Traynor YGM-3 (early) - Selmer cab

[Reeltarded]

I bet it would kill with 6v6s..

kidding.

sort of.

[Barks]

What about another pair of EL84's?

re: the bias trim.
Is there any reason why I shouldn't mount it on the back chassis panel?

There plenty of space to make a mounting bracket there and the old power switch hole could be an access hole.

Would long wires be a problem here as in inducing noise or interference etc?

Tomorrow I'm going over every solder component I've done to make sure there are no bad "mook" points by me.
All the other parts have arrived to we are nearly good to go on Traynor Resurrection Part Deux.

[martin manning]

There's not a lot of advantage to making the trimmer accessible from the outside unless you also make provision to measure the current from the outside too. That would mean adding three jacks, one for ground and one for each cathode. Here's an example showing how the current sense resistors can be mounted to the jacks; the pot wiring would be a bit different in your case.

[rp]

Bias_Trimmer_&_Jacks.png

Martin, if that is your pict, what is that very interesting chassis mount trimmer pot?

Barks you don't really need the bias outside, reality is you check bias once in a blue moon and you are capable of opening it up and doing it. You can always add test jacks etc later.

Here's an idea for the fizz, instead of snubbing highs here and there you could try and tweak the very Fender 6L6 PI to make it more EL84 appropriate: change the tail and bias resistors to 47K/820, or any mix btw 6.8K-47K / 470-1.2k. Others can explain this better but the tail sets the overall stage voltage, the 470 sets the bias (plate-cathode relationship). El84 are more sensitive and require less drive than 6V6s. Traynor for some reason used a very 6L6 type set up, which are the least sensitive of the three tubes.

The Deluxe Reverb was 22K/470 which might drive the EL84s a touch less hard and keep the Traynor Fenderiness. I would try 47K/820 right off the bat just to hear the clearest before/after effect and then tweak back from there. If this works for you you could change the 82K/100k plate resistors to 100K/100K as the PI shouldn't need this balancing help any more. I've never had to tweak a PI this way so I'm curious if you try what you hear.

Changing the PI might sweeten it up without cutting treble, not sure what you are after, from the clips I kind of like the bright vicious sound, but impossible to tell from the web mp3s if it's killer vicious or a vicious killer.

I bet it would kill with 6v6s.kidding. sort of.

You know you aren't kidding, we both prolly would have already had 6V6s in this thing. But we must banish evil thoughts, 6V6s, OT upgrades, poor guy shows up for an oil change and leaves with a radiator flush and a new set of tires. But when I looked at the schematic and saw the voltages I also thought 6V6s would be more better.

So, Barks if you ever fall down the rabbit hole, you could go to 6V6s (a fatter fuller warmer tube IMO) Deluxe Reverb OT, and a Master Volume as you already got a hole in the back. Then you could keep all the peeps here happy helping you pull it off.

[Barks]

Thanks RP - more great info to digest!

step two update.

I have gone over every solder point since I started the project to make sure everything is tight. All seems solid now.

I abandoned the idea of mounting the bias trimmer on the back panel. It was just a thought to make use of the empty hole.

I have now gone ahead and mounted it more or less in the position as drawn by Martin.
I assembled the resistor and trimmer assembly first.
Removed the original 22k resistor and measured it at 21.9k and then set the new resistor/trimmer pot to give the same 21.9k reading and marked it on the pot - before installing back into the amp.

I figured that way the bias would have the same reference point and the amp would be functioning as it was before.

[IMG575]http://i650.photobucket.com/albums/uu222/katbarks/Traynor%20-%20Selmer/IMG_20150718_133037154.jpg[/img]

[IMG575]http://i650.photobucket.com/albums/uu222/katbarks/Traynor%20-%20Selmer/IMG_20150718_135556320.jpg[/img]

[martin manning]

Bias_Trimmer_&_Jacks.png

Martin, if that is your pict, what is that very interesting chassis mount trimmer pot?

Those are nice, eh? It's a 1/2" diameter sealed cermet trimmer with a 1/8" slotted locking shaft. I got a few surplus, but they are evidently still being made: http://www.mouser.com/ds/2/427/prv6parv-239985.pdf Mouser doesn't seem to have any except the non-locking type, though.

Nice job, Barks!

[Barks]

Now to screen resistors.

Am I right in thinking they go in series with pin 9 of the EL84 base?

As I see it brown screen lead comes from one of the 500v caps to V4 pin 9 then daisy chains to pin 9 of V3.

Values I have here are 47, 68, 100, 150 and 270. Larger values up to 470 as single resistors seemed hard to get without getting them from the US - according to Farnell!

[martin manning]

Yes, correct on the connection to the cap; the screens are fed by the second filter. You can do something like this, and use a stiff wire jumper from one screen resistor to the other in a "U" shape to support the resistors (which can be stood on end), but it would be best to use a terminal strip mounted to the chassis. They need to be left uncovered too, as they will need to shed some significant heat.

I'd use at least 100 ohms there.

[Barks]

Thanks.
I'm not sure I'm understanding the stiff wire jumper from one resistor to the other?
Is this for strain relief - not electrical contact?

[martin manning]

Just so there is no way that the ends of the resistors can drop down and contact the chassis (or anything else for that matter). There is lots of vibration and knocking around in a combo amp.

[rp]

He means like this where the 5W resistor lead is thick enough to support itself just tacked on one side. Most people do this straight up as it keeps it very far from the chassis. I don't care for it, guitar amps get bashed around hard, everything should be firmly connected especially if it has high voltage on it.

[rp]

I just searched 1K resisters @ Farnell. Given the voltages probably best to knock the screens down as much as possible as you have no choke and only that 470R dropping the B+, 1K shouldn’t affect the feel/tone much. Wire-wound or Metal Oxide flame-proof is what you want, 2-5W is all good.

Do as Martin indicated or install a terminal strip, don’t mount them across an unused tube pin. I asked just this a while back and got these replies:

https://tubeamparchive.com/viewtopic.ph ... stors+pins

Too bad Martin snagged that eyelet for the bias trim, you could have moved the screen B+ from the filter cap to this eyelet and then spanned the two G2 resistors from the eyelet to the tubes.

Resistors:

http://uk.farnell.com/welwyn/wp5s-1k0jt ... dp/2341000
http://uk.farnell.com/vishay-draloric/a ... dp/1735156

http://uk.farnell.com/te-connectivity-n ... dp/1738688

http://www.tube-town.net/ttstore/Resist ... :2349.html
http://www.tube-town.net/ttstore/Resist ... :1286.html

If size is a problem both Farnell and TT have 2W Metal-Oxides.

BTW FYI here’s some useful UK/EU sellers specialised for tube amp parts:

http://modulusamplification.com/Default.aspx
http://www.ampmaker.com/store/
http://www.hificollective.co.uk/

http://www.tube-town.net/ttstore/
http://www.tubeampdoctor.com/index.php
http://www.uraltone.com/

[Barks]

wow - more info. I'm going to be busy reading later!

Here we are as of now. I got a 5 terminal standoff strip and mounted it carefully between the two power tubes. It was a lot trickier implementing this than I anticipated!

It has the 2W 100R as first suggested.

Does this look OK - or should I have left the screen resistors with a bit more wire/room due to heat?

[IMG575]http://i650.photobucket.com/albums/uu222/katbarks/Traynor%20-%20Selmer/IMG_20150718_184544750_HDR.jpg[/img]

I'm was also thinking that the unused could be set with the current sensing resistors as suggested.

[martin manning]

Looks good to me, and yes the 1 ohm resistors can go from the center lug (ground) to the open ones, and cathode leads from there to the sockets.

[Barks]

Great, thanks.

I'll put the current sensing ones in - check over, and it'll be ready to fire up (not the best choice of words)

B