Replacement resistors in vintage equipment

[sssmokin99]

Suppose you were going to go through not only the power supply, but the amp driver boards in a 30 year old receiver or amp. You already have decided to replace the electrolytics and some other parts, check solder joints, etc. You want the thing to work reliably and sound its best for many more years, and so have decided to replace the resistors. All of them! Now, what type would you use? I have read many opinions, and some differ as to the type of circuit (i.e. amplifier versus R.F.). Anyone who has done this care to offer guidance? I should add that I am looking for that sweet spot of cost/performance, the most bang for the buck. Obviously, the largest cost of this is your own time. Many thanks for your thoughts!

 

[rulerboyz]

The only place I've ventured with this idea was in the phono section of a Pioneer A7 integrated amp. As an experiment I changed the resistors that were related to the signal path with resistors available from Parts Connexion. There was definitely a change in the phono section sound, however I'm not sure how much of a role, if any, the new resistors played.
For the most part I used PRP (Precision Metal film resistors). In the very first resistors after the RCA jacks, I used the more expensive Riken resistors.
I also replaced the stock RCA input jacks with the audionote chassis mount jacks and connected them to the circuit board with a light gauge solid core silver hook up wire and cardas solder. I also did this to one of the Tape out jacks so that I could compare the stock versus the "upgraded" jack. I could hear a difference in sound from that one single upgrade alone when quickly comparing between the two outputs.

I think it's going to be generally controversial, the idea of changing the resistors in vintage solid state. It's a lot of work for maybe zero difference. It's probably going to be the least likely part that would play a role in changing the amp's sound.

 

[Fred Longworth]

The general rules are: (1) the higher the resistance of the resistor, the more noise may be reduced by replacing it; (2) the lower the level of the signals being processed at the point in question, the more benefit you'll get from replacing resistors.

We use metal film 1% devices, usually Xicon devices, available from Mouser.

Fred

 

[sssmokin99]

Thanks for this good information, guys. This will possibly be a project for one of those snowed-in days! (not a problem in your neck of the woods, Fred!)

 

[Tube Radio]

I too use 1% metal film resistors from Mouser and have not had any problems yet.

 

[avionic]

If your into a little reading about resistors..http://www.aikenamps.com/ResistorNoise.htm I use mil-spec'd metal film Vishay / Dale.

 

[jblmar]

I replaced all 102 resistors on my Marantz 3650 preamp board. I had a noticeable, constant hiss. Replacing the resistors with the original parts listed in the service manual got rid of the problem.
BTW. The SM calls for (for the most part) carbon, 5%, 1/4 watt resistors.

Ron

 

[SPL db]

 

[Danmp]

I have a vintage marantz 1030. This amp has a warm, very open and real sound. This is very cool with vinyl. I hear about the sonics of hifi 1% film resistors and decide upgrade the preamp resistors. I bought resistors of a brand called PRP. Who should be hifi resistors. But I was wrong. The PRP metal film sounded so unnatural, like a bad mp3 player. The sound was closed without dynamics. So I change again to the originals. I dont know what is the brand of the marantz original resistors, but they sounded a lot better.
I will try takman metal film.

 

[ConradH]

A lot of older equipment used 1/2 watt carbon film resistors, regardless of whether they needed to be 1/2 watt or not. The first thing I do is find the actual voltages across the parts and what wattage is really needed, plus a generous and appropriate safety factor. If the answer is maybe 175 mW or less, I use the Xicon or Yaego 1/4 W metal films you buy by the bag of 200. Above that, I tend towards Vishay RN60, 65 or 70. Watch the voltage limits in tube stuff. You can be well within the wattage limits, but still exceed the voltage limits. I'm still wary of the newer high power miniature resistors. I use 'em, but remember that the little body is going to get extremely hot- keep it raised from the board. Be wary of metal oxide and other technology resistors, as they may have a higher voltage coefficient. A metal film is probably not going to fail even under extreme overloads- sometimes a carbon film will be a better choice if you want some protection, but don't want to pay for an actual fusible resistor. OTOH, they may not be flame-proof! IMO, the most sensitive location is the feedback loop. Any weirdness there will be applied to the transfer function of the amp, so choose wisely. That might be the best metal films, or it might be old carbon composition, depending on your needs and desires. Read data sheets- all resistors are not created equal or intended for the same purposes. I always use a resistor bender, probably OCD.

 

[OMGCat!]

I did not know I needed a resistor bender until just this minute. I now have a set on order.
Up until this point I used a calibrated eyeball and a small pair of smooth jawed needle nose to bend my leads as my own OCD will drive me nuts unless they are perfect. Thanks Conrad, you've saved me some future stress

 

[Phil-from-Tn]

I just rebuilt an old (40 year old) Heathkit AR-15. There are pictures of it in the "Today's Jazz" thread. It didn't sound too bad when I picked it up(a $22 CR find). Because of the way its built, the preamp board is pretty hard to work on as its covered by almost every device in the front of the receiver or overlapped by other devices. So looking at it, and not wanting to have to get to the troublesome board more than needed, I basically stripped it of all the carbon resistors and old poly caps as well as all the electrolytic caps. I went with 1/2 watt Xircons and Nichicon electrolytic caps. For the polys I used modern polys. I also replaced a bunch of front end Transistors on the preamp board. The important thing is to bring the resistances back into design parameters. I had a couple of 220k ohm resistors that had drifted to almost double. Then I also completely stripped the phono preamp board and replaced everything in it. It is another hidden board, covered by the FM tuner board. Of course none of this matters if the power supply board is noisy. Mine had a nice 60Hz and 120Hz ripple on top of all voltages. That was solved by replacing the huge 8000uF power filter cap and also the coupler caps. This amp uses coupling caps for the finals. Then a judicious replacement of the driver and power transistors and this thing sounds completely different. Its warm and wonderful. All the electrolytic caps in the entire unit were replaced. I've got some folded horn bass cabinets in the works (collecting drivers) and when I'm done it will be one great sounding combo. I think so far I have about $300 in the receiver but it will sound this good for a very long time.

So in the end with the quality of todays components and after doing some reading, much of it on this site, a really great sounding system can be had for minimal cost. I really love the sound of my rebuilt AR-15 and it looks cool too. Its kind of neat when folks come over and see it, then hear it. They are usually blown away with the quality of sound. You must invest in some great speakers though. I have a couple of Speakerlab seven knock offs I built when I was 17. They've also been rebuilt. The new design folded horns will blow these away however. I'm looking forward to that project.

I've picked up another AR-15 for rebuild and will be putting it in for the downstairs listening room since the AR-15 is wife approved for "it looks like my dads old receiver". LOL

 

[arts]

I did not know I needed a resistor bender until just this minute. I now have a set on order.
Up until this point I used a calibrated eyeball and a small pair of smooth jawed needle nose to bend my leads as my own OCD will drive me nuts unless they are perfect. Thanks Conrad, you've saved me some future stress

Most everything I work on is terminal-board or point to point. When I started doing more and more full restorations on PCB equipment,I ordered the full set of these little critters. Greatest thing since sliced bread!

 

[Danmp]

I finally changed the resistors of my marantz 1030 to takman film. No one resistors brand can beat the open sound of the marantz original resistors. Anyone know what is the brand of marantz resistors in the seventies?

 

[BinaryMike]

I finally changed the resistors of my marantz 1030 to takman film. No one resistors brand can beat the open sound of the marantz original resistors. Anyone know what is the brand of marantz resistors in the seventies?

Interesting. I've suspected for a very long time that Marantz gear of that era, built by Standard Radio in Japan, owed its characteristic sonic sheen to resistor characteristics. As far as I know, the resistors are carbon film type. I have no clue who manufactured them. I have a Japan-made 3200 preamp, which has many engineering similarities to the US-made 7T preamp but an obviously romantic coloration that's absent in the 7T. Both of these preamps perform well in THD testing. I hope to learn more about this issue before it no longer matters.

 

[Blue Shadow]

You sure did have a large bucket of popcorn if it lasted the nearly 8 years needed to get additional responses to this thread.

 

[EchoWars]

Most everything I work on is terminal-board or point to point. When I started doing more and more full restorations on PCB equipment,I ordered the full set of these little critters. Greatest thing since sliced bread!

Been using one of these for years. Fortunately, I did not pay anywhere near that price for it. But...if I needed another one, I'd probably bite the bullet and pay up. It's the fastest way to make a perfect bend.

 

[Blue Shadow]

Been using one of these for years.

I was thinking about these benders and using them on a populate circuit board and thought that one more like a crescent wrench with the opening on the front instead of the side might make "getting in there" a lot easier some of the time. Not having done a lot of these replacements with specific bends required, I don't have a tool to do the work, but was curious if that front measuring/bending device would be more popular than the micrometer type you linked. Don't even know if a 'front opening' unit is available.

 

[Lavane]

I replace all carbon comp resistors I find with carbon films. Takman is a brand I like to use. I replaced all the carbon films in one Marantz 1060 amp with 1% metal films and left the carbon films in the second one. There really wasnt much of a diffefence Iin sound. There wasnt any hiss or sterile sound from the metal film amp at all, just a tad clearer sounding.

 

[SPL db]

You sure did have a large bucket of popcorn if it lasted the nearly 8 years needed to get additional responses to this thread.

It's a little stale now, but I do have some left...