Oliver G400R no reverb

[pontiacpete]

This particular Oliver does not have an exact schematic but this one for the PA100XR is very close with respect to the reverb.
They both use the 6DR7 tube, which I've never seen used in a guitar amp. I ended up buying one NOS so the tube doesn't seem to be the problem.
When it first came in there was some damage on a small board with PS dropping resistors that had collapsed and a 20w 5K resistor opened up. Replaced that so now there is voltage feeding the 6DR7.
All the components in the reverb circuit so far seem to measure to spec.
The original tank is a Gibbs 031-0005-00. It has an open transducer, so I bought a 4FB3A1A from flip tops thinking this amp will be something similar to an early ampeg.
Still no reverb.
Thanks in advance for ideas where to go from here.

I will post voltages on the 6DR7 and 6EU7 soon.

[nickb]

Tap on the springs - do you get any noise out of the speaker? If that is OK connect the drive cable that goes to the reverb to a speaker - hear anything?

[pontiacpete]

Oh yes, forgot to mention, there is sound of the reverb tank when tapping on it.

[nickb]

So what about the second step?

[pontiacpete]

NOt positive that I did this right , but I clipped a speaker to the 'IN' on the tank. But I hear no reverb.
If I switch the output and input RCAs around the tank still response to tapping.

[nickb]

Disconnect the lead from the IN of the reverb and hook it to a speaker. Play something through the amp - do you hear anything out of this speaker. You might need to use a dummy load on the main speaker to hear it.

If silent, check the voltages around the reverb driver stage.

[pontiacpete]

The 6EU7 has the follow voltages

pin 1 6.3ac
pin 2 6.3ac
pin 3 0
pin 4 2vdc
pin 5 0
pin 6 193vdc
pin 7 135vdc but fluctuates with tremolo, this one has tremolo
pin 8 0
pin 9 .7vdc

tremolo works

[pontiacpete]

Also, I hooked up a dummy load and connected a speaker to the 'IN'. no sound out to the speaker.

[pontiacpete]

Also, the 6DR7, I think this is the info you wanted

pin 1 423vdc
pin 2 0
pin 3 0
pin 4 6.3ac
pin 5 6.3ac
pin 6 248vdc
pin 7 0
pin 8 2.6vdc
pin 9 59vdc

[52 Bill]

Interesting that the drive is taken from the cathode of the 6DR7 and not the plate.

If the springs make noise when rattled, then the 6EU7 return circuit is working. The voltages on the 6DR7 are more important here.

On the original tank, which side of the tank is dead, in or out? If the input transducer is still okay, read the resistance of the coil, that will help you to figure out if the new tank is correct or not.

[pontiacpete]

The input is dead. Output measures 173R

Check the voltages above for the 6DR7, must have posted them at the time of your post

[nickb]

Also, the 6DR7, I think this is the info you wanted

pin 1 423vdc
pin 2 0
pin 3 0
pin 4 6.3ac
pin 5 6.3ac
pin 6 248vdc
pin 7 0
pin 8 2.6vdc
pin 9 59vdc

Yes, that's it

Pin 2 voltage is wrong I would expect to see about 2/3rds of the voltage of pin 9 to be on that pin. The 270k resistor might be open or a bad solder joint thereabouts, or a measurement error.

Also the heaters should both be 3.15VAC - I suspect a typo there.

[pontiacpete]

The resistor seems good measuring 290K.
I'm started to wonder about the socket.

My question is why would pin 2 be any different than pin 3? In this pdf they are connected:

http://www.tubebooks.org/tubedata/hb...art_2/6DR7.PDF

[nickb]

The resistor seems good measuring 290K.
I'm started to wonder about the socket.

My question is why would pin 2 be any different than pin 3? In this pdf they are connected:

http://www.tubebooks.org/tubedata/hb...art_2/6DR7.PDF

You lost me, Pin 2 and 3 do measure the same

A bad socket could not cause that wrong voltage. Measure the voltage at the other end of the 270K it should be around 40V

[pontiacpete]

There's something different here, I think.
The 270K resistor is connected to the .005 cap at the grid. The other end is not connected between the 1K 5watt resistor and the 2.2K 20 watter.
Instead it is connected to ground.