When square wave testing any solid state amplifier, be very careful about your power levels when using higher frequencies. It is very easy to destroy an output stage if you push it too hard.
Good trick with the PS and multimeter. It's amazing how many caps will test good for capacitance & ESR but still fail miserably for leakage.
I use a DE-5000 for checking capacitance, ESR & DF. I often need to match up a bunch of caps for tolerance, and this thing is great for that application...
The one on the left with the butchered-looking plate material is just sloppy Sylvania manufacturing. I have seen this with many of their power tubes. You should have seen some of their 6550's I've encountered; Yikes! Doesn't affect performance, but looks like s**t.
The one on the right has been...
Same here on the temp rating, especially when dealing with compact or poorly ventilated tube gear, and the 105°C types usually have longer rated lifespan hrs. I like a bit more capacitance to compensate for the cheapy tolerance game, and a bit more voltage never hurts either.
Just curious; have...
I could easily see that screwing up a tech who wasn't paying really close attention; quick glance, see the big black arrow. Yep, that's the negativeo_O
If it has lots of copper showing at the plate seams it's a GE. I believe that they used the three-ply plate material for rectifiers, but saved the five-ply for larger power tubes.
The bottle is slightly fatter than a Mullard, but less than a Sylvania. Another excellent tube.
Talk about memory...
That is a Sylvania. In my opinion, likely the best GZ34/5AR4 ever made. Those tubby's are indestructable and last forever. Wish I hadn't wasted so many in guitar amps :(
Tape noise in the Echoplex? Guy I used to be in a band with used a Les Paul with P90's, through an ancient Vox AC50 head and an equally ancient Marshall 4x12 bass cab. I never heard any tape noise. In fact, it's surprising that I can actually hear anything at all after that :oops:
While you are in there, I would highly recommend that you check all of the carbon composition resistors, as they've usually drifted all over the road by now. I believe that most can be verified in-circuit.
Also, if you have a cap tester that can do leakage testing at the necessary voltages, I...
I have several pressings, and they range from WOW! to yikes, that sucks...
The best? the original party-platter from my teens, despite having more beer and cigarette ash on it than most stages. The worst? The brand new copy from amazon.