School me on BF-SF Vibro Champs

[N0_Camping4U]

Thinking of getting a Vibro Champ as a little portable amp when I jam with some friends. I know BF ones are the most sought after, and the early SF ones are close or almost as good (Right?). But what about the later SF ones? Are there specific eras to stay away from? How has the circuitry changed over time? I've heard videos of BF ones and the trem is to die for, does that diminish over time?

Thanks for any information!

[cestlamort]

I don't believe the circuit ever changed.
The cabinets changed construction at some point in the 70s, though.

Insider tip: the old Bronco Amps are exactly the same as SF Vibro Champs (and often much cheaper).

I loved my 1968 Bronco with a Vanamps Solemate (the extra switch for the trem) and I only let it go to fund a Princeton Reverb.

[N0_Camping4U]

Are there really no differences between the two? Hm, I'll look into those. I'm really into the tremolo on the Champs, and now the Broncos, so looking for a good price and good trem - wasn't sure of the internal changes/trem changes over time.

Thanks for the tip!

[pineder]

I have BF/SF VC amps. Cosmetically the only difference is the faceplate/drip-edge/grill cloth. Internally, I also believe the circuits are the same. Amps sound very similar but the blackface breaksup easier.

IMG_2890

[PixMix]

I have a '74 silverface, same as pineder's. It's a nice home amp with great sparkling clean tone that stays clean all the way up.

[N0_Camping4U]

Tremolo remains the same throughout its line? There's a 79 I'm looking at but wasn't sure if it was drastically inferior other years.

[cestlamort]

Tremolo remains the same throughout its line? There's a 79 I'm looking at but wasn't sure if it was drastically inferior other years.

I think it'll be more-or-less the same throughout. Even though the circuit stayed the same, they used different components, etc. People have also reported the later one stayed cleaner longer, but I don't know if there's a decisive verdict on that.

The later cabs (plywood) are noticeably heavier than the pine ones (just like all fenders). But that shouldn't be a deterrent.

[N0_Camping4U]

When did that transition occur?

[sookwinder]

the components only changed when they changed for all the other amps.
For example the lobby blue smurf tone caps replaced the blobby brick-red caps sometime in the early 70s.... does one hear a difference ... well I can't
The real early ones may have even had the blue molded tone caps... I just can't find a pic to confirm this
The BF VCs had the paper covered electrolytic caps, while the SF usually had the white plastic covered Mallory electrolytic caps
T
he biggest change to the circuit was the size of the power filter caps... the filter caps are in a can (cap can) and should be replaced every 20 or so years as a matter of course.
Very very early circuits show 5/5/5uF but I have never seen a VC actually built with this... maybe out there , but I haven't seen any.
As the cost of electrolytic caps became cheaper Fender changed the circuit so to improve the hum reduction.
So we then get 10/10/10uF, then 20/10/10uF and finally by the early 70s with the Bronco (Bronco = VC) we get 20/20/20uF
No matter what vintage VC or Bronco, when I replace the cap-can I always go 20/20/20uF

Also to improve the sound of the VC look for a vintage (50s, 60s, 70s) Jensen C8R speaker. These are THE best speaker for the VC.
The VC (and bronco) need a 4 ohm speaker ... the most common out there is the 8 ohm version.... this will still work ok and you probably won't really notice that much difference (a little darker sound maybe) .... but if you can find a 4 ohm version ... grab it.
The stock Oxford is still OK but the vintage C8R Jensens are the best.

Modern Jensens are average ... not good not bad.

If you want to gain a little volume, get a RCA plug, shot it and stick it in the RCA female plug for the tremolo... this will ensure voltage isn't lost to ground via the trem circuit.

[HH1978]

Apparently, the circuit stayed the same througout all years of production, but the voltages were increased during the SF, which would be the explanation for the increased headroom.
http://vibrochamp.org/

[HH1978]

Sorry, just realised the previous post answered the question.

[muchxs]

Aside from a few details they're all the same.

Blue caps as seen in larger Fenders amps are rarely seen in 1960s Champs. Fender used the lower cost "dog turds". Same goes for Princetons and Princeton Reverbs.

Champs, Vibro Champs, Princetons and Princeton Reverbs all use the same power transformer within a particular era, typically the 022772 through 1970 and the 010020 1971 and later. A "harder" power supply shouldn't make a difference in a Class A amp but somehow it does.

Supply voltage is generally excessive at over 400 volts.

Some 1968 amps got Better Coil transformers. As the name implies they seem to be a little better than the usual Schumacher transformers.

Later silverface amps got a small snubber capacitor across the 6V6. Otherwise the circuits are almost identical from the 1960s through the 1970s.

Like everything else they got a washer under the pilot light jewel in 1973 or so.

Late 1970s versions get push- on knobs instead of set screws.

Around 1974 Fender starting hosing their circuit boards with paraffin to reduce moisture intrusion.

[jdr1014]

Great info and response - didn't know you were over here too, muchxs. Thanks for sharing your vast knowledge and experience on another forum!

[finboy]

Best mod I did to mine, getting vibrolux legs and having them shortened by 1.5" by a machine shop

[HorseyBoy]

^ That looks great, finboy! Ace idea.