Building the Dumble Amp?

[Mark]

This is a builders only question.

I was wondering what process or considerations you go through prior to building the amp.

This could be measuring the signal and filter caps prior to soldering them in, or even the brand of resistors/caps/valves you prefer and why you prefer them.

Valve sockets is another issue, some of the sockets I've seen lately aren't a patch on the old NOS ones I have.

Do you ensure the surfaces to be soldered are clean or are the happy to let the flux do it's work?

The type of solder used is another consideration harder solder will be less prone to dry joints but requires a hotter soldering and is more difficult to work with.

The order you build the amp is important too as it allows you to test parts of amp as you complete them. Nothing is worse than building the amp and then wonder what isn't working.

This is one of the things we rarely talk about, and I think it is due some consideration.

[Homebelly]

I'm very much a novice.
The first time i had my hands in a build was to help salvage a 1987 Plexi.
There were all kinds of crackly solder joints in it. We went through pretty much every joint with a chop stick to find the baddies.
Since then i have done three builds of my own. Before every build i take a fine sand paper and run the ends of every Cap and Resistor through it. I've had a couple of hic-ups along the way, but a bad solder joint hasn't been one of them.

[sonicmojo]

I measure every resistor before I place it. I don't have a way to measure capacitors yet but I think I'll get that tool soon. I do test for the coil side on all the Orange Drop type caps and mark them.

I use 60/40 solder since it is much easier to work with but I use different gauges of it depending on the application. I've tried the non-lead but since it is harder to work I don't use it now but haven't had a problem. Once I got an adjustable heat iron and made a proper cradle to hold the amps, work got much easier.

Sockets, especially on PCB fix-er-up combo amps are always a problem. I tend to replace them or at least touch up every joint and use a push-pin to tighten them up. I've had better luck with the brown Belton sockets since they seem to resist solder getting in the socket, like some of the cheaper ones, especially on the power tube sockets, don't go cheap on those.

Some used combo PCB based amps are almost unsalvageable due to many years of vibration but they often can gain a second life as a head. I did this recently with Fender Super60 whose cabinet was just loose - I don't think Fender used glue on those things in manufacturing since when I cut it, it just basically wiggled.

After working with PVC wire on a couple of amps, I started to add shrink tubing to every join due to the PVC peeling away sometimes. I think I'm going with 20 gauge teflon from now on for most wiring to avoid the extra step since it deals with the heat better. It is a little more expensive but leaves a cleaner result in the chassis due to being thinner.

My two cents....

[zimm]

You should try searching, there is a thread where some of the more notable builders describe their build sequence, I think funkalicious groove, henry, and glassman, among others, are in that thread.

[Luthierwnc]

Yeah, the build sequence thread is worthwhile -- even if everyone does it differently.

The first thing I do is the schematic. I still hand-draw them because: a) I want to see how it all goes together and b) that is the document I use just to test the build before the spark-test. Then I do the layout diagram. From those two I put my parts list on an Excel sheet and sort it by vendor. Next I go to the shop and see what I already have on the list and isolate it from the rest of the bins so I don't double count them later.

In the ordering phase, I often get extra cheap or commonly-used parts like; resistors, caps and diodes. I'll also get some spares in nearby sizes for later tweaking on the power supply and couplers. Since I only make one at a time, most of parts for each build need to be ordered every time.

I don't know what to tell you as far as socket quality. I generally get mine from Hoffman but Angela and Triode Electronics often have NOS stuff. Tubes -- you're on your own.

Good luck, sh

[talbany]

Here is one I consider the last in the build process that for me is rather important one and sometimes perhaps overlooked or ignored..
If you started from one of the layouts.. https://tubeamparchive.com/viewforum.ph ... beb4c4fe71
After your smoke test and basic checks and usual tube rolling and PI balance, the amp is functioning properly and is stout, hold off on any tweaking for the moment..Considering after all the tolerance checking that amp will still have it's own personality, certain things it might excel in, others not so much.Take the time to experiment with different guitars, speakers, and performance environments. Start a small diary on the amp (w/settings) of certain things you like or dislike about the amp, double check them over time to make sure they have not changed, try to look for the nuances of that amps personality, do this over a course of say a month so your ears and playing style have a chance to adapt and in the process try not to compare that amp to something else especially one of a different generation, take it on it's own merits..In the process you will put in some break in time and when and if the time comes for some tweaks you'll have a better handle on the amps strong points and less likely to tweak yourself away from them..

Hope This Helps!!

Tony

[Structo]

Good stuff Tony!

Some guys like to hold off on installing the transformers until they are close to the end.
It makes handling the chassis a little easier without the extra weight and awkwardness of the OT and PT.

I use a amp cradle when working on amps so when using that it doesn't really matter if the trannies are mounted or not.

Try to wire the little stuff first before other stuff gets in the way, like front panel switches, jacks.

Here is a pretty good design for a cradle.

The arms holding the chassis are critical to get right.
If they are not situated correctly on the cradle, the chassis will want to flip over or be unstable.
The transformers throw the center of gravity off so plan that part carefull.
I did not use these plans for mine as I found them after I built it.

[Zippy]

The order you build the amp is important too as it allows you to test parts of amp as you complete them. Nothing is worse than building the amp and then wonder what isn't working.

This is one of the things we rarely talk about, and I think it is due some consideration.

Perhaps this is what you are looking for:

https://tubeamparchive.com/viewtopic.php?t=4657

[Mark]

Thank you for all the replies and links. The links are handy as I've done searches on this site before and I've spent days looking for info.

Here are a few more thoughts that have come to mind that I should have added to the original thread.

To clean corroded leads crocus paper is good as it is very fine, cotton buds and alcohol can be used to clean the eyelets.

Alcohol is great for removing the flux after soldering the joint.

If there still are impurity on your surfaces to be soldered, Flux is your friend as say in the workshop where I use to work, it is messy but it but very helpful.

Teflon coated wire, MUCH easier to work with than PVC wire.

Wire gauge is important too, in a valve amp I have typically used 18 to 20 gauge wire, but I suspect 20 to 22 gauge wire would work better with eyelets.

Tony, the other factor when evaluating amps is the room, try and do it in a decent sized room that isn't too live (reverb due to hard surfaces). I have a small room upstairs which I discovered is terrible, the larger lounge room works for me.

Zippy I like Funk's work order, though the builder should think about the time he or she has and the steps that can be carried out. Prior to commencing a new step the previous days work should be checked, everyone makes mistakes and lets not forget familiarity breeds contempt.

What are components are people using?

I have been curious about resistor choices (excluding the Dale RN65's.)

[heisthl]

Flux is your friend as say in the workshop where I use to work, it is messy but it but very helpful.

We had one batch of Keystone (Mouser) eyelets that did not take solder well so we used liquid flux and yes they soldered great - almost every amp from that time period had to be rebuilt after some time went by. The liquid flux will soak into the garolite and cause conduction! Weirdest thing I've ever seen - you could put your voltmeter probe on the board edge and measure voltage DO NOT USE LIQUID FLUX ANYWHERE NEAR GAROLITE. You could dip or soak a part in it but make sure it is completely dry before it gets anywhere near your eyelet board.
FYI the garolite we use is 1/16 G -10/FR4 from McMaster.

[Structo]

Interesting Henry.
What was the flux you were using?

I have a bottle here of MG Chemicals Rosin Flux.
Doesn't say much else on the bottle than "Instant Wetting".

The MSDS says it contains Rosin, 2-Butonal and Ethanol.

I bought it at Fry's.

I don't believe I used it much if at all in my amp.

[heisthl]

no idea on brand - after the conduction discovery, the bottle went into the trash (somewhat violently!). Rosin conducts.

[Structo]

I'm almost afraid to ask but, what were the symptoms of the conduction on the board?

[Mark]

Heisthl that is amazing, you'd think this shouldn't have happened as conductivity is a quality you don't want.

I assume you did clean the flux off the board, though you did say it soaked into the board, do you still use garolite or did you move on to something that isn't porous?

[heisthl]

I'm almost afraid to ask but, what were the symptoms of the conduction on the board?

DC Voltage readings on points that should not have DC on them, adjacent to points that did have DC. The voltage measurement would diminish with distance away from a DC point..