RCA U70 UHF Converter - Videokarma.org TV - Video

bandersen · #1 10-17-2010, 12:15 AM

I decided to take a break from my GE 810 project and take a quick look at this guy. It a top of the line RCA U70 UHF converter.

There's some separation in the upper right, but otherwise it's in good condition.
I wonder what the UHF jack in the lower left and the RCA jack center bottom are for

Most converters just have a 6AF4 oscillator and converter tube, but this adds two 6CB6 amplification stages.

It's also very well built. Check out the tuning cavity. Several slugs move in and out of coils when turning the dial.

Heavily shielded 6AF4 tube.

Just a 3-section electrolytic to deal with. Not a single paper cap.
Does anyone have a schematic ?

bandersen · #2 10-17-2010, 12:25 AM

I found this old VK thread with some good info http://www.videokarma.org/showthread.php?t=39714

bandersen · #3 10-17-2010, 04:32 AM

After a quick recap and new 6CB6s, it's working fairly well. I was able to pick up four analog UHF stations.

Here it is hooked up to my Sentinel 430 and tuned to MeTV. That's a network that broadcasts classic TV shows and movies.

Reece · #4 10-17-2010, 10:09 AM

That is a hefty unit, power xfrmr and 5Y3 rectifier, no details spared. Nice pix on TV. This is the sort of thing you'll find for sale that people think is a radio, "powers up, but can't get any sound out of it."

jr_tech · #5 10-17-2010, 11:06 AM

Nice! I played with one of these units about a year ago... the UHF antenna terminal on the back did not appear to work... the only way I could get a picture was by using the SMA connector on the back as the UHF input. I assume that yours is working ok with the "normal" connection of the stacked bow-tie to the 300 ohm UHF terminals?

jr

bandersen · #6 10-17-2010, 01:39 PM

Quote:

Originally Posted by Reece

That is a hefty unit, power xfrmr and 5Y3 rectifier, no details spared. Nice pix on TV. This is the sort of thing you'll find for sale that people think is a radio, "powers up, but can't get any sound out of it."

Yeah, I have three other UHF converters that all use selenium rectifiers.

Quote:

Originally Posted by jr_tech

Nice! I played with one of these units about a year ago... the UHF antenna terminal on the back did not appear to work... the only way I could get a picture was by using the SMA connector on the back as the UHF input. I assume that yours is working ok with the "normal" connection of the stacked bow-tie to the 300 ohm UHF terminals?
jr

Ah, so that's a UHF input on the back. Any idea what the RCA jack is for ? Maybe VHF input ?

Yes, I'm using the 300 ohm UHF terminals.

jr_tech · #7 10-17-2010, 02:05 PM

Quote:

Originally Posted by bandersen

Ah, so that's a UHF input on the back. Any idea what the RCA jack is for ? Maybe VHF input ?

Yes, I'm using the 300 ohm UHF terminals.

Ok, thanks! I could get nothing through the "normal" 300 ohm UHF input terminals. I don't think that the SMA connector was intended to be the antenna input, but that was the only way I could get a signal through the converter.

I believe that the RCA connector was right at the mixer diode, before the amplifier stages.
jr

Jeffhs · #8 11-27-2012, 03:35 PM

Quote:

Originally Posted by bandersen

After a quick recap and new 6CB6s, it's working fairly well. I was able to pick up four analog UHF stations.

Here it is hooked up to my Sentinel 430 and tuned to MeTV. That's a network that broadcasts classic TV shows and movies.

I'm amazed there are any analog TV stations left in the US. Until I saw your post (and one from radiotron), I thought all analog TV in this country had disappeared forever. I live near Cleveland, and all of the city's TV stations, with no exceptions in town, are digital. There was one analog translator in an outlying suburb that carried a religious station on channel 51, but I don't know if that station is still around. The same goes for the three UHF translators carrying the PBS station in Cleveland, although they might still be on until 2015 (the year, exact date escapes me, by which all translators and low-power TV stations must convert to digital) for those viewers still using antennas.

Your Sentinel TV and MeTV sound like a perfect match -- a retro-TV channel viewed on a vintage television receiver that was new when most of MeTV's now-classic shows were new as well.

Do you get Antenna TV in Chicago as well as MeTV? If so (in Chicago, I would think one of the VHF network stations should have it on a subchannel), that network will provide even more good retro programming for your Sentinel 430. I've been watching both networks since they arrived on subchannels of channels 8 (FOX) and 19 (CBS) in this area, and I enjoy them both as they show almost all the TV programs I grew up watching. One of my favorites is Kojak, which I watched every week on CBS in the early '70s. MeTV shows these programs in reruns at 12:30 a.m. Eastern time, and I think they are on earlier in the evening as well, although the time of the earlier airing escapes me as I write this.

DavidGoncalv · #9 11-27-2012, 03:54 PM

Thread is from two years ago.

jr_tech · #10 11-27-2012, 04:08 PM

Quote:

Originally Posted by DavidGoncalv

Thread is from two years ago.

Very true, but this thread was referenced in a more recent thread:

http://www.videokarma.org/showthread.php?t=256471

Now we can get stuck in a loop, stuck in a loop, stuck in a loop.

jr

bandersen · #11 11-27-2012, 05:08 PM

It may be two years old, but we still have analog broadcasts in Chicago

I just did a fresh scan and found analog broadcasts on channels 6, 23, 34 and 41.

wa2ise · #12 11-27-2012, 08:19 PM

I suppose you could use this UHF converter to downconvert ATSC DTV UHF TV stations and set the ATSC converter box to channel 6. I tried it and I did get a few DTV stations coming in on channel 6, though as we all know DTV is kinda fussy to get to work. You could place this UHF converter next to a HDTV, feeding it, flat panel, and amuse your friends by tuning the UHF converter to get stations in Hi Def.

jr_tech · #13 11-27-2012, 08:41 PM

Quote:

Originally Posted by wa2ise

I suppose you could use this UHF converter to downconvert ATSC DTV UHF TV stations and set the ATSC converter box to channel 6. I tried it and I did get a few DTV stations coming in on channel 6, though as we all know DTV is kinda fussy to get to work. You could place this UHF converter next to a HDTV, feeding it, flat panel, and amuse your friends by tuning the UHF converter to get stations in Hi Def.

Wow! I tried the same experiment and could not get anything out of the DTV converter... I figured that I did not have enough signal (outdoor antenna about 12 miles to the transmitter) to overcome the terrible noise figure of the old UHF converter, or perhaps the UHF converter was not stable enough.

jr

josephdaniel · #14 11-27-2012, 08:54 PM

Slightly off topic here but i turned through the dial of sever of my tvs and I pick up about 7 channels all of them are rebroadcasts of the cw (the seem to have several low power transmitters going so they can cover a larger area) and one or two was religious or PBS couldn't really tell too much static.

DavGoodlin · #15 11-30-2012, 02:00 PM

Bob, That is one of the BEST indoor vintage UHF antennas you're using there. I had several of those and gave them all away with sets I sold.

BTW , I cannot find any analog in Southeastern PA or Maryland