Replacing unknown reverb tank in Airline 62 9017 amp

[hearforever]

I am repairing an Airline Deluxe Professional 9017 amplifier. The reverb was not working. Upon inspection 2 of the wires were frayed and broken and one of the 2 springs in the tank is completely disconnected on each side. The wires are easily fixable but the spring seems difficult or impossible to repair properly.

The tank is marked with a manufacturer's label: Gibbs, a subsidiary of Hammond. On the side it is stamped 6441. Any idea what kind of new tank I could try in its place? I'm not sure how to calculate the input and output impedances so that I could shop for an Accutronics tank.

Thanks a lot!

Here is the schematic-
http://www.ampix.org/albums/bargainb..._gvc-9017a.pdf

[Enzo]

Looking at the high impedance drive, I'd say you need a 4FBxxxx or 8FBxxxx reverb pan.

[Tom Phillips]

I agree with Enzo but...a couple of additional thoughts.

1) If you have a good meter then you can measure the DC resistance of the input and output coil in the existing reverb tank. Then you can look up the cross reference to impedance rating in the attached table.
2) You may want to repair the broken wires in the existing tank since you said it looks like an easy fix. Then you be able to test out the reverb and determine if the rest of the circuitry is working. If you are interested that is.

Cheers,
Tom

[hearforever]

I agree with Enzo but...a couple of additional thoughts.

1) If you have a good meter then you can measure the DC resistance of the input and output coil in the existing reverb tank. Then you can look up the cross reference to impedance rating in the attached table.
2) You may want to repair the broken wires in the existing tank since you said it looks like an easy fix. Then you be able to test out the reverb and determine if the rest of the circuitry is working. If you are interested that is.

Cheers,
Tom

Thanks for that chart, I'll make sure to save that- its very helpful. I got 260 ohm on the output and 275 ohm on the input so if I'm reading it right that gets me exactly where Enzo had guessed. The amp has 2 12" speakers so its plenty wide. I would think the type 4 accutronics sounds nicer than the type 4 (shorter with 3 springs)
Thanks again to both of you

[hearforever]

One question I have about the Accutronics tank...should the input or output be grounded? The original reverb tank is in a cardboard box and is thus not grounded. Each side of the coil must be grounded inside of the chassis though

[Tom Phillips]

One question I have about the Accutronics tank...should the input or output be grounded? The original reverb tank is in a cardboard box and is thus not grounded. Each side of the coil must be grounded inside of the chassis though

As you see on the schematic there is a ground connection via the shielded cables to each RCA phono connector at the tank. However, the barrel of each connector is not necessarily connected to the tank's metal case. The reverb tanks were actually manufactured in many variations which allowed the original designer to choose if the input connector barrel and/or the output connector barrel were electrically connected to the tank case. You can determine which variation is in your amp by looking for an insulating ring between the connector and the sheet metal or by using your ohm meter with the tank unplugged from the amp. The purpose of all this is to prevent ground loops and thus lower the hum level. One side of each coil is grounded in your amp but the ground connection does not pass through the metal shell of the tank. The metal shell of the tank IS grounded however at least at one of the connectors. In the classic Fender amps it is the output connector that is grounded to the tank case.

Cheers,
Tom

[hearforever]

As you see on the schematic there is a ground connection via the shielded cables to each RCA phono connector at the tank. However, the barrel of each connector is not necessarily connected to the tank's metal case. The reverb tanks were actually manufactured in many variations which allowed the original designer to choose if the input connector barrel and/or the output connector barrel were electrically connected to the tank case. You can determine which variation is in your amp by looking for an insulating ring between the connector and the sheet metal or by using your ohm meter with the tank unplugged from the amp. The purpose of all this is to prevent ground loops and thus lower the hum level. One side of each coil is grounded in your amp but the ground connection does not pass through the metal shell of the tank. The metal shell of the tank IS grounded however at least at one of the connectors. In the classic Fender amps it is the output connector that is grounded to the tank case.

Cheers,
Tom

As far as I can tell the input and output are both insulated and there is no grounding connection to the shell. The tank in this amp is inside a cardboard box which is strapped to the top of the amp behind the preamp section. If I get an Accutronics I will be screwing it to the top of the cabinet and so the shell will be exposed... I guess I should get one with a grounded output connector then?

[52 Bill]

... I guess I should get one with a grounded output connector then?

If you get one that isn't grounded, it can easily be converted to a grounded version by adding a small jumper wire at one of the jacks.

When you mount it, you should orient the tank so that the output side is as far away from the power transformer as possible.

[Tom Phillips]

Since your existing tank uses isolated Input and Output connectors then I would order your new one in that configuration. As 52 Bill said, you can always add a ground jumper if needed. Much easier to add a jumper than to isolate a grounded connector.

Regarding the physical mounting of the reverb tank I was assuming that the old Gibbs is the same form factor as the current Accutronix type 4 tank. I can't picture the physical installation in your amp. I believe that your amp is a combo configuration. Correct? If so it could cause feedback problems if you screw a bare tank to the cabinet. Please post photos if you can.

Tom

[Enzo]

I suspect there will only be so many 4FBxxxx types available. SO the choice of what is grounded may be moot.

[g1]

The MOD brand tanks (sold by CE or AES/tubesandmore) have little boards at the jacks, which have solder bridge jumpers to configure the grounds. So you can easily get whichever ground scheme you want by adding or removing the solder bridge at each jack board.

[hearforever]

OK thanks for all the help everyone...
Here's an update. It turns out that the input and output jacks on the original tank were both grounded. I found a good replacement tank that had a grounded output so I wired a jumper from the input jack to that. It sounds good but has very bad noise once the reverb intensity is turned up past about 1/4 or 1/3. and yes it wants to feedback a bit- I haven't figured out how to dampen that although I know I could order a bag for it or put some rubber or some dampening material between the wood cabinet and the tank.

Is there anything I can do about the noise?

[52 Bill]

Is there anything I can do about the noise?

What sort of noise, hum? With the power transformer mounted in the center of the amp, there is no easy way to keep the output transducer away from it. You could try and remount the tank over to one side of the case.

[hearforever]

What sort of noise, hum? With the power transformer mounted in the center of the amp, there is no easy way to keep the output transducer away from it. You could try and remount the tank over to one side of the case.

Yep. Hum- there's not really room to mount it on the side. Maybe its best to plug in some rca extension cables and see if I can position it away from the cabinet for less hum

[52 Bill]

Yep. Hum- there's not really room to mount it on the side.

What I meant was to slide the tank to the right or left side to get the output as far away from the power transformer as possible.