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Say Douglas; Hows the Mods coming along?
I sent Wayne an updated Merlin schematic, along with the TX coupled unity gain linestage. Hopefully, he'll be able to post them soon. I am waiting for my modified Peerless S265's to arrive from Heyboer. I figure some time soon...:) Still trying to find a matched pair of plate Iron for the new amp. I need 1k2-1k3 VCT at 300 mA or so, plus filter chokes. On the new Merlin schematic, I forgot the Zener clamps for the gate-source voltage protection. 18V Zeners. Cathode( the banded end ) to the gate, anode to the source of the IRF820. I also left out the CCS details. They can be brought forward from the original. I investigated some 500 mW types from Mouser. Wide variation in impedance, and leakage. I went for a low Z, low leakage type BZX55C18, when BZX79C18 was not available. Small diff between them, but a large diff from the 1N**** type. Lots less leakage, and impedance. It does pay to read the data sheets carefully. Anyway, lots of cool stuff to play with, and I am getting good sound. cheers, Douglas
Hey-Hey!!!, The Merlin build is moving right along. The OPT's should be done and ready for shippment soon. I also got some bigger OPTx's for the 813 project. Going to really enjoy that one. Much Iron to acquire though. 750V at 350 mA is no small PS to build. And that's only one channel...:) It is supposedly quite good Iron, and of just the right a-a load for a Class A/U-L rigged pair of 813's. Going to be quite the project to decide where to place the E-Linear taps on the big 16431 Peerless. Had to gut a Heath W6 I found in the basement of a TV shop in Detroit. At least I won't have to cut up a Citation II. The HV of the 813 supply has put me searching for higher voltage MOSFET's. Getting the low R_drain-source along with low capacitances is an exercise in trade-offs. Better now than when I have the soldering Iron warm. The cool thing is that the two gates are tied to drains which are moving in opposite directions. The overall capacitive load at the gate node should be quite minimal. Planning to play with the Merlin PCB design over the holiday weekend. The CCS and voltage reference and Hybrid cascode will all be on a single card. cheers, Douglas
Going through my bookmarks last light, and I ran across this site. Might be an intersting place to look for those one-of-a-kind parts......Colin http://www.oldradioparts.com/pg2a23.htm
>"The CCS and voltage reference and Hybrid cascode will all be on a single card." I`m glad that you`ll going to do that, with all SS parts on single PCB "Merlin" project is now "within the reach" of "average" builder, and project is ready for group build!
it will be easier to play with. New or experienced. Same result, it will be easier to deal with. I may try some SMT devices for the gate stoppers while I am at it. I got a good recomendation on those, and it makes a whole lot of sense. cheers, Douglas
lots of cool old bits there. I have had them bookmarked for a while. Haven't looked there in a while. I think I'll start again! cheers, Douglas
A friend who restores old radios told me about that place around 4 or 5 months ago, after I bought Antique Electronic Supply's last two Miller 10.7 mHz IF transformers with the correct topology for the Dynaco FM-3. If the slugs ever seize up in those dread little beasties, you can forget it! He claims that the owner is a really sharp guy who'll go out of his way to sift through his tons and tons of stuff to help you out. My friend claims that they have any and every thing you can think of, and even a lot of stuff you HAVEN'T thought of, that his stock is just unreal. Thermionic
This guy is an hour up the road from me but seems to be working out of his house from the Medina address. I can't find an address on his website for the Cleveland store. Have I missed it?
Looks like the guy moved. See link for details. http://www.oldradioparts.com/pg2a30.htm