What happend to 320K resistors ?

[coppercone2]

link to 300mW 0805 320k thin film?

[Siwastaja]

You need to realize TH technology is mostly obsolete, want it or not. So no matter how much you prefer TH over SMT, no matter how good reasons you have, the selection of parts available is poor and gets worse every day. You can whine about it until cows come home, or you can just use the parts that are available and get the job done. Side effects are almost all positive, but attitude needs to be fixed first.

My observation is that people who most whine about lack of TH parts are those who have no idea about circuit design and their designs would fail even if all the parts in the world would be available in TH. As always, coming up with excuses is a sign of something.

[ogden]

My observation is that people who most whine about lack of TH parts are those who have no idea about circuit design and their designs would fail even if all the parts in the world would be available in TH.

Your observation is correct. People who have no idea about circuit design do exist. They are beginners. Even today it is nothing wrong about using breadboard or learning circuit design using through hole components and perfboard.

Thou beginners shall listen too. If many people are telling you that your approach is wrong - then most likely it is so. In this case apply best engineering practices - use your head and parts that are available (E24):

300   +   20   =   320      (0 %)
220   +   100   =   320      (0 %)
200   +   120   =   320      (0 %)
160   +   160   =   320      (0 %)

calc used: https://www.qsl.net/in3otd/parallr.html

[srb1954]

stop forcing SMD on people for no reason other then its cheaper or desirable for YOUR process.. stop thumping the 'new testament' of SMD being better at everything, not everyone wants rice.

SMD is not only cheaper but also takes less space, is faster to assemble and have less of parasitic inductance. Not to say TH parts go away, you simply cannot find most of modern parts in TH.

SMD may have some advantages for non-critical applications but it has some severe disadvantages in high power circuitry:

• The power handling capability for pulse loads for most types of SMD resistors is abysmal
• The ability of SMD resistors to withstand high peak voltages is poor
• The ability to withstand thermal cycling stress with pulsed loads is poor, especially when using lead-free solder
• If the application requires power dissipations more than several watts the heating of the PCB material and surrounding components becomes excessive with SMD parts

If any of the above situations applies the best option is often to stick with leaded parts.

[Siwastaja]

stop forcing SMD on people for no reason other then its cheaper or desirable for YOUR process.. stop thumping the 'new testament' of SMD being better at everything, not everyone wants rice.

SMD is not only cheaper but also takes less space, is faster to assemble and have less of parasitic inductance. Not to say TH parts go away, you simply cannot find most of modern parts in TH.

SMD may have some advantages for non-critical applications but it has some severe disadvantages in high power circuitry:

• The power handling capability for pulse loads for most types of SMD resistors is abysmal
• The ability of SMD resistors to withstand high peak voltages is poor
• The ability to withstand thermal cycling stress with pulsed loads is poor, especially when using lead-free solder
• If the application requires power dissipations more than several watts the heating of the PCB material and surrounding components becomes excessive with SMD parts

If any of the above situations applies the best option is often to stick with leaded parts.

Also large capacitors and connectors benefit from the mechanical support you get with THT.

90-99% of parts in such designs are still likely SMD. The control side tends to have large number of components, especially large number of pins.

It's not a choice whether to build the entire thing in THT or SMT, that would be stupid.

Right component is used for the job, each component chosen separately based on what is needed.

Fully SMT designs are rare in power electronics. Fully THT are even more rare.

It's all about availability and suitability. If you want a modern microcontroller, there is no TH type available. If you want a 10000uF 50V capacitor, there is no SM type available. If you have decided not to use certain technology for no good reason, you can't do the job because you need both types.

[ogden]

SMD may have some advantages for non-critical applications but it has some severe disadvantages in high power circuitry:

• The power handling capability for pulse loads for most types of SMD resistors is abysmal
• The ability of SMD resistors to withstand high peak voltages is poor
• The ability to withstand thermal cycling stress with pulsed loads is poor, especially when using lead-free solder
• If the application requires power dissipations more than several watts the heating of the PCB material and surrounding components becomes excessive with SMD parts

If any of the above situations applies the best option is often to stick with leaded parts.

Limiting factor is PCB heat handling properties, not SMT resisors as such. 35W SMT resistor for example: RHFH4Q050R0FE. If you need smaller heater on your PCB, then consider Vishay RCP series or similar.

Low voltage rating of small SMT resistors is due to their (surprise surprise!) size. Simple solution - put multiple resistors in series or use higher voltage rating SMT resistors, usually both. Open parametric search of your parts distributor and see for yourself - plenty of choices.

[ogden]

It's not a choice whether to build the entire thing in THT or SMT, that would be stupid.

Stupid would be to not try to build entire thing using SMT only. To state obvious: THT is added cost. Here I talk about electronics manufacturing in general.

[Siwastaja]

Yes, I always try to default to full-SMT design whenever possible. The opposite, trying to default to THT, is becoming a masochistic act I think.

At some point I realized that TH parts isn't as much extra cost you could think it is. If you do a proto batch of 10, just solder them yourself, takes an hour. If you do 100, let the Chinese CM solder them for you. What I have seen, the quality is OK.

So I don't feel bad using TH parts when there is an advantage, for example the large caps, bulky connectors and high power resistors, high voltage parts. And TH pin header takes less board area than SMD pin header.

BTW regarding resistors that dissipate a lot, sometimes this is a sign of bad circuit design. Always when dissipating power, ask the fundamental question, why do you need to dissipate? Sometimes you can just make the circuit more efficient, save space, assembly cost, and energy. For example, instead of dissipating 5W in a current measurement resistor, use a higher gain, lower offset amplifier and dissipate only 1W. Or instead of "regulating" current by CV supply + series resistor, design a CC supply.

[langwadt]

1/4 watt

you want a 1/4 watt smd you get 1206 minimum , depending on what your customers believe

You can buy 0.3W in 0805. In 1206 you can get up to 1W.  And you don't need 1/4W in 99% of cases, 1/16W or 1/8W is more than enough usually. Just because small TH resistors usually come with 1/4W rating does not mean you actually need it.

they don't exactly give them away but digikey has plenty 0.4W, 0.5W and some 1.5W 0603

[ebastler]

I dont have anything SMD, searching for normal axial resistors.
Soldering more resistors is not the plan, i still have some 320K resistors, i want more.

Bit stubborn, are we? 
I guess you have two plausible options:

(a) Take one of the various recommendations given in this thread, or
(b) keep searching for 320k resistors, quietly please.

Digging in your heels here in the forum until someone makes 320k resistors for you is not one of them, I'm afraid.

[TimFox]

Just an important mathematical point:
The "E" series of component values, which are very common for resistors, split each decade into approximately equal (ratio) increments, so that if a value R exists, then so shall 10 x R.  (Analogous to the tempered division of octaves in piano tuning.)  Your requirement uses resistors that are in a binary power sequence, proportional to 2^N.  Obviously, at some point the binary sequence will reach a value not in the E sequence.  Therefore, it seems prudent to include the capability of two resistors in series (or parallel) at some places to obtain the values needed.

[Jan Audio]

Digging in your heels here in the forum until someone makes 320k resistors for you is not one of them, I'm afraid.

Dont forget for cheaper then 50 cent, not wanto pay more then 5 max.

The solderability of components deteriorates over time so the distributor is only going to stock items that can be turned over every 6 months or faster.

Thank you, i did not know this was a problem, i thought those resistors stay good forever.

[Jan Audio]

I would add one more question - what's wrong with people designing in thru-hole passives in year 2021?

I like the 80s better.
80s tech is my favourite.
I want to invest in SMD this year, if only i had as much money as i have thru-hole parts.
I like being a hobbyist, not a professional.
With SMD you are no hobbyist i think.

[wraper]

link to 300mW 0805 320k thin film?

Why would you want 320k thin film (for which op did not even ask) in 0.3W? You would need to apply 309V on such resistor to get 0.3W dissipation. And it would be a lot more than max allowed voltage for resistor in such package.
Here is usual 330k https://www.tme.eu/en/details/hp05-330k1%25/0805-smd-resistors/royal-ohm/hp05w3f3303t5e/

[wraper]

With SMD you are no hobbyist i think.

So far from truth. Hobbyists use SMD a lot. Especially considering they can order PCBs for a few bucks. Are you professional if you are reflowing PCBs on a pan?

[daqq]

I'm not sure what the problem is - you were relying on a part that was fairly obscure even in its heyday. The market for obscure non-SMD resistor values is simply not that large and explains why it's no longer an option.

Several suggestions here solve your problem, all of which you have refused for silly reasons.

I like being a hobbyist, not a professional.
With SMD you are no hobbyist i think.

Wrong.

[bdunham7]

You need to realize TH technology is mostly obsolete, want it or not. So no matter how much you prefer TH over SMT, no matter how good reasons you have, the selection of parts available is poor and gets worse every day. You can whine about it until cows come home, or you can just use the parts that are available and get the job done. Side effects are almost all positive, but attitude needs to be fixed first.

Actually I'm continually amazed at what is available still.  In repairing stuff from 100 years old to 3 years old, I actually run into more obstacles with obsolete SMT parts than I do TH.  And in repair, I often have less flexibility, although I generally don't quibble about cost.  I can get brand new 12AU7 dual triodes from several manufacturers, but a relatively common MP2363DN buck converter is obsolete, although there are some still out there.  I'd have to stockpile them if I thought I would need more.

Yes, I always try to default to full-SMT design whenever possible. The opposite, trying to default to THT, is becoming a masochistic act I think.

To a novice, TH might seem easier until they have to lay out a space-constrained board and they realize that a TH PDIP will obstruct all the layers of the board. 

[Jan Audio]

Several suggestions here solve your problem, all of which you have refused for silly reasons.

The reason is i already have those parts.

[Jan Audio]

I'd have to stockpile them if I thought I would need more.

Stockpiling obsolete parts is a serious thing in this hobby, and you can make good money also if you buy enough.

[bdunham7]

The reason is i already have those parts.

What tolerance are your other parts?  It makes no sense to have this value at any tolerance greater than 1%. 

How many of these 6-bit DACs are you making that cost is such a concern? 

[Kleinstein]

The main use for THT parts is for test circuit on the bread board or manybe perf board and a few higher power parts. With a PCB it is much easier to use SMD parts and build to oder PCBs have become relatively cheap.
It does not take much practice to solder 0805 resistors and caps and 0603 as also not hard. One used to it one hardly wants back to THT, even on a perf board.

Especially for DAC and 1:2:...:32  resistors it is absolte normal to combine 2 resistors , as this reduces the number of unique parts.  I would even consider just 2 values and us each as 2 in parallel, as a single and 2 in series.   The 320 K resistor in the circuit is the least critical, so 314 K and maybe even 330 K  should be good enough. 

[Siwastaja]

Several suggestions here solve your problem, all of which you have refused for silly reasons.

The reason is i already have those parts.

Trying to design around what you have is all fine, but you tend to run in trouble as soon as you are building more than you originally expected and run out of those "free" parts.

For this reason even though I like using my existing stock, I'm very careful when doing that so that I don't need to redesign suddenly.

Using your own stock works as long as you know the parts are either easily orderable with product lifetime left, or generic enough to have acceptable replacements.

Most components are very cheap; I just buy new components by default, and use excess stock for one-offs and prototypes where I know I'll only build that one piece.

BTW most good practices are the same regardless of being a professional or a hobbyist. For example, you want your circuit to work nevertheless. Similarly, you want to use parts that are available. And miniatyrization, often a professional product can be arbitrarily large, or a hobby project needs to be small, or vice versa.

[bdunham7]

Stockpiling obsolete parts is a serious thing in this hobby, and you can make good money also if you buy enough.

Oh I know--I recently bought 10 resistors for $5 each plus an hours drive to get them and I was quite happy to be able to acquire them.  But that is for a repair scenario where there aren't good alternatives.  If it was something I was making, I'd try to use parts with good availability.

[Jan Audio]

$50 for 10 resistors,
you make me think those $50 ( excl. tax ) for 100 resistors are worth it.
For $50 i build a whole synthesizer.

[Monkeh]

Or you could just alter your design and use series and parallel combinations of more common values to get the desired value instead of whining about how hard it all is.