Ry Cooder's Borderline Special

[sluckey]

There are so many schematics on this thread that I don't know which one you are using.

[erwin_ve]

Did you adjust the cathode resistor for the triode where the trem circuit is connected? The sound sample sounds like giant positive feedback.

[Bombacaototal]

There are so many schematics on this thread that I don't know which one you are using.

There you go!

[Bombacaototal]

Did you adjust the cathode resistor for the triode where the trem circuit is connected? The sound sample sounds like giant positive feedback.

Thanks for the suggestion Erwin. Do you mean the PIN8 of the Tremolo circuit or the PIN3 of the tonestack (vide schematic above)

[erwin_ve]

There are so many schematics on this thread that I don't know which one you are using.

There you go!

Exactly! you have 2 cathodes tied on a resistor that is ment for 1 cathode; change the tonestack cathode to 820 Ohm.

[Bombacaototal]

There are so many schematics on this thread that I don't know which one you are using.

There you go!

Exactly! you have 2 cathodes tied on a resistor that is ment for 1 cathode; change the tonestack cathode to 820 Ohm.

Thanks Erwin! I will try that. When I was re-tracing the amp I noticed the 2 yellow connecting wires to PIN3 of the first tube (one being the trem) and could confirm the topology, but the resistor of that tonestack cathode is turned so I could not tell the value, and therefore assumed 1.5K like the visible one. That never occured to me, but I will try! I have plenty of 820R at home

[erwin_ve]

Rafael: Before putting the 820 Ohm in could you check:
What is your plate voltage of the trem triode (that has a shared cathode point with the tonestack cathode?) and the plate voltage of the tonestack triode?

[Bombacaototal]

Rafael: Before putting the 820 Ohm in could you check:
What is your plate voltage on the cathode of the trem triode (that has a shared cathode point with the tonestack cathode?) and the plate voltage of the tonestack triode?

So with the tremolo connected to the circuit and active, following my schematic, ZD (ie the plate of the driver) was 203V and ZC (ie plate of LFO) was 205V. I have this circuit on a switch for now (between PIN 3 of stack and PIN 8 of the driver) and with the circuit disconnected they went to 250V range (I can double check tonight). The cathode voltages for the driver (Tremolo PIN8) was 1.8V and for the LFO (Tremolo PIN3)was 1.1V with the tremolo ON

I will check the tonestack and report back

[erwin_ve]

Rafael: Before putting the 820 Ohm in could you check:
What is your plate voltage on the cathode of the trem triode (that has a shared cathode point with the tonestack cathode?) and the plate voltage of the tonestack triode?

So with the tremolo connected to the circuit and active, following my schematic, ZD (ie the plate of the driver) was 203V and ZC (ie plate of LFO) was 205V. I have this circuit on a switch for now (between PIN 3 of stack and PIN 8 of the driver) and with the circuit disconnected they went to 250V range (I can double check tonight). The cathode voltages for the driver (Tremolo PIN8) was 1.8V and for the LFO (Tremolo PIN3)was 1.1V with the tremolo ON

I will check the tonestack and report back

I wil have to look in to this deeper, but is the ZD and ZC B+ voltage decoupled from the dropping string? Positive feedback can have different cause.

[Bombacaototal]

Rafael: Before putting the 820 Ohm in could you check:
What is your plate voltage on the cathode of the trem triode (that has a shared cathode point with the tonestack cathode?) and the plate voltage of the tonestack triode?

So with the tremolo connected to the circuit and active, following my schematic, ZD (ie the plate of the driver) was 203V and ZC (ie plate of LFO) was 205V. I have this circuit on a switch for now (between PIN 3 of stack and PIN 8 of the driver) and with the circuit disconnected they went to 250V range (I can double check tonight). The cathode voltages for the driver (Tremolo PIN8) was 1.8V and for the LFO (Tremolo PIN3)was 1.1V with the tremolo ON

I will check the tonestack and report back

I wil have to look in to this deeper, but is the ZD and ZC B+ voltage decoupled from the dropping string? Positive feedback can have different cause.

This is how the dropping strings are on the original. I am using 3x10uF. The supply comes right after the PI 2.2K (think ODS). My PI is 6.8K and therefore I had to adjust my dropping resistors (after hours of alligator clips and a number of valules) to 83K - 17K - 6.8K

Does this answer your question?

[erwin_ve]

yes thanks! That looks decoupled!

[sluckey]

If you turn the intensity to zero does the pumping sound go away? If so, can you turn the intensity up to get a good trem effect without the pumping? Or does the pumping begin as soon as you touch the intensity pot?

[Bombacaototal]

If you turn the intensity to zero does the pumping sound go away? If so, can you turn the intensity up to get a good trem effect without the pumping? Or does the pumping begin as soon as you touch the intensity pot?

Hi Sluckey, as it is now everything is interlinked and dependable. For example, If I have master and volume very low (like 9 oclock), I can use the intensity almost entirely with the pumping only at the very end. If both volume and master are at 1 oclock then the pumping will start earlier (maybe it is more audible or maybe more intense the pusle?). The position of the speed seems to afect the pumping as well. I can set some tests and report back on how the intensity responds with different volume, master and speed levels. Probably in 1:30hrs I am home and can start the test. Any specific paramentes you would like me to try?

But in short usually the low levels of Intensity and speed don't have the pumping but the tremolo is super subtle.

[Bombacaototal]

Checking at voltages, the Supro will nod to 250V at the 270K plate and the Gibson 235V and 220V at the 2 plates..I don't think I am far off

[sluckey]

Take a look at this Supro schematic. Basically the same as your trem circuit. Don't be concerned with the component differences in the oscillator. But look at the circuitry between the oscillator plate and the cathode follower grid. There's an extra RC filter stage. Your circuit has one, the Supro has two. These filters help smooth out the LFO (trem) signal and also act as a voltage divider to reduce the LFO signal some more before hitting the CF. I think it would be worthwhile to add the extra RC filter to your circuit.

If I understand correctly, you're not 100% sure how the trem was implemented in the original?

http://sluckeyamps.com/supro/supro.pdf