GE Console RC 7100 A - need some help!

[Eli Duttman]

Keep all control functions near the electronics. Mount the new I/P RCA females where it's convenient. Run shielded "twinax" wire between the new RCA jacks and the source selector switch. Connect the shields only near the selector switch, to the chassis. The shields do not carry signal. That's why you use "twinax" wire.

There are 4 ganged, stereo, pots. (volume, balance, bass, and treble) in the unit. Refer to the model RC4640 schematic. Notice that the "extra" wires go to taps on the ganged volume control. Those taps are associated with a Fletcher/Munson bass boost at low listening levels.

Simplify, simplify, simplify! Sweep all of the nasty signal shaping circuitry away. A pair of mono, L/R, volume control pots. are the least expensive way to have control over both listening level and channel balance. Connect the wipers of the source selector switch to the new volume controls. The wipers of the new pots. connect to the 'X7 grids. Mouser stock # 31VJ501-F is what you need.

[j.english]

first thing I need to do is get it running!

so i hooked up the new electrolytic capacitors, and nothing exploded! but then i noticed the 12ax7 wasn't lit. i'm going to attach some pics showing some damage (?) to the original 12ax7 and some damage (?) to the 2 big capacitors (?) that are next to it. does anyone know if that is a serious problem, and if so, what do i need to do? i've never seen these orange 7-pole things on any other amp, so i'm stumped. thanks in advance!

[j.english]

the damage on the big capacitors

[j.english]

close up of the information on them

[Eli Duttman]

Dude,

Those damaged parts, with multiple leads, are composites. Look at the schematic.

The circuit boards GE used appear to be low grade phenolic. Examine the Copper traces for damage.

JMO, you'll get the unit working faster if you get rid of all the signal shaping guano. The damaged composite parts are in the signal shaping stuff. Put the 100 KOhm pots. in and drive the unit with a CDP (perhaps a portable), during the shake down period.

[j.english]

!

the light came on! i think i understand what you're talking about now! thanks so much for helping me with this.

so, what do i need to do to bypass the tone stuff?

[Eli Duttman]

so, what do i need to do to bypass the tone stuff?

Cr@p! I just double checked the RC4640A schematic and the composite parts that are damaged are in the "real" part of the circuit, not the tone shaping stuff. Notice the dashed boxes around the parts intimately associated with the 12AX7 and 6AQ5s (1/channel). Those are the damaged composites. OUCH! Since you are probably forced into acquiring new, discrete, parts, make the topology change to RH84 style circuitry. The OEM PCB is of little use, unless a source for NOS composite parts exists.

[j.english]

haha! yeah, someone on another site pointed that out to me...

and, they weren't damaged...it was just some wax that had built up on it...i felt like such a dumbace when i figured that out, believe me!

so, i've isolated the problem to the 12ax7 not lighting up. somehow, it's not getting power, so no sound. i need to get that working before i go and start taking the tone stuff out. any ideas on how to test that?

[Eli Duttman]

so, i've isolated the problem to the 12ax7 not lighting up. somehow, it's not getting power, so no sound. i need to get that working before i go and start taking the tone stuff out. any ideas on how to test that?

Examine the PCB for broken traces with a hand lens in strong light. Insert a new 'X7 to eliminate a dead tube. Jim McShane charges $10.75 for the very nice Sovtek 12AX7LPS.

[bcrescen]

J.

How's the project going. I just pulled the attached out of a GE Console left out for the trash man. It sounds pretty good with a cd source. I'm thinking about making a tube IPOD docking station.

The control panel includes a on\off selector switch, volume, bass, treble, and balance. I would like to replace all with a dual volume pot.

Any thoughts as to whether this amp is worth the effort?

Bruce