New guy intro, looking for scavenged parts for guitar amp

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New guy intro, looking for scavenged parts for guitar amp

Postby ddr » Tue Dec 15, 2009 6:28 pm

Hi Folks,
I am new here. I have not touched a tube since the 70's. Back then I used to collect old tube CB radios. I just picked up an electric guitar and would like to learn by building a tube amp.

It looks to me that parts are fairly cheap except for transformers. I live in Chicago, so there are lots of old businesses around here; I am thinking of going hunting around for an old TV repair shop that might sell/give me some old carcasses. Can anyone suggest particular models of TVs or radios (or other devices) that I should look for? I saw in one of the announcements for a board that a Dynaco SCA-35 is a good donor for parts.

Is this a good idea (scavenging), or is it more trouble than it is worth?

Thanks for pointers, and I look forward to "talking" with you.

Dan
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Re: New guy intro, looking for scavenged parts for guitar am

Postby ChrisAlbertson » Tue Dec 15, 2009 6:36 pm

Yes the transformers are the most expensive part of an amp. Using salvage is good because it teaches you how to design amps around the parts that you can find.

But. I'd suggest as your first amp following a well known and tested design. The problem is in crafting the sound and predicting how the distortion products will sound and the balance of highs and lows. It's an art. To gain the experience take baby steps by changing the design of each amp you build starting from a known working design.

Start with low poered amps. 5W or maybe later up to 20W. The parts are cheaper and you don't need so much power -- beginners will not be playing in sports stadiums
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Postby dhuebert » Wed Dec 16, 2009 8:46 am

I have to agree. I've said it again and again; the Fender 5E1 is a great starter project. It's simple, cheap to build with new parts and works like hell. One of the easiest and most fun amps I've built. The best part is it's easy to get it quiet, which for me is the biggest challenge of guitar amp building.

Don
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Postby ddr » Wed Dec 16, 2009 2:45 pm

Thanks both of you for the advice. I have ordered the book "Building vacuum tube guitar and bass amp, Volume 1" from Antique Electronics. Between now and the time it comes I will do some hunting for parts.

This book includes instructions for a Champ AA764, which from my read of the schematics is a 5E1 (or probably a 5F1) with bass and treble adjustments. I had been looking at the 5E1 schematic already based on posts read here and on other boards. So, I think I will follow along with the build instructions in the book, but use the 5E1 schematic.

Thanks again, I will post more as I learn.
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Postby nyazzip » Thu Dec 17, 2009 2:36 am

as far as "scavenging" parts, i'd say eBay is the way to go...you can type in your distance/cost/model/etc parameters, and there are your results.
i have gotten at least 3 carcasses which supplied me with enough carrion for: an 18 watt style PP, a 6V6 PP, and another EL84 PP.
of course i am too dumb to have done anything constructive yet, but stay posted. none of these cost me more than 25 bucks each. 25 isn't bad for a tranny set, chassis, and tubes in my book, but we all have different definitions of "scavenging" i suppose...
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Postby ddr » Thu Dec 17, 2009 8:16 am

Hi neighbor,
Thanks for the tip. That is a great idea. I have been looking on Craig's List, but not Ebay. I will take a look there also.
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Postby jonnyeye » Fri Dec 18, 2009 5:46 pm

Here's an amp I built on a chassis (from a Silvertone organ) I got from eBay - I paid about $15 two years ago, but this price might be hard to match today. The transformers are both Woodward-Schumacher (the same kind Fender used) and it came with 6GK6s (which I have replaced with 6P15P-EVs) and phenolic sockets (most of which I've replaced with ceramics). It's based on the 18W Marshall, but with an EF86 preamp and a one knob tone control (like Big Muff). It's kinda ugly, but functional (the only thing is the screens are dissipating 1.6W at idle (!), which is above spec for the 6P15P-EV (!!), so I need to install some dropping resistors - it works fine with 6BQ5s, however) and the ugliness will be covered up when I get around to building a case and faceplate for it.

Image

(further notes: the RCA inputs are the original inputs from the organ circuitry, but are too difficult to remove, so they stay. The extra socket is for experimenting with other pentode input tubes in the future.)
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Postby ddr » Fri Dec 18, 2009 6:52 pm

I am on my way :)

I ordered the "Tweed Champ Style Small Parts Kit (Caps, Resistors, Screws, Etc.)", an output transformer, and a couple of other small parts from mojotone.com tonight. I was trying to buy the caps etc. through an electronics house, but I could not bear to pay the premium prices associated with buying less than ten of each component. I will source the power transformer, speaker, and tubes locally.

This should be fun :)

Thanks again folks,
Dan
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Postby EWBrown » Fri Dec 18, 2009 7:38 pm

Since you are in Chicagoland, maybe you can drop in over at Triode Electronics. They have just about everything "Fender" over there.

Then there's Ned Carlson's "Tube Zone" which spun off from Triode.

Re the "Gerauschklingen" amplifier:

6P15P-EVs (or SV83s) are kinda "squirrely" with thir screen grids, the manufacturer's recommendation is to keep them around 200VDC. Of course, I never follow the recommendations, and built up my "super-Zen-clone" SE using 6P15P-EVs with around 380V B+ (at way too much cathode current), and with the screens tied to the plates through a 1K, 2W resistor, and left the G3s just floating in the breeze (as did Decware), and it works just fine for me, though I haven't put a large amount of hard hours on it. It should be easy to revert to 6P14P-EV's they can take a licking and keep on ticking... They are more like 7189s than EL84s.

/ed B
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Postby ddr » Fri Dec 18, 2009 8:19 pm

[quote="EWBrown"]Since you are in Chicagoland, maybe you can drop in over at Triode Electronics. They have just about everything "Fender" over there.

I tried going to triode yesterday (they are about 8 blocks from me) but they were closed. I emailed them to find out when they would be open, but no luck. I was dying to get in there, the place is jammed to the ceiling with carcasses :)
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Postby nyazzip » Sat Dec 19, 2009 2:52 am

Triode just officially moved to the suburbs(St. Charles); i was down there at the new location last week to pick up an order. i guess the old building on Irving Park is going to be in operation for awhile...
i've got an "18 watt" turretboard currently on backorder with them. i sure wish there were more "brick and mortar" electronics shops to pop into when you need something, or just for browsing. Radio Shack is absolutely useless when it comes to vintage style audio. a fun store in Chicagoland that sells weird junk is "American Science and Surplus". i was there the other day and they even had a couple of oddball(to me) tubes
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Postby ddr » Wed Dec 30, 2009 9:01 am

I am about ready to get started. The chassis blank arrived yesterday (one of the guys on the ax84 forum bent one for me) and I received the "small parts kit" from mojo on the 24th. I am getting transformers from Weber sometime soon. Tubes I will get from Triode, Jim is meeting me at the old Irving Park store Tuesday as he has some NOS there.

Before I get started (on a 5E1), here are some questions:

1) If I cannot get a NOS 5Y3GT should I use Weber's Copper Cap or a Sovtek (with the higher output voltage of the Sovtek)?

2) Other than the 5E1 schematic "error" on the 2K7 resistor are there any other errors in the schematic?

3) Where should I place the choke on the chassis? Should the choke be as close to the two 8 MFD caps as possible to reduce the length of the leads, or does it matter? Should it be perpendicular to the PT?

4) Where should I place the OT on the chassis? Should it be as far away from the PT as possible, or as close to the speaker jack as possible? Should it be perpendicular to the PT?

5) I had been planning to wire this point to point, but now am thinking of using eyelets to allow me to place the components closer to the chassis wall. Is this the right decision? I have fiberboard and have ordered eyelets from Weber, so I can do either.

Thanks again folks,
Dan
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Postby dhuebert » Wed Dec 30, 2009 12:49 pm

1) Don't worry about NOS 5Y3, they are used very gently on this amp and any good one will do.

2) I looked at the schematic on duncanamps for the 5E1 and didn't see any errors, I built as shown and it worked first try.

3), 4), 5) see the link for photos of how to do it right, This amp is dead quiet.

http://www.diytube.com/phpBB2/viewtopic ... highlight=

6) You didn't ask but... The critical tube in this amp is the 6V6, it can have a major impact on the sound of the amp. My favorite is the black plate RCA 6V6. It makes distortion differently that any of the other tubes I looked at and sounds the best, I thought.

Don
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Postby ddr » Wed Dec 30, 2009 4:33 pm

Thanks Don,
that build looks great. I will build point to point, I think it looks nicer than eyelets.

The reason I am worried about a Sovtek 5y3 is that I have read that the output voltage of the Sovtek is about 60 volts higher than the original.
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Postby EWBrown » Wed Dec 30, 2009 9:56 pm

Apparently the SV83 / 6P15Ps are equivalent to EL83 / 6CK6s, though I have to fully check and verify all of the operating characteristics

At least the base connections appear to be the same

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