The return of the Rickenbacher

[Diverted]

I could use a set of eyes or two, on the Rickenbacher I posted about a few weeks ago.

To recall:

When I first got it playing maybe three weeks ago, the original speaker sounded horrible. Lots of distortion, and flubbing when hitting the E, A and D (bass) strings. I tried a PM speaker with resistor in place of the field coil, and it improved, so I sent the speaker off for repair. The speaker tech re-set the voice coil, cleaned out the air gap and sent it back. He said the original cone is in great shape and it didn't need a recone.

I got it back in the mail today, plugged it in and while the distortion issues are lessened, the more I play with it, even at low volumes, the more I have to admit they are still there. It sounds a lot like a rattly cabinet, but I'm sure it's not.

So I today I tried a few things to make sure I wasn't hearing things: Two separate PM speakers using a resistor in place of the FC and the original output transformer, then a different transformer. I tried the speakers (all three) in the cabinet, out of the cabinet and in separate cabinets. I'm still getting poor bass response even though the PM speakers are somewhat cleaner, and I'm starting to think that while the misaligned voice coil in the original speaker didn't help, it's not the only thing going on.

The tubes are good, as far as I can tell — I don't have any to sub in in place of them as they're oddballs compared to what I'm used to. But they tested very strong with no gas, shorts etc. on My Hickok TV-10D/U.

This amp had been recapped in the past and sloppily ... I drew out the circuit (updated voltages added today, see below) and recapped the amp based on what was in there when I got it.

Anyone see any possible areas in this circuit that I might investigate? I thought paraphrase phase inverters were supposed to be relatively clean, but something is definitely amiss. I'm sorry, I no longer have a scope.

Thank you!

[sluckey]

I would not expect too much from that amp.

[Diverted]

I'm with you 100 percent, I'm definitely not expecting Twin Reverb But still I have to think something's up as the E, A and D strings are flub/fart/fizz city, even at low volumes. It definitely ain't right.

[Diverted]

I just checked the bias on the 47, and they're pretty poorly balanced. I'm wondering how much of the issue is due to this ... unfortunately I'm out of 47 tubes at the moment, this is all I have.

47#1
Plate to CT resistance: 42.6
Voltage drop from CT to plate: .8V
Current: 18.7ma

47#2
Plate to CT resistance: 46.3
Voltage drop from CT to plate: 1.3V
Current: 28ma

Also, cathode voltage on the 47s is 17V right on the money. Cathode resistor is 301 ohms.

[Diverted]

Hi all,

I've got a question about the phase inverter in this amp, as I found it and as it's drawn out in the schematic.
So I've been looking at a lot of paraphrase phase inverter schematics in the past week or so and this one differs in one area from all the others I've seen. I'm wondering if the wiring I found when I opened the amp is incorrect (it had been recapped before).
Anyway, the PI circuit looks identical to others I've seen, except that pin 5 on the 53 phase inverter (section A grid) has about 2vdc on it because it's connected to the shared cathode via a 500k resistor. In all other paraphrase schematics I've seen, this grid only has the audio AC voltage from the first stage on it. I haven't seen a resistor connecting the cathode to grid in any others. Why is that there?
Is that 2v screwing up the bias on this half of the 53?

Thanks,

Ted