A few basic questions about tweaking, components

[greiswig]

Hi, all,

I can't seem to find the answers using the "search" feature, so...

1. Why are we able to measure bias on both tubes when we only have one bias adjuster for both tubes? I have a set of 6L6s where biasing one to 35mV sets the other to 28mV. Are the measuring points just to tell us that we have an issue with one tube?

2. How important are voltage values on the orange drop caps? For example, can a 400V coupler cap be used at the entrance to the OD stage instead of a 600V?

3. I know that ideally solder shouldn't be required: you should be able to run the circuit without solder because your wire wraps are soooo good. On eyelet boards, when you assemble the board the wires get hooked around the eyelet, and after everything is put through the eyelets it gets soldered. So changing out a cap there is difficult, because you have to try to pry the hook out while applying the iron. Then, since you can't easily lift the circuit board, you can't really hook the lead on the underside of the board. How do you guys deal with this? How do you make sure your tweaks have connections that are as solid as the first components were?

[Normster]

1. Why are we able to measure bias on both tubes when we only have one bias adjuster for both tubes? I have a set of 6L6s where biasing one to 35V sets the other to 28V. Are the measuring points just to tell us that we have an issue with one tube?

It lets you know if your tubes are reasonably well matched. I typically adjust to the highest reading.

2. How important are voltage values on the orange drop caps? For example, can a 400V coupler cap be used at the entrance to the OD stage instead of a 600V?

400V is probably OK, but 6PS caps are 600V and I've never seen 4PS caps.

3. I know that ideally solder shouldn't be required: you should be able to run the circuit without solder because your wire wraps are soooo good. On turret boards, when you assemble the board the wires get hooked around the turret, and after everything is put through the turrets it gets soldered. So changing out a cap there is difficult, because you have to try to pry the hook out while applying the iron. Then, since you can't easily lift the turret board, you can't really hook the lead on the underside of the board. How do you guys deal with this? How do you make sure your tweaks have connections that are as solid as the first components were?

Turrets are a PITA in my opinion. I much prefer eyelets. Either way, good mechanical connections are a must.

[heisthl]

1. Why are we able to measure bias on both tubes when we only have one bias adjuster for both tubes? I have a set of 6L6s where biasing one to 35V sets the other to 28V. Are the measuring points just to tell us that we have an issue with one tube?

3. I know that ideally solder shouldn't be required: you should be able to run the circuit without solder because your wire wraps are soooo good. On turret boards, when you assemble the board the wires get hooked around the turret, and after everything is put through the turrets it gets soldered. So changing out a cap there is difficult, because you have to try to pry the hook out while applying the iron. Then, since you can't easily lift the turret board, you can't really hook the lead on the underside of the board. How do you guys deal with this? How do you make sure your tweaks have connections that are as solid as the first components were?

1. You need to be measuring mv not volts. Put a 1 ohm resistor between the cathode and ground or in your case both cathodes and ground to measure the total load. Maybe you're already doing that and typed V instead of mv. When mismatched go for a happy medium where both are above 30mv and less than 42mv.

3. snip one of the leads next to the component, heat and unwrap. Try and not interleave the wraps when building.

[Bob-I]

3. I know that ideally solder shouldn't be required: you should be able to run the circuit without solder because your wire wraps are soooo good.

I disagree. Solder is the "glue" that holds things together. Just like glue on wood, if you don't have a solid joint the glue will not hold. A good mechanical connection to me means the metal-metal contact is solid. The solder should hold this together but not be the conductor.

[greiswig]

3. I know that ideally solder shouldn't be required: you should be able to run the circuit without solder because your wire wraps are soooo good.

I disagree. Solder is the "glue" that holds things together. Just like glue on wood, if you don't have a solid joint the glue will not hold. A good mechanical connection to me means the metal-metal contact is solid. The solder should hold this together but not be the conductor.

That's what I was trying to say: that the circuit should be able to work without solder because the connection is good in the first place, and the solder just holds things in place.

heisthl, good catch on the volts versus mv. That's what I meant. And I have a better understanding of why two bias measurement points are needed. Thanks!

I screwed up something else in my OP, too: I said turret, but I meant eyelet. I have a stock D'Lite with eyelet boards. But I still have a hard time picturing how to get that good mechanical connection on an eyelet that has already been soldered once and has other components in place already. How do you guys do it?

[Structo]

Really the only way is, to insert the component leads and bend them flat on the backside then clip them short so a little is still securing the lead on the backside.
That's why when you look at guys finished boards you see a little bit of the lead sometimes protruding from the side of the eyelet.
I don't think that you get a great mechanical connection with an eyelet board.
Maybe I'm all wrong, since I have only built one amp with eyelets.

[Bob-I]

Really the only way is, to insert the component leads and bend them flat on the backside then clip them short so a little is still securing the lead on the backside.
That's why when you look at guys finished boards you see a little bit of the lead sometimes protruding from the side of the eyelet.
I don't think that you get a great mechanical connection with an eyelet board.
Maybe I'm all wrong, since I have only built one amp with eyelets.

Again, the contact is made metal to metal, then the solder holds it on. If you insert the component into the center of the eyelet and fill it with solder (I've seen this done, even on Fender amps) the solder will be the conductor. This is just a failure waiting to happen.

[phsyconoodler]

Turrets are a royal pain to work with compared to eyelets.As far as good mechanical connections,the eyelet board is not where problems happen.It's in high-vibration areas like tube sockets.You can get carried away with 'mechanical' connections too.One wrap is more than sufficient.
The solder is definitely the electrical connection.Case in point:many amp techs have laboured over problem amps only to find those great 'mechanical' connections made by mil-spec technicians are actually poor conductors because the solder was poorly applied because of over-confidence in the 'mechanical' connection.You could lift the amp up by that connection but the solder was not making a good electrical path and had high-resistance.
Clean contacts and a not overly-paranoid mechanical connection is more than good enough.

[mlp-mx6]

Just to offer a contrary opinion - I prefer turrets. I do not try to force more than one component per pair of turrets. I don't understand what "problems" or "pain" are caused by turrets. I have had zero issues. In fact, I'd appreciate it if someone would detail the problems inherent in turrets, just so I could understand.

Eyelets are fine, too, and I have built amps using them. I just prefer turrets.

[ampgeek]

Clean contacts and a not overly-paranoid mechanical connection is more than good enough.

+1 on that!

I also wanted to mention that a couple of different sizes of hemostats have become invaluable tools in my arsenal when setting out to build or tweak an amp. You can also have a pretty darn good excuse for the "burnt" tips!

Merry Christmas,
Dave O.

[Structo]

About the only negative thing I have heard about using turrets, since I haven't used them, is that it takes more heat to get them up to temperature before the solder flows. Not sure if that is a negative thing, just what I have read.

[ampdork]

Well being the guy that built greiswig's D-lite I am going to staunchly defend my use of the mechanical connection. I most often build amps that are sold. That being the case there is little thought to folks modifying the amps. Certainly I have no problem with that happening but I don't build my amps catering to the notion. So old habits die hard. I do bend the leads under the board across the eyelet edge. Pain in the ass to remove.? Well not for me but surely for some it can be. However as pointed out there isn't a connection in the world that will stay if one wants it free. Parts are arguably cheap enough that even if clipping occurs it shouldn't be a terrible loss. Of course in 30 years these inexpensive caps could be priceless but I digress.
While I may be a bit paranoid on the mechanical connection I am equally anal about solder joints. I wear nitrile gloves to prevent grease grime and dirt, clean all leads to be soldered with scotch brite. I have been known to degrease all new eyelets with acetone, etc. etc.
So at least for me I don't lean on the mechanical connection alone.

The solder is definitely the electrical connection

Certainly not trying to create waves but this is not what my experience is, nor does it fall in league with numerous articles I have read on the subject. Solder is not meant to be the electric connection by any means. The two metals should be in good mechanical contact. The solders job is to keep that connection, not to be a bridge between contacts.
While I have seen plenty of real world examples that do not follow this thinking and are still putting out great tone, some of them 60+ years old, I am still subscribing to the methods I was taught. My apologies to greiswig for making his D-lite tweaking a PITA but like I said old habits are very hard to break.

On the subject does anyone know where to source turrets for a lot less than mouser sells them for? I personally wouldn't mind using them but the cost is pretty high compared to eyelets...

[phsyconoodler]

The problem I have with turrets is indeed for repairs and mods.I am never satisfied with an amp until it is teaked to perfection and wrapped components on turrets are a pain to remove.Sure they look cool but they also lift components off the board and the component and lead dangle in mid-air.Surely that is not a good practice.You spend all that time wrapping a component's wire around the contact point to be soldered and you leave the component hanging in mid-air.Contradictory at best.At least flat on a board does not stress the connection.
Of course we both know point-to point amps have been in service for many years with flying leads with no problems.
To me the solder joint is far more critical than the mechanical connection any day.A multi-wrapped connection with a poor soldering job is very hard to diagnose.Oxidixation gets between the best mechanical connections and ruins the contact no matter how well it's been prepared.It is not the mechanical connection that ensures contact.It's the solder.

[ampdork]

Some good reference material:
http://snebulos.mit.edu/projects/refere ... 39-3-2.pdf

George had a good idea in email about using a "v style notch, thus creating a mechanical connection in two places.
In doing some quick research I found another fellow who uses a U shape.
The U is bent into the lead, the lead is inserted in the eyelet, then the free end of the lead comes out of the eyelet and is bent over on the top portion instead of the bottom. This to me sounds like a good method and I'll be giving it a try in the future. Always looking for a better method.
I also agree with you phsyconoodler that when using turrets one should not have the components dangling in mid air the way we have seen it done a thousand times. Somewhere in the .pdf I posted it seems NASA agrees too. They have a pic with the components bent to lay flat on the board.
Good stuff.

[ampdork]

It is not the mechanical connection that ensures contact.It's the solder.

Well true but it is the mechanical connection that creates the contact in the first place so I suppose both are critical but you can't have a good solder joint without first having a solid mechanical connection. One begets the other.
Honestly I don't see these things as being different or more important one against the other. I feel both are required and the work together for a unified purpose. Solder and mechanical joints unite!