Princeton build from he!!

[ElPedro]

 

Well, as some of you know, I enjoy building Princeton Reverbs.  I have built several that work and sound great.

Being adventurous and wanting to save a little cash on transformers, I found some iron on eB@y that fit the spec.

I proceeded with my build.

I finished my build.  This amp was the best looking wiring job I had done to date. I was proud of myself.  I went through a checklist (apparently not thoroughly enough), hooked up to my lightbulb current limiter, and thats where the fun began.

1) Apparently, with this particular power transformer, there is a center tap for the 5v.  It's an Allied something or other tranny. I learned not to hook that up.  When you apply power the lightbulb dims (good) and as the tubes heat up, the lightbulb got brighter (bad). 1/2 hr later I figured out that 5v center tap was a no-no.

2) Why am I not getting heat to one of the ax7's?  Well, the wiring job isn't quite as neat any longer... somehow I skipped pin 4/5 on that tube socket. There goes another 15 minutes I wont get back.

3) Might as well replace the 100k resistor on the bias board that smoked when you had the 5vct hooked up...Dummy.

4) OK, let's throw some power to B+ now... WTH - this thing sounds like a 1 watter!  Double check voltages, connections, trannys, inputs... Looks OK to me. Oh, wait a second...What resistors are those there on the first input stage?  Sure don't look like 100K to me...Nope, there's a 100K right next to them (going towards the bass caps)...Those color bands don't match.  Holy crap, dude, you put 1.5K resistors instead of 100K!  How did you manage that, they arent even in the same bin!!!!

Now its loud.  It sounds great.  Looks like crap inside.  I'll fix that tomorrow.

Sometimes I hate myself for the stupid crap I do.

Thanks for reading...Feel free to bash me, I deserve it.

ElPedro

[JJones]

No bashing from me!  I just finished a build and it took me two days (even after several reviews) to see I left out a grid load resistor.  Not the wrong value, just missed it! 

I'm glad you sorted it out!

[eleventeen]

No bashing here, you made some goofs and fixed them. May the worst thing that ever happens to you is you fry a resistor or two!


These new resistors......I am used to very distinct color bands a la 1960's Allen-Bradley or Ohmite. Unmistakable. These new ones I cannot read at all. On the other hand, I am both forced to and pleased to measure them and find them *incredibly* accurate these days, usually within 2%.


Also, if you built the prior PRs you built using kits....that segment of the process is made pretty easy. Yes, gathering all the parts is a chore.

[p2pAmps]

Making mistakes is how I learn personally.  Nice job troubleshooting. 

[HotBluePlates]

First off, congrats on the build! Mistakes happen to everyone; good builders know when it doesn't work that they made a mistake, so they find the error pretty quickly. And that's exactly what you did, so great job!

1) Apparently, with this particular power transformer, there is a center tap for the 5v.  ... I learned not to hook that up.  ...

Well, not to ground. You could use the 5v center-tap as the output from the rectifier to the first filter cap. There's a very little bit less ripple with that hook-up.

4) OK, let's throw some power to B+ now... WTH - this thing sounds like a 1 watter! ...  Holy crap, dude, you put 1.5K resistors instead of 100K!  How did you manage that, they arent even in the same bin!!!!

Yep, everyone's done that! In my last build, I had a single wire run one lug away from where it should be. Turned the amp into a 25w power oscillator! But it was only a 1-minute fix to find & correct.

So like I said, congrats!!