First of all, thanks to all for the nice comments. Yes, the P.L tech manuals I’ve shared have ended up on a few other sites. I didn’t write them and don’t have legal rights to them. I was fortunate to get approved as a P/L service provider in early 1984. That brought all of the service manuals that were available at that time. Eventually i’ll get my stagnant website updated and all of the manuals will be there for download. Is there a Wordpress expert out there?
Having repaired a boatload of 400’s, many of which were in P.A. racks, I developed the 400 board after researching tons of circuits and data sheets. This was partially due to economics as the number of 400s far out weighs the 700s. Blame Gibsonian for pushing me to do the 700 board. I’m not embarrassed to say I adapted the original P/L 200 design for use in the 700. It didn’t bother me when other people copied my 700 design.
At my day job I have access to all kinds of ice cube relays. I welded at least 40 relay contacts trying to find an R/C network that would protect the contacts from 80 volts DC. Nothing but failures. It’s no accident that most relay contacts are rated fo 30VDC and 250 VAC. Using the normally closed contact to short across the speaker acknowledges the difficulty of finding a suitable relay. For a good tech note on snubbers search for “quencharc” or PM me.
On a different note I was at the Saudi oil company Aramco last week in Jeddah, Saudi Arabia. It’s just down the road a ways from Israel. I originally considered a detour through Israel on the way hone. Previous experience in that part of the world said get out as soon as you’re done at the job site.