Everything You Ever Wanted to Know: Pictures & Diagrams

[ayan]

The time has finally come for the sharing of over a hundred pictures of an amp I had the pleasure to thoroughly test drive yesterday. The photographs provide enough detail to draw a complete schematic of the amp, especially considering that among the shots are a few of wiring diagrams with component connections, values, etc. The hand-drawn diagrams and the opportunity for me to take these pictures are courtesy of my good friend Billy, who insisted that this information be shared with all amp enthusiasts without restrictions. Billy would post this himself, but he bid farewell to the Internet last year and claims he won't be coming back, indicating he now feels "liberated."

These are probably the only things that are not noted on the diagrams and that cannot be made out from the pictures:

1. 500pf cap bypassing V1B's grid stopper.
2. The "Level" pot is 250K, and although the taper is not shown on the notes, it acts like it's linear since the amps gets very gainy very soon in overdrive mode.
3. The pre OD network is simply a 220K resistor in series with a 500K trimmer. There are some pictures of the trimmer removed from the board, and although labeled 500K, you can see that it actually measures just shy of 350K. It was set at approximately 100K to ground, and it appears as though it may have been taken apart and put back together. Billy and I wondered if maybe the builder had determined he needed that custom value and went through the hassle of taking apart the pot and shaving off a portion the carbon trace? We probably will never know.
4. B+ is 440VDC on the 6L6 plates, which seems low. The remaining plate voltages are: V1A and V1B approximately 190VDC each; V2A and V2B 10 volts higher; on the order of 280VDC for the non-feedback side of the phase inverter plate, and about 10 volts higher for the feedback side.
5. Other than the Dale plate load resistors for V1 and V2 and the precision metal films for their respective cathodes, all other resistors used seem to be carbon film.
6. The only stranded wire used seems to be for the filaments, the rest is solid core and looks like 20 AWG, high quality PVC (not teflon).

A couple of comments on the amp: it was purchased in 1984 and was modified by the builder in 1988 to bring it to Skyliner specifications. Some of the electrolytic caps are starting to bloat and will therefore be replaced, and I suspect the voltages will go up noticeably after the recap job... I will be curious to hear the amp again then to see how the sound has changes. As of now, only the caps on the bias and relay boards have been replaced, which can be seen in the pictures. The chassis is made of 1/8" aluminum, built very solidly, is heavy and uses weld nuts to mount to the cabinet.

How does the amp sound? Absolutely terrific, and I think part of the reason is the old caps, otherwise I don't see how the thing could be so deliciously gainy. You can live on the clean channel alone as it sustains very nicely, and adding the PAB to it results in a wonderful singing tone with a tendency to feedback on just about any note at will. The overdrive channel adds more of the same. Even though I would have thought the amp should be bottom heavy based upon its design (Skyliner EQ and larger than usual cathode bypass caps), the amp sounds perfectly balanced. The best of its kind I've ever heard, absolutely no traces of harshness or otherwise "ugly" breakup to be found.

A few notes:

1. All the information available about the amp is either already stated above or shown on the website below. So that's really it, folks. If you fee like you have any questions, please re-read the information above or have a close second look at the pictures.
2. I prefer to not be sent private messages, please. I don't want to come across as being rude by not replying to them, but at the same time, I don't have a lot of free time and I think that the purpose of a forum is to post information publicly so that many can benefit form the questions of one, a few, or many as the case may be. If there is something I have been asked to not say, I will not repeat it either on the forum or via PMs, so PMs don't really buy anything IMHO.
3. The pictures belong to me and you're free to download them and use them for your own edification. Please do not link the pictures themselves, at their current location, to posts either here or on other bulletin boards. If you want to copy them and host them at another location, that's your prerogative.
4. Finally, the pictures can be found at: http://s55.photobucket.com/albums/g159/amp_guy/ods_amp/. The password to enter the site is "ods_amp" and once you get in, click on the ods_amp link to get to them.

Last but not least, enjoy this! I hope you learn from it, and if you ever run into Billy (if you don't know him, I suppose it doesn't really matter) thank him for his generosity. If you're of the mindset that it's not in your best interest to share information you have, that you have acquired yourself and that could make other people happy, that's cool. However, perhaps then you should refrain from having a look at these pictures as they're coming from a very different place.

Cheers,

Gil

[oldmacman]

THANK YOU!!!!!!!!!!

[Normster]

Gil, I don't even know what to say. Thank you, and thank Billy very much for being so generous with your time and information. As a visual learner, I'll be studying these pics for a long time to come.

[Chad]

A MILLION THANK'S to Billy and also you Gil for such great info. You both are generous many times over!! Thank's again, Chad

[pedro]

Yes indeed, thanks you very much Gil

Pedro

[Noel Grassy]

Thanks Gil & thanks Bill. These should provide many hours of eyestrain from staring at my monitor. If anyone's interested I'm having fabric printed up with these layout pics and having it made into pajamas and possibly a smoking jacket, just joking. Now I'll raise a glass to or friend HAD in honor of his exceptional creativity. I'll bet chimeboss pooped himself when he got a glimpse of these! I'll cherish these forever!

[Robert]

Thank you so very much Gil and Billy!!! You are most generous.

[stompjunkie]

Thank you thank you thank you.....I cannot say it enough.....

[paddy]

Unbelievable effort guys!
Thankyou sooooo much.
I'm running riot with the soldering iron right now.changed the treble cap
to .002uF as per the layout and like what i hear.
My eyes aint what they once were,can anyone confirm that CL1,CL2,OD1
and OD2 all have 100k plate resistors?

Thanks Gil and Billy

Absolutely MAGNIFICENT!

[bluefireamps]

Wow! That is awesome! Thanks much to you, Gil and Billy. I can't imagine how difficult it was to de-goop that thing. Were you able to measure the resistor value for the feedback loop on the second stage?
Dave

[mlp-mx6]

Gil,

SERIOUS thanks!

Michael

[Bob-I]

You da MAN Gil!!!

[skyboltone]

Yes indeed, thanks from me too. A couple of notes; That's not the build quality I had expected. It has all the highest quality caps and resistors but the tube sockets are nothing to write home about nor are most of the mechancal components. It's no surprise I think, that there are mostly carbon film resistor's. Unless I'm badly mistaken metal films were not easy to come by in the eightys. At least in ratings over 1/4 watt. The foot switch/relay power supply kind of leaves one a little wistfull doesn't it?

In '84 there were lots of surplus sources for military phenolic and ceramic tube sockets. Especially in the south bay area. I know, I was there rebuilding Dynaco stuff. The hardest things to get in those days were the high voltage caps and OUTPUT TRANSFORMERS. That one looks like it was used when the builder put it in there.

With all the goop scraped off the boards and the deep scratches on the power transformer, this old boy has been on somebody's bench a time or two.

I wonder who bought it new?

My dumble reworked Rhodes from the early '70s was all point to point with the filter caps above board, and below board components strung between solder strips. It had the interior look of a piece of Collins military gear. Very sturdy, right angles to all leads, real workmanship. Interesting too is the two 20 meg feed back resistors really look chunky. That's the tweeking bit. He wasn't happy with 20 so cobbed the other resistor in there. Was he in a hurry? I can imagine that this was at his peak production. The Guitar Player article about to come out. Lots of customers. Interesting. I'm going to go back through some of the other pictures and do some comparisons.

All this is more or less worthless speculation and wonderment. YMMV.

Dan

[Chris G]

Hi All,
Is anybody else haveing problems loging in? I enter the password and get sent to my daughters account????? This is how I'm entering the password
ods_amp......is this correct?
Thank-you
Chris

[Noel Grassy]

Hi All,
Is anybody else haveing problems loging in? I enter the password and get sent to my daughters account????? This is how I'm entering the password
ods_amp......is this correct?
Thank-you
Chris

tes. That's what did it for me