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OK, so we are dancing around a bad OT. Disconnect the OT promary wires and tack solder some other OT in its place. Just run the secondary right to a bench speaker. If the volume restores, then it is indeed a bad OT. It doesn't have to be the right OT, most anything will work well enough to tell us what we want to know. I have an old Fender Bassman 50 watt OT on the bench that I use for this test REGARDLESS of what the amp is. ALl it has to do is kinda work for 10 seconds, and I know the answer.
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Education is what you're left with after you have forgotten what you have learned. -
thats my next move enzo. i will post the resultsComment
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Sorry bout that dude but you said you sent it back to the power amp so I was thinking return. The ohmage value you gave is a tad high but seems somewhat legit. Let us know what you find on Enzo's test.KBComment
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Tranny shorted turns tester
Dart,
If you've got a spare OT Enzo's got the test - if not -since you seem to have good continuity/resistance measures on your OT you might cobble up the shorted turns tester that Doc Horner provided on Ampage about 8 years ago - as best I know the info is available on R.G. Keene's site. 'Tis a simple device consisting of little more than a neon light bulb, a switch and a 9 volt battery. Basically you DC pulse a winding of the unloaded tranny and determine if you get a flyback ring by seeing if the neon bulb flashes. If not you've got a shorted turn which absorbed the induced pulse. A simple but elegant circuit.
RobComment
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May I ask what you found out to be the problem with the Princeton? I know this was back in Aug of 2006 but I seen this here and really am running into the same problem with the faint volume and the fact all the voltages tested fine. Was it your OT or something else? All help is greatly appreciated. ThanksComment
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Originally posted by Rich M View Post
man...ive worked on so many amps since then, i honestly dont remember what the fix was ! sorry !Comment
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Hey Rich ,post your exact problem,type of amp (model AB763 ?) theres several people here who may have run across it if everything here doesn't work. Theres only a few things that will cause loss of volume if everything checks out. Loose or corroded tube sockets,jacks, bad tubes,pots or a solder joint. One good way to troubleshoot it is isolate the preamp from power amp and cut your time in half. Since the SF doesn't have loop jacks you could make one off of the coupling cap after the peak inverter and send that to another amps input or return jack. If it's still low in volume it's back in the preamp somewhere.KBComment
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Princeton Help
Thanks for the reply Amp Kat, The amp I built is from the original 5F2 schematic and layout from Fender. I also used Angela Instruments as a reference site also. This amp is wired 100% to the original layout. The only deviation was I added a standby switch. The voltages check out good . The cathode (pin 8) on the 6v6 is somewhat high around 27.5v and it should be about 18v. But this really shouldn't effect my problem. The amp has very faint volume. The tone control works good. No freaky things going on. Overall in my opinion I believe I have a bad OT. The 8 ohm or 4 ohm connection has the same low volume. I have around 410v on the plate and grid of the 6v6. The voltages except for the cathode one seem to be in great shape. I guarantee there are no wires crossed. It's built solid and no different that the othe rbuilds I've done. This time it just sorta went a little south with this low volume thing going on. Anyone have any suggesstions? Help!Comment
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Princeton Help
I briefly only mentioned the most important thing. The main problem with this 5F2 build is the volume is veryt very low and everything else checks out fine, voltages, etc. This goes with the last post I put here. Help!!!Comment
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Without reading through the whole thread, before you replace the OT as a guess, what signal level is at the output tube grids? FOr that matter, have you traced the signal through the amp? A scope would be the best, but a signal tracer will work, or just set your meter to AC volts and use ut. APply a steady signal to the input and follow stage by stage and see where the signal goes away. If you have full signal at the output grids, then the OT is suspect, but if not much signal is there, then the amp has nothing to put out.
And just for science, disconnect the OT output wires entirely from the amp and connect them to a speaker with clip wires. Does that make any difference? A faulty output jack could short across your OT secondary. I had to diagnose that exact failure on a friend's home build.Education is what you're left with after you have forgotten what you have learned.Comment
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maybe I'm not understanding...what are "loop jacks" doing in a silverface princteon?Comment
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I'm also having problems
I have a 64 princeton reverb and it has this crunch to it all the time... the clean tone is going down the drain. I just biased it and put in new tubes... Any ideas anyone?Comment
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Idea #1 - start a new thread. Link to this old one, sure, but it's almost 2 years old and kinda long to wade through for the new stuff.
(I don't mean to come off like a tool here - just trying to help your problem get the attenetion it needs)Comment
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