How to repair enhance gain performance Fender Silver Face Vibro Champ tub guitar amp easy mod
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- Опубликовано: 10 янв 2025
- Another great Fender amp comes across the bench at D-lab Electronics. This one is in perfect condition, no mods. Has been in a closet for over 40 years. The owner made the choice to send it to me for evaluation. Needed the typical cap job. Made a minor gain adjustment, and bam! Fender Chime was reborn! What a great sounding Class A amp. I really love the engineering that Fender did back in the day. What a great time in life! Wish I was there.
I was there! My first amp was borrowed from a wealthy friend, a 1964ish Fender Pro Reverb.. dual 12". After moving, and having to return the Pro to its owner and his vast collection of Fender amps, I found my own Fender, last run of Blackface, Vibrolux Reverb. We knew these were good amps back in the day, but had no clue that they would become legendary. The Blackfaces and early Silverfaces remain among the best amp line ever made in mass production. Nice to see you fixing this gem up. The gain mod is a great tip. 100K is a little low for a 12AX7A. YES much better to use above 200K plate R on 12AX7A to get more gain.
Yes, I agree, This is a great amp, just needed a jump start
YES! "Born On the Bayou" with the Tony touch! Sounds much "bigger" than a Fender Champ now.
After finally getting around to it, I did the modifications that you described, changing the Grid resistor to 560 K, and the plate Resistors to 220 K.
The difference is absolutely incredible. It's a completely different amp. It has more punch, more power, and a Stratocaster through it makes it sing.
I consider this to be a genius move on your part. So much so that I made the same changes to my 5F1 Tweed Champ (from a kit). I thought it would have the same effect. It did. I'm planning on doing this to every Champ I can get my hands on. The VibroChamp that I initially did this to now has a happy new home with a harp player in Vegas. He thinks it's a miracle. I didn't have the heart to tell him it's only three resistors.
Keep up the good work, my man.😅
Are these mods same on regular silver champ? (no vibrato)
Completed all the mods on my '79 VC today, and I can attest that this video is 100% as advertised! Wow! Couldn't be happier with the new-found chime! And if you've never played through one before, it also has the best tremolo circuit Fender ever designed. Telecaster master, Jim Campilongo, will attest to that. Thank you much, Terry!
The tips on the change in plate resistors is just what the novice needs to here, anyone with a soldering iron can make that change. Thanks
Yes Sir, Thanks
It would help some if u explained why it added the gain, thanks i enjoy your videos
Wow, you've made that amp come to life Terry.... well done... It's easy to tell when an amp is singing nicely just by looking at Tony's face... awesome brother.
A re-born Fender amp..christened with CCR...nothing can stop it now.
Terry, if Tony had come to my house playing guitar and wearing that Knights of Columbus shirt in the 60’s my dad may been more accepting of my guitar playing. The only guitars that were supported at our house were at the Saturday 4:30 Guitar Mass that my old man said the “cool kids” went to. I used to take the dollar that my dad gave me for the collection basket and go to the music store instead.
Terry, You have obviously done your magic on the tremolo, Great sound!!
Another great job by Terry , Marsha the bartender and guitar by Tony........I"m really surprised that you don't have 100K+ subscribers. . .great tutorials !
The best sounding Champ I ever heard
Looks like you got a vacuum tube bobbing in that wine glass you got there, OM!
Excited now to do these mods and upgrades on my '79 VC, which has always underwhelmed me with its blah tone. Thanks so much for posting!
In my 1979 all original Vibro Champ, the bias resistor has drifted to 531ohms, and the plate dissipation of the original 6V6 (with the original 5Y3 Rectifier) is 16.7 Watts, or 139% of "maximum". I will be replacing the resistor with a 1K ohm or perhaps even a 1.2k ohm. You stated that the stock capacitor in the bias circuit is 25uF at 50Volts. Mine has a 25/25 cap. I do have a 25/50 on hand, but I may pick up a 100/100 as you suggested when I buy the bias resistor(s).
I have the exact same amp. I will have to give these mods a try!
Red wine with tubes! - Your wife is worth gold!
By the way ... a nice and informative video. Keep on the good work! 👍
You really do a nice job with the mods and the presentation.
Great video! Thanks for sharing some more tips and tricks. I’ll probably watch this again with the schematic to better learn the “why” behind the modifications made. Really cool stuff
I see Tony re-strung your guitar! Nice repair. Sounds great!
Yep, I hacked it. We work together, His ear, my techie stuff
Excellent as usual Terry. My vibro champ has been running the 6v6 hot. You've just told me why. Great info. You are quite the tube guru.
Nice fix Terry..Great sound, from Tony's picking..love it..Ed..UK 😁
Very cool mod! Thank you!
All the wishes for the 100k subs Terry, you deserve it! How about something on a small tube bass amp design?
Cant wait to use this on my champ. Well done
Great stuff! Thanks for sharing your info on raising the gain to preferred levels! I mention your channel every time I get a chance. Good luck on 100k !
ótimo vídeo congratulações
Jorge Sul do Brasil
Great sounding mods Terry, thank you for sharing.
sounds awesome Terry.
Hey Terry, I have been playing the modified Vibro Champ daily for two weeks now and it sounds amazing. Great job on the mods and excellent video! Kevin J
Got you a bad ass little fender amp there Kevin. Congrats. Nothing like playing an amp that's been modified to your liking.🤟🤟👍🍻
Excellent. I'm betting a blurs harp player would LOVE that amp
You're an Ghoulardi (Ernie Anderson) fan? Cool! He was also the announcer famous for "...this week, on The Luuuuuuuv Boat."
Next time a Champ or Vibro Champ 6V6 is running over-hot, try increasing the value of the dropping resistor in the power supply that runs to the screen filter node (here, 1kΩ). That will lower screen voltage, which will lower plate current. But better, retaining the lower-resistance cathode resistor retain sensitivity at the 6V6, because bigger bias voltage = bigger signal required to distort the 6V6.
The AMP sounds great! Is there not a hot, rocking, young player to really fire up these amps? Love Tony but once in a while a musician would really be a welcome addition.
“I can’t say no”…..(best line on RUclips!)
Fenders are SO nice to replace components compared to a chassis from something like a Hammond organ. Those things are incredibly well built but will take weeks off your life working on them.
That's one happening amp Terry!
I need to do this to my Vibro Champ.
subbed!
there is nothing wrong with silverface models up to about 74 and even then it is the big box models that have some issues (most of which are fairly easily modded away, and that is if you think there is an "issue" in the first place. I actually prefer 68's as i like the aesthetics of the drip edge and they are the exact same circuits - in fact most of the AB circuits are improvements over the AA ones
Happy Twenty Twenty TUBE!
Any of you guys try swapping the two power dropping resistors with each other? Seems like a fairly common mod to keep the grid mellowed out with such a hit bias. Curious if anyone has any strong opinions on that.
Great job as always ... If only I could sub more times ... :) I'm sure you will succeed in your goal for 100k.
Love the power tube in your glass of fine wine, lol.
Damn I wish I was testing these . I wanna hear a strat and srv through that one
Your wife has got to be just as crazy as you are. Cheers! AF 427X5.
I have a late seventies early eighties 100 W Ampeg tube combo amp that recently stopped working would like to find a way to get it to you
Tony is awesome!
Saved into the file, your videos are always good. Keep up the corny, that "beckoning forth for the wine" could turn into yer signature intro real funny, real fast. Gong show with hot solder and trippy oscilloscopes
Jeez, and snozzeramus, this ones got it all!
Yes my friend, a lot of stale Dad jokes
So in a Fender Deluxe Reverb that has two 6V6 tubes and two 220k grid resistors. Does a single 6V6 sees a 220k or a 440k grid resistor ? Cause that would make a lot of sense bumping up that grid resistor.
What a difference. I plan to mod mine accordingly! One more thing. Is that a Cabernet or Bordeaux? Could be Merlot though. Whichever, they all are good.
Mod done - fabulous! Sounds much much fuller.
I modified my Champ to have only the first audio jack input be used. I swapped the 68K resistor with a 33K. With all the mods you did in this video, is there any that you did which would negatively interfere with my current mod? Would it be fine or would there be too much gain?
Would like to have heard some bass tone on this amp…
Interesting, and sounds great. but I'm a little confused . the tubes tested with "excessive gain" , but were actually 12AT7 instead of 12AX7. the gain factors for each tube are (approximately):
12AX7 = 100
12AT7 = 60
So how would the 12AT 's be more excessive?
Then you made your upgrade for even more gain - but we never heard the amp with just the correct 12AX7s for comparison
Can we put a potentiometer to set cathode bias?
Hey man, have you heard of a rare vintage sano 300s tube amp?
Wow, the gain is to much for the Celestion 8-15 (15 watt). External 12" speakers do work well.so I know the weak link is the speaker. I want to keep the speaker in it. Should I back off on the 560k resistor to 440 or 320k to tune it better to the 15 watt speaker? Would the 220k resistors be a better source to back off on? Around 6 on the volume pot starts to get bad distortion as is. Thanks in advance.
What are your thoughts on adding a switch to lift the tone stack out of the circuit, rather than changing those resistor values? Was your intention here to do this without modifying the chassis at all, or do you think there’s a tonal benefit? On my silverface champ (non-vibro), I did the tone stack lifting switch, and also added a negative feedback (removal) switch. Between the 2 mods, I found that I can get the silverface to behave very close to the Tweed Champ.
Hi Bob, yes good idea. In this case, it was a customer unit, so I have to do as requested. TD
You don't even have to drill a new hole, just change one of the pots for a push-pull one and use it's switch.
I actually have an unfinished project (1x 12AX7 + 2x PCL82) that used one to change the bass and mid caps in the tone stack to change it from fender-ish to vox-ish with such a potentiometer.
Hello! Your videos are awesome! I learned a lot about my VC thanks to you! I have a little question about the mod. My VC is already running a little hot on the preamp tube plate (around 240V). Could in my case this 220k plate resistors damage the tube or the tone stack caps? Thanks!!
The original owner who bought it in 1980 and has been sitting ever since but yet has had work done on it? Maybe somebody lied to the original owner.
Hey D-lab. From experience I can say drinking wine and poking about HT B+ supplies is not a good mix
Sounds good, but just so long as there isn't any mercury leaking from that tube in your glass. ;)
HI, I have my dads dynaco 70 built in 1966 and i want to get it working, If i cant can i send it to you.
Thanks
Thanks Terry D. For the tips on the champ amp
I have a 66 black face
Champ that I added a
Tremolo cirquit to.
I will be doing those
Resistor adjustments
I do have the 1k on the
6V6 cathode.
I'm putting in a new
Can cap with 40 20 20
I know it might be alittle
Hard on the 5Y3 but it
Helps with hum.
I'm puting 2watt res.
In the 1st and 2nd
B+ nodes making it
An AB instead of
an aa764 cirquit. See you more on Utube.
Dwight.
Great channel. Maybe the best one.
Is that a 12ax7 floating in your wine at the end?!
Question : Would swapping out the 100k resistors for 200k work on a 5f1 build? And does anything else need to be adjusted in order to “bump up” the capacitance of the cathode cap(s) like you do on these? (Other than adding the new value caps)
I see you never got a reply, bummer, I'd like to know if the 5f1 and 5f2a would benefit too.
Once you install a 3wire power cord in the fender amp can you put a death cap from the hot lead in series with a 1meg ohm resistor to chassis ground?
Would that help with
Noise filtration
With out causing a shock hazard?
No. Clip out the death cap and do not reinstall it.
560k is hard to find. what about half meg. If I have to, I can get them from Mouser.
.5 meg is fine. 560K is also very common
Hey Terry, what happened to Mojo ?
Are You Still With MojoTone?
👍👏😊😉
cool
and less amplification?
Doesn't increasing the plate load resistor result in a decrease in plate voltage?
The voltage developed across the plate load resistor is the signal voltage. If the was no resistance the plate would be at the supply voltage but there will be no signal…because E=IR. This is a “voltage” amplifier. The music signal is not actually traveling through the tube…a change in current in the tube causes a change in voltage across the plate resistor.
your wine is tubealishis
R.I.P A.S.D. headphone users at 4:16
Edit: Why have you got a 12AX7 in your wine glass, sir? I feel I might be missing out on something here..
Tony!!!
How many watts does this put out?
5-6 watts
Your Good
to get 100k you may need some youtube guitar stars on there maybe pete thorn?
That’s the funniest thing I ever seen !!!!
Keep the booze away from Tony before you let him try to play on the videos. Lol