First tube amp build: Fender Deluxe AB763 style amp (no reverb).

[bob p]

Bob, since I don't have the chops to be able to calculate current/voltage and so power throughout the circuit, can I go by the wattage of the resistor to guess which ones will put off more heat?

Sure, you've got the chops. Just measure the voltage drop across the resistors and calculate power using Ohm's Law.

If the resistors in your kit are properly sized then you can just go by the power ratings on the resistors. 1/2W resistors won't generate a lot of heat, but the 470R 1W screen resistors will put out some heat if you drive the amp hard, as will the resistors in the PSU rail.

[Justin Thomas]

I found another photo of a 70's fender amp, where they put a lug on one of the transformer posts and soldered the safety ground wire to that, but also put a bead of solder around the edge of the lug to the chassis.

First, I don't drill holes in chassis that do not yet have extra holes drilled in them on vintage amps. I will reuse the grounding scheme that exists already in BF & SF Fenders etc. If the chassis has already had extra holes drilled, I will add a separate terminal IF the chassis has not yet been converted to a three prong (most amps that have holes drilled already have been converted 3-prong, that I see...). However, when I build an amp from scratch (bare chassis, recycled organ, or even if I had a kit), I always put the safety ground on a terminal lug BY ITSELF, and I will use my extra-big-ass 80W iron to solder the whole thing securely to the chassis. The safety codes say that that wire must be bonded securely to the chassis and by itself, so I do. I also leave it a few inches longer than the primary wires, so that if the power cord is ripped out internally and shorts to anything, that ground is last to detach. You know, for the times your bass player gets pissed and dropkicks your amp to the ground.

Granted, I don't always follow codes for internal fusing aside from mains, because... Well, I won't make excuses. But that 3rd Wire? Yup. Mains sucks getting bit by.

Justin

[mikepukmel]

Made some progress, getting used to soldering stuff again. Tore out the heater wiring, and redid that, came out better the second time around. Getting used to using my 4 left thumbs, and 7 right thumbs.

I gave up getting a full set of the same brand/type resistor, so its a mishmash. Got the wrong 220k's, way too big wattage, but its what I had after too many small orders.



Still fighting with hardware. The cap board screws stick out of the bottom of the chassis too far, so they come too close to the underside of the main eyelet board.

Wow, is that shielded wire hard to work with, the signal cable is very small, and hard to strip and solder. I got the first one hooked up with too much solder, and the wire broke off after working the cable too much.

All in all, making progress. Goal is to have it making sound by end of month.

Thanks for all the help and answers to questions, and suggestions, everyone.

[mikepukmel]

9 pin socket (noise) question

Hi All.
I bought these for the 9 pin tubes:

"9 Pin Belton socket and shield"

They mounted just fine, and soldered in fine as well. After I got the heater wiring in, I took one of my 12AX7's and made sure it would mount into the socket correctly. The tube went in all but one socket.

On one socket, the tube goes in OK, but meets slightly more resistance than the others, and the pins make a squeak sound when I try to pull the tube out. I took a piece of solid core 18ga buss wire, and pushed it into each pin hole to find out which one(s) it was. Turned out to be one pin that I didn't solder on at all!

My question is: the pin wipers seem fine. I don't see any solder in there or other contamination with a magnifying glass. The piece of buss wire goes into the pin hole just fine, but it makes an awful sound when I pull the pin out and push it into just that one hole.

Is there something I should clean this out with, maybe try alcohol? Has anyone seen this before on these sockets?

Thanks,
Mike

[catalin gramada]

Belton novals seems allright .bend a little bit the terminals to outside to hold contacts into position. The aluminium retainer is a little bit "weaky". First, there are some russian tubes which need to be forced to put the tube in socket due to diameter (I never checked if the retainer is smaller or tube dia bigger but happened to me with many new russian -no problems with NOS) and also hard to pull off. Second the aluminium retainer not keeping good in position all tube cap shields, not all tube cap shields can be secured properly or secure well at beginning and become loosy in time...I think the Belton retainers are a little bit smaller. You option was for "integrated" sockets I suppose. They sell also sockets and retainers by pieces. Check the cap shields size to be for small novals.

[mikepukmel]

Thanks Catalin.

[catalin gramada]

No worries
and a disclaimer. never try to bend pins from Belton octal, or if necesary bend it very very gently and carefully and not too much. The Belton octal pins are made from hard bronze and broken very easy. I think for octal you can find better options if is better to keep the octal pins as much apart

[mikepukmel]

newbie build mistakes

Message to other tech newbies: Lots of mistakes along the way, so far didn't ruin anything, I think.

Mistake #249:

Bend leads and mount components and rough wiring onto eyelet board. (note: did not clip long leads off)
Flip board over, start soldering.
Long leads make nice heat sink, solder runs down the long leads makes a big blob of solder. Eyelets don't fill up, thinking to myself "Where the hell is all this solder going???"
Have to flip board over, heat, remove solder blob, clip leads, clean up mess, flip board back over, reflow to neaten up solder in eyelets.


***
I found a few 'how to solder' videos on youtube, some were instructional bits from big companies that want to sell $4,000.00 videos. None had any tips on soldering eyelet or turret boards. I think eyelets are harder, great big metal ring with big air hole, solder runs through. At least the PCB boards have holes very close to lead dia.

Learn by doing.

[eschertron]

I'm a relative newbie myself, having done only a few eyelet boards. IME, the thin resistor leads, et. al., may heat up much faster than the eyelet (depending on eyelet composition). I've found resting the iron on the eyelet itself (as primary heat sink) helps get the solder to stick to the eyelet and stay in the hole. In general, solder work is a matter of doing something a few times to get the feel. Practice on some scrap, or find a corner of the board where you can install and remove some components (again, scrap - or at least not rare and valuable) to get the timing and technique.
Don't forget to let the iron do its work to bring the joint up to temp before applying solder.

[mikepukmel]

I'm a relative newbie myself, having done only a few eyelet boards. IME, the thin resistor leads, et. al., may heat up much faster than the eyelet (depending on eyelet composition). I've found resting the iron on the eyelet itself (as primary heat sink) helps get the solder to stick to the eyelet and stay in the hole. In general, solder work is a matter of doing something a few times to get the feel. Practice on some scrap, or find a corner of the board where you can install and remove some components (again, scrap - or at least not rare and valuable) to get the timing and technique.
Don't forget to let the iron do its work to bring the joint up to temp before applying solder.

Thanks for the tips!

[eschertron]

I hope I don't sound like I'm talking down to you - I certainly do not have the elevation to do that - but I want to read that you are enjoying the build process, so I thought I'd chip in. Thanks for the regular updates. It's been educational for me, too!

[mikepukmel]

Although that's not the best practice, I've seen it done often, and with factory builds. Since you have that big 80W iron, there's no reason the AC power ground can't be directly soldered to chassis. I generally do that on the strip between power transformer and chassis side gusset. It helps to scrub the chassis surface with wire brush or 600 grit paper or crocus, also apply a dab of Nokorode or similar flux for a solid connection.

Leo, you weren't kidding, man, that iron is awesome, thanks! It arrived a few days ago, got a chance to crank it up tonight. I did just what you suggested: sanded the chassis a bit, put a little dab of nokorode, the iron made a really nice bead of solder on the chassis and side of the lugs. I wasn't sure if 80 watts would be enough, but its perfect for this task.

I made a little star ground type thing near the power transformer out of 3 lugs screwed to the chassis, then soldered the side of the lugs to the chassis as well. No chance of a bad ground now.

Now if I only can get over the fear of the final solder up of the wiring . . . Im reading all of the dozens of posts of people complaining about awful weirdness in their basement built tube amps, and all of the gurus suggestions for how the wiring should be routed. Not sure I have a solid picture yet, but getting there...

[mikepukmel]

I hope I don't sound like I'm talking down to you - I certainly do not have the elevation to do that - but I want to read that you are enjoying the build process, so I thought I'd chip in. Thanks for the regular updates. It's been educational for me, too!

Not at all!!! Any and all suggestions welcome, thanks for your posts. Oh yeah, enjoying this project immensely. There is so much stuff going on in these amps, its amazing. And everyone on this blog have been great.

[Leo_Gnardo]

Leo, you weren't kidding, man, that iron is awesome, thanks! It arrived a few days ago, got a chance to crank it up tonight. I did just what you suggested: sanded the chassis a bit, put a little dab of nokorode, the iron made a really nice bead of solder on the chassis and side of the lugs. I wasn't sure if 80 watts would be enough, but its perfect for this task.

Good to hear that Mike. It's a rare satisfaction to give advice & hear someone has made good use of it. Thanks for letting me know!

[mikepukmel]

When is a "star ground" not a star ground . . .

OK I have the basic idea about a star ground. In comic book terms, if you have a bunch of ground points scattered all over the chassis, then eddy currents swirl around, and could induce currents in nearby wiring. So I got a 'star ground', or at least 3 lugs screwed and soldered to the chassis at one point. But I have a couple of other places inconvenient to move, like the 2 resistors tied off to ground on the pilot light since my power transformer doesn't have a center tap on the 6.3v secondaries.

Is this going to be a problem? I have: 1 wire coming from the cap on the bias board, 1 wire from the main cap board that runs through a grommet hole in the chassis, and one main center tap from the power trans, and 1 wire main safety ground coming from the power cord all tied to lugs on that main ground point. But the 2 resistors that make the fake center tap for the heater wiring is on the other side if the power trans.

If so, would this be a 60hz hum issue, or something else?

Thanks,
MP