New smaller technology resistors

[Randall]

I just got an order in from Newark that contained several bags of Vishay 1 watt 5% metal film resistors. All the other bags of Multicomp 1 watters are the normal size, but the Vishays are the size of 1/4 watts. I called and spoke to tech support, and the guy assured me they were 1 watts, and that new technology makes them able to be so small. Problem is, I don't want so small in a hand wired point to point amplifier. They just look wrong. I might use them on a pcb repair, but would you put them in your build? Not me.

[JoeM]

Where are you using them, ie. plate resistors? Maybe use 1W Carbon film, I've used some that are physically larger than some MF. Of course once you've got the amp built and buttoned up you're not going to see them. I had a Twin Reverb RI with a burnt screen resistor that I fixed over the weekend. All I had to work was an old CC 1w that looks huge in comparison.

[Enzo]

SO order a different brand or higher wattage. YOu concern is cosmetics rather than electronics then. The vendors like Mouser et al have data sheet links if the dimensions are not already in the selector grid.

[JoeM]

Randall,

A friend does conversions for the Fender RI models. You might find some info here useful.
Some of the cleanest wiring I've seen.

Classic Re-issue Re-builds

[g1]

What irks me the most about the "new" sizes is not being able to guess what the wattage is. At some point we will have to calculate required wattage for every resistor we replace. The schematics usually don't show the wattage. At least with caps, even though they keep getting smaller, they have the voltage written on them.
From a repair perspective, calculating wattage requirement is just an extra, time consuming step.
Maybe the solution is to just use overkill wattage for all resistor replacements?

[Enzo]

Or realize that the 100k plate resistor for a 12AX7 is not going to have any different needs from any other 100k 12AX7 plate resistor. If in doubt, think about what it would have been in the equivalent position of any old Fender you have worked on.

If you normally stock 1/2w resistors, and the new ones look like 1/8w. Then just stock somwthing the same size as the old ones, even if they are now rated at 1 watt. It may be overkill, but resistors are dirt cheap, and besides, how many things in your shop have as attractive a markup as a resistor? I pay a penny or two for a resistor, and sell them for 50 cents or more, so pushing the cost up to 2 or 3 cents is not an issue for the retail price.

[bob p]

http://music-electronics-forum.com/t21277/

[bob p]

metal films have gotten really, really tiny. i started that thread a few years ago after buying some Vishay MF resistors from Newark that were so darned small that I couldn't identify them visually.

What was really amazing to me was the huge discrepancy in size (see photo) between the various MF resistors -- the cheap-quality chinese Multicomp resistors were the worst -- huge resistors, lots of noise.

The only real drawbacks I've found to the teenie-weenie resistors have been:

- size is so small you can't read them, and you have to ID them with a DMM
- leads are ultra flimsy
- can get very hot.

one plus that you may not have thought of is that those teeny little laser carved MF resistors can get really, really hot without changing value. so hot that you might get lucky when it comes to exceeding power ratings.

i have no qualms about using the smaller resistors, though i do hate the flimsy leads. i used the teenie-weenie vishay-branded 1k5 MF resistors on my Super Twin, and just wired them across the tube socket. nice and small, easy to fit. i had no problems mounting low power grid stoppers and 2W screens across the same socket... plenty of room.

the good side of this is that I've ordered 1W and 2W MF resistors which on delivery turned out to be about as small as an old style 1/4 W resistor. the result is that I've used some 1W or 2W resistors in lieu of 1/4W resistors in stompbox builds.

edit: aargh. attachment of photos not working.

[Randall]

YOu concern is cosmetics rather than electronics then.

Actually it's both. I do a lot of vintage amps, and looks are a valid part of a restoration for me. Smaller may be great for some things, but for me not on the fiberboard of a vintage amp build. Plus, I also do not like the smaller leads, or harder to read codes. And they just look like heat would be a factor, maybe not. So yeah, I am going to be using the larger wattage resistors for their size.

[Enzo]

I didn't mean that in a snotty way. Nothing wrong with cosmetic concerns. Just defining the goals.

[Randall]

No sweat Enzo!

[Randall]

Randall,

A friend does conversions for the Fender RI models. You might find some info here useful.
Some of the cleanest wiring I've seen.

Classic Re-issue Re-builds

Wow. Beautifully done!