Question for the gurus.

[marcoloco961]

What the hell is this?????
The part in question is circled in yellow. I have no idea what it is. The pic on the schematic for it doesn't help me either.

Anyone know off the top of their head?

[David Root]

It looks a bit like one end of a power zener diode, 25W or so. Often used between the high voltage CT of a PT and ground, to reduce plate voltage. These are usually tied directly to the chassis to dissipate heat.

[marcoloco961]

It is weird. It has two heavier wires coming out one end, and 2 thin wires out the other. One of the thin goes to ground, the other goes back into the circuit. The two heavier wires go to a high voltage plate connect and the cap can stack.

[Andy Le Blanc]

whats the amp? any date codes?

I haven't seen that particular trick.

looks hand fab'ed, whats under it?

[skyboltone]

Looks to me like a heat sink for a power resistor, but the wire compliment doesn't support that. As Andy said, open it up.

[marcoloco961]

Ahhh no. The amp works. I was just curious what the hell it was. LMAO.

It an old sears silvertone 1484 amp head. 2 - 6l6's, 4 12ax7's and 2 6fq7's. It has reverb, and tremelo, all of which still function with the original caps and all but 2 original tubes. Here is a link to the schematic. The part is just above v6 attached to the plate. It is in a dotted lined area.


http://www.schematicheaven.com/bargai ... e1484.pdf

Some kind of inductor?? It says 2H (henries)?

[skyboltone]

It's the tremolo gizmo. There's a little light in there and a photo resistor. The trem driver tube oscillates and makes it glow in time with the speed control setting. There's Tremolo which varies amplitude of the power by fooling with the bias of the power tubes then there's Vibrato which actually bends the freq a little bit. You got Vibarato like the Fender Vibroluxe and a few others. That's good.

Retraction, retraction, that does fool with the bias on the 6L6 outputs. It's tremolo.

[marcoloco961]

Here are a couple more pics

[marcoloco961]

It's the tremolo gizmo. There's a little light in there and a photo resistor. The trem driver tube oscillates and makes it glow in time with the speed control setting. There's Tremolo which varies amplitude of the power by fooling with the bias of the power tubes then there's Vibrato which actually bends the freq a little bit. You got Vibarato like the Fender Vibroluxe and a few others. That's good.

Retraction, retraction, that does fool with the bias on the 6L6 outputs. It's tremolo.

Interesting, sort of like a modern opto switch used as more of a waivering dimmer, rather than an on off switch, right? I had never seen that symbol in a schematic anywhere. Thanks for the information. That's a new one on me.

[skyboltone]

It's the tremolo gizmo. There's a little light in there and a photo resistor. The trem driver tube oscillates and makes it glow in time with the speed control setting. There's Tremolo which varies amplitude of the power by fooling with the bias of the power tubes then there's Vibrato which actually bends the freq a little bit. You got Vibarato like the Fender Vibroluxe and a few others. That's good.

Retraction, retraction, that does fool with the bias on the 6L6 outputs. It's tremolo.

Interesting, sort of like a modern opto switch used as more of a waivering dimmer, rather than an on off switch, right? I had never seen that symbol in a schematic anywhere. Thanks for the information. That's a new one on me.

Go to schematic heaven and look up Gibson GA-20 for one I think. It's called z-1 and is located between V3A and V5B Anyway, new ones come from Antique Electronic Supply.

[Andy Le Blanc]

Saw one in an old Ampeg that was a copper tube with an auto lite soldered
in one end and a bung with a couple wires crammed into the other.

Saw a Dan-electro reverb once that was balsa wood, one spring, 2 wires,
and a lot of masking tape, still dont know why it worked. the tape dried out.
replaced the tape and it worked great.

[skyboltone]

Interesting, sort of like a modern opto switch

Opto switch? What's an opto switch? What's the filament voltage? Do you need glasses to use one?

[Structo]

Yep that is a doodle bug or whatever they used to call them.
Light bulb and photo resistor.