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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Sun Jan 15, 2017 11:11 pm
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Be very interested in that Valco amp. Esp, restoration process. I just missed out on a 1936 Gibson EH-150 amp, on EBay. Things are getting more and more $$$ these days.


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Mon Jan 16, 2017 11:50 am
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Location: Coastal Bend, Tx.
I got lucky w/ a min bid and no body bidding against me.
What I've been able to pick up since that post is that it was made in 1951, the ref to the 1948 Supro is the closest schematic I could find. I still don't know the model, but its not a "Chicago 51" and it appears to have a mod done already. Someone added a control to the top of the cabinet behind the handle, probably a volume or tone control. Unfortunately the leather handle is also missing but the hardware is there. It looks to be in otherwise very good shape. I should have it around the 26th.


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Mon Jan 16, 2017 12:16 pm
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Very cool, I am looking forward to pictures and the go through
Good luck
mud


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Mon Jan 16, 2017 6:38 pm
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Post some pics of the little beastie once it arrives.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Mon Jan 16, 2017 7:57 pm
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There is another one on ebay tagged as a Supro for a couple hundred last I saw today. It is the same model and year as mine except for the skin of the cabinet and the speaker code.
http://www.ebay.com/itm/Vintage-Valco-Supro-Amp-untested-/272519957295?hash=item3f73748b2f:g:pVgAAOSwo4pYd~o3
I'll post more pics as soon as I have it.


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Tue Jan 24, 2017 1:30 pm
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To my surprise it arrived today, wasn't supposed to be here until Wednesday.
No pics yet, gotta get a full charge on the battery. A little later for sure though.

From what I can tell from just an external inspection, its in very good condition.
The tubes are all date matched RCA 0-35 and I'll assume they are original. The sockets are tube specific marked.
The serial number is X7xx and dates it to 1951.
The chassis is relatively clean and paint covered w/ a few small chips.
The output transformer is riveted to the speaker.
All the fasteners appear original.
The cabinet is in remarkably good condition, no water stains. Minor warping likely caused by heat(one rubber foot glide doesn't make contact)
The spare fuse packet and fuse is present but paper is torn/brittle. The 2amp fuse is undamaged.
The extra control pot is still a little confusing to me and has a .1uf-500v cap in series w/ the middle tab of the pot. The pot from what I can see has 4 tabs?, can't read any markings yet.
Original 2 prong Belton power cord.
Discoloration of the Tolex is most likely from cigarette smoke, small scuffs here and there, aged smooth texture.
Weighs approximately 13lbs. my scale max is 11,doh.
13 1/4" wide, 13" tall, 7" deep

Haven't opened the chassis yet.


Last edited by sfceric64 on Tue Jan 24, 2017 4:33 pm, edited 1 time in total.

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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Tue Jan 24, 2017 4:28 pm
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Edited due to photobucket...Link to 1951 National
http://forums.fender.com/viewtopic.php?f=12&t=105210


Last edited by sfceric64 on Wed Jul 19, 2017 1:55 pm, edited 1 time in total.

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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Tue Jan 24, 2017 9:14 pm
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Got it cleaned up a bit and prepped for a new 3 prong.
Took parts inventory and will measure resistor values, install new power cord, order new electrolytics on Wed.

Anybody have ideas on what the mod pot is? Tone control, I'm thinking.
What is the fourth lug on that pot?

Thanks


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Tue Jan 24, 2017 11:20 pm
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sfceric64 wrote:
Anybody have ideas on what the mod pot is? Tone control, I'm thinking.


That was my initial thought as well, given that it's wired in conjunction with that axial cap to create an adjustable RC network.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Wed Jan 25, 2017 3:08 am
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Finally found the model, National Comet 1610 and the actual schematic#(510-6) Dtd 1947. The schematic is nearly identical to the Supro Comet Dtd 1948. I'll post a link later.
http://www.valcoamp.com/download/valco_amps/valco_1610_1625.pdf

Removed the death cap
Installed 3 prong
Tested all the resistors- 1 out of spec (20% over) 1 near out of spec
Ordered electrolytic's and replacement resistors


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Thu Jan 26, 2017 10:17 am
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Quote:
What is the fourth lug on that pot?

Well it turns out that the pot is configured to operate at 1Meg using the three standard lugs or by using the fourth lug(opposite side) it operates at 500K. Never seen one of these before.
I'm going to leave this in place but out of the circuit for the first fire.

Also got the replacement handle ordered yesterday and the original hardware off.
Whatever jig/tool they used to separate and bend the tangs on those old handle clasps sure is impressive workmanship and surely designed to never be removed. Much leverage required.

Anybody familiar with Philmore output trannies?
I picked up a 4ohm universal replacement model on ebay, NOS w/ original box and wiring instructions. The size seemed right for a Champ style amp.


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Sat Jan 28, 2017 2:40 am
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sfceric64 wrote:
Anybody familiar with Philmore output trannies?
I picked up a 4ohm universal replacement model on ebay, NOS w/ original box and wiring instructions. The size seemed right for a Champ style amp.


A more critical spec is the primary impedance -- a pair of 6V6GT's typically measure around 8KΩ plate-to-plate in class AB operation.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Sat Jan 28, 2017 6:59 am
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Looks like amp may have output stage in Class "A" push-pull. Impedance maybe lower for those 6V6GT. Closer to 5-6k-ohms. Prolly not important.

Idle bias dissipation will be much higher than Class AB. Around 70-75% of 6V6GT rated max.


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Sat Jan 28, 2017 10:34 am
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BMW2002Ti wrote:
Looks like amp may have output stage in Class "A" push-pull. Impedance maybe lower for those 6V6GT. Closer to 5-6k-ohms. Prolly not important.

Idle bias dissipation will be much higher than Class AB. Around 70-75% of 6V6GT rated max.


Good call, Steve. I should've examined that schematic more closely.

:oops:

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Trying to buy my 1st Vintage Amp
Posted: Sat Jan 28, 2017 2:56 pm
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Both are right on as usual, that's why I picked up the O/T. Its spec sheet shows wiring for class A@5k, AB@10k and Parallel@2.5k w/ 6v6.
I don't think there is a problem w/ the original, but thought it'd make a good spare to have around.

Supposedly this amp operates like the Champ, w/ a little more frequency range/kick from the 2nd 6v6.

I should have the new electrolytic/resistors next week. Went w/ F&T's 30/10/10@500 and Sprague 25x25.
The resistors that are outta spec will be replaced w/ C-film or CC and there W rate doubled.

Any opinion/issues on amps w/o a chassis soldered ground?
This uses a solid wire from the Elec. Caps to each tube socket/pot/component connection. Seems ok as I measured for continuity and ohm's to everything as I did with the Deluxe. The C/T's from the power tranny included and my ground from the 3 prong are soldered to the sockets ground tabs.

Also, I was thinking of just snipping the leads from the old twist-lock caps and covering the exposed surface w/ epoxy to preserve and protect the chassis. The original primary cap has a visible small leak at the lead.


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