67 Vibro Champ

[dude]

Getting too much hum, original can. Everything is pretty much original, except l ditched the tiny 5 watt OT for an old paper wrapped 8 watt OT. Also, made a new baffle for a 10” speaker that matched the impedance of the OT I swapped. Of course l kept the baffle with original speaker, grill and logo along with the tiny original OT.
The can is the original and most likely the cause of the hum, do I install single caps inside (not making any new holes in chassis or bd) or do I spend the bucks and get a replacement can..?
I guess l’m just a cheap skate..! 
I usually don’t buy vintage expensive cap cans and use singles but it’s a 67 nice condition Vibro Champ, just need a push to do the other right thing.

[dwinstonwood]

I would use a 32uF/32uF can for the 6V6 plate and screen, and a separate, single 16uF for V1 and ground it separately. That still adds up to a total of 80uF like the original 40/20/20 can (I don't know if that really matters).

[thetragichero]

i would get the proper can cap from ce manufacturing. we're talking 40-50 bucks. in good condition these easily go for around a grand. save anything you take out in the event that you decided to sell the amp, because for whatever reason the vintage amp collectors enjoy having the original caps (as a musician i don't care what's in the thing as long as it works reliably, but also as a musician i wouldn't pay hundreds of dollars for a little combo amp so my opinion doesn't particularly matter)

[drew]

I vote single caps inside.

[72Blazer]

I saw an Uncle Doug video where place new caps in an original can.  Might be best of both worlds-cheap and vintage looking.

[dude]

place new caps in an original can.

Now that’s a challenge too, l’m always up for a challenge, good idea. I’ll investigate what fits, might find three 16’s and a 20, l think that’s the cans values… Any suggestions where to find the right values that would fit in a Vibro Champs can…..?

[mresistor]

https://www.tubesandmore.com/products/capacitor-ce-mfg-525v-40202020-f

[66Strat]

https://www.tubesandmore.com/products/capacitor-ce-mfg-525v-40202020-f

About the price of a twelve pack of Fat Tire and a box of Merlot. Why hack butcher a vintage amp when the correct part is available at a reasonable price?

[dwinstonwood]

dude, you had mentioned a hum issue. Separately grounding the power filtering/B+ from the preamp filtering/B+ has helped with a couple of my builds. The 32/32 will fit without modification where the original can is, and is only $11.30 from Hoffman. The 16uF can be secured inside the chassis without drilling holes. Hoffman has that cap for $3.75. That's $15.05 vs $40.90, and it will most likely reduce some of the hum.
You can always save the original cap.

[dude]

https://www.tubesandmore.com/products/capacitor-ce-mfg-525v-40202020-f

About the price of a twelve pack of Fat Tire and a box of Merlot. Why hack butcher a vintage amp when the correct part is available at a reasonable price?

Tax and tags , $50. I like the idea of installing (3) 20uf's inside the vintage can once gutted. Schematic shows three 20uf's, no 40...? Also, this way, I can separate the preamp ground too.

[mresistor]

The 32/32 will fit without modification where the original can is

Actually two holes will need to be drilled in the chassis for the can clamp.  The original cap can is soldered onto the chassis using the mounting tabs. If it's not a museum piece or he's not interested in keeping it stock for future sale, then it's no biggie. All the caps can be mounted inside as well if a person wanted to, I've done that and covered the hole with a round piece of 3M aluminum tape.
The 32uf/32uf is a good idea and it's the rated max capacitance for a 5Y3GT.  It's more filtering for sure. 
With the CE cap can with 4 capacitors you can use one cap to make an extra filter node right off the rectifier and this facilitates dropping some high voltage too and it's helpful since the wall voltage is higher these days.
Many options actually.

[dude]

Good suggestions, thanks. I have no hesitations just disconnecting the can, leaving it in. I mean it still works and installing three 20uf's or even better 32,20,20. Now-a-days, they make very small E caps @ 450v. Might just do that as I have changed the filament wiring, not using the chassis as a ground, anyway. If I decide to sell it to a vintage freak, very easy to return to original. The filament wiring using the chassis ground created hum, it's much better rewiring, Leo was a cheap sake,  . The 10 in speaker did miracles too. I'm not a vintage freak, I'm a guitar player, tone to me comes first. The more I think about it, raping that original can, I can never go back...!
I think, for the sake of tone, I'll add one 32, and two 20's, singles inside, leaving no evidence if I remove them and add the can back.  Thanks again for all the good suggestions,
al
 
   

[66Strat]

https://www.tubesandmore.com/products/capacitor-ce-mfg-525v-40202020-f

About the price of a twelve pack of Fat Tire and a box of Merlot. Why hack butcher a vintage amp when the correct part is available at a reasonable price?

Tax and tags , $50. I like the idea of installing (3) 20uf's inside the vintage can once gutted. Schematic shows three 20uf's, no 40...?

Let's say the expected life of the caps is 15 years. The cheap parts, excluding shipping, cost $15. The OEM part including shipping costs $50. Amortized over 15 years, the difference in cost $35 (50 - 15) is $2.34 per year ($35 / 15). To me, that is an insignificant expense to replace a failed part with an OEM replacement. It could make a significant difference in sales price, if you ever need or want to sell the amp. Excluding shipping, the cost is comparable to the previously mentioned cost of beer and wine. The beer and wine is literally pissed away in a matter of weeks. It's your amp. Do as you please.

[dwinstonwood]

Actually two holes will need to be drilled in the chassis for the can clamp.  The original cap can is soldered onto the chassis using the mounting tabs.

Oops! You're right! My bad.

[HotBluePlates]

Getting too much hum, original can. ... do I install single caps inside (not making any new holes in chassis or bd) or do I spend the bucks and get a replacement can..? ...

Do either, but do yourself a favor and use 4 caps (or a 4-section can).  Add a 470Ω 5-10w resistor between caps #1 and 2 after the rectifier, and attach the output transformer feed to cap #2.  See below:

[dude]

l assume the forth mode would help eliminate any left over him the three caps wouldn’t..

Do either, but do yourself a favor and use 4 caps (or a 4-section can).  Add a 470Ω 5-10w resistor between caps #1 and 2 after the rectifier, and attach the output transformer feed to cap #2.  See below:
I

l assume the fourth cap would eliminate any left over hum the three wouldn’t…

[PRR]

Stock, the first node has high buzz. Which gets into the 6V6 plate circuit.

The mod adds a new node in front of "the first node" so now the 6V6 eats "second node" with two filters and far less buzz.

(Yes, this also cleans the preamp/driver nodes but they were not a big deal.)

When a Champ was a practice amp it was not worth the extra buck for filtering. Heck, if they don't like it, sell 'em a DeLuxe!

Now that a Champ is a studio (or bedroom) tool, and appreciated for being different from DeLuxe, it is time to fix that cheap-out.

[dude]

The cap can at AE supply is, 30uf ,20uf x3, the tolerance is -10%,+50…? Does that mean values could be 10% less up to 50% more, if so wow.
The 30uf could be as highly as 60uf, not good for a 5y3, the 20uf could be 40uf..? Much more than Fenders 20% tolerance…? They have a 40uf, 3x 20uf but 40uf is getting kind of high for 5y3 especially if the 40 could be 80uf.
Forgive my ignorance but hopefully l’m not correct..?

[66Strat]

Look at what HBP and PRR posted regarding the 4 section 20uF cap can. The first 20 uF cap connects directly to the rectifier. There is a 470 ohm resistor between the first cap and the second cap. The 6V6 plate connects to the second cap. The screen grid connects to the third cap and the preamp to the fourth cap. In this configuration the rectifier only "sees" 20uF. If the cap were out of spec +50% that would only be 30uF which is within spec for the rectifier. The resistance within the power transformer secondary winding and the output transformer primary winding provides cushion to slow down the current surge when the amp is first turned on.

[thetragichero]

+ 50% is 150% of the nominal value not 200%. i'm sure those specs are taken from the original part, although quite likely a lot closer to nominal value than what's currently in there

[dude]

So, the new cap can route would be 20uf x 4, not 30uf and 20uf x 3?
Some suggestions here mentioned first value 30uf

[66Strat]

So, the new cap can route would be 20uf x 4, not 30uf and 20uf x 3?
Some suggestions here mentioned first value 30uf

Either way will work. The 6G2 Princeton had three 30uf caps in a can. The 30-20-20-20 option would offer better filtration. Hook it up with a 20uF cap first in line to see the rectifier then resistor between the 20uF and the 30uF cap and connect the 30uF to the 6V6 plates.

[PRR]

...the tolerance is -10%,+50…? Does that mean values could be 10% less up to 50% more....?

Those are very traditional tolerances on electrolytic caps. Low-volt caps in 1966 could be +150%: "10uFd" could really be 25uFd.

If you buy beer by the 6-pack, and get 12 or 15 beers, do you complain? Maybe, but mostly no.

1966 catalogs:
https://www.technicalaudio.com/pdf/Electronics_Catalog_Extracts/Mallory_capacitors_1966_REM_E30.pdf.pdf
https://www.technicalaudio.com/pdf/Electronics_Catalog_Extracts/Sprague_capacitors_1966_REM_E30.pdf
Many old brown pages:
https://www.technicalaudio.com/pdf/Electronics_Catalog_Extracts/

All old-school designers knew this and allowed for it. You protect rectifiers NOT by aping the suggested cap value, but by having enough series resistance (typically HV transformer DCR) to limit the peak currents.

[HotBluePlates]

l assume the fourth cap would eliminate any left over hum the three wouldn’t…

... When a Champ was a practice amp it was not worth the extra buck for filtering. Heck, if they don't like it, sell 'em a DeLuxe!

Now that a Champ is a studio (or bedroom) tool, and appreciated for being different from DeLuxe, it is time to fix that cheap-out.

First, all of what PRR said, plus:  push-pull cancels hum in the power supply, but the Champ ain't push-pull and doesn't get the benefit of cancellation.

Second, everyone inexplicably copies the late-model Champs but few seem to look at the earlier versions:
5E1 Champ:  Cap --> Choke --> Cap --> Output Transformer
5C1 Champ:  Cap --> 500Ω --> Cap --> Output Transformer
5F2 Princeton:  Cap --> Choke --> Cap --> Output Transformer
5E2 Princeton:  Cap --> Choke --> Cap --> Output Transformer
5D2 Princeton:  Cap --> 470Ω --> Cap --> Output Transformer

Literally every Champ & Princeton prior to the final tweed version (and then the Champ/Vibro Champ that followed in the blackface/silverface era) had the extra stage of filtering I'm proposing.  I don't know why Fender chose to de-volve their power supply in the 5F1 Champ and 5F2-A Princeton, but that's what happened.

Until recently, I had a 1965 Vibro Champ with an original cap can and it didn't hum when I played it.  But plenty of folks have originals or home-brews that do hum, and in roughly 100% of cases adding the extra filter stage before the output transformer feed eliminates the hum.

[PRR]

> I don't know why Fender chose to de-volve their power supply in the 5F1 Champ and 5F2-A Princeton

NFB is a heap cheaper than filtering.

It doesn't help the buzz modulation in clipping, but should you play that loud? (And if you do, and do it a lot, you will learn to like it.)

[HotBluePlates]

...  I don't know why Fender chose to de-volve their power supply in the 5F1 Champ and 5F2-A Princeton ...

NFB is a heap cheaper than filtering.

This seems like it could be correct.  But look at what Fender did:

The 5E1 Champ has the same negative feedback (22kΩ, 1.5kΩ divider) as the 5F1 Champ but the latter rearranges the power supply and uses a 16µF 1st filter instead of the 5E1's 8µF.  Still 3 filter caps overall.  Could Fender really have saved money on a new 16µF instead of the 8?  Leo saved the cost of the choke, but why not use the known-good power supply?

The 5F2 Princeton also has the good power supply plus the 22kΩ, 1.5kΩ feedback loop.  The 5F2-A Princeton has the same feedback loop, but switches to the worse power supply while bumping the 1st filter up to 32µF!  A to top it off, they're using two of the 16µF caps where they could have gotten great performance with one 8µF cap.

The usual profit-motive argument doesn't seem to make sense here.  Maybe we'll never know, unless Leo pops up at the next seance.

[66Strat]

...  I don't know why Fender chose to de-volve their power supply in the 5F1 Champ and 5F2-A Princeton ...

NFB is a heap cheaper than filtering.

This seems like it could be correct.  But look at what Fender did:

The 5E1 Champ has the same negative feedback (22kΩ, 1.5kΩ divider) as the 5F1 Champ but the latter rearranges the power supply and uses a 16µF 1st filter instead of the 5E1's 8µF.  Still 3 filter caps overall.  Could Fender really have saved money on a new 16µF instead of the 8?  Leo saved the cost of the choke, but why not use the known-good power supply?

The 5F2 Princeton also has the good power supply plus the 22kΩ, 1.5kΩ feedback loop.  The 5F2-A Princeton has the same feedback loop, but switches to the worse power supply while bumping the 1st filter up to 32µF!  A to top it off, they're using two of the 16µF caps where they could have gotten great performance with one 8µF cap.

The usual profit-motive argument doesn't seem to make sense here.  Maybe we'll never know, unless Leo pops up at the next seance.

It would be hard to say whether or not it made economic sense without looking at the capacitor supply chain for the entire amp product line. For example it may have been cheaper to buy 16uF caps in the quantity to satisfy Champ, Princeton, Harvard, and Deluxe production than to buy 8uF caps for solely for Champ production. The carrying cost to maintain a separate inventory of 8uF caps would also be eliminated.

[HotBluePlates]

... it may have been cheaper to buy 16uF caps ... than to buy 8uF caps for solely for Champ production. ...

This also seems reasonable.  But there are also 8µF caps in the Champ & Princeton, so still a need to keep buying them.

And keep in mind that while Fender introduced the 5F1 Champ and 5F2-A Princeton in the late 50s, they continued to be produced during the brown face years of the early-60s.

• The Champ was produced in tweed right up until the blackface amps appeared in late 1963, and made its own appearance in the tweed 5F1 format but black tolex covering. This 5F1 Champ has an August 1964 date stamp on the tube chart.
• Fender didn't pull the same stunt with the 5F2-A Princeton, as the Princeton was made over into push-pull with the 6G2 brownface model.  However, Fender took the "Harvard" name which had been a push-pull amp in the 50s, and slapped it on the tweed Princeton chassis/cab to create the 6G10 Harvard.  As with the Champ, this kept being produced in tweed in the early 60s, apparently until the stock of 5F2-A/6G10 chassis were all used up.

[66Strat]

... it may have been cheaper to buy 16uF caps ... than to buy 8uF caps for solely for Champ production. ...

This also seems reasonable.  But there are also 8µF caps in the Champ & Princeton, so still a need to keep buying them.

And keep in mind that while Fender introduced the 5F1 Champ and 5F2-A Princeton in the late 50s, they continued to be produced during the brown face years of the early-60s.

• The Champ was produced in tweed right up until the blackface amps appeared in late 1963, and made its own appearance in the tweed 5F1 format but black tolex covering. This 5F1 Champ has an August 1964 date stamp on the tube chart.
• Fender didn't pull the same stunt with the 5F2-A Princeton, as the Princeton was made over into push-pull with the 6G2 brownface model.  However, Fender took the "Harvard" name which had been a push-pull amp in the 50s, and slapped it on the tweed Princeton chassis/cab to create the 6G10 Harvard.  As with the Champ, this kept being produced in tweed in the early 60s, apparently until the stock of 5F2-A/6G10 chassis were all used up.

True. But I bet that Leo analyzed his production needs to come up with economic order quantities for his capacitor inventories. Part of this may have involved ordering more 16uF caps to hit a quantity discount. As you said, we will likely never know without contacting Leo on the other side. Halloween's coming up............

[PRR]

> contacting Leo on the other side.

Spiricom.  (NOT the Hammer of Witches group.)

[dude]

Getting too much hum, original can. ... do I install single caps inside (not making any new holes in chassis or bd) or do I spend the bucks and get a replacement can..? ...

Do either, but do yourself a favor and use 4 caps (or a 4-section can).

Used four caps, added HBP fourth on OT (separate cap). Way less hum, ditch the ground on the filament wiring and did the traditional BF Fender way. I disconnected the original cap can but left it in, stacked the four caps on standbys on transformer bolts and one of the can bolts or leg, can't remember. Does the job. Added a screen grid 750 ohm R, used 750 so I could use a 6L6GC. Eventually if I decide to sell it to a vintage collector, amp can easily be put back to vintage, CC and and all if they pay...    
Thanks HBP

[jordan86]

I mean no disrespect but I wouldn’t worry too much about originality with that one. Looks like nearly every component has already been replaced.

[dude]

I mean no disrespect but I wouldn’t worry too much about originality with that one. Looks like nearly every component has already been replaced.

You’re right, drifted components, leaking cabs, new filters, this amp has been serviced by many before l got it. Looks messy, not all my work but l’ll admit l didn’t strive for looks.


Not to change this topic l started but now l have the famous tremolo ticking, (no roach). I’ll change the tube, try the tremolo cap next then lead dress, l did move some wires around. I’ll pay attention to trem pot wires away from any HT, other than that, any other suggestions for a bias tremolo?

[jordan86]

I think the three trem caps are a good place to start. I’d gator clip in a .01 in parallel with each one, one at a time, to see if that stops it. When it does, I replace the bad one with a .02

[HotBluePlates]

... now l have the famous tremolo ticking, (no roach). ...

It is not "ticking" precisely because there is no roach.

You might hear a pulsing background noise, but that is pretty normal for a Vibro Champ, which pumps a preamp tube stage to inject trem.  That's why Leo Fender created the circuit found in the mid-50s Tremolux, and patented in US2973681A.

Unless the pulsing noise is extreme, it's probably best to ignore it.

[dude]

Pulsating is not extreme, very low level ticking or pulsating is a better description. I  changed the trem tube, no go, checked  tremolo caps, no go. But changing power tube to a 6L6 reduced it, doesn’t affect tone when playing. Could have been there before l added 4th filter.  The replacement OT l used has a ratio of 34:1, using a 4 ohm load for 4k2 impedance and a 6L6 the pulsating is way less then using an 8 ohm load with 6V6.

I noticed with trem off, turning the intensity pot on 1  increased volume. As HBP mentioned above the trem is affected by the preamp, l assume this is normal for a Vibro champ.