3, Interfaces, Ohmite resistor?

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Hank Cantor2004-02-23 22:21

Do you know anywhere that currently has available the replacement Ohmite resistors? I can\'t find a source that has any in stock. Maybe another poster has a few extras or knows where to get them. Thanks for your help in my as yet fruitless search. Hank Cantor (Acoustat 3 slimlines)

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Andy Szabo2004-02-23 22:21

When you say ”wirewound golds”, I assume you are referring to aluminum-bodied resistors that have a yellow-anodized finish. These are made by several manufacturers, including Ohmite. From an audio perspective, I\'m not convinced there is any advantage to using these. As far as I know, the resistive element inside these resistors is the same as the resistive element in more conventional tubular ceramic wirewounds. The advantage of these resistors is that they are more stable in harsh environments, and are smaller in size for a given wattage, due to their ability to be bolted to a larger heatsinking surface. I\'ll admit they do look pretty cool.

I see no harm in replacing R1 and R4 with the ”wirewound golds”. They should be mounted to the metal chassis to maximize heat dissipation capacity. I do not recommend using ”wirewound golds” for R2 and R3. Because of the way these resistors are mounted to the edge of the printed circuit board, they should be replaced with the same type of tubular ceramic wirewounds. Due to the high voltage application for these resistors, you definitely do not want to mount them to the chassis. They need to be mounted to the board just like the originals.

For your reference, these are the values and suggested sources for replacement parts: (see www.mouser.com)

R2 and R3
50,000-ohm, 50 watt, tubular ceramic wirewound.
Mouser # 71-HL50-06Z-50K (5% Vishay brand).

R4
1-ohm, 25 watt, aluminum-body wirewound.
Mouser # 71-RH25-1.0 (1% Vishay brand).

R1 (for ”C” conversion from 6 to 16 ohms)
10-ohm, 25 watt, aluminum-body wirewound.
Mouser # 71-RH25-10 (1% Vishay brand).

Andy Szabo2004-02-23 22:21

I have been collecting some data on Acoustat replacement parts (as yet unpublished), and have found several sources for Ohmite resistors. Try these websites:

www.digikey.com
www.mouser.com
www.newark.com

You didn\'t mention which resistor(s) you need. I have already identified specific part numbers from the above companies for some of the resistors, so if you can tell me which resistors you need, I may be able to give you more detailed help. For some of the resistors, several brand names are available as suitable replacements, increasing the chances that someone will have the correct value(s) in stock.

Thank you for your question. It will serve as motivation for me to get that information published!

Hank Cantor2004-02-23 22:21

Andy, the ohmite resistors that I am looking for are the wirewound golds to replace the original tubular ceramics on the multiplier board and at the bass panel selector (orange for my model threes), but most importantly the resistors added to the high pass filter bypass caps. I don\'t have the values in front of me, but I\'m sure you know them. I\'d appreciate any info on where to locate the appropriate resistors. Thanks for your time. Hank

I have functional original resistor for all but the high pass filter location. Although I seem to want to upgrade/replace them as well.

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