Failure to Launch: 5E3 Tweed Deluxe Project.

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Failure to Launch: 5E3 Tweed Deluxe Project.

Postby Cygnus X1 » Mon May 05, 2008 6:00 pm

Assembled this amp into a solid state chassis. New Weber PT and OT.
The PT is the international version. I'm using the brown 120V tap on the primary.

The tubes light up, but I am getting zero sound out of the speaker.
Not even a faint hum. I must have done something incredibly stupid, but I can't see what.

I'm not getting any DC voltage at the filter caps. I swapped rectifiers, same result. I have the primary center tap of the OT at pin 8 of the rectifier.

I'm using red/red (680V) off the PT into the 5Y3. Should I be using this, or the 540V? Seems like something ought to happen!

I know, I should have started it with a light bulb current limiter, but I haven't built one. Too lazy, or overconfident.
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Postby Sal Brisindi » Mon May 05, 2008 6:57 pm

Do you have the secondary of the power transformer going to the plates of the 5Y3 on pin 4 and 6? Check to see if you have AC from the power transformer across those pin and pin 4 to the center tap then pin 6 to the center tap. Remember to set you meter on AC, if you do have AC on pin 4 and 6, then set your meter on DC and check from the transformer center tap to pin 2 and or pin 8, you should have B+ DC there. Let us know what you find.

Regards,
Sal
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Postby TomMcNally » Mon May 05, 2008 8:15 pm

Do you have the centertap of the HV winding grounded ? red/yel should go to your ground bus, ideally at the grounds of the filter caps.
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Postby Cygnus X1 » Tue May 06, 2008 2:44 am

Alright!
That did it.
I also forgot to ground the green/yellow.

Thanks, all.

:)
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Postby Cygnus X1 » Wed May 07, 2008 9:23 am

Alright...it sounds pretty good, not much noise.
But, two "problems".

Actually three. It's too loud! I don't own a 12ay7, so I put a 6025 in V1, a
12AT7 in V2. Also tried an 12Au7 in V1. Not much difference...it's still too loud, even with an open back 2X8. For reference, it seems like it's louder than my 67 Deluxe Reverb. I'll probably end up putting it into a combo with a Weber Signature 25 watt 12". I don't know whether to use ceramic or alnico.

Problem 1: No sweep on the volume controls. It gets real loud at 2, then
after that, more saturation. I understand the Tweed Deluxe has this characteristic, but it starts getting loud by just cracking the volume knob.
I went stock by the 5E3, using a 1 meg linear taper pot.

Problem 2: Maybe this is normal, but just like the volume...the tone knob
seems to provide a lot of volume while increasing from bass to treble.
At least it has a large effect on tone, but it seems to also act as a volume pot. I have the .005 and .0005 caps on the pot, wired correctly. I made sure the legs were not hitting ground, somehow.

So, should I change the volume pots from stock to a different value (or maybe audio taper?)

I know one thing, this amp will be great for a gigging musician. It cuts!
I just don't need all that volume in the garage.
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Postby EWBrown » Wed May 07, 2008 10:25 am

Volume controls should be "audio taper" or "logarithmic taper", as linear pots will get too "loud" too early in the pot's roration. Otherwise you will hit "eleven" far too soon :o

Also, try using the guitar's volume controls, too, that combined with the amp's volume control settings will give you a combination of different "sounds" from soft and mellow to hard and metallic or that "fat" blues sound. If the individual pickups have their own volume controls, so much the better Yellow_Light_Colorz_PDT_06

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Postby Cygnus X1 » Wed May 07, 2008 10:42 am

Now I have to track down where someone said a linear taper would work fine. Probably a Spinal Tap fan (LOL).
Thank you E.

I'm learning slowly.

But, at least in one month, I've done a Champ rebuild, a recap and some other restoration to a Deluxe Reverb, and a complete 5E3 build.
I have been bitten by the amp bug!
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Postby nyazzip » Wed May 07, 2008 10:26 pm

...most unusual for a guitar player to complain about too much volume.....!
peak drum noises can be as loud as a 100watt guitar amp, cranked, i have found. my marshall jcm800 (50 watt) barely cut it for jam rehearsals with hard hitting(read: amateur) rock drummers
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Postby EWBrown » Thu May 08, 2008 6:50 am

Linear taper is OK for balance, "presence" or tone controls, but it comes up waaaay too fast for volume controlling.

Rat Shack has a selection of volume pots, for mono purposes I use the "Alpha" 100K audio taper pots. tTey are marked 100K A, and have a fairly long 1/4 inch shaft, so they will have to be cut to length. BEst approach is to clamp the shaft in a bench vise and use a hacksaw to cut to the right length. I do it wit hthe pot's three terminals pointing downwards to avoid any bits of metal debris from getting into the pot. :o

FWIW AES sells the same pots, pricing is about the same in either case.

For a guitar amp, the volule pots are usually 1 meg, I'd SWAG that RS has them as well...

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