Looking for some Fender twin help here ???

John Davis · Post by **John Davis** » 12 Sep 2009 12:32 pm

Well I have my Steel King and I still love it but every now and then I still need the valve amp (its like an itch that I just gotta scratch!) so when this Fender twin became available on fleabay I had to go for it .....built in 93 modeled on a 65/66 twin an all hot wired not a pcb in sight an all dressed in tweed it looked "The canines genitalia!"
but when I plugged it in lack of power and terrible buzz so it goes of to my amp techee he has done loads of work on it repaired dry joints ,replaced wrong value resistors and various other parts that he tells me were wrong but he has not been able to eliminate the hum completely as he tells me there should be a brass plate linking all the pots together to give it the correct earthing... can anyone please tell me where I can aquire one of these I love this amp and I am not giving up on it!!
Thanks for any help you can give...John Davis

J Fletcher · Post by **J Fletcher** » 12 Sep 2009 1:30 pm

I think Weber VST has the part you are looking for. Check out their website..Jerry

Jon Light (deceased) · Post by **Jon Light (deceased)** » 12 Sep 2009 1:37 pm

https://taweber.powweb.com/store/chassis/chord2.html

Scroll down to the 6A80. You can get just the plate.

I'm confused as to what point-to-point 90's twin reverb this might be. But I'm no expert. Might be a Custom Shop model I'm not remembering.

Jim Sliff · Post by **Jim Sliff** » 12 Sep 2009 2:02 pm

Same here - I don't recall Fender making ANY hand-wired Twins in the 90's, and certainly not in tweed.

I'd check the dimensions VERY carefully before ordering the 6A80 plate. If your twin has a master volume it won't fit; and even some of the newer custom-shop models differ slightly in hole spacing from the originals.

some pictures would be very helpful in giving solid advice.

Jon Light (deceased) · Post by **Jon Light (deceased)** » 12 Sep 2009 2:06 pm

Yeah--I meant to say that but forgot---you will have to do your due diligence to be sure this part will fit your chassis.

I suppose one possibility is that this is a rewired/rebuilt amp, ditching the PCB.

John Davis · Post by **John Davis** » 12 Sep 2009 11:54 pm

Thanks for the quick response and the help.

The amp has been built in 93 by someone who obviously had limited knowledge but the componants used are all good quality. Apart from the tweed colour it looks just like any other Fender twin.
I think some of the hum may well be from the step down transformer in the back to make it run on our voltage, if the brass plate makes a reasonable difference then it will be worth doing something about the transformer......will sort out some pics

Blake Hawkins · Post by **Blake Hawkins** » 13 Sep 2009 2:47 am

John,
Look at how the heater wires are installed.
In the originals, they were twisted and mounted
above the bottom of the socket. Please check some
of the previous posts on these amps for a picture of how it is correctly done. Check Ken Fox's posts.

Some years ago, I repaired a hum problem in a twin
in which the owner thought he could improve the amp
by untwisting those wires.

Also be sure the heaters are earthed properly.
Different Fender models used either fixed resistors or a hum balance pot.
A center tap on the heater winding of the power transformer is also correct.

John Billings · Post by **John Billings** » 13 Sep 2009 11:40 am

You might also try turning the "step down" transformer 90 degrees. Maybe even moving it to a different spot.

John Billings · Post by **John Billings** » 13 Sep 2009 11:56 am

How about just using a buss wire to connect the pot's bodies to ground? This is commonly done. Solder all the bodies to a fairly stout bare wire, then connect that buss to ground.

Charlie Powell · Post by **Charlie Powell** » 13 Sep 2009 12:39 pm

There are lots of possiblities for a source of hum. Could be grounding, loose connection, mutual inductive coupling... I thought I would mention one possiblity. On the last AB763 amp I built, I had a fairly loud hum that I eliminated by re-routing and shielding the wire from the tone pots going to Pin 2 on V1 (normal channel) and V2(vibrato channel). Shield is grounded at the pots end of the wire. In my case the hum was mainly in the Vibrato channel, and not the normal channel. Is the hum louder in one channel than the other?

John Davis · Post by **John Davis** » 13 Sep 2009 1:20 pm

Thanks for the input...
I have emailed Weber to see if they will supply the brass plate.
Not sure if the hum is even between the channels my techee has spent a lot of time redoing wiring that was badly done and replacing resisters where the wrong value had been used the previous guy that built it must have been colour blind! The amp now has loads of power and if it was`ent for the hum ......really good sound.
I will seperate the cabinet from the 110 transformer and I am sure it will help , but I think he may be right about that brass plate

Donny Hinson · Post by **Donny Hinson** » 13 Sep 2009 2:05 pm

Is the chassis aluminum? If it is, a brass plate won't do anything but provide an easier surface to solder to. Tell your tech to take his scope, and trace down where (stage-wise) the hum is coming from. I'd suspect a missing ground somewhere. Or, as one poster said, improper lead dress. Do you have shields on all the small tubes?

John Davis · Post by **John Davis** » 14 Sep 2009 1:51 pm

Donny my magnet sticks to the chassis so its not ally, and no I have not got the shrouds around the small valves (yet) my techee says its an accumalation of inperfections the wiring has not been done right wires too short ,wires too close to heater wires he says it really needs a rewire from scratch (or thereabouts)and the brass plate not being there is just another part of the problem....
anyway! I am not yet ready to throw in the towel yet, if the weber plate fits, (and it looks like it might)I am fixing to throw another handfull of money at it......no retreat no surrender! by the way I took the 110 transformer out of the back rotated it through 360 even moved it well away from the amp and it made no difference........tommorow is another day

Bill A. Moore · Post by **Bill A. Moore** » 14 Sep 2009 3:02 pm

I have an old Airline, that I bought used in 1968, and it had a hum then. I was in the Navy, and had one of the ETs look at it, and he changed tubes, and a few other things, and it was better. I rediscovered it a few years ago, and decided to fix it. Replaced a grid resistor, some of the electrolytics, and a couple of tubes, and it was working again,(still had a hum). This amp is truely point to point, with stand offs supporting components. I started moving things around with a drum stick, and separated many of the wires, it now idles with only the slightest hiss. It sure could be worth a try on your amp.

Clete Ritta · Post by **Clete Ritta** » 15 Sep 2009 1:54 am

Jim Sliff wrote:Same here - I don't recall Fender making ANY hand-wired Twins in the 90's, and certainly not in tweed.

I'd check the dimensions VERY carefully before ordering the 6A80 plate. If your twin has a master volume it won't fit; and even some of the newer custom-shop models differ slightly in hole spacing from the originals.

some pictures would be very helpful in giving solid advice.

Jim,
Heres a pic of my 93 Custom Shop Fender Dual Professional.

Made in Scottdale, AZ. I think they only built about 15 that year, and this one is practically new condition. Tested @ 85 watts to a pair of Vintage 30 8ohm Celestions. Only two Inputs, and the Channel and Fat Switches arent on any Twin Ive seen. The Dwell, Mix and Tone on the left are Reverb controls, not the typical Normal Channel as well. Killer Vibrato and active EQ. This isnt tweed though is it?

John Davis · Post by **John Davis** » 15 Sep 2009 10:02 pm

This is the beast thats giving all the trouble.....

Mike Fried · Post by **Mike Fried** » 17 Sep 2009 10:00 am

Check the continuity of the tube heater wiring - the power tube wires should alternate "sides" each tube, and the preamp tube heaters should all be wired the same (it's a common wiring error). If that's all in order and all the grounds are okay, I'd say your tech is likely correct about rewiring the chassis from scratch - the AB763 circuit requires good knowledge of lead dress to pull off without excess hum and/or parasitic oscillation. I seriously doubt that an inexperienced builder would have done it correctly without a lot of help.

Jim Sliff · Post by **Jim Sliff** » 20 Sep 2009 8:27 pm

Clete - I'm well aware of the Dual Professional; Fender wanted me to use one but is was overpowered for my needs at the time. Doesn't seem to be really relevant here. ???

I agree with the lead dress comments - an inexperienced builder will often put things in what appear to be the right place - but are wrong for the specific parts values. tube wires have to be precisely placed to reduce hum - and the filament wires need to be twisted with a power drill or some other rotary tool to REALLY get them tight or you'll have hum for sure.

Also, many of the cabinets have a metal screen or plate on the inside of the top that you would ever know about unless you looked up inside the cab with the chassis out - it blocks external interference and is connected to ground via chassis contact. Sometimes on balky amps that just insist on humming no matter what some of us have added another layer of metal screen with pretty good success.

There are just SO many things to look for, it's really a job for a qualified tech to sort out.

John Davis · Post by **John Davis** » 21 Sep 2009 11:23 am

Brass plate came today so amp goes back to techee this week and we are looking good will keep you posted and thanks for all the suggestions and help it will all be included in this project......

John Davis · Post by **John Davis** » 2 Oct 2009 12:32 pm

Its back!! Whoop-de-do! and I am one happy camper.
Techee (Les) has done a wonderful job and it was almost silent but me thinking I would fit a fan in the back to save the bottles now I have fan noise! the amp is fantastic! you would not know it was on apart from the red light and the fan noise. Thanks to all you guys for the helpfull suggestions.....can anyone reccomend a really silent fan that will run on 220/230??

JD

John Billings · Post by **John Billings** » 2 Oct 2009 1:04 pm

See if your tech can slow the fan down. Seems I just read somewhere of a guy using a 220/240 fan, and running it at 120. You don't really have to move a lot of air for it to be effective.

John Davis · Post by **John Davis** » 4 Oct 2009 5:43 am

I don`t think I can slow down this fan as its A/c 230...I havejust fitted a smaller version and improved the mounting.... it has helped a bit >>

John Billings · Post by **John Billings** » 4 Oct 2009 5:46 am

You're right. Didn't notice that you were in the U.K.. You have double our voltage.

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Looking for some Fender twin help here ???

Looking for some Fender twin help here ???

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