Fender deluxe from scratch

[Ernest]

covered in tan naugahyde over the weekend

 

[Default]

It was from a Ampro Movie Projector.

No model# though.

a google search on ampro projector images turns up the specs for a model Stylist 16.
http://www.film-center.com/ampro.html

not the same tubes listed but all the speakers listed are 8 ohm.

Also looks like there is a resistor hanging from the speaker jack. It is there incase someone turns it on without a speacker plugged in. If there still is one, what is the resistance marked on it?

 

[Ernest]

Is there? I only see the big white one attached to Input. I've taken all the pieces out but I'll take a look at the output jack and speaker cable to see if there is a resistor. Not sure If I mentioned that I located someone using the same Ampro Amp http://www.talkbass.com/forum/f15/ampro-2x12-all-vintage-826548/ and he confirms it comes with a 16 ohm speaker as well as a second 15 ohm ouput for a second speaker. He also sent me the label attached to the case.

 

[Default]

Well, there you go!

 

[Ernest]

yeah, I would love to have a cool AlNico Blue or Tone Tubby, but not a lot of money to spend so I'm going to have to start out with a 35w 16ohm ceramic mag Celestion G12 with modified aluminum coil and Hemp cone. It may sound awesome, may sound like a turd. but it was $40

 

[Csquare4]

Ernest -

To find the output impedance that the OT is looking for you can use a low voltage AC-AC Wall wart (I use a 120V/12V AC-to-AC) to determine the turns ratio by connecting to the primary side, measuring voltage coming out of the wallwart, then measuring voltage on the secondary side. The turns ratio is the relative difference between the two voltages.

Then use this to figure out what the tubes are looking for as an output (typically 8-10k ohms for 6V6's in Push-pull). Use the turns ratio to calculate what the output speaker load impedance should be.

Here is a tutorial I found that may help explain it better:
Determining Output Impedance of Unknown Transformer

Hope that helps.
Craig

 

[Ernest]

cool, thanks. I got similar info from Bruce of Mission Amps that helps explain this as well.

put a small AC voltage into the secondary winding... measure across the full primary winding ... divide the small number into the big number... take that new number and square it...
Then multiply that sq'd number by the speaker load impedance (4 ohm, 8ohm etc) and you have the primary impedance.
EX:
6vac into the secondary wires... measure the primary wires at say 180vac. Oh and that will knock you on your ass.
180v divided by 6v = 30 a 30:1 voltage ratio
30^2 or 30x30 = 900
900 x 8 ohm speaker = 7200 ohms
900 x 4 ohm speaker = 3600 ohms

etc

 

[Ernest]

This chassis is kickin my ass. blew a hole through it with a welder so I'm going to have to make some sides and pop rivet them instead. spot welder would be nice.
and the holes for tube sockets, got to be a better way then drilling.

 

[Ernest]

I'm using the Hoffman schematic instead of the original layout just to be different. and also using newer Caps instead of paper/wax, they have a feature on their website that adds the entire kit to your shopping cart and you can pick and choose what to remove from there. I found this to be so helpful I just bought all my stuff from Hoffman except for resistors which I got from tubedepot.

Unfortunately I found some discrepancies with Hoffmans parts list and the two schematics they have up. Not sure if this would have been resolved if I just added my resistors from Hoffman to the cart as well.

unsure about the first 250ohm resistor on the board. Parts list 5w but it's shown as 10w on the "newer schematic" not sure if this will be an issue or not.

also unsure of what they are calling 1.5k/22 on their schematic....I have these noted as green stars....I don't even see those on the parts list? Is that the same as what they are calling a 22/50v cap on their parts list?

Parts list

schematic #1

schematic #2

 

[Default]

Are these the cathode resistors from the first 12ax7? If they are, it's the 1.5k resistor and a 22mfd/25-50 volt electrolytic cap. Don't worry about the wattage of the 250 ohm resistor. 5 watt is good enough, and 10 watt is fine.

 

[Csquare4]

Are these the cathode resistors from the first 12ax7? If they are, it's the 1.5k resistor and a 22mfd/25-50 volt electrolytic cap. Don't worry about the wattage of the 250 ohm resistor. 5 watt is good enough, and 10 watt is fine.

Yes it looks like the layout diagram is saying 1.5k||22 which is the V1A, V1B and V2A cathode resistors and caps - they are in parallel.

For the tube socket holes try these...

Or for a bit more coin try these.

A lot of folks use step bits for the 9-pin holes, but they generally won't work for the Octals.

Craig

 

[Ernest]

Oh, I see, the two are just put together!

thanks

 

[coastie99]

This chassis is kickin my me.
Got to be a better way then drilling.

There is. Greenlee Hole Punch .............. http://www.mygreenlee.com/GreenleeDotCo ... mber=02408

Expensive new, but there are usually many for sale on Ebay at any time. Using one of these for the first time, after drilling / filing / hacking will put a big wide grin on your face !

 

[Ernest]

laser etched face plate.

 

[Ernest]

tube sockets in.

 

[Ernest]

getting close....

 

[Ernest]

success....

 

[Default]

Unless we get sound clips, it never happened.

 

[Ernest]

true, :lol: just finished the last solder only a couple hours ago. too late in the evening to get personal with it but it breaks up so nice through this cheap guitar I got plugged into it. It will still be awhile before I get back to the Guild project so I'm stuck with a very special amp and a cheap plywood les paul. I'll see what I can post in a couple days to let you hear it. :wink:

 

[Ernest]

no progress on the M-80 but I said I would put up a vid

5e3 Clone Hoffman