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Author Topic: Solid State Airline, Valco, Montgomery Ward, Schematic  (Read 1853 times)

galaxiex

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Solid State Airline, Valco, Montgomery Ward, Schematic
« on: December 25, 2016, 07:02:19 PM »

Finally got this one done.  :o

This thing was a basket case when I got it.
Cracked circuit board and broken copper traces.
4 transistors NFG. Q4,5,6,7 all measured open across B>E B>C
One burnt resistor (R15) , so bad I could not read the color bands.

Interesting Power amp section... Very similar to the Sears 40XL.
Because of the similarity, I used the value from the Sears amp (R17, 68R) for this amp (R15).
Seems to work ok.

This amp is waaaay louder than the Sears amp!
Even going to the same speaker.

No mods to this other than to use 2200uf filter caps for C31, C32, and the mentioned R15.
I did replace ALL other electro caps with same value, and all ceramics with mylar "greenies", with the exception of the 4 trem osc "tootsie roll" 470nf caps.
Those I left alone as they work ok, and the trem speed is fine. Maybe not quite as slow as I like, but ok.

Other things... Added 3 wire grounded AC cord, removed the "death cap" and disconnected the line reverse switch.
The original Q7 markings are unreadable except for "RCA". Installed a Motorola 2N297A in its place.

It sounds surprisingly pretty good! Loud with nice "transistor breakup" above 6 or 7 on the volume.
Could gig with it thru a decent cab.

Q5,6,7 all get very hot, so much so that you cannot touch them for long when the amp has been on at full vol for a few min.
Also R16,17 get hot too.

I rewired everything and made a harness and connectors so it's easy to remove the board to work on it.
The vintage reverb tank is fine and functional.  8)

Here's the schematic and layout,
and the Sears amp schem for reference.

Edit; I didn't have a 2N3711 for Q4 so I used a metal can 2N2222. works ok.
« Last Edit: December 27, 2016, 12:01:30 PM by galaxiex »
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phatt

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Re: Solid State Airline, Valco, Montgomery Ward, Schematic
« Reply #1 on: December 27, 2016, 06:35:54 AM »

Hey nice work,, that takes a lot of time to backtrack all that. :tu:

BTW What's J4 socket on the airline schematic?
I assume it's a mute for the reverb but I can't see how it mutes the signal? ???
Phil.
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galaxiex

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Re: Solid State Airline, Valco, Montgomery Ward, Schematic
« Reply #2 on: December 27, 2016, 10:28:50 AM »

Thanks phatt!  :) Yes a lot of work on this one.

J4 is (or seems to be) the reverb foot switch mute.

At least it's mounted on the front panel as such....

To be honest, I never tried it.  :-[

I thought the circuitry there was a bit strange....

I'm curious now.... I'll have to try it.
Will report...
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galaxiex

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Re: Solid State Airline, Valco, Montgomery Ward, Schematic
« Reply #3 on: December 27, 2016, 12:44:59 PM »

Well the reverb F/S J4 does indeed mute the Reverb....

Seems to work exactly like you would expect.  :)

The only anomaly is, if you thump the amp when in reverb mute,
there is a faint clanging of reverb springs coming thru the speaker(s).

Strumming the guitar, there is no reverb effect when in reverb mute.

Weird... but it works.

The reverb sound is pretty nice.
Not too obvious, and of course, not as lush as a Fender Twin, but usable.
« Last Edit: December 27, 2016, 03:50:07 PM by galaxiex »
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phatt

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Re: Solid State Airline, Valco, Montgomery Ward, Schematic
« Reply #4 on: December 29, 2016, 05:28:25 AM »

Well obviously is works so I guess some things will always be above my ability to decipher. xP
 I'm too old to go back to school now so I'll just play my guitar and learn to sing and play some more songs.

BTW,, How did you get that board layout? Is that some kind of special software?
thanks Phil.
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galaxiex

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Re: Solid State Airline, Valco, Montgomery Ward, Schematic
« Reply #5 on: December 29, 2016, 08:01:57 PM »

Ha ha! Me too!   xP  :)

The board layout was done with Paint.net

I pull the board from the amp and scan the copper side.
Then the tracing and editing begins...
Several hours in this one, spread over a week or 2.
No way I could do it in one sitting.
My eyes can't stare at a computer monitor for that long....  :o

TBH this was the toughest one I've traced so far.

Edit; now that I have the technique/procedure down, any future boards should go quicker.
I kinda had to learn Paint.net as I was doing this.  ::)
« Last Edit: December 29, 2016, 08:05:33 PM by galaxiex »
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galaxiex

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Re: Solid State Airline, Valco, Montgomery Ward, Schematic
« Reply #6 on: January 13, 2017, 08:34:46 PM »

Well..... I just got the Jack Darr book "Electric Guitar Amplifier Handbook" Fourth Edition, Second Printing, 2006

And what do I find on page 153....

A schematic for the Wards Airline Model GIM-9103A that is almost identical to the schematic I show in this thread!  :o

Even right down to the voltages I measured, they are almost identical!

Too funny!  :lmao:

Some differences in transistor part numbers, but some of mine had "house" numbers and some were unreadable.

Not sure if it would be a copyright or other infringement to scan and post the schem from the book....
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phatt

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Re: Solid State Airline, Valco, Montgomery Ward, Schematic
« Reply #7 on: January 14, 2017, 08:22:59 AM »

I think copyright is out of date on that book so I doubt it's a problem. :tu:
Phil.
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galaxiex

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Re: Solid State Airline, Valco, Montgomery Ward, Schematic
« Reply #8 on: January 14, 2017, 10:02:55 AM »

Ha ha, Thanks phatt, ya probably out of date.  :)

Ok, so here's the schem from the book for reference.

Sorry about the lousy scan,
its tough to get the book to lay flat, and I didn't want to tear the page out.

So, a couple of things I notice....

In the JD schem, R28 is 560 ohms. (emitter of Q4)
Thats the one that was burnt FUBAR in my amp.

In the schem I drew, the corresponding resistor is R15,
I copied the value from the Sears amp, R15 68 ohms.

Also JD schem R22 560R, my schem R13 330R. (emitter of Q3)

Anything significant about these values?
Thanks!
« Last Edit: January 14, 2017, 10:27:33 AM by galaxiex »
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joecool85

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Re: Solid State Airline, Valco, Montgomery Ward, Schematic
« Reply #9 on: January 14, 2017, 07:21:18 PM »

Well the reverb F/S J4 does indeed mute the Reverb....

Seems to work exactly like you would expect.  :)

The only anomaly is, if you thump the amp when in reverb mute,
there is a faint clanging of reverb springs coming thru the speaker(s).

Strumming the guitar, there is no reverb effect when in reverb mute.

Weird... but it works.

The reverb sound is pretty nice.
Not too obvious, and of course, not as lush as a Fender Twin, but usable.

I don't think it is an anomaly.  I believe that the reverb mute only kills the audio path going into the reverb circuit, not the path coming out.  Therefore there is no guitar sound getting the reverb effect when muted, but you can still hear the reverb springs.
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galaxiex

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Re: Solid State Airline, Valco, Montgomery Ward, Schematic
« Reply #10 on: January 14, 2017, 08:36:32 PM »

LOL  :)

Ya, anomaly was maybe not the best choice to describe this,
but in most other amps this does not occur.  ;)

So to me, its an anomaly... LOL  :cheesy:
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monfi

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Re: Solid State Airline, Valco, Montgomery Ward, Schematic
« Reply #11 on: July 26, 2017, 09:58:09 AM »

Hello, if i will reply this Airline Valco Amp, what kind of transformer i need(46volt and how much ampere)? and someone had a suggest for replace old transistor(40409/40613 and 2n297A)  that are hard to find and/or too much expensive? tnx in advance
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