looking for a schmatic for a '72 GE color set

[drh4683]

I got a chance to sit down and really check out the latest no HV regulation problem this evening. HV corona is caused by some carbon build up on the HV lead that is soldered onto the HV rectifier socket. GE used some interesting type of HV "caulk" on and around those pins. When it drys, it drys very pourous and very flexible. Well, it carboned up and was shorting to ground. I pulled that junk off and still had a little bit of hiss to deal with as the HV lead has a carbon hole burned through the insulation which just needs to be snipped and resoldered, its right at the end of the wire.

Fortunately, I got the HV regulation issue fixed. Diode Y252 in the HV regulation circuit (to the grid circuit of the 26HU5 HOT) was wide open. I had a variable grid voltage from -65 through -72 volts. Supposed to be -70, but no rectified pulse. I didnt get any reading with my vtvm when checking the diode forward or reverse biased. Its a rather large diode, brown in color about 3/4" long, 3/16" OD. I used some gator clips and attached a 1000 PIV 1amp silicon diode and the HV hiss arcing suddenly dissapeared (HV finally dropped down!). I now had a perfect control of HV from 20KV to 27KV.
Since I only have tekfax (schematic only, no parts list), Id like to find out what the proper substitution is for this diode Y252. Just so you know, this particular chassis only has the one diode. Supposedly there were other versions that had two diodes in parallel (Y252, and Y253) and the circuit in my C2 is slightly different as this chassis has a focus potentiometer, and not a focus coil like the schematic shows, so I dont have the two 430K ohm resistors nor the 3900pF disk cap. My C2 chassis was built in April, 1972. I dont know enough about these GE sets. I dont know if my set is an early or late production.
Thanks again for all your help.

[Findm-Keepm]

Originally Posted by drh4683

I'd like to find out what the proper substitution is for this diode Y252.

Y252 is an EU57X31 - equivalents are ECG119, and GECR-2. Basically, it's a boost rectifier. So dig through your Zenith 212-?? diode stock, find one, and git'er fixed.

Cheers,

[Findm-Keepm]

Doug, if you need an exact GE replacement, lemme know. I have one in stock.

Cheers,

[drh4683]

Brian,

Thanks for checking. I did contact moyer's yesterday and had the part number K122J177-2 as printed on the diode. Moyer had a sub for it, but its not an NTE or ECG. If I remember correctly, he said it was a GECR-2 which you mentioned. I should get it hopefully tomorrow or saterday. I'll let you know how it works out.

[Findm-Keepm]

GECR-2's are little red bullet shaped buggers made by Siemens for GE - pay attention to the polarity or you'll get some nasty smoke (they're Selenium, after all..) The ECG119 is exactly like your original diode, cardboard tube with crimped metal caps on the ends. Workman also had their "WEP119" Boost Rectifier. When I worked at Cain Electronics in the 80's, and stocked both, and servicers preferred the WEP over the GECR-2, based solely on the looks.

Oddly enough, I'm in the somewhat stalled process of replacing the focus coil in my CTC-16 set, and decided to replace the Boost rectifier while I was in there.....with a GECR-2.

FYI, I have seen boost diodes replaced with Silicon fast rectifiers. Fagor makes an excellent "RGP" series diode - some go to 2KV/1.5A, plenty enough for TV boost rectifier applications. And they're cheap.

Cheers,

[drh4683]

Its all done! The GECU-2 arrived from moyer today. I installed that, set the HV and converged the set. Works perfect. For a GE, the picture is quality is very good. If you want to see other pictures of this TV, look at the 2-16-08 posting in "estate sale finds in 2008" thread as thats the day I found this TV. The C-2 chassis is pretty much an all tube chassis like a portacolor but on a bigger scale.
There are very few of these left and glad I was able to bring it back to life. It gets a last gasp of true analog reception!
The sweep transformer is of very high quality, much like a thordarson which is good to see. It was an interesting TV to work on to say the least. I think Ive had my fix of GE color sets for a while. Im ready to go back to a zenith, even though a ctc-25 is on the bench right now.
More estate sales for tomorrow, so more TVs might be found.
Thanks again for the help, parts and info guys. It is always appriciated!

[radiotvnut]

That's the best picture that I've ever seen on one of these sets! Glad you got it going!

[Tony V]

Thats the first time i have seen a GE set of that vintage have correct fleshtones. Most of the ones i've seen would have red tomatoes, green grass and blue skies but have green or purple tinted fleshtones. If you tried getting the fleshtones right it would throw everything else off. Nice job! Does it have the loud flyback ringing like most of the older GE's have?
-Tony

[drh4683]

Actually, the TV is very quite. No flyback ring at all, and I can hear up to 17kHz. The fleshtones really are good, nice range from purple to green on both ends and the color can really over saturate if you want. Its quite an impressive working TV considering its a GE. This is a low hour set, so that might have something to do with it.

[bgadow]

Ditto what others said-you really got that one tuned in right! And growing up in an all-GE household, I just assumed TV sets were supposed to make that whine!