docc Posted June 16, 2017 Author Posted June 16, 2017 So, I'm a little surprised . . . Young son gave me an energy monitoring device for Father's Day and I began checking the amperage draw of various circuits in my proximity. The Fender Bassman LTD (reissue) is on one of them and shows to be only drawing about 3/4 of an amp (0.73A). I expected those 6L6 output tubes-etc to be much less efficient, creating a significant current draw. But, no?
docc Posted January 5, 2019 Author Posted January 5, 2019 OHHHH, NOOOOOO! My Fender Bassman re-pop went ded, Jim! I cried out like a baby. Loverly wife came running down two flights of stairs thinking I was trapped under a jacked car. Two 6L6 output tubes still lit, and the one on the far left is dark and cold . . . What to do? Just re-seat it with some Caig DeOxit®? Or is it "ded, Jim?"
raz Posted January 6, 2019 Posted January 6, 2019 Made in China WTF!? Did they retroactively own your country? 1
raz Posted January 6, 2019 Posted January 6, 2019 I'm pretty sure you will find some replacement for that tube docc, just breathe through your nose and consult ebay 1
docc Posted January 6, 2019 Author Posted January 6, 2019 Die-am! Cleaned the connections with CRG Electronics Cleaner, treated with Caig DeOxit® and back to hot!!!! :thumbsup:
docc Posted January 6, 2019 Author Posted January 6, 2019 What a terrible scare! I have a session tomorrow to practice for . . . 1
al_roethlisberger Posted January 6, 2019 Posted January 6, 2019 Here is a photo of the underside of my rehabilitated 30-A mono amplifier after recapping, etc This and the FM-50 mono FM tuner will power a 1950s cabinet for which I've built custom crossovers, etc Some vintage NOS GE EL84 tubes provide the amplification, with vintage 12ax7 and rectifier tubes. https://www.radiomuseum.org/r/fisher_audio_amplifier_30_a30.html 1
al_roethlisberger Posted January 6, 2019 Posted January 6, 2019 FM-50 underside after restoration. The big coupling cap has actually been changed to a Mundorf oil capacitor since this photo was taken. The FM-50 is unique in that it has a recording level circuit, which is actually a simple preamplifier via a 12ax7 tube, so the tuner has a volume control built in. So I can connect the output of the FM-50 directly to the 30-A amplifier. I think I've either got a vintage NOS Telefunken or Bugle Boy in there now. https://www.radiomuseum.org/r/fisher_fm_50.html
al_roethlisberger Posted January 6, 2019 Posted January 6, 2019 I'll try to remember to post some finished photos once complete, which should be in a week or two, but here is a photo of the rear of the cabinet open with the crossovers and rear firing bi-polar dome mid-range speaker which makes the mono speaker sound a lot more spacious. Since the tuner and amplifier have no tone controls, I have pots on the horn tweeter and midrange themselves, as well as the ability to switch the crossover in/out for the mid-range making it full-range. 1
al_roethlisberger Posted January 6, 2019 Posted January 6, 2019 Speaker compliment, all high efficiency to match the 12-15W 30-A amplifier. One might be amazed how loud 12-15W is when the speakers are high efficiency. Kids today chasing 100s or 1000s of amps of power just don't understand. Exponential horn loaded tweeter 5" midrange 12" woofer 2
docc Posted January 6, 2019 Author Posted January 6, 2019 What a terrible scare! I have a session tomorrow to practice for . . . Nice stuff, Al ! Is the rectifier tube the most likely to go in an amp like this (Fender reissue '59 Bassman Ltd) ? The tube still shuts down when it heats up. I'll search a good replacement. Like, something OSRAM, and made in Sweden . . . ? Maybe, keep a spare on hand like we do a Hi-Current OMRON relay in the monkey-paw-trap of a V11 ?
gstallons Posted January 6, 2019 Posted January 6, 2019 Here is a photo of the underside of my rehabilitated 30-A mono amplifier after recapping, etc This and the FM-50 mono FM tuner will power a 1950s cabinet for which I've built custom crossovers, etc Fisher-30-A-post-recap.jpg Some vintage NOS GE EL84 tubes provide the amplification, with vintage 12ax7 and rectifier tubes. https://www.radiomuseum.org/r/fisher_audio_amplifier_30_a30.html Is it ok to discuss "reforming" & or replacing caps on this topic ?
docc Posted January 6, 2019 Author Posted January 6, 2019 Here is a photo of the underside of my rehabilitated 30-A mono amplifier after recapping, etc This and the FM-50 mono FM tuner will power a 1950s cabinet for which I've built custom crossovers, etc Fisher-30-A-post-recap.jpg Some vintage NOS GE EL84 tubes provide the amplification, with vintage 12ax7 and rectifier tubes. https://www.radiomuseum.org/r/fisher_audio_amplifier_30_a30.html Is it ok to discuss "reforming" & or replacing caps on this topic ? For sure ! While I know what "caps" (capacitors) are, how to do anything with them is beyond me. I noticed my amp *sizzling* a little from time to time. Is that something with the caps or was that this rectifier going bad? A couple more questions on the rectifier, if you please: 1) If I press it really hard or rock it toward one side it come on. It looks to have a "retainer, but the tube won't stay plugged in. Is this just a connectivity problem with the chassis? 2) I've heard that these amps should not just be left on, but I'm guilty of that more lately without using the "standby." Has this contributed to my rectifier problem?
al_roethlisberger Posted January 6, 2019 Posted January 6, 2019 What a terrible scare! I have a session tomorrow to practice for . . . Nice stuff, Al ! Is the rectifier tube the most likely to go in an amp like this (Fender reissue '59 Bassman Ltd) ? The tube still shuts down when it heats up. I'll search a good replacement. Like, something OSRAM, and made in Sweden . . . ? Maybe, keep a spare on hand like we do a Hi-Current OMRON relay in the monkey-paw-trap of a V11 ? Not that I'm a fan of just tossing things out and buying new without trying to fix it.... but honestly, the rectifier tube has nothing to do with the sound of your amplifier unless of course the tube is malfunctioning ...and in that case the amplifier just doesn't work. So I'd really recommend buying a new tube and be done with it. Years ago I would have said stay away from Russian, Chinese and other tubes, and instead search for some NOS 1950-70s tube. But I don't think that really matters as much anymore since some new tubes have gotten quite good with the resurgence in popularity of tube amplifiers (guitar and HiFi), and again I think this is especially less of an issue for a non-signal tube. There are a bunch of online vendors, even Amazon, that sell the GZ34/5AR4 tube from $15-40. I suspect if you go to a Fender amplifier or other guitar forum you can find some quick recommendations for a new GZ34/5AR4 replacement that is reliable and will last. 1
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