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To me, that square wave on the test point raises concerns. Maybe there is something wrong in the snubber network. Something shorted there can definitely give those transistors the blues.

Now that I think about it I bet some of these triodes could be replaced with depletion mode N channel FETs. In fact the ones I've seen in the front ends of scopes are common plate so all they do is

George, I wasn't around in the group 5~10 years ago so, I`m not sure if I`m entitled to welcome you back... But feel welcomed anyway. I am from Brazil and here is very difficult to find or get Tek

Hello from Lions Head Ontario Canada. I was on the yahoo board much more often five ten years ago when I was near Georgetown ON. I got a lot of help and ideas (Thank You!) and was also able to help

Some progress. First to answer your questions; D940 appears to be good. I do not have either a ring tester or a bulb tester. What I use is a metered Variac and put a Triplett 630A across the fuse

For some time I have been compiling an index to receiving tube manuals. It is currently complete through 1955, and can be downloaded or read in PDF format

Hi Lorn, You're right... 2N5245 is indeed recommended as a replacement to 2N4416 and, as Chuck mentioned, the 2N4416's 4th pin can be cut-out. Just don't cut the wrong one. I`m looking right now at a

Chuck and other Simple Green interested folks, The FAA may well have put out a notice, but I have not seen it (a pointer to it would be appreciated), BUT: The Army did put a notice in it’s

Lorn, I have some matched pair 151-1042-00 OEM Tek parts if you need them. Message me off list - I tried to message you but for some reason it's not allowing me to do so right now. I'm on the east

Vaclav, If your ACE hardware store does not have that setscrew, I may have one I can send you. I *think* I just saw some among the huge mess left behind here after a disaster. Let me know, and

Yes, thanks Walter! I'll get some of those, too! Thanks for sharing your history with these things. I think adding vent holes to the side panel is a good idea; now that I have a real drill press I

Indeed. Component lifetime is strongly dependent on temperature via the Arrhenius equation. That is basically a diode-like equation with an "activation energy" on the top line, and kT on the bottom.

I find that Z-axis transistor is always too hot, and have routinely added a "tophat" style heatsink that radiates from the top surface, and usually avoids the adjacent parts. late cases have a vent

When you and Tony were discussing the inputs to U1275 it reminded me of the Tek Made parts book and later the Tek Xref book. Bob.

in this instance the 4th pin usually connects to the case for shielding, as it is not a dual gate device. (depending on the environment (other uses- noisy places)? adding the shielding may be

I will check the resistors in sensing sircuit just to be shure for it when find a time for this. But I think that the problem is with some caps in the main frame. It make the same start with other one

ahhhh....now I understand .....D1224 and 5 failed before you disconnected C1224....that makes sense...I could not understand how the failure occurred after C1224 was disconnected......never

Fabio, Thank you for your valuable and informative suggestions! The 20k resistors shown are 1W metal film...but you're right they could and should be beefier. I'll work on that. In the meantime I'll

Hello Al, Ops... As I was re-reading your original post, I realize that I advised you to do measurements you already reported done from the beginning. You already tested the 3k9 resistors and measured

O.K. Thanks for the response Pete. I guess that s/n >17,000 is probably pretty close to the end of production. I don't recall ever seeing anything in the 20,000 range. Marty.