Fender 5a3 Deluxe service?

[Mike62Jazz]

I have a friends '51 5a3 Deluxe he wants me to go thru and service. It appears original except for the 2 orange drops. If you were going thru this amp, what would you change as a precautionary measure. I would assume all the electrolytics and the 2 prong cord, correct? Any comments would be appreciated. Also, what is the purpose of the 100pf/1000volt cap across pin 2&5 (plates) of V2? Btw, this amp has 6sl7 preamp tubes, not 6sc7. The 6sc7 on the tube chart is lined out and 6sl7 handwritten.

[Gibsonman63]

Definitely change the electrolytics and add a grounded power cord. Keep the originals, though. Some of the collectors want all of the original parts.

Clean and retension all of the tube sockets.
Clean the pots with Deoxit.

If it sounds good after that, just play it. If not, start checking for leaky capacitors and componants that have drifted in value.

[Enzo]

I'd have to say that I'd be surprised if those wax coverd caps were not begging for replacement. Lytics for sure though.

[ThermionicScott]

Before you change anything, would you mind tracing out the circuit as-is and drawing a schematic? There's a "5A3" schematic floating around that was modified from a 5B3 schematic, but some of the component values were dubious IIRC. I agree with Enzo that all of the electrolytics will need to be changed, and most of the coupling caps probably will, too. (Those wax-covered caps have a tendency to absorb moisture over the years and become leaky.)

That cap across the PI plates is to quell high-freqency oscillation. Most of the TV-front/wide-panel amps had that cap, but some later ones (like the 5F6A Bassman) did, too. Being a wax cap, I'm sure it needs to be replaced as well. A ceramic would work (I used one on my 5B3/5B5 clone), or you could try 1.5K grid stoppers on the 6V6 tubes instead.

- Scott

[dchang0]

If you don't feel like tracing out the schematic, please at least take close up photos of the wiring and components so that we can draw one up.

Several macro-setting camera shots taken side by side and overlapping can cover the entire circuit in high detail (except any under-board wiring).

Thanks--you'd be helping out the entire amp community at large for possibly decades!

[Mike62Jazz]

I'd be glad to take pics. Drawing a schematic is probably beyond the scope of what I can do. The pics you have seen so far are of this amp about two years ago. I am probably replacing the orange drops that were installed about 15 yrs ago. I think that the schematic you've seen is pretty close. However, some of the resistor values in the amp are not what is on the schematic. For instance, all the 250k ohm resistors shown on the schematic are actually carbon comp 220k's. Also, both preamp tubes in this amp are 6SL7's. How would you like for me to upload the pics, and where, when I get to that? I probably won't be getting into it until next week. I have most parts on the way. BTW, how would you wire a 3-prong plug in this amp? I know that an 18 gauge cord will not fit through the chassis without drilling out the hole. I don't know if a polarized 2-prong might be a better way to go, thoughts?

[dchang0]

It'd probably be best to upload the pics to this thread (or start a sticky one in the Schematics section). One of us will use the pics to improve the schematic for everyone's benefit. As long as the photos overlap obvious "landmarks" in the chassis, we'll figure out what goes where.

Should be pretty easy to get component values with a digital camera in macro mode--you don't even have to pick up a pencil!

You'll have to take the pics before you start modding, but you can put off the uploading till later.

-----

I'd definitely put a 3-prong plug in. Does your friend object to a permanent modification like drilling the chassis? If so, there may be other options:

1) This is sorta cheesy, but it would work fine without modifying the chassis. Get your 3-prong cable, strip the outer cover back as far as you need. Run the black and white wires in through the original chassis hole. Solder a ring tongue lug (available at even your local Ace Hardware) to the green wire and bolt it to the OUTSIDE of the chassis, using one of the power transformer bolts and arranging the tongue BETWEEN the PT and the chassis. In effect, this is the same as if you were bolting it on the inside of the chassis to one of the PT bolts. You'll have to remove all four PT bolts to insert the round tongue/lug, though.

Use cord retainers or shrink wrap as needed to protect the black and white wires from getting chafed/cut by the chassis.

You can order many sizes of tongue lugs at Digikey:

http://ca.digikey.com/1/3/ring-tongue-lug-8awg

It's not worth the shipping. I buy mine at the little mom & pop hardware shop down the street. They also happen to carry different sizes of push-in cord retainers, which you might need to buy if the white + black wires are thicker than the original two-conductor power cord and its retainer.

2) Get a higher-gauge power cord (could be dangerous if you go too thin--watch your current and voltage limits).

[ThermionicScott]

Fwiw, the orange drops are probably fine -- they don't absorb moisture and leak like the wax ones do. I'd replace all the others, power it up, and see if anything is leaking at all.

[Mike62Jazz]

Here come the pics! Hope this is good enough.

[Mike62Jazz]

A couple more! Let me know if there is something else needed.

[dchang0]

AWESOME! Thanks, Mike! The same goes for you--let us know if we can help you out.

[Mike62Jazz]

It'd probably be best to upload the pics to this thread (or start a sticky one in the Schematics section). One of us will use the pics to improve the schematic for everyone's benefit. As long as the photos overlap obvious "landmarks" in the chassis, we'll figure out what goes where.

Should be pretty easy to get component values with a digital camera in macro mode--you don't even have to pick up a pencil!

You'll have to take the pics before you start modding, but you can put off the uploading till later.

-----

I'd definitely put a 3-prong plug in. Does your friend object to a permanent modification like drilling the chassis? If so, there may be other options:

1) This is sorta cheesy, but it would work fine without modifying the chassis. Get your 3-prong cable, strip the outer cover back as far as you need. Run the black and white wires in through the original chassis hole. Solder a ring tongue lug (available at even your local Ace Hardware) to the green wire and bolt it to the OUTSIDE of the chassis, using one of the power transformer bolts and arranging the tongue BETWEEN the PT and the chassis. In effect, this is the same as if you were bolting it on the inside of the chassis to one of the PT bolts. You'll have to remove all four PT bolts to insert the round tongue/lug, though.

Use cord retainers or shrink wrap as needed to protect the black and white wires from getting chafed/cut by the chassis.

You can order many sizes of tongue lugs at Digikey:

Ring Tongue Lug #8awg

It's not worth the shipping. I buy mine at the little mom & pop hardware shop down the street. They also happen to carry different sizes of push-in cord retainers, which you might need to buy if the white + black wires are thicker than the original two-conductor power cord and its retainer.

2) Get a higher-gauge power cord (could be dangerous if you go too thin--watch your current and voltage limits).

I take it that with a 3 prong cord, besides the ground going to the PT Screws, The black would go to the fuse end and the white to the back of the on/off tone switch as the 2-prong was wired. How about the .05 mfd/600v Wax cap going from the side of the fuseholder to chassis ground? It also has the other black wire from the PT going to the side of the fuseholder. Should I remove the cap or leave it in place?

Thanks

[dchang0]

Yup, you got it. Green safety ground goes to PT bolt. Black goes to fuse end (tip). White goes to on/off power switch leg.

And yes, the .05mFd cap goes from the body of the fuse holder to ground, and the black from the PT goes to the same tab on the body of the fuseholder.

Replace the 0.05mFd/600V with an equivalent new cap (I have a 0.047mFd/600V Orange Drop 415P in my tweed Champ) just because the wax cap is too old. I remember reading somewhere that you *could* remove the cap entirely, but I'd rather keep it in place for noise reduction.

[Tom Phillips]

I take it that with a 3 prong cord, besides the ground going to the PT Screws, The black would go to the fuse end and the white to the back of the on/off tone switch as the 2-prong was wired. How about the .05 mfd/600v Wax cap going from the side of the fuseholder to chassis ground? It also has the other black wire from the PT going to the side of the fuseholder. Should I remove the cap or leave it in place?
Thanks

Per modern code and practice both the fuse and the ON/OFF switch should be in the hot (Black) line. The hot line should be connected to the rear of the fuse socket. The green earth ground should be soldered to the chassis or be connected to its own dedicated locking hardware to the chassis. It's also good to make the green wire a little longer such that if the line cord is forcibly pulled out of the strain relief the green wire will be the last to break off. The cap from one side of the line to ground should be removed.

You can reference modern commercial schematics to see examples and Goggle the wiring code. It would be good to learn about this and understand it well. Especially of you are going to work on other people's equipment.

It's also good to buzz out the line cord you are installing. I received a whole batch once that had the green wire connected to the hot side of the line.

Always new things to learn.

Tom

[Mike62Jazz]

Per modern code and practice both the fuse and the ON/OFF switch should be in the hot (Black) line. The hot line should be connected to the rear of the fuse socket. The green earth ground should be soldered to the chassis or be connected to its own dedicated locking hardware to the chassis. It's also good to make the green wire a little longer such that if the line cord is forcibly pulled out of the strain relief the green wire will be the last to break off. The cap from one side of the line to ground should be removed.

You can reference modern commercial schematics to see examples and Goggle the wiring code. It would be good to learn about this and understand it well. Especially of you are going to work on other people's equipment.

It's also good to buzz out the line cord you are installing. I received a whole batch once that had the green wire connected to the hot side of the line.

Always new things to learn.

Tom

Thanks Tom! What about the neutral wire?