Traynor YGM-3 Reverb Help & Tremolo Tick

[misterc57]

After getting my YGM-3 running again, the reverb is not working. I pulled the tank out and had to fix two bad connections on those very thin wires connecting the RCA jacks.

Still no reverb. I measure and noticed the following.

Gibbs tank probably original. I cannot find any specs on the tank, the pan is very rusty. I am reading 1.2 ohms input impedance, and 170 ohms output impedance.

Original tank input cable reads good continuity tip to tip and ground to ground.

Original tank output cable reads good continuity tip to tip, but there is no ground to ground continuity. The ground is connected at the pan side RCA plug, but there is no ground connection at the amp side RCA plug. I think this may be intentional to prevent ground loops?

I tried a different set of cables, still no reverb. At this point I think the tank and original cables are good. Although the impedance readings seem low especially on the input.

I also sometimes notice a tick sound when I dial up the reverb knob. I think this is the tremolo pulse.

I still have more research to do on these problems. Any help and advice greatly appreciated.

Thank you. MarkO

[g1]

Did it ever work for you? They used a higher input impedance tank in those, 4FB, so I think it's either the wrong tank or the input transducer is shorted.
Should read around 200ohms at both ends.

[g1]

Just remembered hearing of very early units that may have used reverb transformer drive. So in that case it would be a low impedance input like you have.
Does it have a schematic in the lid? Or do you see a reverb drive transformer in the chassis?

[misterc57]

Yes there is a transformer (T3). Attaching the schematic that i am using.

[Bloomfield]

That's interesting that the schematic shows a 4F tank, which is a high (c. 1475 ohm) input impedance tank being used with the transformer. Of course the transformer is not the same as the Fender unit so may have a very different secondary winding. I have an early YRM-1 out in the shop which also has a reverb transformer and is missing the tank. I was planning to try a 4A (Fender-type) tank but haven't got back to it yet. If I get a chance some time I'll try to measure the impedance ratio of the Traynor transformer vs. the Fender one.

Andy

[misterc57]

This amp was missing bias filter caps when I got it. I am thinking another cap C15 tied to the primary side of T3 may also be missing. I do not see it.

In the pictures there is a large brown disc capacitor, above that is a nut/bolt holding the board in place, to the right of that is a large 220 1W resistor, R36. R36 connects to one side of T3 primary and there should also be C15 40uF/450V. I do not see this. Anyone else see it?

I have measured 250 ohms across T3 primary and 1 ohm across T3 secondary.

Thank you. MarkO

[g1]

That's interesting that the schematic shows a 4F tank, which is a high (c. 1475 ohm) input impedance tank

That is what I thought originally as well. But I'm starting to wonder if there were some earlier codes used by Traynor. On their YRM-1 schematic they refer to a 'Accutronics 4L' type tank. There are no 'L' impedance tanks of the modern designations, so it must have been something else in the YRM example.
Why use a transformer to drive a high impedance tank when a couple years later they drive it straight through a cap with no transformer? I think the transformer would have been required only to drive a low impedance tank.

A bit more digging leads to Gibbs tanks stamped with an F that are equivalent of 4AB type. Do you see an 'F' stamped anywhere on the tank?

[g1]

In the pictures there is a large brown disc capacitor, above that is a nut/bolt holding the board in place, to the right of that is a large 220 1W resistor, R36. R36 connects to one side of T3 primary and there should also be C15 40uF/450V.

Coming off the 220R1W, I see a red wire and a blue wire. The red wire is T3 primary, right? So the blue wire should go to C15.

[misterc57]

Coming off the 220R1W, I see a red wire and a blue wire. The red wire is T3 primary, right? So the blue wire should go to C15.

Yes, you are correct, that blue wire is going to C15 which is one side of the 40/40 can cap. So there it is, thank you!

But still no reverb.

[misterc57]

The tank is very rusty on the outside. I just made out what looks like the number 1122 stamped in the middle top side. I do not see any other stampings except INPUT and OUTPUT.

[g1]

I think the tank and the transformer are good and probably stock. I only got the idea it might be wrong when I thought this was the more common version without the drive transformer.
So back to usual reverb troubleshooting. If you disconnect the jack at the tank 'out' and touch the plug tip with your finger, do you get a good hum that is adjusted by the 'reverb' control?

[misterc57]

So back to usual reverb troubleshooting. If you disconnect the jack at the tank 'out' and touch the plug tip with your finger, do you get a good hum that is adjusted by the 'reverb' control?

No hum. Even tried a different cable, no hum. Swapped tubes at V6 and V5, no hum.

[The Dude]

What are the voltages on V6A plate and cathode? Also, reverb footswitch was not grounding signal when you did this test?

[misterc57]

tubes and layout

This may not be related to my reverb issue but I am trying to better understand my amp.

There are several versions and schematics out there. Mine has 3 inputs and a Reverb transformer. The schematic I am using is the only one I could find that shows a Reverb transformer. So I am assuming it is the right one.

I notice in the schematic that V2 and V5 are 12AT7. My amp has one 12AU7, (3) 12AX7, and (2) 6BQ5 at V4 & V3, which correlates to the printed tube chart inside the cabinet. There is no mention of a 12AU7 in the schematic.

According to the tube chart in the cabinet, the 12AU7 is the first tube, V1?

If I understand correctly when looking at the back of the amp from left to right, I believe the tubes are V4, V3, V2, V6, V5, V1

Also, I want to understand which preamp tubes does what. I am thinking;

V1A first gain stage
V1B second gain stage

V2A third gain stage
V2B phase inverter

V5A reverb drive
V5B reverb drive

V6A reverb recover
V6B tremolo

[The Dude]

That's the rub with a lot of the Traynor schematics. There are lots of transitional changes that were not noted in the schematics. It's hard to say exactly what you have, but I'm wondering if it isn't closer to this YGM1 schematic. You'll have to compare and see.