Anyone have docs for the Foster WF-100k plate amps?

Ron_E

I found an FAQ for them but the links to the spreadsheet and schematic no longer work.

Ron

Tom_S

I think I have a pair of those amps squirreled away somewhere. I may even have the docs on an old drive. I'll have a look.

There's a little info on this thread - https://www.diyaudio.com/forums/solid-state/146228-foster-wf-100k-plate-amps.html

Tom_S

This might be it - https://web.archive.org/web/2015*/http://home.comcast.net/~jhidley/WF-100K_schematic.zip

Tom_S

Spreadsheet even works on my Mac!

https://web.archive.org/web/20151009110333/http://home.comcast.net/~jhidley/2nd_order_HP_filter_calculator.xls

Ron_E

I got the spreadsheet but the schematic link won't go anywhere. DIY audio is being backed up. I'll try again later.

Ron

Tom_S

I grabbed them last night using the Wayback Machine. But I can't get the jpegs to load even after reducing the file sizes.

barryv

I have them. About 5Mb of tif files. I can email or post or ???

Ron_E

I was able to find and download the files and unzip the schematic. The images are tif files which may be why you can't open them.

Ron

Ron_E

Here are the schematic files in jpg format.

Thanks for the help Tom.

Ron

Ron_E

The FAQ referenced some files I didn't have so I went looking on the Wayback machine.

Ron

Ron_E

I got around to modifying a pair of these this week. The FAQ says you can turn VR603 CCW all the way to almost get rid of the spectral tilt which was true. When I put a 10K resistor accross pins 1 and 3 it didn't seem to change anything.

I ended up setting the high pass filter to 26Hz with no boost and a Q of .6. This graph is from the first one I did which has the 10K accross VR603. The red trace is the original filter and the cyan trace is the new filter. Low pass was set at 200Hz

This is the second amp which doesn't have the VR603 mod.

I plan to use these with the MCM 8" BP sub I'm working on in another thread.

Ron