Mercury TV-220A restoration

[jr_tech]

Originally Posted by bandersen

That tuner struck me as odd right away. Eventually, I found some service info in Riders vol 6 and 8.
It looks like Mercury was only around a very short while and only made sets with this basic chassis which is also listed under S.M.A. I don;t know who S.M.A is, but I'm guessing they made it for Mercury.

.....snip....

Meanwhile, any info on Mercury or S.M.A. would be much appreciated.

Oddly the same eBay vendor that listed the Mercury TV brochures also has some trade show pictures featuring S.M.A. , Chicago:

http://www.ebay.com/itm/TELEVISION-P...MAAOxyThVTX-ny

jr

[Eric H]

There's another thread here about Mercury sets, seems Brando is seen with one in Streetcar, or maybe it's On the Waterfront? it's different model however.

http://videokarma.org/showthread.php...ghlight=brando

[bandersen]

Originally Posted by old_coot88

That canvas strap holding the jug on might be deteriorated enough to break easily. This has been the case with some split-chassis Philcos with canvas straps securing the CRT.

Not to worry - there's a steel band underneath the cloth.

Originally Posted by jr_tech

Oddly the same eBay vendor that listed the Mercury TV brochures also has some trade show pictures featuring S.M.A. , Chicago:

http://www.ebay.com/itm/TELEVISION-P...MAAOxyThVTX-ny

jr

I think I see this tuner down at the bottom.

[Polaraligned]

Originally Posted by bandersen

Because it's so pristine I figure I'll restuff all the caps.

That is impressive. Most guys just give their chassis "yellow" disease, unless it is a particularly rare and valuable set.

[KentTeffeteller]

It is the same Mercury as the record company, they began by manufacturing radios, televisions, and phonographs, and in 1947 founded Mercury Records. And were purchased in 1961 by Philips of Holland. A beautiful early postwar set, and a very scarce set.

[bandersen]

I got the set up on the workbench today. Looks like serial # is X4136. I wonder how many were made ?


Super clean inside the HV cage. Interesting focus and centering magnet assembly. It is both a permanent and electromagnet.


I pulled the 5U4 rectifier and tried a power up. I quickly discovered a blown fuse and replaced it.


Success! Unloaded HV secondary is around 750 VAC.


Encouraged, I decided to give it a brief try with the rectifier in while carefully monitoring the B+. Things looked good but after a coule power cycles, the 5U4 died. I then worked on the frozen tuner a while and was able to free it up. I popped in a new 5U4 and gave it another go. It held up and I was able to pick up some FM stations

I also removed the weak CRT and installed a 8XP4 bench CRT. I have to keep it at an awkward angle because the grounding strap makes contact with the HV button.
No luck - 0 HV. Still not bad for a first power up. I'll get to recapping next.

[dtvmcdonald]

Mercury Records produced the finest sounding recordings ever made, in
many people's opinions. The main reason was the exact polar pattern
vs. frequency curve of the microphones they used ... plus the extremely
low noise and high dynamic range (up to 140 dB!) of the tube used as
the microphone cathode follower. Google "Wilma Cozart".

[bandersen]

I replaced the four corroded sand coated power resistors and recapped the horizontal circuits. I gave up on restuffing after the first two cardboard cap tubes crumbled.

There is a funky assortment of resistors like I've seen in other early 50s sets. Perhaps due to Korean war shortages plus the huge demand for TVs.
Also seeing some deviation from the schematic like this 39 ohm plus two 1M in parallel. The schematic shows a 47 ohm and single 1M. I figure it's best to stick with the values I find in the set.


Did another power up and started hearing some arcing in the HV area. Some investigation revealed a splice in the HV lead and a dirty HV rectifier socket.





Eventually, I also discovered the 1B3 had a crack in it. Not sure if it was always there or if the arcing caused it.


With that sorted out, I finally got raster


Swapped out a bunch of weak or shorted tubes and got better sound and contrast. Think I'll focus on the vertical circuits next.

[bandersen]

I replaced the electrolytic caps in the B+ supply and vertical output circuits. All four of the can electrolytics in this set have cardboard covers over them which I was able to remove with a little heat. Then, I cut them open and installed the new caps. Once I'm done, I'll pop the cardboard back on to hide them.


Now I've got full height and good linearity. I also installed a new, longer HV lead so I can flip the test CRT around and avoid that grounding strap.

[bandersen]

I finished recapping the set and popped the original CRT back in. Since it had tested so poorly I wasn't surprised that the best I could get was a dim, out of focus image. I had to dim the lighting to take this photo. The brightness control has virtually no effect.


Replacing it with a good 16RP4 made a very noticeable difference!


Tweaking the controls improved the focus and brightness is most definitely much better. I do have some streaking though. I'll check the peaking coils and video amp circuit.

[timmy]

That chassis looks similar to the RCA 630 set.

[Radiotronman]

Starting to look pretty good!

[timmy]

Amazing what new caps can do.

[decojoe67]

Looks good! Nothing like seeing a set that was dormant for so many years come to life.

[bandersen]

Here's a look inside the continuous tuner. They use a three position cam to skip the FM band and move it to the end so it goes 2-13 then FM. That also gives it a nice wide FM tuning range so it's not all bunched up.
Power to the flyback is also killed while in the FM band so the screen goes dark.