Not long after I built the ETI-466 units into the 3U rack mount, I was managing a Tandy Electronics store where I kept the 'Black Beast' for demonstrating our Mach 2 speakers 'properly'. At the time, Tandy/RS only had a (Sherwood) Realistic 100w/ch receiver and it did nothing to let those big speakers breathe...
When the Mach 2s were on sale, I'd bulk stack them on a 8ft long, narrow chipboard panel with 6 castors on the bottom in a 4x2 combination and wheel them out the front of the store, into the mall (with 1/2 price ($249 ea) sale signs on them).
The entire 4 pairs were run in a series parallel combination on my 'brute' amp driven from a Realistic 19" mixer and a Realistic (Pioneer) CD player. I'll never forget playing Phil Collins' Another Day in Paradise and George Michael's Faith album for customers who wanted a 'demo'. It lit up the entire courtyard and food court so much, that I had more than a few calls from centre management or security threatening me with a breach of lease or having my power cut-off. Haha. That said, it generated a lot of sales and foot traffic into our upstairs location- something other tenants loved.
There were many occasions where we lit up the twin festoon 12v 5w bulb 'protectors' on the Mach two crossover PCBs and the bright light was visible through the reflex ports. Never blew a driver however.
That big ETI-466 dual mono made me a lot of money in commissions and I will never forget the joy of manhandling it (the handles were spare part SSM-2100 Realistic mixer handles) into a cabinet with the sticky rubber feet I used. (I can't believe I remembered the model number of the mixer!)
🙂 🙂
When the Mach 2s were on sale, I'd bulk stack them on a 8ft long, narrow chipboard panel with 6 castors on the bottom in a 4x2 combination and wheel them out the front of the store, into the mall (with 1/2 price ($249 ea) sale signs on them).
The entire 4 pairs were run in a series parallel combination on my 'brute' amp driven from a Realistic 19" mixer and a Realistic (Pioneer) CD player. I'll never forget playing Phil Collins' Another Day in Paradise and George Michael's Faith album for customers who wanted a 'demo'. It lit up the entire courtyard and food court so much, that I had more than a few calls from centre management or security threatening me with a breach of lease or having my power cut-off. Haha. That said, it generated a lot of sales and foot traffic into our upstairs location- something other tenants loved.
There were many occasions where we lit up the twin festoon 12v 5w bulb 'protectors' on the Mach two crossover PCBs and the bright light was visible through the reflex ports. Never blew a driver however.
That big ETI-466 dual mono made me a lot of money in commissions and I will never forget the joy of manhandling it (the handles were spare part SSM-2100 Realistic mixer handles) into a cabinet with the sticky rubber feet I used. (I can't believe I remembered the model number of the mixer!)
🙂 🙂
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I will use a transformer at 49.5x2 Vac, Dont have the spec on it. I can upload pic tomorrow, a pretty cool one.
but it would not be any problem to use mj15022 then.
but it would not be any problem to use mj15022 then.
mj15022
I Got mj15022/23 so they can take about 200 VCEO, so I learned something today. Thanks.
I Got mj15022/23 so they can take about 200 VCEO, so I learned something today. Thanks.
I thinks it cool.
anybody know if it has any value
2x49.5 volt and 1x16.5v
but maybe have plans for this in a build of mine.
can you tell us how it weighs in kg?
what is the primary dc resistance, and dc resistance of the secondary
windings?
what is the primary dc resistance, and dc resistance of the secondary
windings?
It does look cool, but I'd be concerned with the insulation and the condition of the wire in general. It must be 80 years old by the looks. It looks like a ceramic outer frame?
Get it thoroughly tested by a transformer winder.
Get it thoroughly tested by a transformer winder.
Twickenham
It a iron cast around as frame, and it insulation i dont know but it Works good.
It a iron cast around as frame, and it insulation i dont know but it Works good.
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The smaller ETI-480 50/100W unit was far more prevalent. I ran a pair of them for hifi for years, slightly modified to clean them up, since they were designed as an instrument amplifier and intentionally left a bit dirty. I did come across one of the 300W beasts being used by a musician and performed one of the cleanup mods on that as well.
That's unimportant, since it is shorted by the coil. I'd probably use 1 ohm myself.
Thanks for the response, ok 1 to 4.7 ohms then, did you like my redraw of this design PCB? 🙂 also any suggestions on mods for this design?
Best Regards
Juan
Best Regards
Juan
Hola Juan,
PCB redraw looks fine here. You'll find a ton of information on them, including the original ETI article, at ETI-466 Amplifier Technical Review
Mods, ah where do I start?
1. First thing, get rid of the electrolytic at the input and insert a 10 uF bipolar cap.
2. Next, replace emitter resistors in the output stage with good quality low inductance types (if necessary) to ensure it doesn't explode and take out all the output transistors. Noble and IRH brands are known to be suitable. I wouldn't use anything except genuine Motorola parts there either.
3. Lift the collector leg of Q9 (BD139) and insert the circuit attached, which consists of one new transistor and two resistors. You will need to then remove the fuses and redo the bias adjustment procedures.
Hope that helps.
Rob
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I just read the original article, they say to use any 1W resistor over 100 ohms and to wind a single layer of 26 swg wire over it. Number of turns isn't so critical either. In those days the only common resistors were carbon and they were quite large so you might need to use an old one, or a new one with higher wattage rating.
oh nice thank you haiqu I think I can do that on the layout sure, this resistor is also 100R? I'm going to do the changes then later will post layout to see if I did it correctly 🙂
regards
Juan
regards
Juan
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