View Full Version : Won an RCA 'Colorvolt'

06-10-2016, 02:34 PM
Now that I finally tracked one of these down, does anyone know how they work? I can't seem to find any schematic info on it, but being a piece of test equipment they are often tougher to located than the actual sets. Also am I wrong, or does this thing not even have enough current to power a color Roundie? Seems to defeat the purpose if it tops out at 3.1 amps, I can't think of a set that runs less than around 375 watts till transistors came along. Will be neat to play with, maybe I can copy/beef up the circuit to make it work for sets that draw more power.

06-10-2016, 02:53 PM
It will in fact run a color roundie. It's just a Sola CVT in a dressed up housing. Sola played fast and loose with their ratings; I've drawn 575 watts from a 500 watt unit for hours on end, countless times, with no ill effects.

For what it's worth, I have a Colorvolt and have run a CTC-5, CTC-7, CTC-9, and CTC-10 on it. It handles the current draw of each with no problems.

Eric H
06-10-2016, 02:56 PM
Is this the one from Colorado that was on eBay?
I remember a discussion on one of these but I don't know if it was here or over at teh A.R.F. site. Isn't it basically a Sola constant voltage transformer

06-10-2016, 03:13 PM
Yep, Bennett CO. I didn't figure it had any actual active circuits in it, guess I'll just trace it out and go from there. If it is just a CVT, there are plenty of those on Ebay so maybe I should get one for each set instead of cycling them through the variac? It gets tiresome after a while...

Electronic M
06-10-2016, 04:29 PM
I've got 3 CVT/VRTs for my regular use sets.

Phil Nelson
06-10-2016, 10:46 PM
does this thing not even have enough current to power a color Roundie? Seems to defeat the purpose if it tops out at 3.1 ampsI noticed that item and had exactly that hesitation.

Those of you using a dedicated CVT for this purpose, do you have a model number or specifications?


Phil Nelson
Phil's Old Radios

06-10-2016, 11:26 PM
I use Sola CVT Model Numbers 23-23-112, 23-23-125, and 23-23-150. They're 120, 250, and 500 volt-amp models respectively. The rating is fairly arbitrary; with decent ventilation a 500 volt-amp model will supply 600 volt-amps all day long.

There are four things I'd keep in mind when using a Sola:

1) They are most efficient when supplying a load near the maximum limit. Having multiple sizes around helps best match the load to the transformer.

2) The case and transformer core MUST BE GROUNDED. NEVER USE A SOLA THAT DOESN'T HAVE A 3 CONTACT PLUG. Never use a Sola plugged into an improperly wired socket.

3) Older Sola CVTs use capacitors that spew all sorts of know carcinogens and teratogens when they fail. They should be replaced as a matter of course. The value of the capacitor is critical.

4) They're rated in volt-amps, not watts. Power factor matters here. Luckily for us, the wattage rating of most vintage electronics is actually the apparent power draw, not real.

06-13-2016, 10:35 PM
Why does the colorvolt need to be grounded? it is not hot to the case or anything..


It is ALSO NOT ISOLATED. It is wound as more of an AUTOFORMER...with an additional winding for "resonance". on MINE.the big, PCB-filled cap FAILED in short order...on a SMALL load of maybe 100 watts. it SHORTED. No bulge or anything...just a DEAD short on it.and that "PCB "odor..

WHEN you replace the cap..use at LEAST a 660 volr one. I tried a 500 volt one--thinking it was high worked...BUT...I could TELL it did not like the over-volts. I measured the volts on the cap--it was OVER 700 volts on my dmm. Not unusual...a meter will NOT properly read the output from a VRT..