Silvertone-ish build

[showsii]

Hello everyone,

I have decided to build a Silvertone 1483 for a friend. I found the schematic and used a layout software that I found here on TAG to draw out a layout. Great software by the way, DIYLC!

This is my first attempt at drawing out a layout straight from a schematic, so I'd really appreciate it if someone could double check my work. Also maybe some tips in the layout design it self. I am just coming out of a Rocket build, (had a few road bumps in workmanship but was resolved and the amp sounds great). My layout is similar to what I am use to seeing here on TAG and a few other Ceriatone amps I have built in the past. I realize that the original 1483 was laid out with no turret board and looks nothing like this. I plan to use a Cap can in the filtering stage, this however is not represented in the layout. (I will redraw it when/if I get some confirmation that the circuit is correct).

I think this will be a fun build, my friend really seems to like these amps. He is going for that nasty Jack White tone. (he is a guitar player by the way)

The thought behind the build is to produce essentially the same amp with out the extra input and controls, different cleaner layout and use quality parts to make a reliable amp. Hopefully it will sound close to the original as well!

I have labeled the Input primitively, my apologies. Also I labeled the expected voltages coming off the OT and going to pins 4 and 6 of the rectifier tube. Also the heaters are not shown on this layout.

Please ask me where there is some confusion in my layout.

Here are some general questions about changes I would want to make from the original schematic.

1) On the filter caps, Could I use one cap can 20-20-20 at 450v instead of the 5-10-20 in the orignal? (I believe I read this somewhere on TAG but just wondering what tonal changes would happen if any?)

2) How do you guys feel about a solid state rectification to reduce the size of the PT thus cost? Or is the 5Y3GT the way to go?

Thanks in advance for the future help, I'm excited to learn more through this build. I learned a ton on my last one.

Ian

[overtone]

Ahoy Ian,
aha, I see you have been bitten!

The cap can you mention is after the first filter cap, so it should have no negative effect on the tube Rectifier. To my mind this is not a huge step-up in cap filtering and should not make too much difference to the feel of the amp. The choice of the first filter cap, after the tube rectifier, should stay inside the value quoted on the tube data sheet. It is usually voltage dependent so you can fudge it but you need to be checking the data sheets of your tubes for their requirements against the voltages being used. While you are there you should check what the tube rectifier wants to have as resistance on the PT.

The whole power supply design is critical if you want to get close to the original sound or feel. Changing to a SS rectifier makes sense to me in a single ended amp, but it in a push-pull you need to consider that the sag can be a major factor of the character of the amp. Then, with the SS option for the same AC voltage, you will have much more B+ so usually a dropping resistor is used and this does a pretty close imitation of the tube rectified power sag.

Have not checked the layout, but if this was mine I would improve the grounding. Do some research on star grounding or "galactic" grounding, that will pay off in keeping the amp from buzzing. This may lead you away from the cap-can towards individual caps for each stage and possibly brining them on the board closer to the stages they serve.
Did you take some marker pens and trace your way progressively through on both sheets checking for errors & omissions?

Maybe the Mr White sound also needs to have a drive pedal full-on going into the amp?

By the way, I converted a junked oscilloscope last month for the smaller Silvertone 1482 circuit. It sounds cool and I got away with using the original PT and rectifier, but it would have been better if I could have used the old ray tube to show the signal too!

[showsii]

Tony,

That looks awesome! I bet it sounds great.

Thanks for your reply and sugesstions. I am doing my research on star grounding amoung other things. I will redraw and implement that into my layout.

I have decided to go with a tube Rec. Now I have to decide on PT and OT. Could you guys lend some suggestions to which ones will suit my needs, and not take 4 weeks?

PT schematic values that I can gather.

Primary- 120v
Secondary
720V- current?
5V- 2a?
6.3V- (at least 3a?)

Here is a noob question. There are 70ohm? values on the schematic, or at least that is what it looks like to my eye. Can yall tell me what that means?


OT values I can gather

Primary
8Ohm

Secondary
350v (going to the plates of the 6L6)
I dont know the center tap..

Also what does the 230ohm values on the OT mean?


Its my understanding that I will not need the choke, and was only used for the orignal 15inch Jensen?


Thanks for the future help,


Ian

[overtone]

Hey Ian,

just a quick answer before I have to go out with the dog:
70 Ohms and 230 Ohms are the resistances of the transformer windings. That is pretty cool and I had not noticed that on the schematic before.
I am going to point you to the Merlin's page:
http://www.freewebs.com/valvewizard/fullwave.html
and you need to read up the Minimum Limiting Resistance thing.

Then check that site, especially anything that he says on grounding.

Best,
Tony

[overtone]

...
OT values I can gather

Primary
8Ohm

Secondary
350v (going to the plates of the 6L6)
I dont know the center tap..
...

8 Ohm is the secondary.
Your OT primary will be rated in k Ohms, probably around 6k6 (6600 Ohms), I think. I would try and find out what value was used in this case. It all helps.
Have you bounced your question off RJ?
350V is the plate voltage on the 6L6
Your center tap is B+1, look at the first filter cap C16: 360V, drawn coming off pin 2 this time, which if I remember correctly is OK with a 5Y3GT.

I'll leave the PT questions for others to chime in because I have a hunch that the Silvertone PT would have been under specified. That could influence the feel of the amp in a large way.

[RJ Guitars]

I looked at that schematic and the first thing I saw was the 117v Primary going in and the 360-0-360 AC secondary coming off of that power tranny. If that is true then that little puppy is wound pretty hot... but then I see that they show a voltage of 350 going to the plates. There is a world of difference between 360AC and 350DC. I know very little of the reality of what they used in these amps. Does anybody know for sure?

As mentioned some of these older low budget guitar amps ran minimal iron with no expectation that anyone would enjoy the distortion that results from punishing them. This is in drastic contrast to something like a Traynor or trainwreck so keep that in mind.

if we can learn a bit more then we can look at the options. No doubt there is something that will work well.

rj

[showsii]

I looked at that schematic and the first thing I saw was the 117v Primary going in and the 360-0-360 AC secondary coming off of that power tranny. If that is true then that little puppy is wound pretty hot... but then I see that they show a voltage of 350 going to the plates. There is a world of difference between 360AC and 350DC. I know very little of the reality of what they used in these amps. Does anybody know for sure?

As mentioned some of these older low budget guitar amps ran minimal iron with no expectation that anyone would enjoy the distortion that results from punishing them. This is in drastic contrast to something like a Traynor or trainwreck so keep that in mind.

if we can learn a bit more then we can look at the options. No doubt there is something that will work well.

rj

Rj,

Thanks for the reply and insightful information.

What do you mean by.."if we can learn a bit more then we can look at the options."

Is there some research that I need to do to get some more values?

I am picking up an original 1483 Sunday and will have access to the guts for a while. If there is some measurement that I could grab from the orignal that will help with the choice of Iron for my build, let me know and I will get it!

Thanks alot

Ian

What do you mean by

[RJ Guitars]

Ian,

Measure the voltage coming off of the primary. See it it's 360 AC or whatever. It would be best if you could do that with no tubes in it. Then after that put all the tubes back in it and measure at all the spots they give you a voltage on that schematic and see how it compares. If you get all that you'll have the info you need.

BTW - I think my buddy "Moose" Gardner (weighed 101 pounds soaking wet in high school) has one of those amps. If not the "Silvertone" then it's a Wards "Airline". I kinda forget since it's been a while.

rj

[showsii]

I got the silvtertone yesterday from my friend. I played it today with my tele, and I have to say I am very excited about this build hearing how this thing sounds. (Also now wanting to build it as close the original as possible because of this)

It doesn't sound "good" and that's why it sounds so good to me. The sag is great, and this thing really lends it self to a rock and roll mix. IMO.

So, I will take some voltages tonight and post them up and hopefully the wise ones will help me nail out which transformers will suit me best.

I am currently reading a couple of books dealing with the math side of building and radio tube electronics so when we do come to a conclusion about the transformers I would love to know the math that lead there.

Tony, thanks for all the help so far in all of these areas!

Ian

[showsii]

Hey everyone,

Here are some voltage readings I took off the 1483

Pin 4,6 off Rec- 332 Vac

Plate of V1 Pin 6/1- 112V

Plate of V2b-Pin 6- 118V
Plate of V2a-Pin 1- 121V

Plate of V3 Pin 1/6- 146V

Plates of 6v6GT- Pin3- 323V

So, What is the next step? Can I now search for a PT with 330-0-330, or is there more to it that I am missing? (I am sure there is)

How does everyone feel about this OT for a 6l6 push pull in this context. Attached is a screen shot.

Thanks for the future help,

PS: Please help me!

[RJ Guitars]

Ian,

The info you've gathered will be very useful. if you still have that amp, get some photographs of the trannies. Maybe lay a scale or a quarter down next to it so there will be some sort of size reference.

Sounds like you enjoyed the amp.

rj

[showsii]

Rj,

Thanks for the quick reply!

Here are some pictures of the transformers..

[RJ Guitars]

Are those 6V6GT's or 6L6GC's?

[showsii]

Woops my bad, that was a typo

6L6GC!

Sorry about that

[RJ Guitars]

OK Good - I wanted to believe my eyes, they looked too big for 6V6GT's.

If you don't mind indulging my interests here - verify for me that I have this correct:

330V -- AC voltage going into the rectifier?
323V -- DC on the plates

Can you get the DC voltage going into the center tap on the output tranny? I think this is pin 8 on the rectifier tube.

Are you planning to follow the Silvertone layout? While you have that thing there and open, you might want to get some photos of the inside and outside views to use for references on your layout drawings.

If it's not too much trouble, I would be curious how many volts you have (AC) on the tube rectifier tube socket at pins 4 and 6 if you remove the rectifier tube.

Should be a fun project.

rj