented anywhere. It was running when I got it, but BADLY butchered. I have a different thread regarding the restoration of this amp so I don't want to duplicate that here. But I'll be updating that thread as soon as I'm done with this post. But, look at this cleaned up chassis which shows the essential features of this specific amp in question. Small tag board near the power transformer. Main board is perforated but not in a grid pattern. Only the holes that were needed were drilled. Terminals are simple tubular terminals with lightly grooved surfaces. What year range, specifically, do these features indicate? And, the rectifier is a solid state four terminal diode bridge rectifier pack that was apparently bolted directly to the chassis originally. Here's what I started with.
It looks mid-69 to me based on the metal front panel and the "short" board. By late '69 into the beginning of 1970 the rectifier block was mounted to a now longer board rather than to the chassis. Also the stand up power transformer would indicate April '69 on. The earliest 100W metal panel I have run into was in the 107XA range from around May 01, 1969.
The metal front panel is not original. The chassis originally bore adhesive residue with gold paint on it, both front and rear, indicating that it originally had real plexi panels. For the post-restoration chassis pic, the panel pictured is one of the ones I make. I took off the metal panel that came with it to save as a pattern. I believe it to be a later reissue part for a reissue variant 1959. It gets my own front and rear panels and hopefully will get my first plexi reproduction panels rather than my metal ones.
The chassis is clearly 1969 and onwards. Now, if the four speaker jack holes are original then your looking at roughly mid July 1969 and onwards. Taking into consideration of the turret/tag board styles, I'm thinking your in the mid July thru September 1969 area.
The original speaker jack hole configuration was four with the unused footswitch socket hole in the middle between them. They lined up perfectly and on the right spacing and with THIS amp, any hole that was the right size and in the right place must be factory original. Thanks. Got any idea what the estimated serial number range should be?
For the metal panel amp I'd say a serial number range of 2000 thru 3000. This range could be further narrowed down if additional mounting holes are present for the additional little turret board that would have held the diodes for the bridge rectifier and snubber caps. If it was a plexi panel amp then it could be any number.
As I said previously, the chassis has been totally reworked, rewelded, repaired, and regalvanized and chromated. So it's looking like late '69. I spent HOURS over at the amparchives galleries and only found matches for this configuration in late '69. And only one exact match. Seems like this configuration wasn't made for long at all.
