The Amp Garage

Just tried a different DMM (Fluke 7-300) for the heaters and I’m getting 1.4 vac on each pin (2&7) at the first power tube with the limiter (40w bulb). Does this seem more correct?

Ok - smoke test results: I’m still upright and the house electrical system is still working, lol. Current limiter with 40w bulb worked. Followed the start-up process and got both quick flashes with consistent “low glow”. No burning smells or odd sounds; in fact it was very quiet with just the very s...

Understood, thanks Martin👍 I had about 30 minutes to spare for fun projects today, so I made the corrections you suggested re: heater wires and OT primaries. Then I wrote out a “dummies’” checklist incorporating your test process above (and ending with “drain the power supply caps”) so that once I d...

Hey, this is excellent information Martin! I truly appreciate it and will follow it to the letter. I’ve got my 40w bulb in the limiter ready to go. We got some bad weather a couple of days ago here in the N.E. so I’ve been cutting downed trees and repairing fence line - which I finished today. Barri...

Understood, thanks Martin. These are the details that I appreciate learning. I probably could have found some time to hurriedly run through this before now - but I’d prefer to take my time and move slowly. To be honest; I’m also slightly apprehensive. Retrospectively, I’ve learned and done much more...

Ok, quick new guy question: should I have heaters wired up to the power tubes for this testing?

Haven’t made a lot of progress this past week due to seasonal chaos, but hoping to light this thing up for power testing this weekend.

Thank you for the explanation Martin; it helps me interpret the diagram and make sense out of the flow of things. Very much appreciated!

After reading many build threads, I opted for the MIDI cable with jacks on the amp and foot switch. Seemed like a better practical solution.

Understood, thanks Martin!

Should I be connecting pins 1 & 8 to ground with these? Also - I’m getting tripped up by the foot switch. Here’s the connections on the chassis side looking at the DIN Jack from the rear with the square tab at 12 o’clock: Pin 1 - PAB power in from power board Pin 2 - PAB out to manual switch (with r...

Thank you Martin, I appreciate the feedback! So I should keep the 1R resistors from pins 1 to ground on both power tubes that were part of the bias test point “network” then? Sure thing, easy enough to put back. I removed them and the test points after considering Jelle’s advice about reducing add-o...

Here we go: power section, IMG_0157.jpeg pre-amp area, IMG_0160.jpeg and view of the back panel from inside. IMG_0161.jpeg The bias pot has the 27k 1watt resistor, but my gut tells me that might need to change. I also need to neaten up the wires coming over the PT. Trying to compensate for my lack o...

quick clarification:

Do I need tubes in place for this test? If so - which ones? My hunch is that I don’t, but honestly I’m just not sure.

Thanks!

Thanks very much guys! Always appreciate both of your feedback for sure 👍 Martin, as usual your direction is clear, concise, and even a NEMF like me can follow the logic. Let me run through this mentally a few times and I’ll report back with what I discover once I do the actual testing. Thanks very ...

Ok, I think I have everything in place to test everything to the left of the power board/pre-amp board gap (looking from the back). Got a couple questions: 1. Was my calculation for the 3 amp mains fuse correct? I’ve seen some charts showing a 2 amp was the fuse for old Fenders with similar specs. 2...

I agree Martin; especially this being my first “complicated” build. Incremental progress checks are far more preferable than deconstructing layers to find problems. In my previous professional life - that was part of the culture I lived for just under 28 years and is a “comfortable” routine, lol. Ha...