An Unsung Classic | 1968 Fender PRINCETON Amp Repair Pt.1
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- Опубліковано 4 лип 2024
- 1968 Fender Princeton Non-reverb amp repair
00:00 - First look!
04:27 - SO CLEAN!!
05:31 - My process
07:21 - Circuit check
07:27 - Our findings
11:29 - HOLY MOLY BATMAN
12:25 - Can cap
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I just got one of these, literally yesterday. It's been serviced over it's lifetime and that's the beauty of these amps, we can keep them going and going forever. I hope more people get into the technology involved here. So much more dependable and repairable than all the pcb stuff available nowadays. Glad to own a Blackface Fender Circuit from the year of my birth. We're both old , rode hard, and got a few replacement parts. Lol
Thanks for sharing this video. Fortunately I have an expert tech in my corner to help keep my amps healthy and I am in the early stages of learning amp repairs and troubleshooting. I'm reading Gerald Weber books as well. Thanks again, I am sure I will be referring back to this video at aome point in my amps life.
Another piece of history that will be magnificent upon its rebirth.
Eeeep...Those 'Reynolds' fuses are scary!!
What a sweet little amp ; )
😬
The last time it's fuse was bypassed, the amplifier grumbled "curses; foiled again"!😉
I wouldn’t automatically worry about the resistors unless they are more than 30% out, unless they are noisy or the circuit isn’t behaving properly.
Is that your typical tolerance range for the normal stuff (not 5%ers)?
More than 30% can indicate a failing resistor. But within the tolerance window sometimes it just gives an individual amp a subtle unique character. And sometimes it can sound a little meh. It’s a judgment call, but listen to the circuit before changing because of not-tight tolerances (after changing electrolytics of course).
@@PsionicAudio Roger that! I've been looking at it as future proofing, if the resistor is drifting up it's only going to drift higher and higher over time but that makes sense too. Would the cathode bias resistors being 1.8k vs 1.5k affect the tone noticeably with the change in bias on the tube(s)?
Subtlely less gain there but slightly more gain from the slightly higher plates.
Sometimes these random drifts result in particularly good sounding amps, so sometimes I’ll replace an old plate that has drifted with a new plate with that drifted value. But I want to hear the drifted resistor unless it’s extreme.
@@PsionicAudio As always, appreciate the insights!
What a great little amp.. I like your filter can solution a lot. May I suggest for cleaning, use naptha on the chassis, wet and dry cloth, and a Q tip in tight places? I've seen other techs use WD-40, but that smells bad! To preserve from future white oxidation, maybe try dry silicone spray, applied with a cloth. This method would render the chassis clean and dry, and not become a dust magnet as an oil film would be. (not saying you would use WD-40, but have seen this, unfortunately)
Thanks! I was thinking I'd try isopropyl and Naptha, that tends to be my combo of choice for cleaning most things. We'll see how it works!
Love your vids!
🙏
Can you please provide a link to the custom can cap you are going to use in the servicing of this amplifier..?
hayseedhamfest.com/products/20-x-4-uf-500v I can't confirm this is what the owner bought, since he purchased it, but basically you can contact them and they'll build one to the specs you want with the caps you want.
A box of 100 stainless keps nuts isn’t that expensive. 6-32 & 8-32 are the typical Brown/Black/Silver Fender sizes. You may run into a 4-40, 10-28, 10-32 & 1/4-20 in older amps also.
Ahh yes, the old aluminum foil fuse fix! A NOS 5V4 rectifier would work great in this amp if the owner doesn’t want to buy an old Mullard GZ34 or roll the dice on a new GZ34.
One of the reasons, I love having a local Ace Hardware. Those nuts, and plenty of other odd sizes, needs mostly available.
@@numberfourthree, Ace has a fairly extensive hardware selection, but it's always the really small sizes that are hard to find locally, like 2/56, 4/40 perhaps, and similarly small Metric fasteners; or the ones they stock aren't the length or head type that you prefer. Sears Hardware had the best selection of unusual fasteners, but sadly they're long gone....
PS, I suspect they are called Keps nuts because the built-in star washer "keeps" [sic] the nut from vibrating loose easily without needing a separate lock washer.
That's actually a good shout, I'll have to go to Ace and see what they've got since there's one kind of near my work.