Fender Blackface ProReverb. Let's repair the hum, make it sound great and learn about amp repairs.
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- čas přidán 1. 07. 2024
- I call the Blackface Pro Reverb the “Mini Twin”. It has the same DNA as a Twin but with less than half the power at a manageable weight. Perfect for the 21st century! The sound is back to pure Fender Tube Tone Heaven but it arrived with a horrific hum.
Let’s repair this together and you may even pickup some tips on the way.
If you appreciate the time put into producing this video and got something from it, please LIKE and SUBSCRIBE.
Video Index
00:00 Introduction
04:50 External Inspection
07:55 How to fill loose holes in wood cabinet
10:10 How to Date a Fender Amp from the Tube Chart
12:25 Poor Workmanship caused the loud Hum
15:05 What is the purpose of Totem Resistors
24:28 When to change, and when to preserve, Carbon Composition resistors
28:15 Upgrade the Bias Circuit
37:18 How and why test leaking coupling capacitors
44:55 Bias method using the oscilloscope.
53:50 Select the best tube for each position
50:35 The Sound Test of the Fender ProReverb - Hudba
I like the way Uncle Doug wires the main power supply, he takes the hot lead straight to the on/off switch first, so that when you switch the amp off, there is no power at the fuse holder at all. Safe.
I truly admire Doug, and am a proud Patreon supporter of his channel @uncledoug. But I take a different view on his power wiring. What if the switch is faulty and stuck in the ON position, or someone, even you, accidentally hits the switch? There’s a reason why the safety codes say “fuse first”.
You got it exactly right, Geoff! If the fuse blows you MUST turn it off at the wall outlet (In Australia our wall outlets have switches), or even better, unplug the amp. It is the only guaranteed safe way to change a fuse. To gamble your life on an amp’s power switch is too high a risk. The law requires you to have the fuse closest to the point of entry into a device.
Your example scenario is perfect. You’re on a dark stage. Your amp goes down. The pilot lamp is off. With no pilot lamp, you no longer have a cue to say your fuse is still live. Your prompt to turn off the power switch is gone. In the pressure of the moment you forget to flick the power switch, or even worse, the drummer comes over to help you and he tries the switch for you, then you’ll be knockin’ on heaven’s door.
A related fuse mistake I have seen is to wire the fuse holder with the Live wire soldered to the terminal closest to the fuse cap instead of the furthest away.
There is a reason why it is a safety code in any country I know.
(I'm sorry Geoff. I can see your updated comment in Outlook, but not in this Comment area. I hope you didn't delete it because the point you raised is very important and could save a life one day. Thank you for the opportunity to address this very common misunderstanding)
Gotta say, I love your videos.
I love that these people are aware of the best of the best. And as a guitarist of 62+ years, I REALLY appreciate that these techs care so much about what they are doing and in getting it right! There is a general awareness among GOOD amp techs, of the "treasures" as my tech calls them, that they are working on. These amps are works of art when you get right down to it and must be appreciated for the proper design and care that was originally dispensed in their building.
That's the one thing uncle Doug gets wrong. It is understood in electrical circuits that the fuse is always first. His reasoning for doing switch first is flawed. The fuse holder design is that the input power comes into the tip first. That way when you pull the fuse it gets pulled away from the tip. So no power can flow no matter if it's plugged in.
I am on the exact same diet. Respect!
HAHAHAHAA!
I love working on old blackface fenders. I think I know all of them by heart I have repaired so many of them. Great job mate.
Thanks David. I doubt that there is a Tech anywhere on the planet who does not enjoy working on vintage Fenders above all. Leo sure knew his stuff. Happy repairing!
Loved your playing...
That tone wuz just spot on perfection (!)
That is SO nice of you. Thanks Jonny
I thought you English guys sipped on tea! I cut my teeth on my brother's brownface 1960 PRO. Put in some Webers and enjoy life. The PRO is probably only the second handwired, 40 watt amplifier that Fender ever made (the first, perhaps being the low powered Twin). Put some Sprague atoms in it; or at least some F & T's ! Beautiful job on those F&T's. And time is running out for this world! There is only one way out of it, and his name is Jesus. Make him your Savior now, while you still can!!
Hey! I’m not English…I’m Australian! .
You are in for a treat, my friend. I am just finishing off a huge restoration of a 1962 brown face pro. It’ll be a few weeks before I get the editing done, but I think you’re going to love it.
And yes, Jesus is my savior. He saved my daughter from an aggressive cancer last year. I am forever in awe and in His debt.
AMEN!! SO glad to hear all of that! I sort of thought you might be Australian, but I wasn't for sure hearing some of those sounds that usually cue me in. And I WILL be looking for that PRO video!! Once again, so glad for your daughter's good health and to know that I have a brother just a short swim away! (I live in Jacksonville, FL) Happy Easter ... Jesus is coming back soon!@@theguitaramptech
Sincere thanks for an educational trek. I will never be brave enough to fiddle inside my amps beyond the speaker connection but im quite happy to watch someone else.
Thank you Bruce. Your kind words mean a lot to me.
For an aspiring amp tech, there are many fundamental tips in this video. There is a heartwarming, down to Earth feel to your videos. I especially love the pics of you as a musician. You had hair!
HAHAHA! Yes, I had hair!. I remeber that. My daughter had the ALL CLEAR biopsy following her mastectomy last week. I can now let my hair grow back. I have no idea what hair will return. I wouldn't be surprised if only half returned and all grey!
Thank you for your kind words, John. I really appreciate it. it.
@@theguitaramptech Hi Chris, great news, I wish you and your daughter all the best! Greetings from Germany❤
@@markusf.3441 vielen dank, Markus. Thank you for your prayers.
Good work! The owner is lucky to have you. I like your explanations, very insightful.
I bought some NOS Phillips 12AT7(s) and put one in the phase inverter position and it made a world of difference with my '66 Super Reverb. My amp sounded like Jimi Hendrix! Lol! It made me realize how importance of a good phase inverted tube.
That is a very astute observation, Rick. I agree that a good well matched 12AT7 is very important in PI position.
I also like a Cathodyne phase inverter configuration. Not as common as the LTP but very cool.
Just found your channel recently and am catching up with all your repairs, great work by the way. I'm at the end of my gigging days now but when you pulled out that blonde maple cap tele it took me back to 1973 when I bought mine second hand for £165 I regret trading it but that's life. Serial number was 240858.
Thanks Martin. Thank you for Subscribing. As much as I love Les Pauls, my first love will always be my Teles. I bought mine new in 1973 for AUD440 (about £220).
Howdy from Texas! At 31:17 in the video, there is an ink stamp near the power transformer T24 567. Technician #24, May of 1967. That is the date the chassis wiring was completed. Someone probably knows who Tech 24 was at that time.
Brilliant!! Thank you seeing that and taking the time to write the comment, Michael.
Just came across your channel. I like it and you know Brad (The Guitologist?). Super nice amp and teachings. One constructive tip: check your camera/lights for white backgrounds because the schematics are almost impossible to read. All the best from Brazil to "beside under". ;)
Thank you Penny. I have been having problems with my sound clipping. I think you're right about the lights. Maybe they are too bright? I do a white balance, so its not that. It looks OK in my edit, so maybe the CZcams compression somehow affects it. I don't know. Thanks for pointing that out.
Very cool video. I'm an electrical engineer/guitar player who just bought a 66 Pro today, and I was loving the video. Luckily mine doesn't have a hum.
Congratulations on a beautiful amp. Hopefully, yours has not been vandalised by a “replace everything” Tech. Your main filter caps are not a critical element in the sound path, so please check them before you apply power. Otherwise, please don’t replace any components unless you are 100% sure they are faulty, especially coupling caps.
@@theguitaramptech if it ain’t broke, don’t fix it. Mine sounds good, but I’ll open it up later this week.
Another great upload, thanks for taking the time to make the video and upload!
Thank you Alex. Its comments like yours which fuel me to make videos.
Awesome, like always!❤ All the best and keep doing this! Philip from Austria!
Thank you Philip!
My first production run (1965) blackface pro reverb had utah speakers in it originally FWIW
NICE! I like Creambacks but they aren't the original.
Brad is a champion.
And a really nice bloke as a bonus
Another fantastic in depth video Chris, covering the essential voltages and components required to maximise the efficiency of that fab amp..! ( that was a mouthful) Great explanations Chris, learning loads still..Nice Fender sound and demo..Thanks again for sharing your invaluable knowledge..Ed..uk..😀
Hey bartender. Another one for the Pom over here! 😊
Thank you Ed. I watched all of the coronation last night. It was quite amazing. I felt sorry for Charles under the kilos of gold robes holding golden swords while balancing an enormous crown. Quite the spectacle.
@@theguitaramptech Thanks for the drink mate..! Yes we were bombarded with the coronation all day yesterday. They are good for the country, and we do pomp and ceremony to the max..Stay well and your family also..Ed
What a cool old amp. It looks like my old transitional Super Reverb, but with 2x12 instead of the 4 x 10s. Nice work, too, striking the balance between historical preservation and practical amp maintenance.
Pettifogging quibble incoming. At 45.46 you talked about the valve saturating (as opposed to cutting off). My quibble is this: valves don't saturate. As grid voltage rises toward 0 V with respect to the cathode, current begins to flow on the grid. Even if the signal voltage continues to rise, the charge flowing on the grid will hold the grid around 0 V. The harder you push the signal +ve, the more current flows, and the more grid voltage stays around 0 V. Meanwhile, the anode current continues to faithfully follow the voltage of the grid, which has been clamped at 0 V by the grid current. So the anode current is 'clipped' because it follows the grid voltage, which is clamped by the current flowing on the grid. So the anode current stops rising because the grid voltage stops rising, not because the anode can't conduct more current. Meaning the anode ain't saturated.
I blame this on-the-spectrum rant on Merlin Blencowe. 😁
Very well put Bladder. I know I will lose my viewers if I go too deep. I wanted to differentiate that non-linearity from Cut-Off at the other end. Can you suggest a single word that can get the message across? I would be happy to adopt that phrase if it explained the rounding off better than "saturation". Thanks for the clarification.
(I am also a devotee of Mr Blencowe's and have a hard copy of Designing Valve Preamps.)
@@theguitaramptech It's a great little book, innit? :-) He's also re-published his book 'Designing Power Supplies for Tube Amplifiers'. But to answer your question, I dunno. Grid clamping?
@@Splattle101 yes I have just ordered my copy from Amazon 🥰
I can see that grid clamping may be a more accurate expression, but I suspect it will lead to more confusion and ongoing explanations. I’ll stay with saturation, until you, or I can come up with a better word.
Nice job Chris, these are great amps. Love your Tele!
Thanks John. Great to hear from you again. They really are great amps! The Tele was a bit of a basket case when I brought it back home. Aussie pickup guru, Rod McQueen (Sliders pickups) rewound the bridge pickup, and master luthier Frank Grubisa did magic on the neck. Now it is a sheer joy to play and under 7lbs!
I love late 60's Fenders, I have a 68 Strat.
@@johnmarshall3903 nice one, John.
Very nice. You still have the tele chops
50=60
100=120 10-4
Always learn something here.
HAHAHA! Love it!
WRT Bias supply cap size, 25uF vs 100uF -> I've worked on many an amp where this cap size has been increased significantly and it's not necessarily a good idea. If you have a mains interrupt, both bias and HT will discharge then re charge. This can cause a huge over current condition in the tubes depending on how the two supplies track or otherwise.
Hi Terry. Thank you for that perceptive comment. Yes, that scenario is possible.
The other side of that same coin, is that a larger bias cap may hold a negative bias supply to the grids for longer in the event of a power interruption…and I get a less noisy, more stable bias.
While I haven’t had any issues yet but, I will definitely keep your suggestion in mind and tame the increase in future. Thank you.
I usually put in a 50uf @ 150 volts for the bias supply capacitor in BF SF fenders.
I am on the same diet as you !!! lol!!! 🙂
HAHAHAHA! You don't get to have this body of a Grecian god without good prep work, Daniel. Keep up the chocolate biscuit workout (dark chocolate only please).
Hey friend I'm really looking to get into the profession of amp repair. I'm currently building a Champ and enjoying every bit of it. I would love to know of any books I should buy. Schematics are still very difficult for me to wrap my head around.
I'm coming at amp teching (real word...as of now) from a different doorway Julia. I completed electrical engineering many decades ago. An excellent reference book for you is Electric Guitar Amplifier Handbook Paperback - November 3, 2017 by Jack Darr from Amazon.
@@theguitaramptech Thankyou so much
I wonder if the tag strips were an attempt to stop leaking dc from the board getting past the caps
Good thought. Its possible, KB. Because of the number of connections, it looked like a more convenient mounting point.
I've got me Baja Tele where I've swapped out the scratch plate for a
circa late '60's mint green guard and 'Voila!' mine's pretty near a dead ringer for what
you're plunking there... Small world, wot?
Very cool Jonny. I need to come clean on the pickups, though. When I bought the Tele, the back pickup was dead, so I went to one of the best pickup makers on the planet, @rodneymcqueen1706 of Sliders pickups. It now sounds amazing. The neck pickup is the original from 1968. If you ever need to take your gorgeous Tele to the next level, check out Rod's work. He also did the PAFs in my Les Paul Custom ("Doug") you can see in my JTM45 and Tweed Tone 12A videos.
Yeah , what wld they know . Crack me up .
Hahahaha!
hum dinner video working on a music man for noises and hum at the moment
Can I recommend an Isolation transformer, rubber gloves, while siting on a rubber cushion with rubber soled slippers? That B+ makes me nervous.
@@theguitaramptech just lick it for fun I've worked on amp with 2000 volt EHT supplies
@@moodyga40 HAHAHAHA!
Dark chocolate McVitties Digestive. Mmmmmm
A man after my own heart...or should I say "waistline"!
OK, so you are on a diet..... Meanwhile, I'm 37 minutes into the video and the 3 pop-up ads I've seen have all been for junk food like donuts and corn chips!
What! I don’t know whether to laugh or be annoyed, Good ‘un. I can’t tell how many ads appear. Is it an annoying amount of ads? If so, I’ll see if I can get those reduced.
@@theguitaramptech , I lost track after about the 5th set of pop up ads. It didn't seem to go longer than 7 minutes without an ad popping up. Sometimes it'll let me hit skip ads after 5 seconds, and sometimes not. In addition to corn chips and other junk food I saw an ad for chocolate bars and for iced tea in a bottle. Not having posted any videos myself I can't tell you much about the process but it is my understanding that content creators can select "no pop up ads in the middle" of their videos. However, if you do that, the Google algorithm is less likely to recommend your videos to nonsubscribers. Or so I am told anyway. CZcams and Google exist solely for the purpose of putting ads in front of peoples eyeballs. The less cooperative a content creator is in this regard, the less interested they are in showing your videos to a wider audience.
@@goodun2974 thanks for that information. I need to look into this. I confess to being more interested in making the videos, than investigating the business behind the videos. The truth is, I have made so little from the ads that it’s no loss to discontinue them totally. but after what you said, I don’t want to exclude myself from CZcams putting my videos forward to new people. I really appreciate your input.
the condensers are rubbish they need to go you can still buy Alan Bradley resistors for the droppers
Each to their own, but I would never use carbon comps for dropping resistors, Ian. The old Fender I'm working on now has its 4K7 drifted up to 11K2. They may have a place in audio circuits but not in a power supply.
I'm not sure which condensers (capacitors) you mean. I am not precious about filter and bypass caps, but I will NEVER replace a single coupling capacitor unless I can prove that its leaking. I shriek in horror if I see a beautiful old amp where every cap has been replaced with horrid orange disgraces.
@@theguitaramptech Totally agree.
Thank you, John. When the Marshall Master says "it is so", then I feel secure in my approach.
I have a confession, John. The Grounding on JMP & JCM800s annoys me. I have been known to solder (ala vintage Fender) the mains ground, and first couple of filter stages to the same point directly on the chassis. It reduces the earthing buzz and makes the amp a little quieter overall. Your opinion? (send condemnations to amptech@teammania.com.au, and songs of praise and joy to my Facebook page! 😉)
Dude, that 1 resistor was 12% over and you're gonna leave it anything over 10%?You should replace.Why did you leave the twelve percent over resistor that's just bad.
Thanks for your opinion, Thomas. You are very funny.
I would answer your question with a well-explained answer. However, I do not reply to trolls who think they know more than me. They rarely do. Trolls just try to make themselves look smarter, but just end up making fools of themselves. My advice is to go do 6 years of Electrical Engineering at a leading university and work in the field for decades and answer your own question.
Your learning tip for the day: What are the effects of varying cathode resistors? Why does Marshall often use much higher values, up to 10K? Plot the load lines on a tube chart.
Try to learn without exposing your ignorance, Thomas.
I can't hear a 60htz hum, all I can hear is your lips smacking
HAHAHAHA! Don't make me laugh. Now I have to watch the video the hear the noises I make. Sorry!