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Old 5th April 2008, 01:51 PM   #1
higbone is offline higbone  United States
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Default Silvertone Organ Amp

Hello...I'm a newbie and have lots of questions. I tried reviving an old thread that discussed someone's project of turning an old Silvertone organ amp into a guitar amp - to no avail. I was wondering what ever became of the project, or if anybody else has had experience with this type of mod.

I am just looking for suggestions, unique ideas, problems to watch out for, how effective the tremelo mod could be...etc. By the way, I am not knowledgable on electronics, but have a "tubie" friend that will help along the way.

Thanks in advance for the insights!

higbone
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Old 5th April 2008, 02:44 PM   #2
PRNDL is offline PRNDL  United States
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If the amp works, it may be possible to convert it to a guitar amp with a few simple changes. Sometimes, however, that is a lot more headache than its worth. I've done several of these and know first hand.

Perhaps the best way is to find a well known amp (i.e. Fender) that uses the same tubes and controls, and then rebuild the amp with a circuit board from the new amp. You'll end up with a really cool amp.

What tubes are in your organ amp?
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Old 6th April 2008, 01:24 PM   #3
higbone is offline higbone  United States
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Hi...thanks for your reply.

The tube set-up is 12DW7, 12AX7A, 6V6GT, 5Y3GT. From what I am told...it is similar to a Fender Vibrochamp. I have grown fond of low wattage tube amps, but I am cheap and don't want to pay top dollar for vintage (Silvertone/Fender, et al) amps. In the long run, I may end up spending a little money on tube service and materials to build a cool, "retro" cabinet - but a married man with little children needs an honest, late-night hobby!

The thread I previously referenced is at the following link, and my organ amp is exactly like the one described in the thread.

Silvertone Organ amp, weird osc section.

All thoughts are welcome!

higbone
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Old 6th April 2008, 01:50 PM   #4
PRNDL is offline PRNDL  United States
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The two basic options are:
- get the amp working as it is
- use the parts to build a VibroChamp

The first step is to assess the quality of the amp to see how much effort it will take to get it working and sounding good for guitar.

The chassis is pretty small, and it looks like it has a fixed vibrato. You may want to consider making it into a Champ, which is an extremely simple circuit. You'd be removing parts, which will make it a lot easier to work on.

Have you plugged it in to see if it works?
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Old 6th April 2008, 03:58 PM   #5
higbone is offline higbone  United States
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The tubes do not light up...they may have been damaged during shipment. The seller indicated the organ worked prior to removing the amp, but you never know what's going to happen during shipping - even though it appeared to be packed well.
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Old 6th April 2008, 04:21 PM   #6
PRNDL is offline PRNDL  United States
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The first steps would be to check the fuse and measure voltages.

BTW
Where are you in Florida? (I'm in Naples)
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Old 6th April 2008, 08:57 PM   #7
higbone is offline higbone  United States
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I am in Tallahassee. I checked out your Web page...really cool stuff! I am very interested in learning more about amp building, but for now rely on a couple guys at a shop called "Class A Electronics". They build custom amps under the name "Diabolic" amps and do repair work for the Tallahassee area. I'll have them check the amp out and give me an estimate.

How would you recommend getting my feet wet in learning about electrical wiring and tube amp building?

You can check out some of my copies of old blues songs at the myspace page if you like...

http://profile.myspace.com/index.cfm...endid=90288847

higbone
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Old 6th April 2008, 10:54 PM   #8
PRNDL is offline PRNDL  United States
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Quote:
How would you recommend getting my feet wet in learning about electrical wiring and tube amp building?
You're well on the way with the Silvertone.

The simplest way is to start with a well known amp, such as the Champ or VibroChamp. Both are available in kit form.
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Old 11th April 2008, 03:43 AM   #9
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hey I have one of those! I turned it into a champ-like clone.


For a test bed amp its kind of an ugly duckling, but works great. I would sugguest gutting it except for the heater wiring and rewire it as an AX84 P1 (using a 6v6 instead of an EL84, just leave the cathode resistor there and add a 47uf cap across it.)

I messed a little with the tremelo, which was fixed by replacing the bad caps in that section, but as there was no way to adjust the speed I just removed it. I don't use trem anyways.

The power transformer is nice and puts out just the right voltage for a variety of 5 watt SE amps, and the output tranny is larger than your average 5 watt amp too. I will take pics of the amp tomarrow for ya if you want

I think that the chassis you have would be cool to build into a head because of its size. I used a new hammond 8x4x2 chassis for my amp because it was going into a combo. The organ came with an oxford 8" speaker in it which sounds great!

Are your tubes marked silvertone? If so, that 6v6 is either made by sylvania or by RCA, I don't think westinghouse actually made a 6v6. The other tubes are made by westinghouse and sound very good. 5y3 is a sylvania. This was all obtained by looking at the EIA codes on the tubes, as silvertone obviously never made tubes.

To get it up and running, make sure your wires are all there. Someone may have cut off the tremelo pot that was mounted on the front of the organ , that had the power switch on it. There is no fuse on this amp btw, and tubes generally are hard to beat up if their packed well. If they are not lighting up, I can almost garuntee someone cut the power line running to that pot on the front panel, as it takes a lot of work to tear the organ apart to get to the switch.
http://getchellaudio.googlepages.com/myroom001.JPG See where the twisted white and black wires connect on the far right side of the chassis near the power line? If those are cut anywhere it won't turn on. Short those together and it should turn on .
If you could take a high res photo of the underside of the chassis so we can see what the current state of it is.
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Old 11th April 2008, 06:28 PM   #10
m6tt is offline m6tt  United States
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I would note that most organ amps do not light up when simply plugged in. Somewhere near where the powercord comes in, and near the fuse but before the transformer you will generally find a break in the wiring connected to an amphenol or plastic jack which would have run to the main power switch on the organ. You'll probably need to jumper this or add your own switch. I wouldn't necessarily gut it unless the circuit is uninteresting. Some old non-guitar amps had different design philosophies, and they can have a very unique tone. If it's going to be HIFI, you'd probably be best gutting it, but for a guitar amp you might wanna keep it as is. The tremolo can be modified for adjustability by replacing on of the resistors (generally 1-3Meg) in the anode-grid oscillator cap loop with a variable resistor. Make sure it's one between two caps, so there's no DC. It helps to look at other tremolo oscillators. That 12dw7 will make a better drive stage & cathodyne PI than any AX7, use the high gain half to drive the other half (the low gain side will be the split load/ cathodyne pi). Much beefier and reliable in this service than 12ax7s.
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