After the passing of Philbrick Alumnus, former VP Bruce Seddon, in the summer of 2008, his son Leigh, gave me several boxes of Philbrick-related material, along with some original Philbrick artifacts, including the original prototype for the R-300 power supply and corresponding hand-drawn schematic.
Most uploads over the past year have been direct contributions of a few pages that were immediately uploaded. Much work remains in photographing and uploading photos of Philbrick artifacts, and other materials.
Ad Sprenkels has contributed a long series of scans that I just started uploading. Thank you very much for this very large contribution.
With a recent ebay purchase of several Philbrick power modules from former Teledyne-Philbrick employee Martin Liben, he contributed a stack of Philbrick catalogs that contains much new material for upload. Thank you Martin for the generous gift of catalogs.
Measurement of solid state amp SPIFF (property of Dan Sheingold) instrumentation amp.
Measurement of P2 parametric amplifier for comparison with Mike Engelhardt's SwitcherCAD schematic model results.
Measurement of Teledyne Fetrons TR1011 and TR1008. Fetrons were originally developed as solid stage JFET substitutes for tubes like the 12AX7. This development was done for the Bell system, but according to Jim Williams, the volume sales never materialized. Operation in the K2-W should be interesting.
Construct and measure a K2-YJ. Perhaps the most elegant amplifier in the Philbrick tube opamp line. This was the military version of the K2-W, and had superior performance, with twice the voltage swing of +/-100V. The output drive is also increased by using 12AU7 equivalent 5965 for the common cathode middle stage and cathode follower at the output. The SK2-V also uses the 12AU7 in a similar fashion. Bob Pease attributes the K2-YJ design to Bruce Seddon. Bob owns a K2-YJ and has made some measurements of it's performance. All Philbrick Modular tube opamps use positive feedback from the output to the cathode of the common cathode stage to boost open loop gain by 20dB, or more, depending on accuracy of the PFB trim. R11 and R12 establish the positive feedback path in the K2-YJ schematic. The K2-YJ is unique, in that it also feeds back a sample of the load current that is sense at R3, to the input of the second stage to reduce output impedance. The usual PFB raises the open loop output resistance, while this added feedback tends to restore it to a lower value. In practice, the PFB that is used an all Philbrick modular opamps increases the open loop output impedance, but this effect is mitigated by the increase in open loop gain. So, adding PFB has a negligible effect on closed-loop output impedance.
Konny Alagarde has graciously given my some of his Philbrick artifacts, including one K2-YJ (2-27-7). I have made linearity sweeps with various tubes and Fetrons. These will be posted soon, along with other measurements still to be done.
I have now made some 12AX7-like Fetrons using the Supertex LND150 depletion mode mosfet in TO-92 package from www.mouser.com. I used these in the K2-YJ and was able to boost gain over 230Vp-p swing from about 15k to about 500k. The postive feedback between the cathodes of the output dual triode had to be reduced. The increased Avol comes from improved linearity in the LND150, not from higher stage gain. This improved linearity allowed full advantage to be taken from precise adjustment of the positive feedback over a 230V p-p output range. Detailed measurements have been done and will be posted soon (2-27-7).
(8-5-7) A trioderized LND150 could make a direct plug-in replacement without adjusting postive feedback inside OPAMP. An LND150 can be trioderized with negative resistive feedback using 1meg for the input resistor and 100meg for the feedback resistor from drain to grid. A capacitor in the order of 100pf in parallel with 1meg resistor equalizes the frequency response and brings external acess at the virtual grid connection to the internal Miller pole from drain to gate of LND150. The curve tracer shows very good match between a trioderized LND150 and a 12AX7, but I still need to try it in a K2W. Perhaps after my vacation in September 2007.
Measure performance of the USA-3 amplifier.
Finish scanning much data sheet material. I will try using a camera on a copy stand instead of using the very slow HP7130 scanner. The slowness of this scanner has been the greatest barrier in finishing scans of material for this archive.
I have now acquired a Canon EOS 10D used digital SLR camera. I am using this camera mounted on a copying stand for much faster scanning of documents. I was able to scan/photograph 512 pages of new Philbrick material in one day. This material has been graciously lent to me for scanning by Doug Coulter of www.coultersmithing.com This material is now waiting to be edited (2-27-7)
(3-25-7) All 512 pages of Doug Coulter's material has been scanned with the Canon EOS 10D camera and has been edited. I have so far uploaded 116 of these scans.
(3-28-) uploaded so far 154 of 512 scans of Doug Coulter 's material.
Some of the new material to be scanned is a very early solid state digital logic family from Engineered Electronics Company (EECO). I have a catalog for the solid state version of these modules. The Z tube module schematics have already been uploaded above. -this is now scanned, but needs to be edited (2-27-7). Uploaded (3-25-7)
Upload more material about contemporary tube opamps and analog computers from Heath. This was suggested by Philbrick enthusiast Terry Walker.
Photograph and catalog my collection of Philbrick artifacts, and upload the results.
A future improvement project would be to convert all documents to text searchable PDF documents. Acrobat can generate the text with OCR, but it often degrades the quality of the image while increasing file size. After much experimentation, I have found that the best compromise between document clarity and file size is a scan resolution of 150dpi, in 4 or 8 levels of gray scale in gif format.
(5-20-7) finished uploading 512 scans of Doug Coulter's material.
(8-5-7) Former Teledyne-Philbrick marketing/sales director Alan Risley has contributed over 100 scans from his personal archives. His scanning effort made it possible to post the material almost instantly. Thank you Alan!