Silvertone 1484 reverb

[Tiny_Daddy]

That reverb spring in the Silvertone 1484: Is it piezo driven or what? I am considering replacing the worn-out internal tape with Kapton tape. Don't know if this will help or hurt? Changing to fender-style reverb looks like a lot of work.

[tubenit]

Tiny Daddy,

My understanding is that it is a piezo driven  reverb.  My Dano Centurian #275 had something very similar and I changed it to a one tube reverb & it was a pretty easy mod in my opinion.  I just rewired the 6CG7 into a 12AX7 and added a typical Fender reverb trannie to the chassis & put a tank in the bottom of the cab.  The reverb sounded waaaaayyyyy better after the conversion.

http://www.schematicheaven.com/bargainbin/danelectro_centurian_275.pdf

http://www.schematicheaven.com/bargainbin/silvertone1484.pdf

with respect, Tubenit

[Tiny_Daddy]

Thanks Tubenit, I will ask the owner if he wants the mod. I am currently modding his Falcon and Zephyr (both similar amps) with larger output transformer, choke and fixed bias as is popular with Blues Jr. these days. The Hammond 1750H is a tight fit but it can be done.

[SoundmasterG]

I added the Fender Deluxe Reverb reverb circuit and transformer into my brother's 1484. Its a ton of work and really needs a new head box to work right. It also needs a reorganization of the tube order in the preamp area to be optimal, otherwise you have the circuit crisscrossing itself and invite oscillations, especially if you increase gain at all.

Greg

[Tiny_Daddy]

Well I found the problem with the reverb: one of the piezo thingys is broken off. Seems to me that the existing circuit should drive a 3-spring reverb with 800 ohms input. Anyway I will find out.

[LooseChange]

Well I found the problem with the reverb: one of the piezo thingys is broken off. Seems to me that the existing circuit should drive a 3-spring reverb with 800 ohms input. Anyway I will find out.

Yeah, I've thought about that.. Cap coupled reverb, just like an Ampeg. Let us know if that works.
The short 8EBxxxx would do the job and might even fit in the cab.

[Tiny_Daddy]

Silvertone Spring Reverb tank mod:
Use a short 3-spring reverb with 800 ohms input: 8EB2C1B.

First build a tank driver:
Re-wire the reverb driver tube as a follower: remove connections to Pin 2 and wire Pin 2 to Pin 7.
Connect one end of a 1.5uf 250V cap to the cathodes. the other end goes to the reverb tank input.

Now fix the reverb recovery circuit: Jumper the 560K resistor and remove the resistor (and sometimes capacitor) that connect to Pin 2 of the reverb recovery tube. Reason is, these parts make a voltage divider that kills the signal. Install a 220K resistor from Pin 2 to ground as was done in AB763.

Works great!

[Tiny_Daddy]

Here's the flag and a pix of the rear of the amp showing the reverb tank and Hammond output transformer.

[tubenit]

What a cool mod!  And I like the Texas flag too.

Thanks for sharing! 

With respect, Tubenit

[zarfnober]

Tiny Daddy, do you have a schematic for your mod? I sent a pm, thanks!

Rocco

[terminalgs]

I discovered a problem with the original plate resistors on the driver triodes:



If voltage drop across a 27K resistor is 125v, the wattage for that resistor is .578.  I'm pretty sure those resistors are 1/2W rated resistors.  I think they underspec'ed those resistors:



I was all set to re-engineer my 1484 reverb for a hammond tank, when I discovered one of the plate resistors was 0ohm.  When I replaced it, the original piezo box came to life.

Note that the original driver is a para-phase phase-inverter.

[Willabe]

Interesting, a PP reverb driver. IIRC, 6CG7/6FQ7 is pretty much a 12AU7?


             Brad        

[DummyLoad]

Interesting, a PP reverb driver. IIRC, 6CG7/6FQ7 is pretty much a 12AU7?


             Brad        

6SN7   

--pete

[zarfnober]

I've gone through and rebuilt couple of these original verb circuits, and while I enjoy the cheesiness of it, the tank is just not up to snuff. I've taken a couple apart, and the piezo(? they are the 2 inside spring contacts, the outside are covered with tape/fish paper) wafer deteriorates. They are removable, I even tried cutting away the burned/corroded part and reinstalling, not much improvement. Sometimes they are in good enough condition and sound better, but most now are to the point of being junk. So, if you're lucky, they can sound ok, but the odds of finding a good one are slim to none.

Someone PLEASE give us a better, working verb.

Rocco