Ampeg Gemini 1 Tremelo Problem (AGAIN)

[plexi50]

I went through this last year with this same Gemini 1. I have no tremelo. I have all my doc's from many other Gemini amps. You can hear a ticking sound and the speed pot works increasing or decreasing the ticking. But i have to touch a coupling cap to make that happen. Otherwise no tremelo period.Thing's i have done:Installed new Fliptops Trem Module:Installed new Mallory M150 .047 trem caps:Installed (2) Tremelo Cathode Cap's. I have oscillation of voltages across the caps north end. I have 60 VDC on the purple wire going to the lamp.I have 189 VDC on pin#6 when trem switch pedal is disengaged. Lowest voltage during Oscillation of pin 6 is 79 VDC. Last: The INT pot adjusts the volume of the amp.
What am i missing? Here We Go Again.

[Keppy]

Schematic


From your description, the amp is working as though the variable resistor in the trem is open circuit. On the schematic I linked, points X and Y are connected through that resistance, and without it, the trem intensity pot makes a voltage divider with the tone stack that explains the volume change.


Can you observe oscillation on the contact for the lamp itself? You only mention DC on the wire feeding the lamp.


If you have oscillation on the lamp wire, I see two possible explanations:

• The lamp is bad, leaving the trem resistance at max regardless of what the oscillator is doing.
• You wired the bug wrong. This seems very possible to me not because of anything you posted, but because the fliptops site does not appear to have a wiring diagram for it. In your picture, you use the contacts on the right side of the bug, and in the picture on their website, those contacts are broken off.

[plexi50]

There are two choices. This one is the one i have.    VM1 / VM1A Vibrato Module ,  GV and "x" Series Amps UPDATED

And this one that states it works on the Gemini1.
    TM1/M1-R Tremolo Module for Vintage Ampegs


I have used VM1 / VM1A before and it worked in a Gemimi II.
 

[plexi50]

TM1/M1-R Tremolo Module is on it's way to me. What is the difference between these trem modules?

[plexi50]

No oscillation on the purple lamp wire to speak of. Positive 55-60 VDC.
Reply from Sluckey last year on this very same subject on wiring.

Quote: Ignore the cell on the left.Connect the right cell to the pot wires (points X and Y on the schematic). Doesn't matter which wire goes where.
Connect the lamp to the black and violet wires. Doesn't matter which wire goes where.

[sluckey]

VM module contains two LDRs. The TM module contains only one LDR.

[plexi50]

VM module contains two LDRs. The TM module contains only one LDR.

Your a D*m GENIUS!!! So why did he ship me this one? My invoice was for TM?

[sluckey]

Ask him. Did he only charge for the cheaper TM module?

The VM module will work fine in a TM circuit. One LDR will not be used. But the TM module cannot be used in a VM circuit because it only has one LDR. Look at some schematics.

The cheap Fender style roach can be used instead of that way overpriced TM module.

[plexi50]

Ok, reversed the pot wires to the left side Cell and BINGO PRESTO! Beautiful full and room filling tremelo! The guy that makes them does not mark the Cell that has the LDR on the board for the TM1 module. He does not break off the end of the TM1 module anymore.
One more thing. The intensity pot does little to nothing when turned on CCW. Very little tremelo through full rotation. Turned off CW great sounding tremelo. The yellow wire coming from the pot switch to the 22k resistor is in play here correct? I lifted the resistor leg and it reads 22K. Lower or increase this value?

[sluckey]

Ok, reversed the pot wires to the left side Cell and BINGO PRESTO! Beautiful full and room filling tremelo!

The LDR (cell) doesn't care which wire is connected where. I suspect you probably found a bad connection.

One more thing. The intensity pot does little to nothing when turned on CCW. Very little tremelo through full rotation. Turned off CW great sounding tremelo. The yellow wire coming from the pot switch to the 22k resistor is in play here correct?

That doesn't sound right. You should have tremolo with or without the "afterbeat" switch. And the intensity pot should control the intensity.

[plexi50]

Ok, reversed the pot wires to the left side Cell and BINGO PRESTO! Beautiful full and room filling tremelo!

The LDR (cell) doesn't care which wire is connected where. I suspect you probably found a bad connection.

One more thing. The intensity pot does little to nothing when turned on CCW. Very little tremelo through full rotation. Turned off CW great sounding tremelo. The yellow wire coming from the pot switch to the 22k resistor is in play here correct?

That doesn't sound right. You should have tremolo with or without the "afterbeat" switch. And the intensity pot should control the intensity.

Yes intensity pot should control intensity.  When the intensity pot is turned on there is a slight weak tremelo sound. But as you rotate the pot CCW there is no trem at all. Shut off intensity pot and works very nice. It's like it has full intensity without the pot.

[sluckey]

Sounds like the pot is wired backwards. Check this... Turn the pot max CCW (that's zero or 7 o'clock for people that don't understand CCW    ). The resistance across the pot should be zero ohms. Now turn the pot max CW but don't click the switch. The resistance across the pot should be 4M. Does this check out OK? If backwards, swap the two wires on the pot, ***NOT ON THE TM1 MODULE.

[plexi50]

Sounds like the pot is wired backwards. Check this... Turn the pot max CCW (that's zero or 7 o'clock for people that don't understand CCW    ). The resistance across the pot should be zero ohms. Now turn the pot max CW but don't click the switch. The resistance across the pot should be 4M. Does this check out OK? If backwards, swap the two wires on the pot, ***NOT ON THE TM1 MODULE.

Intensity pot full CCW 42.6 Ohm. CW before the click 3.65 Meg.

[sluckey]

The pot is wired correctly. Let's be sure I understand what you have told me. The tremolo is very weak to none as you turn the pot from max CCW to max CW(no click). But when you click the switch at the max CW end of rotation you have beautiful tremolo, but you can't control the intensity. Do I have that right?

[plexi50]

The pot is wired correctly. Let's be sure I understand what you have told me. The tremolo is very weak to none as you turn the pot from max CCW to max CW(no click). But when you click the switch at the max CW end of rotation you have beautiful tremolo, but you can't control the intensity. Do I have that right?

Exactly. Strange.

[plexi50]

Im checking the 390k and 1 meg resistors in the after beat path. 390k is good. Got to lift the purple wire from the board to get a reading on the 1 meg.  1meg is reading 450 in circuit.

[plexi50]

Im checking the 390k and 1 meg resistors in the after beat path. 390k is good. Got to lift the purple wire from the board to get a reading on the 1 meg.  1meg is reading 450 in circuit.

Both resistors check out good in value.

[sluckey]

Put a jumper across the switch contacts. Now the INT pot should control the amount of tremolo. Like what you hear?

[plexi50]

Were on the same path Steve.
Ok are you ready for some more CRAZY? I decided to check the back of the intensity pot switch where the yellow and black wire going to ground connects to the switch itself. I put a screwdriver across the switch terminals. The intensity switch is fully functional. In a way some things about this amp are azz backwards.   

[plexi50]

Put a jumper across the switch contacts. Now the INT pot should control the amount of tremolo. Like what you hear?

Yes it works all the way and sounds great.  *DONE*