EL34 YGL3 -> 6L6 SSS

Overdrive Special, Steel String Singer, Dumbleland, Odyssey, Winterland, etc. -
Members Only

Moderators: pompeiisneaks, Colossal

User avatar
bcmatt
Posts: 665
Joined: Wed Jul 25, 2007 9:35 pm
Location: Canada

Re: EL34 YGL3 -> 6L6 SSS

Post by bcmatt »

Settled on where I would mount the choke and reverb transformer.
You do not have the required permissions to view the files attached to this post.
User avatar
bcmatt
Posts: 665
Joined: Wed Jul 25, 2007 9:35 pm
Location: Canada

Re: EL34 YGL3 -> 6L6 SSS

Post by bcmatt »

So, I've begun settling on how the general layout is going to be, as well as how I needed to alter the layout for the front tubes (V1 and V5).
You do not have the required permissions to view the files attached to this post.
User avatar
martin manning
Posts: 13080
Joined: Sun Jul 06, 2008 12:43 am
Location: 39°06' N 84°30' W

Re: EL34 YGL3 -> 6L6 SSS

Post by martin manning »

Looks like good progress. Looking forward to the power up and play!
bluesfendermanblues
Posts: 1314
Joined: Tue May 22, 2007 12:57 pm
Location: Dumble City, Europe

Re: EL34 YGL3 -> 6L6 SSS

Post by bluesfendermanblues »

Looks good.
Diva or not? - Respect for Mr. D's work....)
User avatar
bcmatt
Posts: 665
Joined: Wed Jul 25, 2007 9:35 pm
Location: Canada

Re: EL34 YGL3 -> 6L6 SSS

Post by bcmatt »

Being a long weekend, I'm hoping I'll finally get this amp to the point of being able to play. I wired up the power section today. The end is finally (almost) in sight!

I'm a little nervous that I may have underestimated the wattage of resisters I need in some places... If anyone notices a resister they think should be bigger, please point it out. Thanks!
You do not have the required permissions to view the files attached to this post.
User avatar
bcmatt
Posts: 665
Joined: Wed Jul 25, 2007 9:35 pm
Location: Canada

Re: EL34 YGL3 -> 6L6 SSS

Post by bcmatt »

Here is yesterday's progress. I got the test of the back tubes wired up. Because I got sent 20 ohm resisters instead of 20 megaohm resisters, I've been using a couple 8.2 M resisters in series. I hope that doesn't throw things off too much.

I'm really hoping I can get this playable today. I'm pretty close to being able to fasten the board down and starting to write the front panel.
You do not have the required permissions to view the files attached to this post.
User avatar
bcmatt
Posts: 665
Joined: Wed Jul 25, 2007 9:35 pm
Location: Canada

Re: EL34 YGL3 -> 6L6 SSS

Post by bcmatt »

Ok, I'm finished wiring/building... or so I thought.
I put in the tubes and put her back in her cab/cradle. A really dull glow with a 300W bulb in my new limiter that I just built when she is on Standby. Starts getting bright and making bad noise when I flip it on. I'm going to swap the OT Primaries and try again...
You do not have the required permissions to view the files attached to this post.
User avatar
martin manning
Posts: 13080
Joined: Sun Jul 06, 2008 12:43 am
Location: 39°06' N 84°30' W

Re: EL34 YGL3 -> 6L6 SSS

Post by martin manning »

300W is too big to start. I usually use a 60W, which will limit current to 500 mA. Also, start with no tubes in to make sure you don't have any direct shorts. Check voltages to see if they are reasonable on all PS nodes and anode pins.
User avatar
bcmatt
Posts: 665
Joined: Wed Jul 25, 2007 9:35 pm
Location: Canada

Re: EL34 YGL3 -> 6L6 SSS

Post by bcmatt »

This light bulb thing is freaking me out. It doesn't help that it is my first time using it and I don't really know what to expect out of it... or if it even is working properly. With a 60 Watt bulb, basically every one of my amps flips the light on and stays on whether on, or on standby. Now I'm freaking out that all my amps that I've been playing for years about to explode or something.

So, with a 60 Watt bulb, I should be able to check voltages on the amp with no tubes in it, and it shouldn't freak me out that the bulb is glowing away?
User avatar
martin manning
Posts: 13080
Joined: Sun Jul 06, 2008 12:43 am
Location: 39°06' N 84°30' W

Re: EL34 YGL3 -> 6L6 SSS

Post by martin manning »

Typical behavior of light bulb current limiter used with a guitar amplifier:

At power on you will typically see an initial bright glow as the reservoir charges, then a dimming down to a steady glow reflecting just the filament current (If the bulb glows steadily at near full brightness there is a short, and the power should be switched off immediately).

When the standby is switched on, you will see another momentary brightening as the remainder of the filter capacitors charge, followed by a glow that will be somewhat brighter than with the standby off due to additional current flowing through the tubes. Be aware that there can be some variation in this behavior depending upon how the standby is implemented.

In amps without a standby switch, expect to see a bright glow which diminishes to a dim glow after a few seconds, then after another 15 seconds or so an increase in brightness as the tubes come up in temperature and they begin to conduct some current.

If no tubes are installed, the initial and sustained glow will be lessened due to the absence of filament current, and switching from standby to play should have little or no effect on the brightness.

Remember also that with a bulb limiter in, voltages throughout the amp will be lower than normal, the cathodes of the tubes will not be at full operating temperature. MPM 2016.08.01
User avatar
bcmatt
Posts: 665
Joined: Wed Jul 25, 2007 9:35 pm
Location: Canada

Re: EL34 YGL3 -> 6L6 SSS

Post by bcmatt »

Ok, with no tubes.... (I'm embarrassed to admit that with all the amps I've built, I've never tested voltages with no tubes... it's about time I started... but I don't know what to expect)


All the B+ Nodes = +387V

Power Tube Anodes = +388V

Cathode Follower Anodes = +402V

PI Anodes = +382V

V4 = +384V

V3 = +386V

V2 + V1 = +383V
User avatar
martin manning
Posts: 13080
Joined: Sun Jul 06, 2008 12:43 am
Location: 39°06' N 84°30' W

Re: EL34 YGL3 -> 6L6 SSS

Post by martin manning »

Those voltages are with the bulb limiter in? If so, how bright is it?

The nearly constant voltage all the way down the B+ rail looks good, but the voltage seems low. The CF anodes should be ~200V, and the cathodes should be close to -200V.
User avatar
bcmatt
Posts: 665
Joined: Wed Jul 25, 2007 9:35 pm
Location: Canada

Re: EL34 YGL3 -> 6L6 SSS

Post by bcmatt »

Those voltages are with the 60W bulb in and with a consistent dull glow... obviously on, but not nearly close to the 40W bulb over my head in the ceiling.

So, I guess I wired that extra transformer up wrong in some way for the Cathode follower, if I want half the voltage I am currently getting. I'll take another look at the spec sheet. I thought I wired it up how you drew it... with translating to the diagram that came with it (so that the dots coordinate between the two transformer diagrams)

What about my other preamp/reverb tube anode voltages? They seem really high, don't they? I actually haven't seen any expected voltages for an SSS before the power section. I'm still hunting around for a schematic that shows some.
User avatar
martin manning
Posts: 13080
Joined: Sun Jul 06, 2008 12:43 am
Location: 39°06' N 84°30' W

Re: EL34 YGL3 -> 6L6 SSS

Post by martin manning »

The dull glow is good; no direct shorts.

With no current draw (tubes out) the PT is essentially unloaded so there is a little extra voltage at the rectifier, but then there is no current draw through the dropping resistors or the plate load resistors, and therefore no voltage drop, so you have nearly constant voltage everywhere.
User avatar
bcmatt
Posts: 665
Joined: Wed Jul 25, 2007 9:35 pm
Location: Canada

Re: EL34 YGL3 -> 6L6 SSS

Post by bcmatt »

So, I figured out what I was doing wrong when measuring the CF Voltages. I was using the same chassis bolt to measure them as when I did the other measurements, but they don't have the same ground potential. When I measure with no tubes and no lightbulb limiter, I do get + 199V on the anodes and -218V on the cathodes of the CF, as long as I measure against the centre tap/ at the negative end of the pair of 220uF caps.

If I measure all three CF Voltages against the Chassis PT Bolt, I get +56(Cathode), +273(CT), +473(Anode)... but they move around together from moment to moment... mostly floating somewhere around +270V above mains ground. So, is this ok, or is this actually supposed to be tied to the main ground reference somewhere? Could this be what is caused the loud hum back when I prematurely put my tubes in?

Then I get around +455V at all my B+ nodes and the rest of my tube anodes with no light bulb limiter.

I'd like to try an be responsible for once, so what is the proper next step for me to proceed? In the back of my mind I remember that loud hum when I turned on the amp earlier (that swapping OT primaries didn't fix).
Post Reply