The skills are being passed on! I'm going to show my kid the bit about "legend up" on the caps. He's not into this kind of thing but it's wisdom that can be generalized. Thanks for these videos, very helpful.
Nice clean fix Stuart, very interesting...Love the way you sneak around the amp and show practical examples of why these faults occur. Like the tea towel, cool info..Thanks for sharing,..Ed.UK.😀
Great channel! I have very little experience with amps but like to fix electronic devices in general. Your channel gives me access to so much experience (that I lack) which makes troubleshooting that much easier! So thank you so much for sharing these videos!
Fantastic show here. I have one just like this from 2017. I have not had this issue, but it's good to see potential problems. It's always nice to seethe simple stuff again as a reminder. Thanks again for your expertise in the use of schematics. Always entertaining/educational. Wonderful job Stuart.
Great video Stuart.. Faultless diagnosis and a valuable lesson in reading a schematic. I wont repeat my mantra about Fenders production policies as I'm sure by now we're all aware of them. We must remember that Leo Fender was a skinflint and cut every cost he could on his product production, but the one thing he wouldn't do was sell you short term reliability.
Well deduced, Stuart! I give full marks for the brilliant modality in diagnosing this odd issue. To confess, it is one I have never seen occur. I am elated the customer agreed to the replacement of the caps in the doghouse. F&T are very reputable, and rarely if ever, fail. Since Leo's death, Fender has become a corporation who is single-minded of purpose to value profit far above quality. He must be spinning in his grave. Since he started with radio repair, his entire mantra was to design his amps to be serviceable. It is shameful that his legacy has been bastardized to the degree it currently resides. Thank you for posting this. I raise a pint to your health. Cheers!
@@goodun2974 Ok. JJ also now produce a range of HT caps. I wonder what they are, really. Hard to believe they make them in house. But they could, I guess.
Funny you talk about solder braid, I've also gone back to using it as my mine solder removal. I have the pumps, and even a good vacuum solder station, but I still like the 'wick' for the most part, especially on older gear with fragile traces.
My Deluxe reissue reverb works fine but not with the vibrato, its one or the other even after changing the pedal! seems these should be called fender electronic issues.. Great diagnostic BTW!
I always find it funny that the capacitor outline on the pcbs better matches the caps you fit than those horrible ic caps, maybe whoever designed it had the better caps in mind originally? Then the budget department stepped in during production
H Stuart. Really enjoying your channel and working my way through all your videos. As I really enjoy your teaching style I wondered if you might be prepared to do a tutorial on using an oscilloscope with guitar amps. I have watched loads of these but haven’t been totally convinced by any. Best regards, Paul
Thanks very much great to see , I have this hum/ buzz on my fender stage 100 it gets louder n louder and you can’t turn anything down to stop it. Turning it off at the mains is the only way , only happens if played load or distortion is switched on , any advice would be greatly appreciated as I’m about to take it apart to find this 4 year old fault.
Back in the day I was an examiner for City and Guilds electronic servicing courses, we always recommended the use of de-soldering braid. I find your videos fascinating and really useful as I use a 1973 pro reverb which has the dreaded turret board leakage problem. I’ve yet to try cleaning it in an attempt to reduce a bit of slight crackling. I’ve been into the doghouse (haven’t we all) and changed all the capacitors and received a shock (not electrical) as to how expensive the replacements were. Now Maplins are no longer in business, are there any similar retail companies in existence?
After watching your videos i think i might get the capacitors changed after buying a fender tube amp. Id quite like a vibrolux reverb or deluxe reverb. They are pretty expensive,you would think fender would use better capacitors. Brill video again,im learning a bit more each time i watch your videos.
Stu-Love your projects, and some of your shortcut methods that you have learned from experience and that seem to work so well. I saw the video of you using a Megger to test a capacitor in circuit for leakage, and thought that would be a great tool to have, so I bought a BM100/4 off of eBay, and now I'm trying to learn how to use it. I have its manual. I wanted to start by testing some old caps that have been removed from the circuit, and I didn't know if the Megger can be used to test out of circuit or not. The manual implies that the testing is done in circuit. Anyway, could you help me with this to get me up and running! Thanks again.
Thanks. It's just a 20uf 300VDC electrolytic cap. So I wanted to do the insulation testing that you did. The Spec Sheet indicates that the Insulation Test Voltage for the Megger is 500 VDC. Since my cap is old, it's from a 1975 Fender Music Master amp, and is only 300 VDC, it looks like the Megger's test voltage would be too high, and it would blow the cap. Am I correct?
I've just learned that you cannot test electrolytic caps for leakage with a Megger! But its still handy for coupling caps where we don't want any DC leakage to pass through with the AC.
65 DRRI ' when the reverb is turned on 10 it sounds like it's on 1 ' barley any reverb. It wasn't like that until I got it back from having it worked on. Has new tubes and supposed to have been recapped. Any idea?
Hard to say. Low revern is a tougher problem than no reverb. Long shot make sure the phono plugs are pushed firmly into their sockets. Sorry can;t help much more.
Hi Stuart, I have a Fender Hotrod Deluxe that the reverb volume is very low, you can hardly hear it. I already replaced the Potentiometer, I already tested the pan, I already reviewed the coax cables and I can't find the problem. Can you give me any more ideas please?
Hi Stuart - thanks for that. I notice you replaced C31 which was 100V 220uf with a new 100V 100uf. Obviously works from the video - but is that a normal thing to do. Thanks!
The 220uf/100v cap is not the bias cap, it’s part of the odd Fender asymmetrical power supply caps, 47/500 + 220/100. All done to give the power supply 600v capacity.
Hi Jerry Okay, wow I didn't know that and didn;t check the schematic for this amp. Thanks for the info. I did wobder why it was 220uF which seemed high for the bias cap.
Yeah, I noticed that on the schematic and wondered "what the hell was Fender thinking"? Dissimilar series-wired capacitors not only increase the voltage handling of the pair, as one would expect, but also form a capacitive voltage divider, where the voltage inbetween those two caps isn't exactly half of the total B+ voltage, which might be handy if they wanted to tap off say 50 or 60 volts or so, whatever the difference might be at that point between the two caps, but it's not being used. (Also note the two different values of bleeder/balancing resistors). Or perhaps they just had a surplus of inexpensive 220 mfd, 100 volt caps. Otherwise, you'd expect to see a series pair of 47 mfd or even 100 mfd caps rated for 350 volts each.
@@goodun2974 I'm thinking the surplus was the case. Otherwise, I don't know what they were smoking that day. I just jumper it and use a 500V axial with capacitance value to user's taste.
Hi Wayne. Not sure but it's just another letter, e.g. the is an X and a Y HT supply so I guess Z follows. No real reason. Oddly the negative bias vvoltage is always called 'C'. Go figure! Sometime the HT is called B+.
@@stuartukguitarampguy5830 , The A, B, and C designations correspond to the batteries used for 1920s American radio sets, back in the days when all tubes were directly heated, 3-element triodes at most, and there were no "screen-grid" tetrodes nor indepently-heated cathodes. You couldn't run these tube types off of AC house current because there would be way too much hum (1920's filter capacitors weren't up to the job, as they were big, expensive, and of low capacitance value), and so the radios were powered by an A battery for the filaments, a B battery for the plates, and a C battery for the grid bias.
@@stuartukguitarampguy5830 , Just a few decades after those early battery radios were prevalent, the convention and nomenclature changed somewhat, so that when you look at a power supply from something built in the late forties or 1950s the highest voltage is usually called the A supply, the 2nd voltage/filter node is the B supply, and then the nodes are named C, D and E going down the line as the voltages are further dropped and filtered. And yet we still use B+ to refer to the highest voltage supply because of those "B" batteries 100 years ago!
@@stuartukguitarampguy5830 Yes it goes back to the old radio days in the 30s and 40's for WWII those letters meant something. Its looks like the voltage is Unregulated voltage and also no power conditioning meaning less power filtering for the reverb unit which I'm not sure why they are use less power conditioning for the reverb circuit stages?
Yeah the gray IC caps are defective. Should always replace them when you see them. They sold the company and the new owner corrected the defect and changed the color to blue.
I bet there are a number of your viewers that would like to build t.heir own "Stuart's Orininal capacitor box". What doe you say, Stu? Would you show a little schematic?
Hi Rich. Ok it's quite simple. Put a 100uF 500V cap in a box and bring out two wires, ground and positive. Across the cap put a 220K 2W resistor. This discharges the cap (slowly) if you happen to leave it charged, so next time you go to use it, it won't be 'live'.. Now put a momentary push switch in series with a 1K 5W resistor across the cap. Pushing the button connects this resistor across the cap, discharging it in a few seconds. Note there is a certain danger with this item. If you put the probes across a live cap in an amp, then removed the probes, then grabbed hold of the end of each probe you'd get a nasty shock as the internal 100uF cap discharges through your body! So you need to treat it with respect. I hope that helps.
