Restoring Modified Vibro-Champ...

[jdarkis]

Hi there folks!

I picked up a great little SilverFace Vibro-Champ today and I need some help from my fellow TDPRI'ers. It appears to have been given a tweed champ mod when it was in for service. The amp has new caps/orange drops but has been modded to use only the volume control...the rest of the pots are disabled, there is no push-pull to enable/disable the mod. What I am wondering is, how much of the circuit appears to have been changed and how much is it going to cost appx. to get this fixed (as I am not so inclined).

http://nerdblog.quickfry.com/vchamp
Large Image Warning ^

The amp also has a new eminence speaker (which sounds like a million bucks!), but it is of 8 ohm impedance when the regular circuit calls for 3.2. Is this safe to operate? Also, the 5Y3 rectifier has been swapped out for a 5U4 Coke Bottle tube. Is this O.K. to run?

I'm rather surprised by the mod, I expected the amp to distort relatively early but it's actually clean well above 7 on the dial and it sounds very warm and has a tight bottom.

Just want to make sure everything is in order before I take it somewhere to have it looked at! Thanks in advance!

Best,
Jason.

[zook]

Jason,

That amp is completely changed. The circuit board looks like it may only have one original part on it.

You'll need to completely rebuild it to get it back to what it was.

Also the original PT probably can't handle the 3 amps the 5U4 requires.

Winnie

[jjmantele]

8ohm speaker should not be used with a VC. At least with a stock OPT. Another poster just told us how he blew his OP tranny from an 8ohmer in a Champ (or VC.) The cap can is no longer in use and caps were added to the board instead. The vibro tube is no longer connected. To me that is the most unfortunate part of it current configuration. The death cap is still there.

I keep the bass and treble maxed on my ’74 and also have an added switch for Tweed mode, lifting the stock mid scoopage. I understand the desire for Tweedifying but merely switching off one resistor gets you pretty close.

I have not idea what it would cost for someone else to bring it back but the parts probably add up to less than $50 (plus the 4 ohm speaker and any tubes needed.)

[jdarkis]

Originally Posted by zook

Jason,

That amp is completely changed. The circuit board looks like it may only have one original part on it.

You'll need to completely rebuild it to get it back to what it was.

Also the original PT probably can't handle the 3 amps the 5U4 requires.

Winnie

Hi guys! Thanks for the quick replies!

I went out today and got a proper NOS 5Y3 rectifier tube...come to find out the 5U4 that was in there had a hole in the bottom of it (no vacuum in there obviously, haha).

This is basically what I was scared of, so I'm wondering how to proceed. I got in touch with a local electronics technician who has worked with these amps before and he is going to look at my amp and the original layout to try and figure what he may need and what it may cost.

Alternatively, several online retailers (can I post links?) offer loaded circuit boards, that I would just have to wire in myself. I could also maybe order one of these boards then just take it to someone to have it installed (I need a new 6V6 tube socket as well, it's quite loose).

As far as a speaker, none of the local music stores have any stock and one can order Jensen in, but it could be weeks/months before they have an order together and it arrives.

*edit* Just ordered a Jensen C8R 4ohm...alnico was a little too much $ considering other work that will need to be done.

Am I safe to assume that I probably shouldn't be playing the amp at least until I get a proper 4ohm speaker in there? I'm a little sad that the amp has been abused like this, I feel like I was taken for a bit of a ride by the guy I bought it from. That's the game we play I guess...it'll be great after the overhaul!

Jason.

[PRNDL]

Sounds like you've got a nice project amp.

Here's a great place for loaded boards with high quality parts. They even let you choose between orange drops and Mallory caps.
http://www.turretboards.com/

It's fine to use an 8-ohm speaker. It might not sound as good as the 4-ohm, but it won't hurt anything.

Your amp tech can tighten the tube socket. That is a very common issue.

As for being surprised ... that depends on the price. If it wasn't heavily discounted, call the guy and ask for money back to pay the tech. You're looking at some fairly expensive repairs.

[jdarkis]

Originally Posted by PRNDL

Sounds like you've got a nice project amp.

Here's a great place for loaded boards with high quality parts. They even let you choose between orange drops and Mallory caps.
http://www.turretboards.com/

It's fine to use an 8-ohm speaker. It might not sound as good as the 4-ohm, but it won't hurt anything.

Your amp tech can tighten the tube socket. That is a very common issue.

As for being surprised ... that depends on the price. If it wasn't heavily discounted, call the guy and ask for money back to pay the tech. You're looking at some fairly expensive repairs.

Thanks for the reply! That's actually the website I was referring to, I wonder how bad the duty/brokerage will be shipping a board to me in Canada?

In everyone's opinion, if I were to order one of these boards...which configuration should I choose? Orange Drops or Mallory's.....Carbon Film or Carbon Comp? From what I have read, the better choice is the latter in both cases but it would be great if someone could validate that info.

Re: tube socket. The socket is secured tightly to the chassis, it's the connections inside that concern me. The 6V6 is able to wiggle about in there quite freely while the Rect. tube socket holds tight and secure.

Thanks again!

Jason.