I cannot locate replacement resistors.

Thread Starter

CJay

Joined Apr 30, 2015
6
I am currently working on an old set of Gemini DJ speakers. There's a 15 watt 75 ohm resistor in the piezo curcuit on the crossover that is shot. It's an old ceramic/cement style. The only place I have found a direct replacement is in Russia, no joke. I'm not sure how to proceed. Are there any ideas on alternatives that will work effectively?
 

joeyd999

Joined Jun 6, 2011
5,220
I am currently working on an old set of Gemini DJ speakers. There's a 15 watt 75 ohm resistor in the piezo curcuit on the crossover that is shot. It's an old ceramic/cement style. The only place I have found a direct replacement is in Russia, no joke. I'm not sure how to proceed. Are there any ideas on alternatives that will work effectively?
Any 75 ohm 15 watt resistor will work. Or are you trying to keep the speakers "authentic"?
 

Thread Starter

CJay

Joined Apr 30, 2015
6
Authenticity is not a concern. I was under the impression that I needed to keep with the same style of resistor ie. non-inductive ceramic etc. Is this not the case?
 

joeyd999

Joined Jun 6, 2011
5,220
Authenticity is not a concern. I was under the impression that I needed to keep with the same style of resistor ie. non-inductive ceramic etc. Is this not the case?
I'd be surprised if a standard wire wound had enough inductance to make a difference. But, non-inductive wire wounds are available at a premium.
 

Thread Starter

CJay

Joined Apr 30, 2015
6
All good info to consider. Thanks a million. I'm still trying to wrap my head around the "need" for this resistor in the piezo circuit. I assume it's for protection only since by design piezo's do not need crossover considerations. This "crossover" is odd anyhow. The woofer wires straight thru from input, there's a 10 watt 19.5 ohm resistor and a 10 mFd 100v capacitor in the horn circuit. If it's only for protection could I not fuse the piezo circuit?
 

Thread Starter

CJay

Joined Apr 30, 2015
6
Answered my own question on that one. I would need to add a pot for that circuit if I would eliminate the resistor and the pot would have to fall in the range of the resistor I'm dumping etc, etc. I'll get this figured out yet. Thanks again for all the suggestions so far.
 

Thread Starter

CJay

Joined Apr 30, 2015
6
No pot....that'll likely become noisy at some point.
Agreed. I'm trying to figure out if there is a formula for changing the values/ratios for this resistor to get the same limiting result ie. can I drop wattage rating and increase ohm rating or vice versa etc.
 

Alec_t

Joined Sep 17, 2013
14,263
Wiring two (or more) resistors in parallel would have the advantage of spreading the heat load and lowering inductance (if that is important?).
 

Thread Starter

CJay

Joined Apr 30, 2015
6
I think I've got the solution. I'm gonna go with Ohmite B12J75RE's. I'll replace them in both cabs. They're a 12 watt vs 15 but that should not be an issue. Axial, wirewound, vitreous enamel; much better platform than the old ceramic bathtubs. I also wanted to say "Thank You" to everybody that offered some advice on this. I look forward to asking more dumb questions in the future!
 
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