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Mac SCR

cliffmac

cliffmac

Member
Hello,

Just picked up a SCR and hooked it up and i get no power. The speaker end of it works fine, but when i plug in the C28 to the 120 outlets i get nothing.

I opened it up and there looks like a relay of some sort.

Any ideas?

Thx Cliff
 
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The C28 triggers the relay in the SCR to power-on the amplifier. It can't be plugged into the SCR.
 
cliffmac said:
Hello, Just picked up a SCR and hooked it up and i get no power. The speaker end of it works fine, but when i plug in the C28 to the 120 outlets i get nothing. I opened it up and there looks like a relay of some sort. Any ideas?
Click to expand...

There are several SCR's: http://www.roger-russell.com/elect.htm#SpeakerRelaySwitches

The SCR 1 here can control only speakers. IIRC, SCR 2 switches both speakers and AC Power. The SCR 1 (with four-pin control cable for the C33) has two relays inside, one for SPKRS 1 and the other for SPKRS 2. Had it out the other day trying to understand how it can switch in TWO pair of speakers, and to what IMPEDANCE taps? or how it can be adapted to switch TWO amplifiers out to a single pair of speakers. Frankly I'm not too big on the idea of cascaded relays to the speakers. The relay in the 2205 is enough thank you.


-Gregory
 
Scr 2

Have another question, i have a 2100 and a c28. I have the 2100 hooked to the amp terminals on the SCR, Lascalas hooked to the main terms, and a set of Bose 901s hooked to the remote terms.

Should i hook the 2100 terms on it to 4 0hms instead of 8 ohms, giving the fact that my main and remote speakers are in parallel?

Thx Cliff
 
Using the SCRs is a compromise.....ideally you would run 1 amp for each pair. Will you run both sets mostly at the same time...then use 4 ohms..if mostly 1 pair at a time use 8 ohms.
 
Ok.... then it depends on how many pair is running. Also they are not in parallel?

Still confused, it won't hurt the Amp running 4 or 8 ohms?

Thx
 
There should be no confussion....buy another amp for best performance...you want to save money and compromise so.....

They are in parallel when both are on....compromise would be 4 ohm since this was usually for backgrond music systems...again higher performance system installations used 2 or more amps.

I sold mac for over 30 years...just a handfull of SCR2s, 3s or what ever just for this reason.
 
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Actually there was 1 more SCR, the 1a that was the original 1 plus had the AC outlets. If the ac sockets are not working while the speakers switch then the 5 volt power source is okay. Most likely the full wave bridge rectifier can be the problem as I've seen quite a few with either 1 or both of the diode packs were dead.

My advice on the C28; do not plug anyhthing in the C28s switched outlets. The power switch wear factor increases dramatically. Especially stay away from the amps as most exceed the power switch capacity. It takes time but it will shorten the life greatly.
 
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