Traynor YGM-3 (early) - Selmer cab

[rp]

BTW & just a thought before the heart transplant: you might exceed the voltage rating of the filter caps with no tubes in place to draw down the voltage, so when checking things like heaters and bias do it kind of quick.

Without going back to read from from the beginning, if that amp's been in storage many years you might want to bring it up slow before you do the transplant just to reform the caps. You can use a series of 25W 40W 60W etc, light bulbs for a few hrs each. The blue filter caps looked replaced so they should actually be ok.

[Barks]

Hi, Thanks for extra advice!

The amp has been in constant use for the last 20 years so no worries there.

[Reeltarded]

It is running. Expected voltages.

[didit]

Fire it up.

FWIW -- I keep a handful of 10k ohm 25W resistors for making a dummy load across main B+ when tinkering with a power supply before tubes go in. As many in parallel to roughly match idle running. Reduces strain on electrolytics and allows more accurate measurements.

Best .. Ian

[Reeltarded]

he had to go to some fnction within an hour of finishing it.

LMAO.. I would totally forget to call in sick....

Poor Barks.

[rp]

I keep a handful of 10k ohm 25W resistors for making a dummy load across main B+ when tinkering with a power supply before tubes go in.

I like this. How do you wire these up? A Jumper off of V1 plate to ground?

BTW Barks when powered up with the power tubes in you need to keep a load on the OT - ie your speakers if that's all you have. If your output jack is shorting that should do for a quick check of things with the knobs down, but keep in mind it's important to always have a load on the OT to protect it.

[Reeltarded]

It's running and makes sound. It's tighter since the output isn't a wobbly mirage of glass melt.

[Barks]

hehe, I'm gonna be late!

Yes fired it up with the OT connected to the speakers.

Cathode measure 6.4v and the Anode measures 422vdc

It sounds fine and tighter in the quickie session I had with it. No funny noises and seemed happy left on for the hour or so - I'm pretty pleased so far.
Tubes are a healthy orange glow...and the Pilot is not like a laser any more.

[IMG575]http://i650.photobucket.com/albums/uu222/katbarks/Traynor%20-%20Selmer/IMG_20150711_111907154.jpg[/img]

[IMG575]http://i650.photobucket.com/albums/uu222/katbarks/Traynor%20-%20Selmer/IMG_20150711_112823968_HDR.jpg[/img]

[IMG575]http://i650.photobucket.com/albums/uu222/katbarks/Traynor%20-%20Selmer/IMG_20150711_115352377.jpg[/img]


When disconnecting I was finding the stumps of the very original PT wiring still in place. Also signs of burns underneath which hint at the originals demise

[IMG:960:539]http://i650.photobucket.com/albums/uu222/katbarks/Traynor%20-%20Selmer/11709626_10153413316281147_8886002519442649898_n.jpg[/img]

[IMG:575:1024]http://i650.photobucket.com/albums/uu222/katbarks/Traynor%20-%20Selmer/IMG_20150711_134021030_HDR.jpg[/img]

[IMG575]http://i650.photobucket.com/albums/uu222/katbarks/Traynor%20-%20Selmer/IMG_20150711_152024019.jpg[/img]

[IMG580]http://i650.photobucket.com/albums/uu222/katbarks/Traynor%20-%20Selmer/Traynor%20post%20mod.png[/img]

Only problem is that the new PT hits the edge of the speaker as it mounts closer to the front panel of the amp than the other one. That's for another day.

Bias trim comes next!

Cheers everybody!

[didit]

I keep a handful of 10k ohm 25W resistors for making a dummy load across main B+ when tinkering with a power supply before tubes go in.

I like this. How do you wire these up? A Jumper off of V1 plate to ground

Depends. For brief checks I live dangerously albeit carefully using just alligator clips, to a good ground and to the B+ at the rectifier. Other times I will "tack" solder on B+ onto whatever is most easily undone and a some close ground point. I keep a single 15k 25W with flying alligator leads (w. insulated covers) on each end, which is adequate for quick and dirty testing as even at 500V that's only about 16W dissipating. I can probe for voltages and ripple in a minute or less. If I don't get what's expected then power down, diagnose and perhaps do something fancier.

[rp]

Just realized, such a dinky OT, especially for those voltages. If you find you have an itchy soldering finger and unable to sleep at night counting flying tubes you could try one of these. Not saying it'll make it better but if you have to mess around it's a better time waster than teflon caps. Maybe for 17 anni?

https://www.tubesandmore.com/products/P-T1750Y

http://www.mojotone.com/amp-parts/trans ... ransformer

Seeing how it's kind of Fendery with the fixed bias and LTP maybe:
http://www.allenamps.com/parts.php#transformers
Allen TO-22 / TO-26

[sluckey]

I have three 1500Ω/25W resistors mounted on a board and connected in series that I use for a load on power supplies. I can put a 100mA load on a 300v supply or 100mA load on a 450V supply just by moving a gator clip lead. I've used it a lot on various Hammond organ amps that I converted in the past few years. Makes a nice hand warmer too!

[cyclone_cj]

I have a very nice original one. I notice that the wiring on yours is bodged. One thing I noticed when looking inside my amp is that the preamp and tone control wiring is layed out very carefully with wires separated and crossed at 90 deg angles. It is so deliberate that it must be intentional. I'm out of town but I posted a pic on ampage a few years back of the layout. I'm too lazy to search for it rt now:) If you search ampage for ygm3 you will find it. If not, let me know and I'll pull my chassis out and take pics, voltage measurements etc this weekend.

I put 1k 5w screen resistors on my amp so the tubes would survive. Dropped 3 watts output, can't hear it. Mine is unmolested, glad to help you optimize yours.

[Barks]

Thanks Cyclone_cj

Yes this amp has been an uber bodge ever since it was stuffed into a Selmer Cab over 20 years ago - not to mention the PT and Mid Boost mod!

I had a look at ampage - very clean indeed.

Yours is the second variant with the bright switch and two inputs whereas mine is the 3 input and the bright cap permanently across the volume control.

The layouts between the two are actually quite different.

Most notably are that V1 on yours is right by the volume control at the front of the amp whereas on mine it is inline at the back of the amp with all the other valves.
The big 450v caps are also mounted outside by the PT

Also the very early models like mine had the tone stack wired across the treble and bass controls - on yours it's incorporated onto the boards.

So it may seem like the wiring in mine at the preamp has been really messed with but in fact it is pretty much stock except the addition of the mid boost inductor and switch.

Here is a pic of the tonestack of another early YGM-3 I found:

[martin manning]

I guess you don't know where your idle current is yet? You can measure DC resistance from the red OT CT to the power valve anodes (pin 7's) with power off, then measure voltage across the same two points and calculate current as V/R. Another way is to put your meter in current mode (mA) and shunt across each side of the OT primary, but if you slip something is likely to get fried. Obviously using 1Ω current sense resistors is easier and safer.

For a bias trimmer set-up, you have an empty eyelet there which you could make good use of (see below).

[Barks]

Thank you Martin - again! - for all the great help.
I've only seen this having just put it all back together - a bit too keen to see how it sounds!
I will order these parts and implement the bias trim as stage two. Will measure again as suggested.

I had to relocate the PT a little so it would fit - a stupid error as i should have checked that it would work physically when back in the cabinet before wiring up.
The speaker cage was in the way.

I had to move it about 1cm inward of the chassis and in the process (to account for the offset that ensued between the PT cables and the chassis holes they passed through) had to raiseit onto four standoffs made from old rack mount bolts.

You can see the issue here:
[IMG575]http://i650.photobucket.com/albums/uu222/katbarks/Traynor%20-%20Selmer/IMG_20150712_141321200.jpg[/img]

Relocated and with standoffs:
[IMG575]http://i650.photobucket.com/albums/uu222/katbarks/Traynor%20-%20Selmer/IMG_20150712_131230091.jpg[/img]

Also had a fright when I put it back in as it was completely dead.
Stupidly I may have been a bit forceful with V1 (which is a fatter Tungstol 12AXY than normal) which was tight in the valve can base.
It bent a pin slightly and cracked the glass base.

[IMG:575:1024]http://i650.photobucket.com/albums/uu222/katbarks/Traynor%20-%20Selmer/IMG_20150712_160038583.jpg[/img]

I have an old Mullard in there now which sounds fine but a little microphonic.