Need help w/Silvertone 1465 reverb

[christopherrgerhardt]

I'm replacing the infamous cardboard tube reverb tank in my Silvertone with a traditional spring box BUT I want to get it functioning the way it was intended first. I can physically knock the tank and get verb but playing doesn't actuate it.

I have one clue though: only one of the two coaxial leads that go to the tank has a decent audio signal, the other one is weak sounding ... I don't know, but I think both should be pretty hot, right?

[phatt]

Hi Chris xyz, (not even gonna try to spell it)

If knocking the tank produces sound then the pickup end is working but the driver end will likely need work.

If you have changed the tank then there maybe a complete mismatch,,, Reverb tanks can be quite different and more often than not a simple swap does not work.

I have no idea what this *Cardboard tank* contains as I've never heard of such a thing.
At a guess it's a very different drive unit.
You might start by measuring the DC resistance of the *Driver coil*,, or Transducer,, note the reading,, then check the new tank *Drive coil*

If they are very different in Ohms reading then you may have found the problem.
A Driver transducer that reads 2,000 Ohms  will not work in a circuit that needs 4 Ohms.
Phil.

[Enzo]

The infamous SIlvertone reverb assembly I know was based on piezos, so good luck measuring transducer impedance with a meter.  They stretched a piece of spring down the body, then they had a small clamp near each end with a hunk of piezo wedged in it.  The piezo stuck up between windings of the main spring.  One piezo was driven, so it vibrated the spring.  The other end acted as a pickup.  I suppose in thinking about it, it didn;t much matter which end was which.

I am not sure the existing drive circuit would be happy with even the highest impedance conventional pan.  Maybe.

I managed to rebuild a couple of them.  I got a piezo element and stuck pieces of it in there.  Be aware that the piezos they used were two sided.  So the two sides of the clamp were the two connections for the piezo piece wedged between them.  The common piezos I find, like the ones in the Motorola tweeters are sandwiches.  There is a central disc, with piezo on either side, then outside contacts are wired together.  SO the two sides are the same electrically, and the second connection comes from the center disc.  SO you cannot just stick one of them in the old clamp without modifying it.

[bry melvin]

Just a thought...I am having trouble visualizing this setup....but wonder if piezo A/E bridge components would work...would be expensive though...

[christopherrgerhardt]

Hi Chris xyz, (not even gonna try to spell it)

If knocking the tank produces sound then the pickup end is working but the driver end will likely need work.

Now that's helpful!

The change-out is fine, it's a match. How would you go about finding and testing the drivers?

[phatt]

Hi Chris xyz, (not even gonna try to spell it)

If knocking the tank produces sound then the pickup end is working but the driver end will likely need work.

Now that's helpful!

The change-out is fine, it's a match. How would you go about finding and testing the drivers?

I test them by wiring a small speaker (i.e. small computer spk) to the *Driver end*.
If sound comes out that small speaker then the driver part is at least functioning,,, how well is a little harder to write about.
Judging from Enzo's comments,, i.e. if it is indeed a peizo unit then Hard to know as I've not played around with one of those.

I need more info:
Try looking at the transducer (inside the rev Tank/tube)
Does it have a small magnet passing through an iron core?
Magnetic units look like a very small transformer and a small magnet sits inside the iron core.
The spring wire passes through the centre of this tiny magnet.

Enzo has already explained the peizo concept for you.
So you really need to establish what the hell we are all talking about before we can be of much use.
Cheers, Phil.

[scooperman]

the cardboard tube Silvertone reverb should have an inductive driver transducer and piezo receiver transducer.   One side of the driver should be grounded.  Follow the wiring back to the reverb driving circuitry, check those transistors in the drive circuit.

[Enzo]

The reverb I am familiar with is Piezo at both ends.  If there are other formats Silvertone used, I just am not familiar with them.   If there is a god in heaven, then SIlvertone didn;t make ALL their reverbs with that piezo.

[J M Fahey]

Most (99%) are piezo both ends; maybe 1% had a conventional (coil/magnet) drive, which would have been an improvement, but not yours.
If you have the original one, please post some pictures from different angles, we are all very curious about them.
Somebody kludged a replacement out of 2 regular piezo disks, if I find the picture I will post it.

[Enzo]

I have no photos of when I did it.