I am working on a ctc22 set that uses 5GH8 tubes (series string) and ALL the tubes were defective, either shorted or low emission. The same applies to the 6GH8 used on all the other RCA chassis, and most magnavox chassis. Anyone know why these tubes frequently fail? The few nos 6GH8s I have are almost totally gone because all I do is replace them and thats like 8 per set.

I would like to know the answer to that as well. I remember back in the "shop days" we always had to order a TON of those tubes. It didn't matter what set they were in, or the brand of the tube, they were ALWAY'S bad.

Don't look at them too hard they will go bad on you! My Magnavox has 4 of those buggers. Had to but eight to get 4 that worked.

polaraman

Don't look at them too hard they will go bad on you! My Magnavox has 4 of those buggers. Had to but eight to get 4 that worked.

polaraman

Originally posted by polaraman
.... My Magnavox has 4 of those buggers. Had to but eight to get 4 that worked.

polaraman

Buggers? You use your but as a tube tester???? :eek: :D

i remember in the late 70's early 80's buying 6gh8's 2-3 hundred at a time.
very failure prone.
i tell ya its a conspiracy to keep tv shops in business!:D

Originally posted by Rob
Buggers? You use your but as a tube tester???? :eek: :D
no wonder all your sets have shitty pictures:D

...

I think I have tried using other similar tubes (6EA8? maybe) with some success. There are several similar tubes with the same pin-out...might have to try some more to see what they do. One time I actually subbed a new in box 6GH8 for an old 6U8 in a Curtis Mathes set and got good performance.

...

If I remember correctly from looking at the tube manual the biggest difference is in transconductance among these types of tubes...I think 6GH8 has higher gm than 6U8. Seems like plate dissipation ratings are almost the same.

I found an old flyer from the late 70s advertising a promotion for Zenith tubes-if you bought however many tubes (100?) you would get a free subsription to TV Guide or Playboy. (such a deal!) There was one disclaimer-6GH8's did not count. Guess they sold too many to throw them into the deal?!

I have not personally had lots of trouble from these tubes, but I think that is just luck. I did have an early 70s RCA 19" that lost color; the first repair shop replaced the 6GH8 & told me not to bring it back. Repair lasted about a week, I fell asleep one night with the tv on and when I woke up it was b/w. Took it to another shop and he changed a resistor plus the 6GH8 and the set worked fine as long as I had it. I seem to recall that the second repair cost less than the first! Of course, today I would just figure it out myself, but I've learned a lot since then (still a ways to go, though)