Vibro Champ AA764 caps

[bonneybear]

Hi, Im inside my VC. So I'de like to recap it . I have a schematic. I dont know much though. The Big brown paper wrapped electrolitic caps of 25 v
they should be replaced, right ? What about the big can type that hangs down by the tubes ? whats that called ? I think I will also put a 10" speaker in it. Should it be 4 Ohm ? Thanks for you patients and help, Mike

[stokes]

When doing a cap job ALL electrolytics should be changed.The big can type thing are your filter caps,the main point of your re-cap.If you are not familiar with working inside an amp I would suggest leaving it to someone who can,there are dangerous voltages inside an amp even when it is turned off and unplugged.Be careful.If you use a 10" speaker it should be the same ohms as the original spkr.

[Bob M.]

Have you tried?

Weber VST makes a sensational Champ/Vibro Champ/ Bronco stock (8" ceramic) speaker that sounds great and is not too expensive - In case you'd care to keep the amp stock. Their AlNiCo is also very good but is more $$. I use the ceramic in my own VC and I'm very happy with it.

Bob M.

[bob p]

just to give a different opinion, i have a Weber Ceramic Signature series 8-inch speaker in my SFVC and "sensational" isn't a word that comes to mind. I think its harsh and raspy. Several years of play haven't smoothed out its tone. Its the one Weber speaker that I really don't like. I have absolutely no idea why it gets the positive reviews that it does, unless people are just grading it on a curve because its a cheap speaker that goes into a low end amp. If you use your VC as one of your main amps, I would recommend spending the extra money on a higher quality speaker. If its just something that isn't used in a "mission critical" role, then the speaker may not be that important to you. YMMV, of course.

[oahu]

fender silverface champ re-cap

hi. i got a late 70's champ today. and it's nice, but needs new tubes, and caps. so I have the same problem. the tubes and 25/25 caps are not the problem, but where can i get the large one? in my case it is a mallory brand silver can 20/20/20/20. can i use the 40/20/20/20 from JJ in this position? i'm living in europe. does anyone know, where to get the right one from? the other question i have is, does a 10 inch speaker really fit in the box?

[stokes]

Oahu,the 40/20/20/20 from JJ will work.It will give you a slightly tighter bass response with the 40uf in the main supply,not a bad thing in my experience.If you want to keep the values stock,you could get a seperate 20uf cap along with the JJ can and dont use the 40uf section and squeeze the extra 20uf inside the chassis somewhere.To use a 10" speaker you will need to get a different baffle board to fit the 10".

[oahu]

many thanks there is one other thing i like to ask: the rectifier is modified to two diodes (on the tube socket, no tube in it, of course). what do you think? should i rebuild it to tube-rectifier?
well, i guess i'll stay with the 8 inch speaker. the baffle-board can't be changed that easy, because it's part of the box. anyway, i will change the speaker connector to a phone-plug and then i can use an external speaker, if i need it...

[stokes]

Whether to change the solid state rectifier back to a tube is up to your tastes,if you opt to keep the solid state rectifier you will probably prefer the extra tightness the 40uf will give you in the filter supply,so the JJ can cap would be good as is.

[oahu]

champ amp caps

many thanks.

i ordered the jj cap-can, an extra 20 µf cap and a new set of tubes including the rectifier-tube + a new jensen ceramic-speaker today.

i'll just try, what works best for me... it's a really simple amp, but there are so many possibilities on it, to change the sound. we'll hear, what it sounds like i'm posting again, when i'm finished... (well this can last a little time i guess)
greetings from vienna.

[Amp Kat]

Certainly always good to change can caps but I just did a bf and sf Vchamp and both can caps were still good so I left them in. Not a tad of hum and they sound great. The main cap to change is the Cathode bias cap and a Sprague 25/50 volter works very well. All the other bypass caps should be changed also and one is a 10uf if I'm not mistaken. I'd change the power cord to a 3 pronged plug and put the tube rectifier back in it. A good NOS 6V6 will give you more life than a current production and those tubes get smoking hot but after all what do you expect with it's topology.

[oahu]

champ amp re-cap (re-build)

first thing I found out, when I wanted to change the speaker, that some stupid guy changed the original speaker to one which was not an 8 inch speaker, but it wasn't an 10 eighter. something in between. so I had to put in a new baffle-board.

next thing was, that I had to make the hole for the jj-filter-cap a little bit bigger.

then I decided to put out the diodes and a new rectifier-tube in, to make the amp sound, like it used to, when it was build, well...

because of some little hum-problems when I finally had changed the caps I rewired the 6.3v heaters and grounded them thru 100 ohm resistors, near the power transformer. this was working pretty fine.

at last the amp sounds nice, but after trying out some different preamp-tubes I still think it could sound better. any ideas which ones to use?