Ry Cooder's Borderline Special

[Bombacaototal]

Take a closer look at the M-10 schematic... the tube type is 12DW7.

M-10 vibrato schematic uses 12DW7, not SSS 001.

Yes I know, which is why I mentioned I was intrigued about it, as I would have expected the #001 to use the same tube

[Bombacaototal]

Has anyone here attempted to build this trem? I tried it on a 50W amp and unfortunately it doesn’t work.

Happy to go into more details, but what is happening now is whenever I engage the tremolo it is as it should be, slow and wobbly but very soon it starts speeding up until the point where there is no more tremolo sound (i e same as when it is switched off). This transition lasts up to 20 seconds.

[Bombacaototal]

I have now lived with this trem for some months and studied a lot, so time to document what I found and report some of the remaining issues.

First of all many thanks to Sergio for his contribution (his layour and schematic are on page 6 of this thread) and for pointing out that this specific tremolo is a replica of the one found on the old Gibson 2RVT amps (schematic attached). All values are the same, including the 6.8K dropping resistor between the two supplies used on this circuit. The original Gibson uses a 6EU7 tube at 235V, but I think HAD went with 12AX7 at around 205V (although on paper these tubes have the same gain factor of 100). The only other amendment HAD did was on the grounding, replacing it from the ground of the Intensity pot to the entrance of the LFO tube. Interestingly this topology is fairly similar to the Supro S6698.

I attach some details of the tracing of the cap can supply. It is grounded at the power tubes ground and it is fed from the PI supply (I added some white lines on the unfinished layout to show the flow of the supply). I use a different PI (with 6.8K dropping instead of 2.2K of the original amp) and my voltages going into the trem were lower. I noticed this trem is very voltage sensitive and I had to play around with my voltages to get the range to work properly (I settled on 83K - 17K - 6.8K insteaf of 100K - 22K - 6.8K of the original). The diode to ground there is due to the occilation..

As far as the supply, given the supply can is as small as the shielding of the pre amp tube, and that it has 3 caps I assumed 3x10uF, but bought a 3x10uF + 1x20uF cap can on my case to allow for a 20uF or a 30uF in one of the positions. I found that 10uF was best for all 3 supplies...

My circuit works, I can hear a tremolo but there is a horrible ticking sound. It seems that with master and volume at 7 oclock I cannot hear it but as I open the pots it gets more and more pronounced (not only louder). I am assuming that maybe the ticking is due to a ground loop?

The intriguing part of this circuit for me was that HAD had the entire circuit grounded together (ie pots ground jumpered together instead of the ground buss). On the board the grounding points also meet together, but there is only one black wire coming to or leaving the board. My first assumption was that, the black wire was the one coming from the pots and that HAD had lifted the tremolo circuit entirely (not grounding it at all). By doing that there is no ticking, but the Intensity pot becomes reverse. Based on HAD wiring his Intenisty pot has the ground to the left, so not reversed (which is a first indication that he may have grounded the circuit). Another thing that happens with the lifted ground is a very loud pop when engaging the circut (via footswitch) and it really drops substantially the gain of the amp. The On/Off difference in gain makes the tremolo almost unusable.

So back to sorting the grounding (assuming this is the source of my ticking): given the circuit's ground is jumpered together with an alligator clip I tried moving to all the individual grounds of my amp (either separate with the supply to the power tubes ground or together with the supply), but no matter where I place it there seems to be no difference to the ticking.

....and this is where I am at....any ideas on how to solve the ticking issue??

One last interesting fact of this circuit is that the presence pot is between the presence capacitor and the ground, and not between the GNFB and the presence cap as it would usually be placed. The master and presence pot are jumpered together and meet the LTPI tail. I tried lifting the Master too and moving it around to see if it would solve the ticking but it didn't.

I also watched uncle doug’s repair of a 1961 Gibson GA-2RT but his tremolo (around 24:24 min) didn’t have similar issues to mine: https://youtu.be/XYJa7V7HjmE
But I ended up with a 250KB on the Intensity (instead of KA), instead of changing the 2.2M like he did

Lastly I have been using the following as reference for possible ticking fixes: http://www.geofex.com/ampdbug/vibrato.htm

"Ticking" Vibrato

Fiberboard contamination: Dust, dirt, and junk can let the LFO signal leak into the audio path. Vacuum the dust and dirt away, and if it still persists, remelt the wax top and bottom with a hair dryer.
Solder blobs from eyelets touching insulating board: Sometimes excess solder drips out the bottom of an eyelet and can intermittetly contact the insulating board, can cause ticking. Remelt the eyelets and examine the board underneath for any blobs dripped down.
Funny ground on some SF Fenders; On one of the signal tubes, the cathode cap was placed on the tube socket, and wired to a ground lug on the vibrato cancel jack instead of across the resistor on the fiberboard. The vibrato shares this ground line, and can the vibrato current can cause audible ticking in the audio path. Rewire the cap to another ground or relocate it to the board.
Poor Signal wire layout: signal wires run too close to vibrato leads can pick up the LFO signal. Move them around and see if the ticking goes away.
Bad repair/replacement foot switch cable: the Fender footswitch cable is not two conductor; it's single conductor shielded, plus single conductor. The reverb wire is shielded, vibrato wire is not. This keeps vibrato out of reverb. If you retrofit with two conductor shielded, you get vibrato ticking onto reverb audio.
Sharp tick in vibrato oscillator: On neon/LDR Fenders, on the neon bulb side of the module there is a 10M to one side of bulb, 100K to the bulb; from the 10M straight across the board is the gnd point of the LDR. Put a 0.02 cap from 10M/bulb to the ground point; this works by filtering the output of the oscillator.

[Aaron]

Hi Raf,

I haven’t looked at this amp for a while but I believe the presence and master are joined for the grounding, not for signal.

Aaron

[Bombacaototal]

Hi Raf,

I haven’t looked at this amp for a while but I believe the presence and master are joined for the grounding, not for signal.

Aaron

Hi Aaron, I hope you are safe and the fires haven't affected your area. Yes, indeed the presence and master are joined for grounding (sorry if my previous post was not clear).

What I found interesting about this amp is that the presence pot is between the presence cap and ground, vs the usual approach where the presence cap is grounded on one side and the presence pot is between the other side of the presence cap and the GNFB (illustration attached)

By the way does anyone have any idea on how to sort the ticking?

[Aaron]

Ah, now I see what you mean. I started tracing this and got side tracked.

Yeah, the fires are really bad. We had a few up our way last year but down south is really, really bad.

Aaron

[Bombacaototal]

Ah, now I see what you mean. I started tracing this and got side tracked.

Yeah, the fires are really bad. We had a few up our way last year but down south is really, really bad.

Aaron

Stay safe my friend!

[Bombacaototal]

I did some further studying on the circuit and on the 6EU7 tube. I realised that the entrace of the tremolo on the Gibson amp is from the grid of unit number 2 (PIN 5) and not from the cathode of the tonestack (with an added triode like in the Borderline).

I then reverted back to the Supro Sportsman S6698 schematic attached (which is an amp Ry Cooder allegedly used a lot during 70's and 80's) and it seems HAD took the entrance of the tremolo from that circuit. Below a pic of a comparison between all 3 circuits.

Today I tried caps of 0.1uF, 0.05uF, 0.02uF and 0.01uF across the intensity pot (like the Supro) but no change to the ticking. The ticking is most sensitive to volume (which is probably due to it being linked to the cathode of the begining of the tonestack).

I measured voltages on the 270K plate and with the tremolo ON it is around 205V, with the tremolo OFF it is around 250V. On the PIN1 underneath it is around 150V but keeps ocillating when I measure to goes all over the place....the cathodes are about 1.8V and 1.1V (not too far from the Supro)

I will try some more things in the coming couple of days before moving on to something else, so if anyone has any ideas please let me know..

[norburybrook]

have you tried chop sticking leads around for the ticking? On my Bandmaster reverb with a ticking trem moving a few wires made a difference.

Just a thought.


M

[Bombacaototal]

have you tried chop sticking leads around for the ticking? On my Bandmaster reverb with a ticking trem moving a few wires made a difference.

Just a thought.


M

Thanks for the suggestion Marcus, I will give it a try. I also want to try some different AX7s to make sure its not the tube.

My ticking is more like a motorboat than what you would have on a AB763. Attached a recording first turning the volume up and then the master up. I don’t remember the exact settings I had on speed and intensity (as I recorded this some time back) but can assure they were between 12 o'clock and 3 o’clock

[norburybrook]

ah yes that sounds like a different 'ticking' than mine did!!!

greater minds than mine will help you I'm sure .


M

[sluckey]

That sounds like the "pumping" usually associated with a bias vary trem. Try adjusting the bias to see if it gets better or worse.

[Bombacaototal]

That sounds like the "pumping" usually associated with a bias vary trem. Try adjusting the bias to see if it gets better or worse.

Thanks for chiming in Sluckey!

By adjusting the bias do you mean via the cathode of the LFO triode or via the voltages on the plates? The triode of the driver has no capacitor/resistor.

By the way I got some red led arriving today (got them after being frustrated with my SSS001 tremolo endavour) which I could use on this one.

[sluckey]

I mean adjusting the bias for the power tubes. Where is the schematic for this amp?

[Bombacaototal]

I mean adjusting the bias for the power tubes. Where is the schematic for this amp?

Ah, ok...but my tremolo has nothing to do with the bias of the amp, in the sense that it is not a bias trem, it goes from the cathode of the first triode of the tonestack. I added the schematic for the tremolo on this thread..