Suggested Maintenance for Silver Face Vibro Champ

[fiveanddime]

Hi,

I just acquired a '73 Vibro Champ. It's my first vintage amp, and I'm really excited. I know almost nothing about these sorts of amps and electronics. It's a little scratchy when turning the knobs (I think the pots need cleaning?), but otherwise, sounds good!

The tubes are a vintage Sylvania 6v6gt, and the rest are vintage RCA. It has the stock Oxford speaker.

I'd like to have it looked at by a tech and have work done prioritizing reliability. I'm not interested in mods designed to change the sound, apart from possibly a speaker replacement.

Any suggestions for what type of work I should expect to have recommended by the tech?

Thanks!

 

[schmee]

That big silver cap can "filter caps" should be replaced.
The Blue "Death cap" you can see on the fuse holder should be removed. (save the cap)
There are 3 white caps on the circuit board, they could be renewed, and usually would be, but often will continue fine.

 

[Boreas]

^^^^^
This.

I still have the original tubes in my '69 Drip Edge. I tried replacing them when I did the caps, but ended up preferring the originals. I did install a new speaker that got rid of some of the flubbiness, but it wasn't a huge improvement at the volume levels I use. Just make sure if you replace the speaker, you save the original.

 

[Powdog]

There is a small “snubber” capacitor across pins 5 and 8 of the power tube. It is meant to control oscillations but ends up affecting tone. Have your tech lift one end (or remove it completely) and see if it oscillates. I’ve removed that cap on every Champ I’ve owned and it never oscillated. Bonus: the amp will have more sparkle.

 

[fiveanddime]

This is all super helpful! I'm happy to learn that not a ton is necessary at this point.

I'll follow up with what is recommended and what gets done.

 

[slider313]

Yes, replace the mulit-section cap can and the white electrolytics on the board. While you're at it, have the tech replace the small RCA speaker jack with a 1/4" Switchcraft shorting jack. There's no drilling needed as it will fit in the existing hole. This not only provides a safety mechanism for your output transformer, should the speaker become unplugged, it also allows you to run the amp to, say, a 2 x 10 - 4 ohm cabinet.

 

[fiveanddime]

slider313, great suggestion. Indeed, for now, I'm going for safety, practicality, and minimally invasive.

 

[SnidelyWhiplash]

Don't mod it too much, if at all. Service & enjoy. A SFVC is a great amp in its stock form.

 

[King Fan]

Nice amp, good find. As the guys said; new cap can, remove death cap, replace white electrolytics, and upgrade to ¼" speaker jack. I also really like the extra tips from @Powdog and @slider313.

Your tech might also want to clean and check spring function on the input jacks plus clean your crackly pots and if still noisy check their coupling caps for DC leak. Finally, it's wise to check resistors for excessive drift or heat damage, especially the big dropping resistors, the bias resistor, and those little guys over the barbecue grills, I mean speaker sockets.

 

[InstantCoffeeBlue]

slider313, great suggestion. Indeed, for now, I'm going for safety, practicality, and minimally invasive.

Good call. Get it serviced, see how it sounds with the stock speaker for sure, but on this amp a speaker swap will give you way more bang for your buck than any mods to the circuit. The speakers that came stock in these were pretty wimpy, and something like a WGS G8C or the Jupiter 8SC will really wake it up and make the amp much more 3D.

 

[ps_electrik]

If you have excessive hum you could consider redoing the heater wiring using dual twisted leads.

 

[fiveanddime]

Ok, thanks everyone!

The amp has been serviced, and no big surprises I think. The tech thinks it likely this was the first time it's been serviced. Here's what was done:

1. Cap can replaced
2. White electrolytics replaced
3. Death cap removed
4. Resistors (and maybe other components?) checked and were within tolerance
5. Tubes inspected. 6v6gt was microphonic, so it was replaced with a new electro-harmonix 6v6gt
6. Pots cleaned

I wasn't able to play it loud last night, but it sounds great so far.

In a few weeks, after I've really gotten used to the sound, I'm going to replace the stock speaker, cable, and jack (and will hold on to all). I feel comfortable doing that myself after finding a couple good resources here and here. I found a used WGS G8C for the replacement, which I thought was lucky as they're out of stock new.

Again, thanks for all the info. I'm worried that my interest in amps has taken an expensive turn...

 

[muscmp]

Ok, thanks everyone!

The amp has been serviced, and no big surprises I think. The tech thinks it likely this was the first time it's been serviced. Here's what was done:

1. Cap can replaced
2. White electrolytics replaced
3. Death cap removed
4. Resistors (and maybe other components?) checked and were within tolerance
5. Tubes inspected. 6v6gt was microphonic, so it was replaced with a new electro-harmonix 6v6gt
6. Pots cleaned

I wasn't able to play it loud last night, but it sounds great so far.

In a few weeks, after I've really gotten used to the sound, I'm going to replace the stock speaker, cable, and jack (and will hold on to all). I feel comfortable doing that myself after finding a couple good resources here and here. I found a used WGS G8C for the replacement, which I thought was lucky as they're out of stock new.

Again, thanks for all the info. I'm worried that my interest in amps has taken an expensive turn...

glad you got it done. i have a 75 vibro champ that is great. i've run it thru different speakers but still like the original. rather subjective. also, make sure you get all of the parts back from the tech including the 6v6 as it MAY be fine in another amp.
play music!