Fender Tube Amp

Jerry Roller · Post by **Jerry Roller** » 7 Nov 2002 3:05 pm

This is Jerry Jr. on Seniors computer.............
I have a Fender Concert tube amp that has the point to point wiring and was wondering how to determine when and if it needs new tubes. I think that maybe I have noticed a slight loss of power. Sound quality is still there.

Thanks, JRJ

Ron Randall · Post by **Ron Randall** » 7 Nov 2002 3:22 pm

Jerry,

Turn it on, let it warm up. Get it ready to play. Play a few notes to know that the amp is working.

Then....

Tap gently on the tubes with the eraser end of a pencil. If you can hear the tapping thru the speaker...it is time.

If it is quiet, and you hear no popping, crackling, probably OK.

Ken Fox · Post by **Ken Fox** » 8 Nov 2002 8:21 am

Jerry, I just finished working on 1960's Brown Concert this weekend! It was a great sounding amp. Preamp tubes wear the least, the onw next to the big power tubes (inverter) works about the hardest of the tubes. Typically it is a 12AT7 in Fender amps. In this older Concert and my newly arrived 1962 Vibrasonic the inverter is a 12AX7. Just replacing that tube alone can really bring up the power levels. Witout a tube tester and a bias level measurement, it's hard to say about the power tubes. If they are extremely microphonic, have a lot of blue light (gassy tube), or have any red areas on the plates when running it may be time. A good tube socket cleaning and bias check of the power tubes would be in order. I would avoid the Sovtek tubes, I have had a lot of failure with them. There is a good discussion about the reliability of that brand over on the Fender Forum that is going on now. Try Svetlana or Telsa J/J tubes, I think you would be very pleased.

James Quackenbush · Post by **James Quackenbush** » 9 Nov 2002 8:19 am

Ken,
If you happen to stumble on another Brown Concert that is for sale, please let me know..
A Brown Deluxe would be nice also...I love the tone of those old Fenders...Thanks, Jim

Ken Fox · Post by **Ken Fox** » 9 Nov 2002 11:05 am

I just got in a 1962 Vibrasonic, with the original D-130 at 16 ohms! It was at Killer Vintage in St Louis. I bought it sight unseen. It was painted black and had sparkle grill cloth on it! I had Dave, at Killer Vintage, send it to Greg Hopkins, at Vintage Amp Restoration. Greg and Dave have business locations near each other. Greg recovered it in the correct Tolex and regrilled it with the correct wheat cloth. The amp had faceplates like new! Looks likes a brand new 1962. I must be nuts, I put $1310.00 in this amp! It sounds and looks great and am glad to add it to collection. There is something about those Brown amps that sounded really sweet! [This message was edited by Ken Fox on 09 November 2002 at 11:06 AM.]

Chris DeBarge · Post by **Chris DeBarge** » 9 Nov 2002 2:18 pm

Ken, I have a 1960 Vibrasonic, also with the 16 ohm JBL (which as you probably know is correct). No doubt it's very cool! Though I have little chance to use it as I rarely need the power. And the vibrato is from outer space.

Ken Fox · Post by **Ken Fox** » 9 Nov 2002 5:44 pm

It is a great amp! They came with two different output transforners and 8 or 16 ohm speakers. I checked and the O.T. in mine is correct for the speaker, looks all original. That tremolo is wild!

Cartwright Thompson · Post by **Cartwright Thompson** » 11 Nov 2002 2:22 am

Chris and Ken,
Just out of curiosity, measure the impedence of your 16ohm JBL's. Believe it or not, there are lots of original cone D-130's labeled 16ohm that are actually 8ohm.

Ken Fox · Post by **Ken Fox** » 11 Nov 2002 9:26 am

Having worked in pro-audio for a lot of years I have an actual impedance meter (University /Raymer model). If you measure resistance the DC of my speaker it is less than 8 ohms, but reads a true 16 ohms with a test signal applied. I just got in another D-130 marked 16 ohms for a Vibroverb clone project. The guy thought it was 8 ohms, too. Same thing, less than 8 ohms D.C. resistance, but the actual impedance was 16 ohms. Two output transformers were used on the Vibrasonics of that era, one for a 16 ohm load and the other was for an 8 ohm load.

Chris DeBarge · Post by **Chris DeBarge** » 12 Nov 2002 5:41 am

Once again Ken is right on the money. I've been meaning to change the filter caps on mine, but unfortunately there's about 100 bucks worth in that thing!

Mike Black · Post by **Mike Black** » 12 Nov 2002 11:28 am

Anyone ever seen or have enough of the "pink" brown tolex for sale to cover 2 backpanels of a Vibrasonic? I'm looking for some to restore one.
[This message was edited by Mike Black on 12 November 2002 at 11:30 AM.]

Ken Fox · Post by **Ken Fox** » 12 Nov 2002 7:22 pm

Mike, I have the newer brown Tolex. I know what you are looking for. I would call Greg Hopkins, at Vintage Amp Restoration in St Louis. He is a leading authority on recovering amps and has the sources to find the right coverings (he also owns the new Victoria Luggage line of amp covers for tweed amps). He recovered my 1962 Vibrasonic, it is perfect. His vinyl is from a different source and closer to the orignal stuff than any other provide. Here is his link, Mike:

http://www.vintage-amp.com/

[This message was edited by Ken Fox on 12 November 2002 at 07:25 PM.]