I know variacs are good for gradually turning on older color sets to protect caps. Has anyone devised a solid state soft turn on device for these that can handle 350 to 500 watts needed power handling for old color. Please post info. if available, I really want several of these as just simply turning on a roundie, knowing it's surge current protected every time , be a would be a nice setup without having to fiddle with a variac, cleaner too. A nice power up time would be gradual 0 to 120 volts AC over a time period over several minutes. Variacs are also getting hard to find & expensive. Please post insight on subject.

You have to remove the Horz. output for a soft start. I could see that being a pain everytime you wanted to watch Gilligan on a roundie. :thmbsp:

You have to remove the Horz. output for a soft start. I could see that being a pain everytime you wanted to watch Gilligan on a roundie. :thmbsp:

If it were several minutes yes but how about just a 5 or 10 second ramp -up to full voltage? Seems like that would serve the same purpose without stressing anything out.

If the caps are good, a slow turn on over a few seconds (before the filaments get warm enough to bring up the sweeps) is OK, but over several minutes is not a good thing. Some horizontal output circuits will draw excessive current if the supply voltages are not near nominal. So, the very slow turn on should only be used in the beginning, with the HO removed, as a way to TRY reforming the caps. It's not necessary or wise when everything is working OK. The few-seconds turn-on may be life-extending, but by how much I'm not sure. Anyone have real info on this? Some brands of TVs used to advertise that they had this feature, but anything that was put in a set and then advertised may have been there half for real effect and half for advertising claims.

I would worry more about monitoring the line voltage and adjusting it to nominal rating.

keep in mind that unlike it's modern counter-part the power supplies have a massive power transformer to help buffer surge voltage, the modern switching power supplies are hand out to dry every time you turn them on.

if you ever put a volt meter on the filter caps it take a little bit for them to come up to full output

If you want to test for shorts I have found the series light bulb of about 100 watts to be best.

If a tube type set is used much it really needs new electrolytics and rectifier diodes and not trying to "baby" the old ones...and you won't have to worry about a cap failure at turn-on. Have seen too many shorted caps and diodes in TV's, even late 60's models.

The CTC-10 or 11 uses some kind of a varistor to limit inrush current, but if you have good new caps and diodes it should not be a problem even without one.
Also in sets with a degausser I think the degaussing circuit in the B+ directs the turn-on surge current through the degauss coils and this helps counteract the surge.

Some sets had a thermistor built into the tv-end of the power transformer circuit, to reduce the initial surge into the set... so maybe if a set's circuit didn't have one it could be added? My ctc-10 had one but it was bad and I just removed it from the circuit.

Once the filter caps and rectifiers are replaced, I can't see any reason to worry about damage. I mean, if you're replaced critical power supply components, then the power supply should be good as new, and these sets were designed to operate this way. If you haven't replaced the filters, then it's really just a matter of time before you need to replace them, and I don't know if trying to soft start the set every time will really help prolong their lives. Also, you don't want to damage the HO tube - these are much harder to find than the electrolytic capacitors are!

-Ian

As I saw it, the Thyrite in the CTC10 was there to limit the filter cap initial charging current, protect the power supply diodes that have to pass the high current surge of the filter caps, and even as a secondary benefit, the on-off switch sees much less turn-on stress. It also gave me a warm fuzzy when I watched the #47 lamp ramp up to full brightness in the two seconds or so that it took, because all the filaments were slow-starting too. To me Thyrite is a Stress Tab for electronics.

In a 1960 Motorola bw set I have there is a device which does something, though I'm not sure what. I think this is the "Tube Sentry". I have an extra that I found in a junk box. It seems to delay application of voltage or ??? Maybe somebody knows what I'm talking about.

As I saw it, the Thyrite in the CTC10 was there to limit the filter cap initial charging current, protect the power supply diodes that have to pass the high current surge of the filter caps, and even as a secondary benefit, the on-off switch sees much less turn-on stress. It also gave me a warm fuzzy when I watched the #47 lamp ramp up to full brightness in the two seconds or so that it took, because all the filaments were slow-starting too. To me Thyrite is a Stress Tab for electronics.

Anybody know of an available online source for a suitable replacement for this part? It is a thermistor, 79 ohms (cold). thanks
Speaking of switches, the switch in my hair dryer went bad this morning, I could see flames shooting out of it thru the white plastic housing. It finally quit and I finished drying my hair (which now smells like a burned transformer!) and then I unplugged it, ran water thru it and tossed it, time to buy another one!

:yes: Thanks for fantastic information on this. :thmbsp:


Does anyone have several thyrites or varistors I can buy from?? Please PM. I was hoping a few seconds would be good enough. Wouldn't this help promote a longer life for ALL tubes, including CRT?? I was looking into this also to limit as much surge current going to CRT as possible to try and extend service life. Does varistor go in power transformer primary circuit, or somewhere a take off in secondary, for a gradual power on for B+ voltages??

[QUOTE=vintagecollectDoes anyone have several thyrites or varistors I can buy from?? Please PM. I was hoping a few seconds would be good enough. Wouldn't this help promote a longer life for ALL tubes, including CRT?? I was looking into this also to limit as much surge current going to CRT as possible to try and extend service life. Does varistor go in power transformer primary circuit, or somewhere a take off in secondary, for a gradual power on for B+ voltages??[/QUOTE]

On the ctc-10 it is just wired in series with the main voltage coming out of the transformer and into all the filtering caps etc. Don't know if it would give longevity to any tubes, unless for some reason filaments are known to last a bit longer if they are brought up to full power slightly more slowly than instantly (?) Don't remember if the voltage for the filaments is even going thru the varistor to begin with, it may not be.

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Open heaters seemed to happen most often on the series string AC/DC radios. Either the 35Z5/35W4 or the 50L6/50C5 would open up.

I have not seen many on TVs.

Ditto here. I had a 35Z5 open up on me this past weekend but I cannot remember the last time I found a dead filament tube in a TV, save for some HV tubes where the glass had cracked.

I had a Zenith 23" b/w set where the filament was open on the crt. Hooked the crt filament leads up to a horiz output tube and the tube lit up, so CRT was definitely bad. There were some other cases of no CRT filament I have seen but it was due to the crt being slightly cracked in a non-obvious area and losing its vacuum.
Also had a 6MJ6 horiz output tube burn out filament on a very well used CTC-39.

On the ctc-10 it is just wired in series with the main voltage coming out of the transformer and into all the filtering caps etc. Frenchy. Are you sure the device is wired into the secondary somewhere? Looked up the original schematic that came with the CTC10 and couldn't find it. Found the CTC10 RCA service literature and ditto, but I could have missed it.

Had to replace the Thyrite in that set in the latter sixties and I'm pretty sure it went in the primary of the power transformer. The fils are definitely in the loop because as I mentioned somewhere earlier, it takes the pilot lamp two seconds to ramp up to full brightness.

Pete

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found the surge device this time. In the CTC10 at least, the 'Thyrite' is R136 and it's in series with the power transformer primary. Listed as 'Surge resistor, 79 ohms cold' part number 107291. A secondary benefit with this design is that room lights on the same circuit don't dim at turn-on!

bgadow mentions having the '60 Motorola with the B+ delay switch. My '59 Motorola 21" has this same switch. I think my late-50's RCA portable has one as well. The switch engages about 30 seconds after turning the set on. This delay switch apparently works well with the electrolytics since both of my sets still have all the original capacitors in them and play just fine.

Frenchy. Are you sure the device is wired into the secondary somewhere? Looked up the original schematic that came with the CTC10 and couldn't find it. Found the CTC10 RCA service literature and ditto, but I could have missed it.
Pete

You are right, I was going on my bad memory, R136 in the primary on my schems, so it would indeed ease the power-on thru the entire set.