Ampeg VT40 Reverb

[Oldsoul]

Having trouble with the reverb on my VT-40 Distortion model. I had to replace the tank with one from Fliptops as the the original Accutronics had broken springs. It seems like I am hardly getting any reverb from the tank. If I turn the reverb all the way up it start to feedback. If I move the amp around and rattle the springs I get an echoey sound but playing through it gives little to no reverb. I replaced many resistors and caps in the reverb circuit and checked the tube.

[Chuck H]

Can you list the model numbers on both the old tank and the new tank?

If the input and the output on the new tank are not clearly marked try reversing the connections.

[g1]

I replaced many resistors and caps in the reverb circuit and checked the tube.

Did you replace C9 ?
What are your DC voltages at pins 6 and 8 of V3 and V5 ? Some of the voltages listed on the schematic are wrong, but that can be sorted out later.

[Oldsoul]

The original tank # code 4FB2D1C. The Fliptops replacement is 4FB3A1B. The input and outputs are labelled. it does make a pinging sound when the amp is jostled so I assumed the input and output are correct. I can try to reverse them just to rule that out. I did replace cap C9 (.47) I will check the voltages on those tubes when I get back in front of it.

[Chuck H]

According to your pan codes the original had the input and output isolated from ground. Your new pan has both the input and the output grounded. That is, the RCA sleeves are attached to each other as well as the pan chassis. This difference could cause a signal short on the input side depending on how the circuit is wired.

[52 Bill]

The original tank # code 4FB2D1C. The Fliptops replacement is 4FB3A1B. The input and outputs are labelled. it does make a pinging sound when the amp is jostled so I assumed the input and output are correct. I can try to reverse them just to rule that out. I did replace cap C9 (.47) I will check the voltages on those tubes when I get back in front of it.

You need to check the wires running to the tank. They both need to be shielded, with the ground connected at the amp end. The original tank had both RCA jacks isolated from the case, the replacement tank is isolated at the input only.

It should work if the wiring is all connected correctly.

[Oldsoul]

Fliptops site states "...our tank has both input and output jacks grounded. This ensures that our tank will work in your amp with no modifications." What is best to do ?

[g1]

With the tank connected, measure resistance from C9 (tank side) to ground. It should measure about 200 ohms.
Also measure resistance across R32, with tank connected it should also measure around 200 ohms. Other than that, the ground scheme of the tank should not cause anything other than hum related issues, it shouldn't affect the reverb level.

[Leo_Gnardo]

Fliptops site states "...our tank has both input and output jacks grounded. This ensures that our tank will work in your amp with no modifications." What is best to do ?

Many modern tanks have the input & output jacks mounted on PC boards with solderable ground jumpers. MOD and Ruby brands for instance. A couple seconds with your handy soldering iron and you can connect or lift grounds as you please.

[g1]

Many modern tanks have the input & output jacks mounted on PC boards with solderable ground jumpers. MOD and Ruby brands for instance. A couple seconds with your handy soldering iron and you can connect or lift grounds as you please.

And from the pictures on the fliptops site, it is a MOD tank. So just remove the solder jumpers that ground the jacks to the casing.